Ecology and Distribution of Major 

Ecotypes in the Southern. Fort Union 

Region of Montana

GEOLOGICAL SHR/VET P R 0- f 1 S &F OM A-L. .P A J» E & 1.2; 8

Ecology and Distribution of Major Diatom 

Ecotypes in the Southern Fort Union Coal 

Region of Montana

By L. L. BAHLS, E. E. WEBER, and}. O. JAR VIE

GEOLOGICAL SURVEY PROFESSIONAL PAPER 1289

Major diatom ecotypes are systematically described 

in terms of taxonomy and morphology, abundance, 

ecology, distribution, and water-quality variables

UNITED STATES GOVERNMENT PRINTING OFFICE, WASHINGTON : 1984
DEPARTMENT OF THE INTERIOR 

WILLIAM P. CLARK, Secretary

U.S. GEOLOGICAL SURVEY 

Dallas L. Peck, Director

Library of Congress Cataloging in Publication Data

Bahls, Loren L.

Ecology and distribution of major diatom ecotypes in the southern Fort Union coal region of Montana.

(Geological Survey professional paper ; 1289)

Bibliography: p.

Supt. of Docs, no.: I 19.16:1289

1. Diatoms Montana Fort Union coal region Ecology. 2. Water quality bioassay Montana Fort Union coal region.

3. Plant indicators-Montana-Fort Union coal region. I. Weber, E. E. II. Jarvie, J. O. III. Title. IV. Title:

Southern Fort Union coal region of Montana. Series. 

QK569.D54B24 1983 589.4'81'Q450978622 83-600056

For sale by the Distribution Branch, U.S. Geological Survey, 

604 South Pickett Street, Alexandria, VA 22304
CONTENTS

Abstract 

Introduction 

Purpose and scope 

Ecotypes and indicators 

Previous work 

Physical setting 

Acknowledgments 

Page 

1 

1 

1 

3

3

4

4

4

4

Environmental measurements 

Chemical and physical measurements 

Biological measurements 8

Onsite methods 8

Laboratory methods 8

Percent relative abundance 9

Discussion 9

Supplementary information 11

Format 11

Taxonomy and morphology 12

Abundance 12

Distribution 12

Major diatom ecotypes 13

Achnanthes lanceolata Breb. ex Kutz. - 14

Achnanthes minutissimaKutz. IQ

Amphipleura pellucida (Kutz.) Kutz. 18

Amphora coffeiformis (Ag.) Kutz. 20

Amphoraperpusilla (Grun.) Grun. 22

Amphora veneta Kutz. 24

Asterionella formosa Hass. 26

Cocconeis pediculus Ehr. 28

Cocconeis placentula Ehr. 30

Cyclotella meneghiniana Kutz. 32

CyclotellapseudostelligeraHust. 34

Cymbella affinis Kutz. 36

Cymbella microcephala Grun. 38

Cymbellapusilla Grun. 40

Cymbella species X 42

Diatoma tenue Ag. 44

Diatoma vulgareRory 46

Diploneissmithiivar.pumila (Grun.) Hust. 48

Entomoneispaludosa (W. Sm.) Reim. 50

Epithemia adnata (Kutz.) Breb. 52

Epithemia sorex Kutz. 54

Fragilaria capucina Desm. 56

Fragilaria construens (Ehr.) Grun. 58

Fragilaria crotonensis Kitton 60

Fragilaria vaucheriae (Kutz.) Peters. 62

	Page

Major diatom ecotypes Continued

Fragilaria species X 64

Gomphonema angustatum (Kutz.) Rabh. 66

Gomphonema olivaceum(Lyngb.)Kutz. 68

Gomphonema tenellum Kutz. 70

Melosira varians C. A. Ag. 72

Navicula cincta (Ehr.) Ralfs var. cincta 74

Navicula cincta var. rostrata Reim. 76

Navicula cryptocephala var. veneta (Kutz.) Rabh. 78

Navicula goersii Bahls 80

Navicula gregariaDonk. 82

Navicula odiosa Wallace 84

Navicula pavillardiiHust. 86

Navicula peregrina var. lanceolata Skvortzow 88

Navicula radiosa var. tenella (Breb. ex Kutz.) Grun. 90

Navicula rhynchocephala Kutz. 92

Navicula salinarum var. intermedia (Grun.) Cl. 94

Navicula symmetrica Patr. 96

Navicula tripunctata (O. F. Mull.) Bory 98

Navicula viridula var. avenacea (Breb. ex Grun.) V. H. 100

Nitzschia acicularis W. Smith 102

Nitzschia amphibia Grun. 104

Nitzschia closterium (Ehr.) W. Smith 106

Nitzschia communis Rabh. 108

Nitzschia dissipata (Kutz.) Grun. 110

Nitzschia filiformis (W. Sm.) Hust. 112

Nitzschia frustulum (Kutz.) Grun. 114

Nitzschia linearis W. Smith 116

Nitzschia microcephala Grun. 118

Nitzschia obtusa W. Smith 120

Nitzschiapalea (Kutz.) W. Smith 122

Nitzschia supralitorea Lange-Bertalot 124

Nitzschia valdestriata Aleem & Hust. 126

Pleurosigma delicatulum W. Sm. 128

Rhoicosphenia curvata (Kutz.) Grun. ex Rabh. 130

Rhopalodia gibba (Ehr.) O. Mull. 132

Stephanodiscus astraea var. minutula (Kutz.) Grun. 134

Stephanodiscus niagarae Ehr. 136

Stephanodiscus subtilis Van Goor 138

Surirella ovata Kutz. 140

Synedra famelica Kutz. 142

Synedra fasciculata(Ag.) Kutz. 144

Synedra ulna (Nitz.) Ehr. 146

Thalassiosirapseudonana(H.ust.) Hasle & Heimdal 148

References cited 150

ILLUSTRATIONS

FIGURE 1-3. Maps showing:

1. Location of study area and water-quality stations 

2. Number of sampling stations in each of the eight hydrologic units 

3. Number of diatom collections from each of the eight hydrologic unitsPage

2

5

7

CONTENTS III
TABLES

TABLE 1. Number of diatom collections from each sampling station 

2. Statistical summary of physical and chemical data 

3. Range of values for six variables considered in the ecological summaries

4. Summary of diatom collections 

5. Classification method for the algae, with a diatom example 

6. Freshwater and brackish-water diatom ecotypes 

7. Clear-water and cloudy-water diatom ecotypes 

Page 

6

6

10

11

CONVERSION FACTORS FOR METRIC EQUIVALENTS

Inch-pound unit

To convert

Cubic foot per second (ft3/s)

Foot (ft)

Micromho per centimeter at 25 ° Celsius 

Otmho/cm)

Mile (mi)

Square mile (mi2 )

Degrees Fahrenheit ( °F)

Multiply by

28.32

0.3048

1.000

1.609

2.590

Subtract 32 and divide by 1.8

Metric unit

To obtain

Liter per second

Meter

Microsiemens per centimeter at 25 ° Celsius

Kilometer

Square kilometer

Degrees Celsius (°C)

The use of brand names in this report is for identification purposes only and does not constitute endorsement by the U.S. Geological Survey.

IV CONTENTS
ECOLOGY AND DISTRIBUTION OF MAJOR DIATOM ECOTYPES IN THE 

SOUTHERN FORT UNION COAL REGION OF MONTANA

By L. L. BAHLS, E. E. WEBER, and J. O.

ABSTRACT

From 1975 through 1980, samples were collected to determine the 

ecology and distribution of the major diatom ecotypes in the southern 

Fort Union coal region of Montana. Altogether, 370 diatom samples 

and 289 concurrent water-quality samples were collected at 52 

surface-water stations. Sixty-eight major diatom ecotypes were 

selected for identification on the basis that their percent relative 

abundance equaled or exceeded 10 following proportional counts of 

300 to 400 frustules.

Each major diatom ecotype is systematically described in terms of 

taxonomy and morphology, abundance, ecology, and distribution in 

the study area. Included are tables of 24 water-quality variables of 

biological significance for each ecotype. Illustrations and brief descriptions of representative specimens are included to document and 

facilitate identification. This information may be used to help establish water-quality criteria for the region's aquatic communities, to 

identify indigenous diatoms or diatom groups that are useful as 

water-quality indicators, and to provide a basis for an ecological classification of the various diatom associations in the study area.

Many of the major diatom ecotypes are identified as having sufficiently narrow ecological amplitudes to be useful as indicators of dissolved solids, suspended sediment, and temperature. These are three 

of the water-quality variables most likely to be affected by surface 

mining and related activities.

INTRODUCTION

The southern Fort Union coal region, the general 

area in southeastern Montana from the Yellowstone 

River south to the State line (fig. 1), contains one of this 

country's largest deposits of shallow coal. Here, the 

coal has a small sulfur content and can be extracted by 

surface-mining methods. Recent emphasis on energy 

independence and a greater reliance on domestic energy 

resources have accelerated coal mining and related 

activities that could adversely affect the environment of 

the region. Of particular concern is water quality and 

the integrity of biological communities supported by the 

region's many streams and surface-water impoundments.

Small, simple plants called algae are key components 

of aquatic ecosystems. Through photosynthesis, algae 

transform basic raw materials into stored energy which 

becomes food for aquatic animals. In the relatively 

small and shallow streams of southeastern Montana, the 

benthic (bottom) algae or periphyton are most important 

in terms of primary production and plant diversity; 

plankton (open water) algae and aquatic macrophytes 

(more complex plants) are of lesser overall significance

(Bahls, 1980). The importance of benthic algae in streams 

draining energy resource areas of the Rocky Mountain 

West is underscored by their inclusion in ecological 

baseline studies recommended by the U.S. Fish and 

Wildlife Service (States and others, 1978).

Beyond their inherent value as aquatic producers, 

algae are useful indicators of water quality. Each species of algae has unique environmental requirements 

and pollution tolerances. To know the requirements 

and tolerances of a species is to know something about 

the water quality of a stream in which the species lives. 

For cosmopolitan species those found in suitable habitats around the world these requirements and tolerances also may reveal something about the water quality 

of a stream in which the species does not live.

'Authors are with the Water Quality Bureau, Montana Department of Health and Environmental Sciences, Helena, Mont. Research supported by the U.S. Geological Survey, Department of the Interior, under contract No. 14-08-0001-G-665.

PURPOSE AND SCOPE

The purpose of this report is to summarize the ecology and distribution of the major diatom ecotypes that 

live in the southern Fort Union coal region of southeastern Montana. This information may be used to 

help establish water-quality criteria for the region's 

aquatic communities, to identify indigenous diatoms or 

diatom groups that are useful as water-quality indicators, and to provide a basis for an ecological classification of the various diatom associations in the study 

area. Illustrations and brief descriptions of representative specimens are included to facilitate identification. 

Only diatoms (Division Bacillariophyta) are treated 

here for three reasons.

First, diatoms are by far the predominant algae in 

the southern Fort Union coal region. In the first phase 

of this study, Bahls (1980) reported the following occurrence percentages in periphyton collections for the 

major algae classes: Bacillariophyceae (diatoms), 100; 

Chlorophyceae (green algae), 78; Cyanophyceae, (bluegreen algae), 52; all other classes (Charophyceae, 

Euglenophyceae, Xanthophyceae, Chrysophyceae, 

Dinophyceae, Rhodophyceae), less than 20. These findings are supported by those of Olson-Elliott and Associates (1977) and Whalen (1979).

Second, diatoms and other unicellular algae are 

grazed by certain aquatic invertebrates in preference

INTRODUCTION
107 105° 104°30'

46°30

CROW INDIAN / /< I /* p^ ^| 

RESERVATION/" f yO fiUSby- /2i4ef ^?'

/ Xl r NC5RTHERW

45°30'

FIGURE I. Location of study area and water-quality stations.

to larger and coarser filamentous algae (Merritt and 

Cummins, 1978). Unlike other algae, diatoms rarely 

build massive standing crops (blooms) that snag fishing lines, decrease dissolved-oxygen concentrations, or 

render the water unsightly (Taylor and others, 1981). 

And unlike certain blue-green algae (Carmichael,

1981), freshwater diatoms have not been reported to 

be toxic to warm-blooded animals (Jackson, 1964; 

Palmer, 1977; Werner, 1977).

Third, diatoms are more practical water-quality indicators than soft-bodied algae and other aquatic organisms for the following reasons. Diatoms are single-celled

2 ECOLOGY AND DISTRIBUTION OF MAJOR DIATOM ECOTYPES IN MONTANA
plants with a rigid, nearly indestructible integument, 

thereby aiding enumeration, preservation, and storage. 

They are ubiquitous on stream bottoms, may be captured without expensive equipment, and almost always 

can be collected in sufficient quantity to meet statistical requirements. A given reach of stream may have 

dozens of different diatom species, each with a different 

set of environmental preferences and pollution tolerances. Moreover, a rather extensive amount of literature 

exists on diatom ecology and taxonomy (Lowe, 1974).

ECOTYPES AND INDICATORS

The bewildering array of closely related and generally intergrading varieties and species commonly found 

in benthic diatom associations is a formidable obstacle 

to one who would use the diatoms to assess water quality. For routine water-quality monitoring, however, it 

is sometimes unnecessary to distinguish between similarly appearing, closely related and co-existing taxa 

because they commonly have very similar ecological 

preferences and pollution tolerances. Consequently, an 

ecotype approach rather than a strict taxonomic approach is adopted here to simplify the use of diatoms as 

water-quality indicators, particularly for those who 

have neither the time nor the resources for a rigorous 

taxonomic analysis.

Hanson and Churchill (1961) define ecotype as a cluster of biotypes, within a species, occupying a particular 

habitat. A biotype, according to this definition, is a 

population of a species within a given microhabitat 

belonging to one genotype. For the most part, an ecotype is designated herein by a species, and biotypes by 

varieties of that species. Each species (ecotype) in this 

report may contain as many as six varieties (biotypes) 

that have similar ecological affinities based on repeated 

co-occurrence in the study area. In several instances, 

an ecotype is identified as a single variety because it is 

presumed to be ecologically distinct from another variety that is also found in the study area. In some instances, a form or even another closely related species 

is designated as a biotype; the ecological counterpart 

for form is ecoform (phenotype) and for another closely 

related species is ecospecies.

Two criteria were considered in clustering biotypes. 

One, they co-exist in the majority of the collections in 

which they are found; and two, they are morphologically very similar to and generally intergrade with 

one another. The ecotype is assigned to the species that 

includes the most common biotype of the study area, 

except in those instances where a variety is designated 

as an ecotype. However, a given species may contain 

additional ecotypes and biotypes in aquatic habitats 

not sampled during this survey, either inside or outside the southern Fort Union region. The ecological

amplitude of the designated ecotype spans the ecological amplitudes of all the recorded biotypes in the study 

area.

The real danger in the ecotype approach is that it 

will forfeit a certain quantity of ecological information. 

Ecotypes of large ecological amplitude generally are 

composed of a number of biotypes or ecoforms, each 

perhaps with a much smaller ecological amplitude. 

The authors believe, however, that whatever information is lost will be more than compensated for by the 

ease with which intergrading and often confusing forms 

may be assigned to a common ecological type.

Certain ecotypes (clusters of biotypes), particularly 

those containing more than one species, will raise 

questions concerning appropriate degrees of taxonomic 

classification. Are varieties and species within the 

same ecotype indeed distinct genotypes or are they just 

phenotypic expressions (ecoforms) of this genotype? 

Posing such questions to serious students of diatom 

classification may be viewed as a secondary purpose of 

this report.

The number of diatom taxa in the southern Fort 

Union coal region is unknown but is estimated to be 

about 500. A diatom is most valuable as a water-quality 

indicator if it is present in substantial numbers. Many 

so-called indicator organisms may be present within a 

broad range of environmental conditions but will 

prosper that is, produce a large number of individuals only within certain limits. A taxon that contributes only a small percentage of frustules to the total 

diatom association may be just barely existing or be 

totally incidental to the aquatic system that was sampled. For example, a taxon might have been introduced 

from upstream, from the soil of the adjacent streambank or as the result of some random and unpredictable occurrence, such as a visit by a transient shorebird 

with feet contaminated with algae from a foreign ecosystem. Consequently, diatoms having relatively small 

populations usually do not make suitable water-quality 

indicators nor are they particularly important in terms 

of the total bioenergetics of the aquatic community. 

Therefore, ecological summaries have been prepared 

only for those diatom ecotypes from the southern Fort 

Union region that accounted for 10 percent or more relative abundance (as determined by a proportional count 

of 300 to 400 frustules) in one or more collections. A 

total of 68 such ecotypes was evaluated.

PREVIOUS WORK

This report is a continuation of data evaluation for 

the benthic biological inventory of the southern Fort 

Union coal region initially sponsored by the U.S. 

Bureau of Land Management and supported by the 

U.S. Geological Survey under research grant number

INTRODUCTION 3
14-08-0001-G-503. The inventory data report (Klarich 

and others, 1980) tabulates chemical, physical, and biological data collected during the inventory, including 

major diatom taxa in each periphyton collection. Bahls 

(1980) explored the effect of salinity on the structure 

(diversity) of benthic algae associations and found little 

apparent effect among streams in the study area. 

Klarich and Regele (1980) described the structure, 

salinity relationships, and other characteristics of benthic macroinvertebrate associations in streams draining the coal-field region. Regele and others (1982) list 

taxa of higher aquatic plants and genera of macroalgae 

and microalgae from the study area along with those 

from the Poplar River basin in northeastern Montana. 

All algal analyses from the southern Fort Union coal 

region performed by or known to Montana Water Quality Bureau personnel were considered in compiling the 

list of major diatom ecotypes described in this report. 

In addition to the collections made specifically for the 

benthic biological inventory are analyses performed 

for the Bureau's biological monitoring program (unpublished data) and the Bureau's Tongue River project 

(Bahls and Bahls, 1977), studies by Olson-Elliott and 

Associates (1977, 1979, 1981) and Whalen (1979), and 

one incidental collection in a previously unsampled 

hydrologic unit the Little Powder River near Broadus 

(station 45). Those collections with concurrent waterquality data form the basis of the ecological summaries 

presented herein.

PHYSICAL SETTING

The study area is approximately that part of the Fort 

Union coal region in Montana south of the Yellowstone 

River (fig. 1). The area extends from the Sarpy Creek 

drainage on the west to the Powder River drainage on 

the east. The southern boundary of the study area 

matches the Montana-Wyoming border except for a 

small part of Wyoming along the Tongue River drainage to near the mouth of Ash Creek north of Sheridan, 

Wyo. (station 41).

The entire study area is within the Yellowstone River 

basin and includes parts of drainages of the Tongue 

and Powder Rivers, Rosebud Creek, and several small 

tributaries to the Yellowstone River between Hysham 

and Miles City, Mont. The study area encompasses all 

or parts of eight U.S. Geological Survey surface-water 

hydrologic units (fig. 2), which are used to plot geographic distributions of the major diatom ecotypes 

within the southern Fort Union coal region.

Descriptions of the area, including geography, hydrology, soils, climate, and water quality have been 

prepared by Knapton and McKinley (1977) and Knapton and Ferreira (1980). The study area is predominantly rural and agricultural, with cattle grazing the 

principal land use.

ACKNOWLEDGMENTS

Duane A. Klarich conceived and initiated the original benthic biological inventory of the southern Fort 

Union coal region, which was sponsored by the Bureau 

of Land Management and the Geological Survey. 

Duane A. Klarich and Stephen M. Regele collected 

most of the samples upon which this report is based. 

Peggy A. Bahls contributed a substantial amount of 

her time toward the tedious task of calculating and 

tabulating diatom percent relative abundance data. 

Sincere thanks also are extended to the Northern 

Cheyenne Indian Tribe and to those private landowners 

who permitted access to sampling stations on their 

lands; to Dan Corwin for scanning electron-microscope 

photographs of difficult taxa; and to Charles W. Reimer 

who assisted the principal author with taxonomic problems on numerous occasions. J. Platt Bradbury, Rex L. 

Lowe, and Cornelius I. Weber provided helpful and 

constructive reviews of the manuscript.

ENVIRONMENTAL MEASUREMENTS

Altogether, 370 diatom samples and 289 concurrent 

water-quality samples were collected at 52 sampling 

stations on 38 bodies of water, including 34 rivers and 

creeks, 1 reservoir, 1 spring, 1 roadside slough, and 1 

discharge from a surface coal mine (table 1 and fig. 1). 

Each flowing-water station consisted of a stream reach 

as much as 10 miles long. Occasionally a different site 

was sampled on successive visits, to a maximum of six 

discrete points within a given reach (station) during 

the course of the study. Collections were made from 

1975 through 1980 and included all months of the year 

except December and January. Nine stations on eight 

significant streams in the study area were selected for 

intensive seasonal analysis, 34 accessory stations were 

sampled less intensively, and nine additional stations 

were added from other biological inventories and monitoring programs conducted by Water Quality Bureau 

personnel (table 1). Sampling stations (fig. 2) and 

diatom collections (fig. 3) are distributed among the region's hydrologic units. Note that unit 10100001 is divided into two parts; the eastern part is represented 

exclusively by six collections from one station on 

Sweeney Creek (station 40).

CHEMICAL AND PHYSICAL MEASUREMENTS

Of the 33 water-quality variables that were measured 

during the initial inventory (Klarich and others, 1980),

4 ECOLOGY AND DISTRIBUTION OF MAJOR DIATOM ECOTYPES IN MONTANA
105°

LOWER 

10 20 30 40 KILOMETERS 46°30'i POWDER

LOWER YELLOWSTONE

TRIBUTARIES

10100001

LOWER TONGUEPUMPKINOTTER

10090102 MIZPAH 

10090210

ROSEBUD 

10100003

MIDDLE 

POWDER 

10090207

LITTLE 

POWDER 

10090208 UPPER TONGUE 

HANGING 

WOMAN 

10090101

FIGURE 2. Number of sampling stations (circled) in each of the eight hydrologic units of the study area. Hydrologic unit 10100001, lower

Yellowstone tributaries, comprises two areas in the northwest part of the map.

24 variables of biological significance were selected to 

construct water-quality profiles for the major diatom 

ecotypes (table 2). One or more of these variables were 

measured concurrently for 289 of the diatom collections. 

Silica, a variable of obvious importance to diatoms, 

was not included because of its consistently nonlimiting concentrations. Measured silica concentrations 

ranged from 2.8 to 30.0 mg/L (milligrams per liter) and 

averaged 15.1 mg/L. Silica becomes limiting to diatoms 

only at concentrations less than about 0.8 mg/L(Hutchinson, 1957).

Grab samples of water were collected in plastic, 

1-liter bottles and appropriately preserved or 

refrigerated for transport and storage according to U.S. 

Environmental Protection Agency (1979) guidelines. 

Most variables (common ions, nitrogen, phosphorus, 

iron, and manganese) were analyzed by the Chemistry 

Laboratory Bureau of the Montana Department of 

Health and Environmental Sciences in Helena, Mont. 

Other variables (specific conductance, pH, temperature, turbidity, dissolved oxygen, biochemical oxygen 

demand, and suspended sediment) were measured

ENVIRONMENTAL MEASUREMENTS
TABLE I. Number of diatom collections from each sampling station 

[All stations are in Montana unless otherwise indicated]

Map number Sampling station 

(% 1)

Intensive stations: 

1 East Fork Hanging Woman Creek near 

Birney 

2 Hanging Woman Creek near Birney

4 Mizpah Creek near Mizpah

Accessory stations:

12 Ash Creek near Sheridan, Wyoming 

13 Bear Creek near Otter 

14 Beaver Creek near Ashland 

15 Bull Creek near Birney

18 Cow Creek near Colstrip 

19 Cow Creek near Fort Howe 

20 Crazy Head Springs (pond) near Ashland

O O T^fifal* (~* Vfafalr n a Q V T"^Of*lr Of*

24 Indian Creek near Kirby

Number of 

collections

19

27 

19 

13 

23 

13 

19 

31 

19

1

5 

3 

2 

7 

2 

4 

4 

1 

3 

1 

4 

5 

5 

9 

1 

5

Map number Sampling station Number of 

(fig. 1) collections

Accessory stations continued: 

27 Lee Creek near Birney 1 

28 Logging Creek near Ashland 5 

29 Muddy Creek near Busby 6 

30 Otter Creek near Otter 7

31 Prairie Dog Creek near Birney 3

38 Slough near Kirby 1

41 Tongue River near Sheridan, Wyoming 5

Af) AATfacrf TTnvlr A vmol 1 c f t**a*alr Tifint* On! erf 1*1 j\ A.

43 Youngs Creek near Sheridan, Wyoming 5

Additional stations: 

44 Decker Mine outfall 1 

45 Little Powder River near Broadus 1 

46 Powder River near Broadus 3

48 Tongue River near Birney 27

50 Tongue River near Miles City 3

TABLE 2. Statistical summary of physical and chemical data

[//mho/cm, micromhos per centimeter at 25 °C; °C, degrees Celsius; NTU, nephelometric turbidity unit; mg/L, milligrams per liter]

Physical and chemical characteristics

Temperature ( °C)

Turbidity (NTU)

Hardness total (mg/L CaCO )

Alkalinity, total (mg/L CaCO3 )

Nitrogen, total NO2 +NO3 (mg/L as N)

Number 

of Minimum Mean Median Maximum 

samples value value value value

9Q1 9QQ 9 9<^1 1 7^9 11 OOO

9QH 1 A 1 O 99 Q 99 Q fin

281 1.0 16.4 17.9 30.5

274 .5 144.5 8.2 11,600

205 .80 9.80 9.58 19.04

1 A K 9 ft 99 fi Q

170 92 804 641 3,485

m l C A 1 f\K 1 QC O QfiH f\

170 5.0 131.6 105.0 645.0

ift9 Q 1 QOQ ^ ifi/i ^ 1 Q^n n

191 15.0 480.9 505.0 913.0

45 .5 11.3 7.2 38.4

191 13 400 424 748

1 QO 1 7 1 HI 7 KQO d Qnn

182 .4 12.9 6.9 174.0

m

r\ n /> 17

170 184 2,040 1,489 10,423

oco o 1 7n a i q q oo K^n

128 .01 .14 .07 .80

159 .01 .04 .02 .57

m mn HQQ r»QQ Q 7nn

194 .001 .048 .013 2.500

1 0Q 090 303 990 9 1 00

95 .005 .087 .060 .410

6 ECOLOGY AND DISTRIBUTION OF MAJOR DIATOM ECOTYPES IN MONTANA
105" LOWER 

n 10 20 30 40 KILOMETERS 46. 30 -, POWDER

LOWER YELLOWSTONE

TRIBUTARIES

10100001 LOWER TONGUEPUMPKINOTTER

10090102 MIZPAH 

10090210

ROSEBUD 

10100003

LITTLE 

POWDER 

10090208

MIDDLE 

POWDER 

10090207

UPPER TONGUE 

HANGING 

WOMAN 

10090101

FIGURE 3. Number of diatom collections (circled) from each of the eight hydrologic units of the study area. Hydrologic unit 10100001, 

lower Yellowstone tributaries, comprises two areas in the northwest part of the map.

either onsite or in the Water Quality Bureau's branch 

office laboratory in Billings, Mont. A summary of onsite and laboratory analytical techniques is presented 

by Klarich and others (1980).

Six additional variables were noted or measured for 

possible inclusion in each ecotype's ecological summary: date, elevation, instantaneous stream discharge, 

stream width, substrate reference number, and drainage area upstream from the sampling point (table 3). 

Elevation and drainage-area values were provided by 

the U.S. Geological Survey (Paul F. Woods, written

commun., 1980). Discharge, stream width, and substrate reference number were measured as described 

by Klarich and others (1980). The substrate reference 

number is the weighted average of the substrate particle sizes at a station; it does not reflect the specific 

substrate of a given ecotype. Computer-generated histograms were used to compare percent relative abundance values of each ecotype with matching values for 

each of these six variables. Each histogram was scanned 

visually, and any apparent correlation or affinity is 

noted in that ecotype's ecological summary. These histograms are filed at the Water Quality Bureau's office 

in Helena, Mont.

ENVIRONMENTAL MEASUREMENTS 7
TABLE 3. Range of values for six variables considered in the 

ecological summaries

Variable Range

Date 

Elevation (feet above sea level) 

Stream discharge, instantaneous

(cubic feet per second) 

Stream width (feet) 

Substrate reference number1 

Drainage area upstream from

sampling point (square miles) 

February 10-November 7 

2,480-4,100

0.01-3,300 

0.4-48.6 

1.4-7.4

2-11,800

'Based on a scale of 1 to 8, where 1 is silt- and clay-size particles (less than .05-mm 

diameter) and 8 is cobble-size particles (greater than 6-cm diameter). Each particle-size 

number was multiplied by its fractional relative abundance at a site and the products added 

to obtain the substrate reference number.

BIOLOGICAL MEASUREMENTS

Diatom collections from the southern Fort Union coal 

region were of seven different types based on mode of 

collection and analytical detail. The types are identified in table 4.

TABLE 4. Summary of diatom collections

Name

Sample 

type

Number 

of samples

Phytoplankton (Tongue River Reservoir) A 4 

Periphyton:

Grab samples for soft-bodied algae B 26 

Composite samples 340 

Total 366 

Artificial substrate (Plexiglas) samples:

Long counts (300-400 frustules) C 36 

Short counts (100-200 frustules) D 2 

Total 38 

Natural substrate samples:

Long counts (300-400 frustules) E 267

Short counts (100-200 frustules) F 29

List only (too sparse to count) G 6

Total 302

ONSITE METHODS

Only four of the collections were of phytoplankton 

associations (type A) and these were all from the Tongue 

River Reservoir, the largest body of water in the study 

area. Phytoplankton were enumerated from composite 

samples collected at 1-meter intervals through the 

euphotic zone using a 5-liter Van Dorn bottle (Whalen, 

1979). Of the remaining 366 periphyton collections, 26 

were selective grab samples of conspicuous soft-bodied, 

non-diatom algae (type B). Only diatoms growing in 

close association with the target algae were collected, 

albeit unintentionally. The remaining 340 samples 

were composite algae collections from natural and artificial (Plexiglas) substrates.

Both diatoms and soft-bodied algae were included in 

composite collections from natural substrates. Conspicuous soft-bodied algae were collected in proportion to 

their importance relative one to another and to the 

diatom association as a whole. These algae generally 

were plucked by hand. Diatoms and less conspicuous 

soft-bodied algae were scraped or lifted from their substrates with a sharp-edged tool, such as a pocket knife, 

single-edged razor blade, or scalpel. Diatoms were collected from each substrate about in proportion to the 

substrate's importance at a station. Samples were 

placed in small jars containing ambient water and preserved with Lugol's (IKI) solution (American Public 

Health Association and others, 1975). The ultimate 

objective was to obtain a replicate, in miniature, of the 

total periphyton community.

Composite collections from artificial substrates were 

made only at the nine intensive stations. Plexiglas 

plates were exposed for at least 1 month prior to sampling, after which time the accumulated periphyton 

association was removed to a small jar and preserved 

with Lugol's solution. Details of periphyton collection 

techniques are presented by Klarich and others (1980).

LABORATORY METHODS

Just prior to processing, each sample container was 

agitated vigorously to attempt to dislodge diatoms 

from their algal substrates and to cause randomization 

of diatom frustules. Conspicuous soft-bodied algae 

were removed individually from the sample container, 

examined microscopically, and identified to genus. (A 

classification method for the algae using a diatom 

example and the different levels of taxonomic identification used in this study are given in table 5.) The rest 

of the sample was shaken again and a small subsample 

was pipetted quickly with a soda straw onto a clean 

glass microscope slide. This subsample was covered 

with a coverslip and scanned until most of the less conspicuous soft-bodied algae were located, identified to 

genus, and recorded.

TABLE 5. Classification method1 for the algae, with a diatom example

division 

class 

order 

family 

subfamily 

genus2 

subgenus 

species3 

variety4 

form

Bacillariophyta 

Bacillariophyceae 

Fragilariales 

Fragilariaceae 

Fragilarioideae 

Synedra 

Synedra 

ulna

oxyrhynchus 

mediocontracta

'Patrick and Reimer (1966). 

'Level to which soft-bodied algae were identified. 

"Level at which diatoms were tabulated. 

 Level to which diatoms were identified.

8 ECOLOGY AND DISTRIBUTION OF MAJOR DIATOM ECOTYPES IN MONTANA
The rest of the sample then was used to prepare a 

permanent, randomly strewn diatom mount (American 

Public Health Association and others, 1975) using concentrated sulfuric acid and potassium dichromate as 

the oxidizing agents and Cargille's "Carmount-165" 

as the mounting medium. A diatom proportional count 

was performed on each slide following the technique 

outlined by Weber (1973), except that in excess of 300 

rather than 250 frustules (cells) were tallied. Such 

counts, generally between 300 and 400 frustules, are 

called long counts (types C and E). Diatoms were identified to variety and occasionally to form. Except for a 

few varietal ecotypes with distinct ecological affinities, 

diatoms were tabulated at the species level (table 5).

In a small percentage of the samples, the number of 

diatoms was insufficient to conduct a long count within 

a reasonable length of time. These collections were 

subjected to short counts of between 100 and 200 frustules (types D and F). In still fewer samples (type G), 

the diatoms were too sparse to count even 100 frustules; in such instances the diatom taxa merely were 

listed as they were observed during a 30-minute scan. 

Similarly, just a list rather than a proportional count 

was prepared for the diatoms in each grab sample of 

soft-bodied algae (type B) on the premise that such a 

selective sample would not be representative of the 

total diatom association at that site.

Second, a larger number of one taxon relative to 

others in a collection may give a mistaken impression 

of successful adaptation to ambient conditions, particularly if the total number of individuals in the collection 

is small. In some instances the conditions may not be 

optimum for any taxon, yet one invariably will be the 

most abundant. A count of frustules per unit area 

would be a more reliable indicator of success. However, 

this approach is impractical when dealing with composite collections from natural substrates, a sampling 

technique designed to compensate for the patchiness of 

diatom populations in stream environments.

Third, maximum division rate and number of frustules may not be synchronized with optimum environmental conditions. Optimum conditions may be present 

at the very beginning of a taxon's numerical growth 

curve and be passed when the maximum percent relative abundance value is recorded.

Finally, a diatom's best physiological condition and 

functional efficiency may not coincide with its maximum percent relative abundance. Conceivably, an 

accelerated division rate may be in response to adverse 

or degrading environmental conditions and the resulting cells may have less vigor than those of preceding 

generations. Nevertheless, percent relative abundance 

is the only practical way of rating diatom success among 

qualitative collections from natural and artificial 

substrates.

PERCENT RELATIVE ABUNDANCE

The 68 major diatom ecotypes identified in this report were selected on the basis of exceeding 10 percent 

relative abundance in one or more collections. Furthermore, in the ecological summaries and water-quality 

profiles that follow, the assumption is made that a preference for particular environmental conditions is directly proportional to a taxon's abundance relative to 

other diatom taxa in the same collection. Consequently, percent relative abundance values in excess of 

10 are used to delineate the ecotype's preferred range 

of environmental conditions, and the ecotype's largest 

percent relative abundance value is correlated with 

optimum environmental conditions. This approach 

requires caution for several reasons.

First, a built-in bias exists against forms that are 

large or those having inherently slow division rates. 

Single specimens of some large taxa (for example, 

Cymatopleura elliptica) are equivalent in size and perhaps functional ability to many specimens of certain 

small taxa (for example, Achnanthes minutissima), yet 

the large taxon may never compose 10 percent of an 

association by number. Two taxa, each under optimum 

conditions, will produce different numbers of daughter 

cells because of inherently different division rates.

DISCUSSION

Several conditions need to be met before a diatom 

ecotype is useful as a water-quality indicator. First, it 

needs to be abundant when and where conditions are 

favorable so that its presence cannot be misconstrued 

as a random occurrence. By definition, all the major 

diatom ecotypes included in this report meet this 

criterion.

Second, the geographic distribution needs to be widespread so that it will serve as an indicator when and 

where conditions are favorable for its growth and division. Fragilaria species X, Navicula peregrina var. 

lanceolata, and Nitzschia supralitorea are so geographically restricted within the southern Fort Union coal 

region that they are of limited value as water-quality 

indicators.

Finally, an ecotype needs to have a relatively narrow 

ecological amplitude in one or more environmental 

variables of interest. Achnanthes minutissima, Cocconeis placentula, Nitzschia frustulum, and Nitzschia 

palea have very broad ecological amplitudes in the 

study area. These are the four most common diatom 

ecotypes in the southern Fort Union coal region. Careful identification and differentiation of the several

DISCUSSION
closely related and intergrading forms comprising each 

of these four ecotypes generally will reveal biotypes 

(ecoforms?) having more discrete and more useful ecological amplitudes. Distinguishing among the Nitzschia 

biotypes may be more practicable when the American 

species of Nitzschia are given the close taxonomic attention that has been given to species of other genera, 

as in Patrick and Reimer (1966, 1975). Even so, to distinguish among these forms during diatom enumeration may require more time and expertise than many 

routine monitoring programs can afford.

Salinity is the water-quality variable of principal 

concern with regard to surface mining in the southern 

Fort Union coal region (Karp and Botz, 1975). Much of 

the region's proposed and existing mining is in the 

drainage of the Tongue River (Montana Department of 

State Lands and U.S. Office of Surface Mining Reclamation and Enforcement, 1981). Ironically, the Tongue 

River now has the best water quality (least salinity) of 

any major stream in the study area (Knapton and 

Ferreira, 1980). Tongue River water is used primarily 

for irrigation, a use that is sensitive to salinity. Waters 

containing concentrations of dissolved solids in excess 

of 2,100 mg/L are unsuitable for irrigation under most 

conditions, whereas concentrations of as much as about 

one-third this amount (700 mg/L) may be injurious 

under certain crop, soil, and climate conditions (McKee 

and Wolf, 1963).

Todd (1970) classifies waters containing 0 to 1,000 

mg/L dissolved solids as fresh and waters containing 

1,000 to 10,000 mg/L dissolved solids as brackish. Concentrations of dissolved solids in waters of the study 

area range from 184 to 10,423 mg/L. Consequently, 

most waters of the study area may be classified as either 

fresh or brackish. For general purposes, freshwater 

may be considered suitable for irrigation and brackish 

water unsuitable or marginally suitable for irrigation.

Most of the major diatom ecotypes of the southern 

Fort Union coal region are euryhalobous; that is, their 

preferred salinity range spans both fresh and brackish 

waters. However, a large number are confined largely 

to one or the other of these salinity classes (table 6). No 

plankton samples were collected from brackish-water 

reservoirs in the study area, hence the nature of plankton diatom associations from such waters is unknown.

Not surprisingly, the freshwater ecotypes in table 6 

are the principal dominants in the upstream reaches of 

Rosebud Creek and the Tongue River, including the 

Tongue River Reservoir. These streams have smaller 

concentrations of dissolved solids than other major 

streams in the study area (Knapton and Ferreira, 

1980). If salinity in these two streams increases significantly owing to mining or other activities, one would

expect their diatom associations to be replaced by associations dominated first by more euryhalobous ecotypes and then by one or more of the brackish-water 

ecotypes in table 6. These diatoms would be available 

for colonization from tributaries and from other streams 

in the area that have larger concentrations of dissolved 

solids. In the foreseeable future, however, concentrations of dissolved solids in the Tongue River are not 

expected to exceed greatly the brackish water criterion 

of 1,000 mg/L, even under the worst possible conditions 

(Woods, 1981).

TABLE 6. Freshwater and brackish-water diatom ecotypes

Freshwater ecotypes 1 Brackish-water ecotypes2

Pei iphyton: 

Cocconeis pediculus 

Diatoma vulgare 

Fragilaria capucina 

Gomphonema tenellum 

Navicula radiosa var. tenella 

Navicula tripunctata 

Synedra ulna

Phytoplankton: 

Asterionella formosa 

Fragilaria crotonensis 

Stephanodiscus niagarae

Periphyton: 

Amphora coffeiformis 

Cyclotella meneghiniana 

Cymbella pusilla 

Cymbella species X 

Diatoma tenue

Diploneis smithii var. pumila 

Entomoneis paludosa 

Epithemia adnata 

Gomphonema angustatum 

Navicula cincta 

Navicula cincta var. rostrata 

Navicula goersii 

Navicula gregaria 

Navicula odiosa 

Navicula pavillardii 

Nitzschia closterium 

Nitzschia communis 

Nitzschia microcephala 

Nitzschia obtusa 

Synedra famelica 

Synedra fasciculata 

Thalassiosira pseudonana

'Diatoms classified as freshwater ecotypes are most likely to have their best population 

development (greater than 10 percent relative abundance) in waters containing less than 

1,000 mg/L of dissolved solids.

2Diatoms classified as brackish-water ecotypes are most likely to have their best population development (greater than 10 percent relative abundance) in waters containing more 

than 1,000 mg/L of dissolved solids.

Another water-quality variable of concern regarding 

surface mining is sediment from disturbed lands (Karp 

and Botz, 1975). Recorded concentrations of suspended 

sediment in the study area range from less than 1 mg/L 

in the Tongue River Reservoir to more than 20,000 mg/L 

in the Powder River (table 2). Concentrations of suspended sediment greater than 25 mg/L may be expected 

to inhibit the production of freshwater fish and associated aquatic life (Federal Water Pollution Control 

Administration, 1968).

Most of the major diatom ecotypes from the southern 

Fort Union coal region can thrive at suspended-sediment 

concentrations spanning the 25 mg/L criterion. However,

10 ECOLOGY AND DISTRIBUTION OF MAJOR DIATOM ECOTYPES IN MONTANA
certain ecotypes are restricted to relatively sedimentfree water and others dominate diatom associations 

primarily in waters that carry more than 25 mg/L suspended sediment (table 7). Notable among the findings 

of this survey is that few if any of the major diatom ecotypes thrive at extremely large concentrations of suspended sediment, such as those frequently recorded in 

the Powder River.

TABLE 1 . Clear-water and cloudy-water diatom ecotypes

Clear-water ecotypes1 Cloudy-water ecotypes*

Periphyton: 

Achnanthes lanceolata 

Cyclotella meneghiniana 

Cymbella microcephala 

Cymbella pusilla 

Cymbella species X 

Diatoma vulgare 

Epithemia sorex 

Fragilaria construens 

Melosira varians 

Navicula tripunctata 

Pleurosigma delicatulum 

Surirella ovata 

Synedra fasciculata 

Synedra ulna

Phytoplankton: 

Asterionella formosa 

Fragilaria crotonensis 

Stephanodiscus niagarae

Periphyton: 

Amphipleura pellucida 

Cyclotella pseudostelligera 

Gomphonema angustatum 

Navicula cincta 

Navicula goersii 

Navicula odiosa 

Navicula pavillardii 

Nitzschia communis 

Nitzschia valdestriata

"Diatoms classified as clear-water ecotypes are most likely to have their best population 

development (greater than 10 percent relative abundance) in waters containing less than 

25 mg/L of suspended sediment.

"Diatoms classified as cloudy-water ecotypes are most likely to have their best population 

development (greater than 10 percent relative abundance) in waters containing more than 

25 mg/L of suspended sediment.

Substrate particle size, somewhat related to suspended 

sediment as well as to bedload, gradient, current velocity, and bedrock geology, also may be affected by activities related to mining. The substrate reference numbers 

derived in the course of the benthic biological inventory reflect average bottom characteristics throughout 

an entire stream reach. They are not specific to microhabitats of individual diatom ecotypes and hence they 

are of little value in circumscribing diatom autecology.

Temperature may be of interest in certain streams of 

the study area. The Tongue River upstream from Prairie 

Dog Creek (station 31) is the only stream in the study 

area classified as a (marginal) salmonid fishery by the 

Montana Department of Health and Environmental 

Sciences (1980). The East Fork Lame Deer Creek and 

an upstream reach of Rosebud Creek on the Northern 

Cheyenne Indian Reservation have self-sustaining wild 

brook trout populations and are classified as highestvalue fishery resources by the U.S. Fish and Wildlife

Service (1980). Unnatural warming of stream water 

could be caused by dewatering, sedimentation, thermal 

discharge, and removal of bank cover. Most of the major 

diatom ecotypes reproduce best between 10 and 20 °C. 

Only one Fragilaria construens clearly preferred 

water less than 10 °C, although others may dominate 

at low temperatures during the winter months. This 

diatom had its greatest population development in 

Lame Deer Creek near Lame Deer (station 26). Five 

ecotypes seemed to prefer temperatures in excess of 

20 °C. These were Epithemia adnata, Navicula pavillardii, Nitzschia amphibia, Nitzschia valdestriata, and 

Rhopalodia gibba.

Additional variables of interest with regard to anticipated development in the southern Fort Union coal 

region might be algal nutrients, heavy metals, and pH. 

Phosphorus in study area streams is largely associated 

with the suspended-sediment fraction of the water 

(Knapton and Ferreira, 1980). Precisely how much of 

this phosphorus and how much sediment-adsorbed 

phosphorus on the stream bottom actually is available 

to benthic algae is not known. Hence, meaningful ecotype classifications based on different nutrient regimes 

are difficult to construct and will not be attempted 

here. The fact that Nitzschia palea, a eutrophic diatom 

(Lowe, 1974), occurred in more than 90 percent of the 

collections from the southern Fort Union coal region is 

good evidence that algal growth is seldom limited by 

nutrient availability in streams of the study area, notwithstanding the generally minimal nutrient concentrations measured in the water column. Despite this 

apparent nutrient enrichment, many streams in the 

study area and in eastern Montana have relatively 

slow periphyton production rates, presumably because 

of turbidity or lack of stable substrates (Bahls and 

others, 1981).

Most waters in eastern Montana, including those of 

the study area, are very hard and would be relatively 

insensitive to heavy-metals pollution. They also give 

an alkaline reaction and are well buffered, indicating 

they would be resistant to acid precipitation and acid 

mine drainage (Bahls and others, 1981).

SUPPLEMENTARY INFORMATION

FORMAT

In the final section of this paper, "Major Diatom Ecotypes," each of the ecotypes is treated in a uniform and 

systematic manner. Coverage includes taxonomy and 

morphology, abundance, ecology, and distribution 

within the study area. The description of each ecotype 

addresses the following elements where applicable.

SUPPLEMENTARY INFORMATION 11
TAXONOMY AND MORPHOLOGY

Ecotype: A valid Latin name of the ecotype and the 

authority for that name.

Biotype(s): Valid Latin names and authors of biotypes composing the ecotype within the study area, 

with the most common biotype (the one exceeding 10 

percent relative abundance) indicated by an asterisk (*).

Reference: A bibliographic reference to an accepted 

description of the most common biotype, including the 

page on which the description begins and the figure 

numbers), if illustrated.

Herbarium slide number: The accession number 

of the slide curated into the Water Quality Bureau herbarium that contains representative, diamond-ringed, 

voucher specimens of the most common biotype.

Illustration: An inked drawing of a typical specimen of the most common biotype from the designated 

herbarium slide as observed under a light microscope. 

All line scales with diatom drawings are 10 /im (micrometers) in length unless otherwise noted.

Description: A brief narrative discussion of the ecotype, including the standard dimensions (length, width 

and striae per lOjum) of the illustrated specimen, distinguishing features, similar taxa, and remarks on 

taxonomy.

ABUNDANCE

Mean percent relative abundance: The total of 

all percent relative abundance values for all collections 

in which the ecotype was found, divided by 370.

Percent occurrence: The total number of ecotype 

occurrences divided by 370 times 100.

Abundance-occurrence index: Mean percent relative abundance times percentage occurrence. This 

index has a maximum possible value of 10,000. It is an 

indicator of commonness and the chances of finding the 

ecotype in a diatom collection from the study area.

Preferred percent occurrence: The total number 

of ecotype occurrences greater than or equal to 10 percent abundance divided by 370 times 100.

Maximum percent relative abundance: The largest percent relative abundance from the study area 

regardless of concurrent water-quality data, along 

with the station number (table 1 and fig. 1), date, and 

type of collection (table 4) producing the record value.

ECOLOGY

Water-quality profile: A table of statistical values 

for the 24 chemical and physical variables listed in 

table 2, giving for the ecotype the sample size (number 

of concurrent water-quality measurements), range 

(minimum and maximum values among concurrently 

measured values of each variable), preferred range

(minimum and maximum values among concurrently 

measured values of each variable for relative abundance readings equal to or greater than 10 percent), 

optimum (the value for each variable associated with 

the concurrent collection in which the ecotype achieved 

its largest percent relative abundance), and the corresponding percent relative abundance.

Only those chemical and physical data are used that 

were generated onsite or extracted from a water-quality 

sample taken at the same time as a corresponding 

diatom collection. Occasionally, concurrent waterquality data are not available for collections in which 

an ecotype accounted for 10 percent or more of the frustules, and in such instances the preferred range column 

is blank. If concurrent data are not available for an ecotype's largest percent relative abundance reading (optimum), then data for the next largest reading are used. 

A water-quality profile does not identify an ecotype's 

growth-limiting variable nor the specific variables and 

values causing optimum growth; it simply presents the 

mixture of values associated with an ecotype's occurrence and peak performance as measured by percent 

relative abundance.

Abbreviations used in the profiles are: /imho/cm, 

micromhos per centimeter at 25 °C; °C, degrees Celsius; 

NTU, nephelometric turbidity unit; and mg/L, milligrams per liter.

Ecological summary: A brief narrative summary 

of the ecotype's environmental preferences and pollution tolerances, covering the 24 chemical and physical 

variables, season, discharge, stream size (width), elevation, substrate reference number, and drainage area 

upstream from the sampling station. Categorical descriptions of water freshness and hardness are based 

on rating tables presented by Todd (1970). Only those 

affinities determined from this study are considered in 

the summary. Emphasis is placed on those variables 

for which the range of values is much more restricted 

than for the study area as a whole (table 2).

DISTRIBUTION

Distribution summary: A brief narrative summary 

of the distribution of the ecotype in the study area, 

including preferred range, notable outliers, and endemic populations.

Distribution map: A map outlining the eight hydrologic units in the study area and the percent relative abundance for each unit. An open circle (O) indicates a small percent relative abundance (less than 10) 

in all collections from a unit, and a closed circle ( ) 

indicates a larger percent relative abundance (equal to 

or greater than 10) in one or more collections from a 

unit. A blank hydrologic unit indicates an absence of 

record for the ecotype in that unit.

12 ECOLOGY AND DISTRIBUTION OF MAJOR DIATOM ECOTYPES IN MONTANA
MAJOR DIATOM ECOTYPES
ECOTYPE: ACHNANTHES LANCEOLATA BREB. EX KUTZ.

Biotype(s):

*A. lanceolata Breb. ex. Kutz. var. lanceolata 

A. lanceolata var. dubia Grun. 

A. lanceolata var. haynaldii (Istv.-Schaarsch.) Cl.

Reference:

Patrick and Reimer, 1966 (p. 269; pi. 18, 

figs. 1-10)

Herbarium slide number: 

1-1-18

Mean percent relative abundance: 

0.7

Percent occurrence: 

49.2

Abundance-occurrence index: 

35.9

Preferred percent occurrence: 

1.6

Maximum percent relative abundance: 

20.7

10 H.ITI

Raphe valve Pseudoraphe valve

Station number: 17 

Date: August 24, 1978 

Type of collection: E

Description:

Striae, 12-14 in 10 nm on both valves. Length, 

16.8 /mi. Width, 6.5 /on. A robust, largely variable species of Achnanthes. Distinguished from 

A. hauckiana Grun. by the central clear area on 

one side of the pseudoraphe valve.

14 ECOLOGY AND DISTRIBUTION OF MAJOR DIATOM ECOTYPES IN MONTANA
Water-quality profile:

Variable

Specific conductance (^mho/cm) -

pH (units) 

TWnnpratnvp ( 0 P^

Turbidity (NTU)

Oxygen, dissolved (mg/L) 

Biochemical oxygen demand (mg/L) 

Hardness, total (mg/L CaCO3) 

Calcium, dissolved (mg/L) 

Magnesium, dissolved (mg/L) 

Sodium, dissolved (mg/L) 

Bicarbonate (mg/L) 

PlafVinTmtf fmtT/T .^

Alkalinity, total (mg/L CaCO3) 

Sulfate, dissolved (mg/L) 

Chloride, dissolved (mg/L) 

Fluoride, dissolved (mg/L) 

Dissolved solids, calculated (mg/L) 

Sediment, total suspended (mg/L) 

Nitrogen, total NO2 +NO3 (mg/L as N) 

Nitrogen, total ammonia (mg/L as N) 

Phosphorus, total (mg/L as P) 

Phosphorus, total ortho (mg/L as P) 

Iron, total recoverable (mg/L) 

TN^flntTflnfcsf tntal vppnvfvnVilf fmcr/T .^

Number 

of Range 

samples

153 

153 

153 

151 

110 

40 

90 

90 

90 

97 

103 

19 

103 

97 

97 

94 

90 

141 

73 

86 

107 

113 

71 

63

OQQ fi400

7 ETA o en

90 97 0

A K 4.QC

4.52- 14.3

0 8 ft Q

m Q99O

97 A QQfl

1 q K fiA^

9

.1- 1 CCK COO

111- 816

0.5 24.0

91- 669 

17 4040

0.4 174

0.1 1.7

1 QR fiOQA

0.2- 893 

0.01- 0.71 

0.01 0.57

0.010 0.60

0.001- 0.38 

0 09 91

0.005 0.41

Optimum (percent 

Preferred relative abundance 

range in parentheses)

ACf) 1 7qA

7

OC Q OCT .00- o.oo

11.5- 19.0 

1.6 4.4

8.50- 10.3 

2.6- 2.6

907 719

4.Q 7 Q4 0

nc A 117

1 $3 q 1 nq

250- 671 

4.1 5.0

213- 557 

41 579

0.4 5.9

19 19

398-1660 

1.5- 19.6 

0.03- 0.39 

0.01-0.11 

0.020 0.068

0.001 0.064

0 14. 0 9Q

0.019-0.075

1730(20.7) 

8.35(20.7) 

13.5(20.7) 

2.2(20.7) 

8.50(20.7) 

2.6(11.7) 

712(20.7) 

92.0(20.7) 

117(20.7) 

193(20.7) 

671(20.7) 

4.1(20.7) 

557(20.7) 

579(20.7) 

0.4(20.7) 

1660(20.7) 

1.9(20.7) 

0.39(20.7) 

0.01(20.7) 

0.01(20.7) 

0.068(20.7) 

0.064(20.7) 

0.22(20.7) 

0.064(20.7)

Ecological summary:

Prefers cool waters with little turbidity and 

small concentrations of chloride and suspended 

sediment; small streams (less than 1 ft8/s) at 

higher elevations; and substrate the size of 

coarse sand or larger (greater than 0.3-mm 

diameter). Summer (June to September) dominant.

Distribution summary:

A widespread ecotype found in all hydrologic 

units except those representing Mizpah Creek 

and the Little Powder River. Prefers Tongue 

River drainage.

 

O

EXPLANATION

PERCENT RELATIVE ABUNDANCE 

EQUAL TO OR GREATER THAN 10

PERCENT RELATIVE ABUNDANCE 

LESS THAN 10

DISTRIBUTION MAP

MAJOR DIATOM ECOTYPES 15
ECOTYPE: ACHNANTHES MINUTISSIMA KUTZ.

Biotype(s):

A. linearis (W. Sm.) Grun. var. linearis 

A. linearis f. curta H. L. Sm. 

A. microcephala (Kutz.) Grun. var. microcephala 

*A. minutissima Kutz. var. minutissima

Reference:

Patrick and Reimer, 1966 (p. 253; pi. 16, 

figs. 9-10)

Herbarium slide number: 

1-1-19

Mean percent relative abundance: 

8.3

Percent occurrence: 

86.8

Abundance-occurrence index: 

721.0

Preferred percent occurrence: 

27.3

Maximum percent relative abundance: 

69.0

Station number: 16 

Date: November 2, 1979 

Type of collection: E

Description:

Striae, 30-38 in 10 ^m on both valves. Length, 

13.0 (im. Width 3.0 fim. A delicate, polymorphic 

Achnanthes. Shape of the ends appears to be a 

function of frustule size and environmental conditions; obtusely rounded or broadly subrostrate 

to distinctly capitate, often spanning a continuum of intermediates in one collection. A. linearis, 

A. microcephala, and A. minutissima may be 

different expressions of the same genome; their 

similarities and intergradations make possible 

genotypic or phenotypic distinctions impractical 

at the level of resolution achieved by many optical microscopes.

10

Raphe valve Pseudoraphe valve

16 ECOLOGY AND DISTRIBUTION OF MAJOR DIATOM ECOTYPES IN MONTANA
Water-quality profile:

Variable

Specific conductance (jimho/cm) 

nTT fun if cA

Temperature (°C) __ ___ 

TurhiHitvfNTTn

Biochemical oxygen demand (mg/L) 

Hardness, total (mg/L CaCO3) 

Calcium, dissolved (mg/L) 

Magnesium, dissolved (mg/L) 

Sodium, dissolved (mg/L) 

Bicarbonate (mg/L) 

f^avHnn sifp fm cr/T ,^

Alkalinity, total (mg/L CaCO3)

Sulfate, dissolved (mg/L) 

Chloride, dissolved (mg/L) 

Fluoride, dissolved (mg/L) 

Dissolved solids, calculated (mg/L) 

Sediment, total suspended (mg/L) 

Nitrogen, total NO2 +NO3 (mg/L as N)

Nitrogen, total ammonia (mg/L as N) 

Phosphorus, total (mg/L as P) 

Phosphorus, total ortho (mg/L as P) 

Iron, total recoverable (mg/L) 

Manganese, total recoverable (mg/L) 

Number 

of Range 

samples

264 

263 

264 

258 

193 

74 

155 

155 

155 

166 

173 

41 

173 

166 

166 

162 

155 

238 

127 

151 

180 

183 

106 

93

239-

7 ^0

1.3- 

o ^

A CO

0 ^

123- 

i a f\

13.5- 

9.1- 

15-

O c

10

17

0.4- 

0.1- 

184 .LO^

0.2- 

0.01

0.01

0.010- 

0.001

0.02

0.005-

11000 

8.80 

30.5 

4200 

19.0 

8.9 

3490 

330 

645 

1950 

913 

38.4 

748 

6900 

174 

1.7 

10400 

8260 

0.80 

0.57 

3.7 

2.5 

2.1 

0.41

Optimum (percent 

Preferred relative abundance 

range in parentheses)

438-

7 CO

2.0-

0 £,

c oo

1.0

222- 

41.8

25.7- 

12.2- 

171- 

n P;

146

17

1.8- 

0.1-

OftQ

0.4- 

0.01

0.01

0.010

0.001

0.02

0.005-

6100 

8.80 

30.2 

94 

19.0 

8.9 

2040 

254 

346 

1230 

755 

38.4 

619 

5450 

51.6 

1.3 

7680 

310 

0.80 

0.22 

0.25 

0.15 

2.1 

0.36

1640(69.0) 

8.38(69.0) 

4.3(69.0) 

0.5(69.0) 

13.1(69.0) 

1.9(69.0) 

500(68.2) 

82.5(68.2) 

71.0(68.2) 

148(69.0) 

534(69.0) 

28.0(48.0) 

438(69.0) 

575(69.0) 

5.9(69.0) 

0.8(69.0) 

1150(68.2) 

0.8(69.0) 

0.80(69.0) 

0.01(69.0) 

0.050(68.2) 

0.043(68.2) 

0.07(69.0) 

0.025(68.2)

Ecological summary:

This complex has a broad ecological amplitude. Prefers waters with good clarity and little 

suspended sediment; small to medium streams 

(0.1 to 10 ft3/s); and substrate the size of fine 

gravel (0.2 to 1 cm) or larger. No apparent 

seasonal preference. The availability of firm, 

stable attachment sites seems to be the overriding environmental requirement.

Distribution summary:

Widespread, but dominant only in the western 

part of the study area. The second most common 

ecotype in the southern Fort Union coal region.

O

EXPLANATION

PERCENT RELATIVE ABUNDANCE 

EQUAL TO OR GREATER THAN 10

PERCENT RELATIVE ABUNDANCE 

LESS THAN 10

DISTRIBUTION MAP

MAJOR DIATOM ECOTYPES 17
ECOTYPE: AMPHIPLEURA PELLUCIDA (KUTZ.) KUTZ.

Biotype(s):

Amphipleura pellucida (Kutz.) Kutz. var. 

pellucida

Reference:

Patrick and Reimer, 1966 (p. 303; pi. 21, 

figs. 2a-b)

Herbarium slide number: 

1-1-20

Mean percent relative abundance: 

0.7

Percent occurrence: 

41.6

Abundance-occurrence index: 

28.9

Preferred percent occurrence: 

1.4

Maximum percent relative abundance: 

52.8

10

Station number: 50 

Date: September 28, 1975 

Type of collection: E

Description:

Striae, about 40 in 10 /*m. Length, 66.0 /mi. 

Width, 7.5 /mi. A very distinctive but lightly silicified taxon. The only species of Amphipleura 

known to date from the study area.

18 ECOLOGY AND DISTRIBUTION OF MAJOR DIATOM ECOTYPES IN MONTANA
Water-quality profile:

Variable

ft'TM^Pl'FlP POTlHllP^OTl f*(* ( liTTt VlO/PTH^

pH (units) 

TWnr>p»ratnrp» ( °P1

TiirhirHtvfNTTTn

Oxygen, dissolved (mg/L) 

Biochemical oxygen demand (mg/L) 

Hardness, total (mg/L CaCO3) 

Calcium, dissolved (mg/L) 

Magnesium, dissolved (mg/L) 

Sodium, dissolved (mg/L) 

Bicarbonate (mg/L) 

Carbonate (mg/L) 

Alkalinity, total (mg/L CaCO3)

Sulfate, dissolved (mg/L) 

Chloride, dissolved (mg/L) 

Fluoride, dissolved (mg/L) 

Dissolved solids, calculated (mg/L) 

Sediment, total suspended (mg/L) 

Nitrogen, total NO2 +NO3 (mg/L as N) 

Nitrogen, total ammonia (mg/L as N) 

Phosphorus, total (mg/L as P) 

Phosphorus, total ortho (mg/L as P) 

Iron, total recoverable (mg/L) 

l\/l OTl fTI Y1OGO ^O^Ol Y*£if*fnrOY*1 r\l O 1 YVIPP/T ^

Number 

of Range 

samples

129 

129 

127 

126 

92 

39 

80 

80 

80 

83 

88 

17 

88 

83 

83 

81 

80 

119 

62 

81 

97 

96 

52 

49

480

7 en

1 3

0.7

5.22- 

n ^

123-

1 C A

20.0- 

11.7

n ^

i j / » 146-

17

1 9

0.1- 

389- 

0.9- 

0.01- 

0.01- 

0.010- 

0.001

0.05

0.010-

11000 

8.73 

30.5 

376 

19.0 

7.8 

3490 

328 

645 

1950 

913 

26.0 

748 

6900 

174 

1.7 

10400 

741 

0.71 

0.22 

0.62 

0.52 

1.1 

0.36

Optimum (percent 

Preferred relative abundance 

range in parentheses)

QQft '

8 Qft

10.00

1.7

9.65- 

0.7

123- 

16.0- 

20.0

7C n

OQK

5.0

949

9ftf»

4 9

0.3-

787- 5 

5.4- 

0.03- 

0.03- 

0.020-0 

0.005-0

O

O A .34-

0.050-0

2460 

8.60 

30.5 

15 

10.9 

0.7 

370 

68.0 

48.5 

562 

776 

5.0 

636 

708 

9.8 

0.6 

2100 

38.6 

0.08 

0.03 

.032 

.005 

0.60 

.054

956(52 

8.42(52 

15.4(52 

15(38 

9.65(52 

0.7(52 

370(52 

68.0(52 

48.5(52 

75.0(52 

301(52 

5.0(52 

255(52 

280(52 

4.2(52 

0.3(52 

787(52 

38.6(52 

0.03(52 

0.03(38 

0.032(52 

0.005(52 

0.60(52 

0.050(52

.8) 

.8) 

.8) 

.6) 

.8) 

.8) 

.8) 

.8) 

.8) 

.8) 

.8) 

.8) 

.8) 

.8) 

.8) 

.8) 

.8) 

.8) 

.8) 

.6) 

.8) 

.8) 

.8) 

.8)

Ecological summary:

Prefers larger streams (greater than 100 fts/s) 

at lower elevations (less than 2,500 ft). Tolerant 

to some turbidity and suspended sediment. Fall 

(September to November) dominant.

Distribution summary:

Widespread, but dominant only in Mizpah 

Creek and the downstream part of the Tongue 

River.

O

EXPLANATION

PERCENT RELATIVE ABUNDANCE 

EQUAL TO OR GREATER THAN 10

PERCENT RELATIVE ABUNDANCE 

LESS THAN 10

DISTRIBUTION MAP

MAJOR DIATOM ECOTYPES 19
ECOTYPE: AMPHORA COFFEIFORMIS (AG.) KUTZ.

Biotype(s):

Amphora coffeiformis (Ag.) Kutz. var. coffeiformis

Reference:

Patrick and Reimer, 1975 (p. 78; pi. 14, 

figs. 11-12)

Herbarium slide number: 

1-2-1

Mean percent relative abundance: 

0.2

Percent occurrence: 

10.5

Abundance-occurrence index: 

2.0

Preferred percent occurrence: 

0.4

Maximum percent relative abundance: 

31.8

10

Station number: 23 

Date: October 28, 1979 

Type of collection: E

Description:

Striae, 16-24 dorsal and 22-30 ventral in 

10 urn. Length, 38.0 /on. Width, 7.5 urn. Distinguished from A. veneta and A. perpusilla by continuous rather than dashed or punctate striae.

20 ECOLOGY AND DISTRIBUTION OF MAJOR DIATOM ECOTYPES IN MONTANA
Water-quality profile:

Number 

Variable of Range 

samples

Specific conductance (jtimho/cm) 

pH (units) 

TYjmnovat nvo ( °C*\

Turbidity (NTU) 

Oxygen, dissolved (mg/L) 

Biochemical oxygen demand (mg/L) 

Hardness, total (mg/L CaCO3) -

Calcium, dissolved (mg/L) 

Magnesium, dissolved (mg/L) 

Sodium, dissolved (mg/L) 

Bicarbonate (mg/L) 

Carbonate (mg/L) 

Alkalinity, total (mg/L CaCO3) 

i^nl'ro^'o f\i ccf~\ iTrofi iTYir^/T i

Chloride, dissolved (mg/L) 

Fluoride, dissolved (mg/L) 

Dissolved solids, calculated (mg/L) 

Sediment, total suspended (mg/L) 

Nitrogen, total NO2 +NO3 (mg/L as N) 

Nitrogen, total ammonia (mg/L as N) 

Phosphorus, total (mg/L as P) 

Phosphorus, total ortho (mg/L as P) 

Iron, total recoverable (mg/L) 

Ivl i n fT on o c o ^~r\^~il vo/^r^fovo Vilo iTYir**T i

37 

37 

37 

37 

27 

8 

19 

19 

19 

21 

22 

4 

22 

21 

21 

19 

19 

34 

11 

22 

26 

24 

11 

9

506 11000

7.62- 8.70

1

O O f\ C .3- 30.5

0.7- 4200 

6.70 19.0

1.5 6.0

m QAQfi

16.0- 328 

20.0- 645 

19.5- 1950 

244- 913 

0.5- 22.0

200- 748 

OQ conn

2

0 -i QC

0 04 12

425 10400

1 °. °.990

0.02- 0.64 

0.01- 0.57 

0.010 2.6

0.003 1.8

0.10 1.1

O noc r\ oo

Optimum (percent 

Preferred relative abundance 

range in parentheses)

11000 11000

8 OK Q OC

Ofi Q 9fi Q

3.5- 3.5

i c q -i c q

q/lQfi Q/lQfi

328- 328 

645- 645 

1950- 1950 

569- 569

466- 466 

6900 6900

qn Q Qfi q

0.4- 0.4 

10400 10400

6.0 6.0

0.02- 0.02 

0.10- 0.10

O cn f\ £jo

0.52- 0.52

11000(19.1) 

8.25(19.1) 

20.9(19.1) 

3.5(19.1) 

15.3(19.1) 

1.5(1.1) 

3490(19.1) 

328(19.1) 

645(19.1) 

1950(19.1) 

569(19.1) 

8.4(1.4) 

466(19.1) 

6900(19.1) 

30.3(19.1) 

0.4(19.1) 

10400(19.1) 

6.0(19.1) 

0.02(19.1) 

0.10(19.1) 

0.62(19.1) 

0.52(19.1) 

0.18(1.5) 

0.025(0.3)

Ecological summary:

Prefers phosphorus-rich, sodium sulfate, brackish to slightly saline waters; and smaller streams 

(less than 10 ft3/s) at middle elevations (2,500 to 

3,500 ft). Summer and fall (July to October) 

dominant.

Distribution summary:

Found only occasionally in collections from 

the study area. Prefers upstream reaches of 

Armells Creek and Hanging Woman Creek.

O

EXPLANATION

PERCENT RELATIVE ABUNDANCE 

EQUAL TO OR GREATER THAN 10

PERCENT RELATIVE ABUNDANCE 

LESS THAN 10

DISTRIBUTION MAP

MAJOR DIATOM ECOTYPES 21
ECOTYPE: AMPHORA PERPUSILLA (GRUN.) GRUN.

Biotype(s):

Amphora perpusilla (Grun.) Grun. var. perpusilla

Reference:

Patrick and Reimer, 1975 (p. 70; pi. 13, 

figs. 8a-llb)

Herbarium slide number: 

1-2-2

Mean percent relative abundance: 

1.5

Percent occurrence: 

62.2

Abundance-occurrence index: 

94.1

Preferred percent occurrence: 

3.5

Maximum percent relative abundance: 

45.4

10

Station number: 37 

Date: November 7, 1979 

Type of collection: E

Description:

Striae, 16-20 in 10 /on. Length, 10.2 jan. Width, 

3.1 fim. Distinguished from A. coffeiformis and A. 

veneta by a shortening of one or two of the central striae on the dorsal side. Distinguished 

from A. ovalis var. pediculus (Kutz.) V. H. ex 

DeT. in that the proximal raphe ends are straight 

and not sinuous. The smallest species of Amphora 

in the study area.

22 ECOLOGY AND DISTRIBUTION OF MAJOR DIATOM ECOTYPES IN MONTANA
Water-quality profile:

Variable

Specific conductance (^mho/cm) 

oH (units)

Temperature (°C) 

Turbidity (NTU)

Oxygen, dissolved (mg/L) 

Biochemical oxygen demand (mg/L) 

Hardness, total (mg/L CaCO3) 

Calcium, dissolved (mg/L) 

Magnesium, dissolved (mg/L) 

Sodium, dissolved (mg/L) 

Bicarbonate (mg/L) 

Alkalinity, total (mg/L CaCO3) - 

Sulfate, dissolved (mg/L) 

Chloride, dissolved (mg/L) 

Fluoride, dissolved (mg/L) 

Dissolved solids, calculated (mg/L) 

Sediment, total suspended (mg/L) 

Nitrogen, total NO2 +NO3 (mg/L as N)

Nitrogen, total ammonia (mg/L as N) 

Phosphorus, total (mg/L as P) 

Phosphorus, total ortho (mg/L as P) 

Iron, total recoverable (mg/L) 

Ivl oyi cro no co ^r\^~ 1 1 V£~I^/~\TT£~IVI r\l fi limr*** *

Number 

of Range 

samples

189 

189 

188 

188 

137 

50 

119 

119 

119 

125 

131 

25 

131 

125 

125 

123 

119 

174 

100 

110 

133 

136 

81 

78

9QQ

7.50- 

1.7-

0 f\

4 *>2

O Q

1 93

1 C A

1 Q C

Q 1

1 ^

0.5- 

13- 

17- 

0.4- 

0.1- 

184

0 9

0.01

0.01

0.010

0.001

0.02

0.005-

11000 

8.72 

30.5 

435 

15.3 

8.9 

3490 

328 

645 

1950 

816 

36.0 

669 

6900 

88.9 

1.7 

10400 

893 

0.71 

0.22 

0.62 

0.52 

2.1 

0.41

Optimum (percent 

Preferred relative abundance 

range in parentheses)

93Q

7.63- 

3.5- 

0 Q

7.00

i a

363-

{ n -i

48.9- 

Uz

QQQ

6.7- 

278- 

70- 

2.4- 

0.3-

C/2O

0 Q

0 09

0.01

0.017

0.003

0.04

0.010-

2840 

8.40 

22.8 

53 

12.9 

1.8 

1080 

134 

184 

322 

610 

7.0 

500 

1070 

12.2 

1.2 

2250 

61.0 

0.38 

0.05 

0.12 

0.058 

1.1 

0.26

2220(45.4) 

8.25(45.4) 

4.3(45.4) 

5.9(45.4) 

12.9(45.4) 

1.8(18.8) 

453(26.7) 

70.4(26.7) 

67.0(26.7) 

322(45.4) 

573(45.4) 

6.7(18.4) 

470(45.4) 

750(45.4) 

12.2(45.4) 

0.4(45.4) 

830(26.7) 

9.4(45.4) 

0.19(45.4) 

0.02(45.4)) 

0.020(45.4) 

0.003(45.4) 

0.24(45.4) 

0.050(45.4)

Ecological summary:

Prefers cool waters at middle elevations (2,500 

to 4,000 ft); and smaller streams (0.1 to 10 ft"/s). 

Tolerates some sediment and turbidity; does 

best on fine to medium gravels (0.2 to 3 cm diameter). No seasonal preference evident.

Distribution summary:

Widely distributed. Most abundant in the 

western part of the study area.

EXPLANATION

PERCENT RELATIVE ABUNDANCE 

EQUAL TO OR GREATER THAN 10

PERCENT RELATIVE ABUNDANCE 

LESS THAN 10

DISTRIBUTION MAP

MAJOR DIATOM ECOTYPES 23
ECOTYPE: AMPHORA VENETA KUTZ.

Biotype(s):

Amphora veneta Kutz. var. veneta

Reference:

Patrick and Reimer, 1975 (pi. 72; pi. 14, figs. 2-3)

Herbarium slide number: 

1-2-3

Mean percent relative abundance: 

0.3

Percent occurrence: 

18.9

Abundance-occurrence index: 

5.1

Preferred percent occurrence: 

1.1

Maximum percent relative abundance: 

15.8

Station number: 6 

Date: July 21, 1978 

Type of collection: E

10

Description:

Striae, 17-27 dorsal and 24-27 ventral in 10 

pm. Length, 14.3 /mi. Width, 3.8 /mi. Distinguished 

from A. coffeiformis by dashed rather than continuous striae and from A. perpusilla by the absence of shortened central striae on the dorsal 

side.

24 ECOLOGY AND DISTRIBUTION OF MAJOR DIATOM ECOTYPES IN MONTANA
Water-quality profile:

]

Variable

<

Specific conductance (/^mho/cm) _ _ 

pH (units) 

Temperature (°C)

Turbidity (NTU)

Oxygen, dissolved (mg/L) 

Biochemical oxygen demand (mg/L) 

Hardness, total (mg/L CaCO3) 

Calcium, dissolved (mg/L) 

Magnesium, dissolved (mg/L) 

Sodium, dissolved (mg/L) 

RipaT*l"innai"p ftmcr/T,^

Carbonate (mg/L) 

Alkalinity, total (mg/L CaCO3)

Sulfate, dissolved (mg/L) 

Chloride, dissolved (mg/L) 

Fluoride, dissolved (mg/L) 

Dissolved solids, calculated (mg/L) 

Sediment, total suspended (mg/L) 

Nitrogen, total NO2 +NO3 (mg/L as N)

Nitrogen, total ammonia (mg/L as N) 

Phosphorus, total (mg/L as P) 

Phosphorus, total ortho (mg/L as P) 

Iron, total recoverable (mg/L) 

l\^i n fTi fiooo i'^i'ol t*iio ^TTii>*o V*l ii ^TYI fT/T i

dumber 

of 

samples

a-\

r*-\

an

CQ

41

13 

32 

32

00

34

QC

10

QC

O A

34

O it o4

00

qo

4QTTV

01

OK

QQ

42

on

17

Range

coo Gnnn

7/11 Q 7Q

1

0 on K.

0.5 11600

0.80 19.0

0.5- 8.3 

92- 1430 

16.0- 192 

5.0 242

12.2- 1230 

15 913

0.5 26.0

1 Q 7/lft

1 7 O7ftH

1

0 1 0C

0.2 1.5

184 4820

0.4 22600

0.01 0.43

0.01 0.21

O m c o 7

0.002 2.5

0.02 0.75

0.010 0.37

(

Preferred r 

range

CQQ 1 QQf)

7.41 8.41

ion nt\ t\

oo oQfjn

O on 7 QH

5.2- 6.0 

339- 339

65.0- 65.0 

4.0 q 4.0 q

350- 350

OKA OCA

ion ion

qin qin

700 7QO

5.9 5.9

0.4 0.4

1610 1610

or Q OK Q

)ptimum (percent 

elative abundance 

in parentheses)

920(15.8)

7.65(15.8)

19.2(15.8)

1500(15.8)

6.70(15.8)

6.0(15.8) 

339(10.4) 

65.0(10.4) 

42.9(10.4)

350(10.4) 

354(10.4)

12.0(10.4)

310(10.4)

782(10.4)

5.9(10.4)

0.4(10.4)

1610(10.4)

25.8(10.4)

0.04(2.4)

0.02(5.4)

0.090(5.4)

0.041(5.4)

0.34(2.4)

0.054(2.4)

Ecological summary:

Prefers sodium sulfate waters; and fine to medium gravels (0.2 to 3 cm) in medium streams 

(10 to 100 ft'/s) at lower elevations (less than 

2,500 ft). Tolerates considerable sediment and 

turbidity. Summer (July) dominant.

Distribution summary:

Widely distributed in the study area. Prefers 

Mizpah and Pumpkin Creeks.

EXPLANATION

PERCENT RELATIVE ABUNDANCE 

EQUAL TO OR GREATER THAN 10

PERCENT RELATIVE ABUNDANCE 

LESS THAN 10

DISTRIBUTION MAP

MAJOR DIATOM ECOTYPES 25
ECOTYPE: ASTERIONELLA FORMOSA HASS.

Biotype(s):

Asterionella formosa Hass. var. formosa

Reference:

Patrick and Reimer, 1966 (p. 159; pi. 9, 

figs. 1-3)

Herbarium slide number: 

1-2-4

Mean percent relative abundance: 

0.1

Percent occurrence: 

8.6

Abundance-occurrence index: 

0.6

Preferred percent occurrence: 

0.1

Maximum percent relative abundance: 

15.2

Station number: 51 

Date: undated 

Type of collection: A

10

Description:

Striae, 24-27 in 10 jan. Length, 50.0 jan. Width, 

3.8 fim. A slender, heteropolar diatom without a 

raphe. Distinguished from species of Synedra 

and Fragilaria by frustules with ends of unequal 

size and by the formation of star-shaped colonies 

(see drawing).

26 ECOLOGY AND DISTRIBUTION OF MAJOR DIATOM ECOTYPES IN MONTANA
Water-quality profile:

Number 

Variable of 

samples

Specific conductance (^mho/cm) 

TWrmarntiirA (°C*}

Turbidity (NTU)

Oxygen, dissolved (mg/L) 

Biochemical oxygen demand (mg/L) -

Hardness, total (mg/L CaCO3) 

Calcium, dissolved (mg/L) 

Magnesium, dissolved (mg/L) 

Sodium, dissolved (mg/L) 

Bicarbonate (mg/L) 

Alkalinity, total (mg/L CaCO3)

Sulfate, dissolved (mg/L) 

Chloride, dissolved (mg/L) 

Fluoride, dissolved (mg/L) 

Dissolved solids, calculated (mg/L) 

Sediment, total suspended (mg/L) 

Nitrogen, total NO2 +NO3 (mg/L as N)

Nitrogen, total ammonia (mg/L as N) 

Phosphorus, total (mg/L as P) 

Phosphorus, total ortho (mg/L as P) 

Iron, total recoverable (mg/L) 

18 

17 

16 

16 

12 

6 

10 

10 

10 

11 

12 

4 

12 

11 

11 

11 

10 

18 

8 

8 

14 

12 

11 

9

Optimum (percent 

Range Preferred relative abundance 

range in parentheses)

9Q9 1 1 KO

7 70 8 4ft

90 91 8

08 Q4

8 no 1 9 ft

1 ft Q Q

14.fi 494

QQ 9 77 0

15.1- 62.0 

9.5 58.0

151- 381 

48 70

m Q19

43_ 308 - 

1.6 4.8

01 0 fi

9^4 783

0 Q 310

0 01 0 9Q

0.01 0.06

0.010- 0.25 - 

0.001- 0.15 

0.04 0.35

0 01Q 019

705(3.2) 

8.48(3.2) 

13.4(3.2) 

3.3(3.2) 

11.7(0.6) 

1.8(0.6) 

359(0.6) 

65.2(0.6) 

47.7(0.6) 

46.2(0.6) 

273(0.6) 

4.8(0.6) 

232(0.6) 

211(0.6) 

4.2(0.6) 

0.4(0.6) 

653(0.6) 

4.2(3.2) 

0.29(0.8) 

0.05(0.8) 

0.020(3.2) 

0.002(3.2) 

0.06(3.2) 

0.040(3.2)

Ecological summary:

Prefers cool freshwater with little turbidity 

and small concentrations of sodium and suspended sediment. Planktonic, preferably in impoundments, on larger streams (greater than 

100 ft*/s) at middle elevations (3,000 to 3,500 ft); 

incidental in streams below impoundments. 

Spring and fall (May and October) dominant.

Distribution summary:

Found in Tongue River and Rosebud Creek 

drainages. Seasonally common in the Tongue 

River Reservoir; incidental in Indian Creek (station 24) and the downstream part of the Tongue 

River.

EXPLANATION

PERCENT RELATIVE ABUNDANCE 

EQUAL TO OR GREATER THAN 10

PERCENT RELATIVE ABUNDANCE 

LESS THAN 10

DISTRIBUTION MAP

MAJOR DIATOM ECOTYPES 27
ECOTYPE: COCCONEIS PEDICULUS EHR.

Biotype(s):

Cocconeis pediculus Ehr. var. pediculus

Reference:

Patrick and Reimer, 1966 (p. 240; pi. 15, 

figs. 3-4)

Herbarium slide number: 

1-2-5

Mean percent relative abundance: 

1.8

Percent occurrence: 

50.8

Abundance-occurrence index: 

89.5

Preferred percent occurrence: 

5.7

Maximum percent relative abundance: 

30.3

10

Raphe valve Pseudoraphe valve

Station number: 48 

Date: August 1, 1979 

Type of collection: E

Description:

Striae, 16-18 in 10 /mi on raphe valve and 

14-16 in 10 nm on pseudoraphe valve. Length, 

25.0 /*m. Width, 18.0 /mi. An elliptical diatom 

with a highly arched pseudoraphe valve. The 

raphe valve is concave in contour, presumably 

adapted for attachment to rounded stems or filaments of aquatic vascular plants and macroalgae. 

Distinguished from C. placentula and varieties 

by having only a marginal hyaline area on the 

raphe valve rather than both marginal and submarginal hyaline areas.

28 ECOLOGY AND DISTRIBUTION OF MAJOR DIATOM ECOTYPES IN MONTANA
Water-quality profile:

Variable

Specific conductance (^mho/cm) 

pH (units) 

Tomnovafnvo ( °C*\

Turbidity (NTU)

Oxygen, dissolved (mg/L) 

Biochemical oxygen demand (mg/L) 

Hardness, total (mg/L CaCO3) 

Calcium, dissolved (mg/L) 

Magnesium, dissolved (mg/L) 

Sodium, dissolved (mg/L) 

Bicarbonate (mg/L) 

Carbonate (mg/L) 

Alkalinity, total (mg/L CaCO3 )

Sulfate, dissolved (mg/L) 

Chloride, dissolved (mg/L) 

Fluoride, dissolved (mg/L) 

Dissolved solids, calculated (mg/L) 

Sediment, total suspended (mg/L) 

Nitrogen, total NO2 +NO3 (mg/L as N)

Nitrogen, total ammonia (mg/L as N) 

Phosphorus, total (mg/L as P) 

Phosphorus, total ortho (mg/L as P) 

Iron, total recoverable (mg/L) 

Ivl i yi rf i noon ^"fi^^il yfi/^fnTfivi Vilfi ITVICT/! i

Number 

of 

samples

145

145

145

140

ift^

^Q

85

or

85 

92 

Qft I/O

oc

Oft

Q9

qo

ftft

ftf^

1 QQ

ftQ

86 

1 c\a

110

£Q

£JA

Range

239 4350

7 cfl ft 79

I

T OA C .7- oO.o

ft <=» 19*40

6

7ft 1 ^ ft

0 7 ft Q

123-1430 

160 179 .LvJ.v/ _L / »7

15.1- 242 

9.5- 662

1 15- C T~IC 77b

O K QC n

1 Q £Q£

1 7 9QQft

0.4 174

0.1 1.5

184 4020

O o ftOfifi

0.01 0.71

0.01-0.19 

0.010 3.7

0.001 2.5

ft ft9 14

0.005 0.39

( 

Preferred i 

range

480 1500

7 Q1 ft Kft

1 A C QC C

17 190

8 7ft 1 ft Q

19 9 3

226- 597 

42.8 69.4

28.8- 105 

15.8- 82.0 

45 514

1.0 10.00

OQ -IQI

1 7 Qftft

1

O CO

0 q i Q

QftQ 1 ft9ft

3.5 413

0.02 0.08

0.01- 0.03 

0.012 0.20

0.001 0.11

0.06 0.16

0.020 0.045

Dptimum (percent 

 elative abundance 

in parentheses)

1 f)£l(\(f)'7 A\

8.40(27.4)

9ft ftC97 4")

cc/'97 A\

Q 7ftC97 A)

1 9f9 Q ft^

597(27.4) 

66.4(27.4)

105(27.4) 

82.0(27.4) 

45(27.4)

1 OT97 4s)

QQC97 4.^

qQn('97 4^

4.5(27.4)

0.6(27.4)

685(27.4)

108(27.4)

O A9/9Q Q\

0.03(22.5) 

0.014(25.3)

O AA9/'9C 0\

0

-i£»/'9Q Q\

O A9A/9Q Q\

Ecological summary:

Prefers fresh waters with small sodium content; medium to large streams (greater than 10 

ft3/s); and substrate of coarse sand or larger 

(greater than 0.3 mm). Tolerates considerable 

turbidity and suspended sediment. Summer and 

fall (June to October) dominant. Almost always 

associated with stands of Cladophora.

Distribution summary:

Widespread in the study area. Prefers Rosebud Creek and the Tongue River.

O

EXPLANATION

PERCENT RELATIVE ABUNDANCE 

EQUAL TO OR GREATER THAN 10

PERCENT RELATIVE ABUNDANCE 

LESS THAN 10

DISTRIBUTION MAP

MAJOR DIATOM ECOTYPES 29
ECOTYPE: COCCONEIS PLACENTULA EHR.

Biotype(s):

C. placentula Ehr. var. placentula 

C. placentula var. euglypta (Ehr.) Cl. 

*C. placentula var. lineata (Ehr.) V. H.

Reference:

Patrick and Reimer, 1966 (p. 242; pi. 15, 

figs. 5-6)

Herbarium slide number: 

1-2-6

Mean percent relative abundance: 

3.9

Percent occurrence: 

81.1

Abundance-occurrence index: 

315.6

Preferred percent occurrence: 

8.6

Maximum percent relative abundance: 

97.4

Station number: 1 

Date: October 19, 1979 

Type of collection: C

10 jim

Raphe valve Pseudoraphe valve

Description:

Striae, 17-22 in 10 /*m on raphe valve and 

28-20 in 10 /*m on pseudoraphe valve. Length, 

22.2 /*m. Width, 16.3 /mi. Distinguished from C. 

pediculus by the relatively flat pseudoraphe 

valve and the submarginal hyaline area on the 

raphe valve. The varieties of C. placentula may 

prove to be different phenotypic expressions of 

the same genotype. Distinguishing variety euglypta from variety lineata is often difficult, particularly in mixed populations, where they tend 

to intergrade.

30 ECOLOGY AND DISTRIBUTION OF MAJOR DIATOM ECOTYPES IN MONTANA
Water-quality profile:

Variable

Specific conductance (/imho/cm) 

pH (units) 

Tprrmpratnrp ( °C*}

Turbidity (NTU)

Oxygen, dissolved (mg/L) 

Biochemical oxygen demand (mg/L) 

Hardness, total (mg/L CaCO3) 

Calcium, dissolved (mg/L) 

Magnesium, dissolved (mg/L) 

Sodium, dissolved (mg/L) 

Bicarbonate (mg/L) 

Carbonate (mg/L) 

Alkalinity, total (mg/L CaCO3)

Sulfate, dissolved (mg/L) 

Chloride, dissolved (mg/L) 

Fluoride, dissolved (mg/L) 

Dissolved solids, calculated (mg/L) 

Sediment, total suspended (mg/L) 

Nitrogen, total NO2 +NO3 (mg/L as N)

Nitrogen, total ammonia (mg/L as N) 

Phosphorus, total (mg/L as P) 

Phosphorus, total ortho (mg/L as P) 

Iron, total recoverable (mg/L) 

Manganese, total recoverable (mg/L) 

Number 

of Range 

samples

245 

244 

243 

240 

171 

65 

147 

147 

147 

157 

164 

38 

164 

157 

157 

152 

147 

228 

125 

142 

169 

173 

99 

87

239- 

7.50- 

1.0

O K

4.52-

O K

124- 

27.4- 

13.5- 

9.1- 

15- 

0.5- 

1 3

17

0.4

0.04

184

0 9

0.01

0.01

0.010

0.001- 

0.02- 

0.005-

11000 

8.80 

30.2 

435 

15.3 

8.9 

3490 

330 

645 

1950 

816 

38.4 

669 

6900 

174 

1.7 

10400 

893 

0.80 

0.57 

0.62 

0.52 

2.1 

0.41

Optimum (percent 

Preferred relative abundance 

range in parentheses)

462- 

7.50- 

3 Q

O c

6.88-

0

0

236- 

49.7- 

25.7- 

18.3- 

226- 

5.0- 

1QQ

QR

1 9

0 1

QQQ

0.2- 

0 01

0.01

O.OlO-i 

0.001- 

0.02- 

0.005-

5080 

8.64 

23.5 

33 

11.7 

7.8 

2400 

187 

467 

662 

754 

28.0 

618 

3150 

45.6 

1.3 

4650 

46.6 

0.53 

0.11 

0.088 

0.12 

0.63 

0.39

1300(97 

8.01(97 

10.1(97 

0.6(97 

9.02(97 

1.1(97 

499(97 

79.6(97 

72.6(97 

133(97 

534(97 

5.0(24 

438(97 

304(97 

6.0(97 

1.3(97 

1130(97 

0.4(97 

0.01(94 

0.01(88 

0.010(94 

0.002(97 

0.02(97 

0.090(76

.4) 

.4) 

.4) 

.4) 

.4) 

.4) 

.1) 

.1) 

.1) 

.1) 

.1) 

.9) 

.1) 

.1) 

.1) 

.1) 

.1) 

.4) 

.0) 

.0) 

.0) 

.1) 

.1) 

.3)

Ecological summary:

Prefers waters with little turbidity and small 

concentrations of suspended sediment; coarse 

sand to fine gravel (0.3 to 10 mm); and smaller 

streams (0.1 to 10 ft3/s) at middle elevations 

(2,500 to 4,000 ft). Summer and fall (June to 

October) dominant. Pioneer species; colonized 

artificial substrates (Plexiglas plates) at some 

sites almost to the exclusion of all other taxa.

Distribution summary:

Widespread, with best development in the 

western part of the study area. This is the fourth 

most common diatom ecotype in the southern 

Fort Union coal region.

O

EXPLANATION

PERCENT RELATIVE ABUNDANCE 

EQUAL TO OR GREATER THAN 10

PERCENT RELATIVE ABUNDANCE 

LESS THAN 10

DISTRIBUTION MAP

MAJOR DIATOM ECOTYPES 31
ECOTYPE: CYCLOTELLA MENEGHINIANA KUTZ.

Biotype(s):

C. cryptica Reimann, Lewin and Guillard var.

cryptica

*C. meneghiniana Kutz. var. meneghiniana 

C. striata (Kutz.) Grun. var. striata

Reference:

Hustedt, 1930b (p. 100; fig. 67)

Herbarium slide number: 

1-2-7

Mean percent relative abundance: 

1.7

Percent occurrence: 

77.6

Abundance-occurrence index: 

135.0

Preferred percent occurrence: 

3.0

Maximum percent relative abundance: 

30.3

Station number: 30 

Date: July 7, 1978 

Type of collection: E

10

Description:

Striae, 8 in 10 /mi. Diameter, 13.8 /urn. A single isolated pore near midvalve. This is a small 

to medium Cyclotella with a distinctive "scalloped" edge. Diameter, number of central pores, 

pattern of the central area, and other features 

are highly variable. Schoeman and Archibald 

(1980) have synonymized C. cryptica with C. 

meneghiniana. Hustedt (1930a, p. 344) indicates 

that C. meneghiniana may be a somewhat less 

salt-tolerant form of C. striata. The only feature 

distinguishing these two taxa is the submarginal shadow line of C. striata.

32 ECOLOGY AND DISTRIBUTION OF MAJOR DIATOM ECOTYPES IN MONTANA
Water-quality profile:

Variable

Specific conductance (^mho/cm) 

T^rT f n T*I i i" <3 ^

Tprrmpratnrp ( °P^

Turbidity (NTU)

OYVCTPTI Hiacinlvprl fmcr/TA

Biochemical oxygen demand (mg/L) 

Hardness, total (mg/L CaCO3) - 

Calcium, dissolved (mg/L) 

Magnesium, dissolved (mg/L) 

Sodium, dissolved (mg/L) 

Bicarbonate (mg/L) 

Carbonate (mg/L) 

Alkalinity, total (mg/L CaCO3)

Sulfate, dissolved (mg/L) 

Chloride, dissolved (mg/L) 

Fluoride, dissolved (mg/L) 

Dissolved solids, calculated (mg/L) 

Sediment, total suspended (mg/L) 

Nitrogen, total NO2 +NO3 (mg/L as N)

Nitrogen, total ammonia (mg/L as N) 

Phosphorus, total (mg/L as P) 

Phosphorus, total ortho (mg/L as P) 

TTOTI tntnl T*f»pnvf»Tsil"»lo fmcr/T A

ATf^Ti m^'nficsf* i~ni"il v£*priT7r*v~j Vil r* ^m rr/T "\

Number 

of Range 

samples

244 

244 

243 

240 

180 

70 

143 

143 

143 

154 

159 

42 

159 

154 

154 

149 

143 

220 

115 

143 

165 

165 

94 

83

qqq i i nnn

7

jrrv o of\ .50- o.oO

1.0 30.5

o "» 4cic,

4 co ion

0.5- 8.9 

123- 3490

1 d f\ QOA

1 O O C.AC.

11.5 1950

1C 15- olb O1 C

0.5 38.4

1 Q RdQ

44 6QOO

0.4 174

0.04 1.7

184-10400 

0.2- 893 

0.01 0.80

0.01- 0.57 

0.010 0.62

0.001- 0.52

0 09 9 1

0.005 0.41

Optimum (percent 

Preferred relative abundance 

range in parentheses)

1880 4200

8.08- 8.49

6

0 o/j n

0.7 17

7.04 14.3

2.2- 3.6

964- 2300 

1 on OQC

153 416

280 480

A O 1? RRR

350 546

1 07O 9 P»QO

8

n QC n

0.1 1.1

2250- 4090 

1.4- 19.3 

0.01 0.02

0.01 0.02

0.020 0.033

0.003 0.017

0.10 0.25

0.025 0.080

2840(30.3) 

8.18(30.3) 

13.0(30.0) 

2.2(30.3) 

11.1(30.3) 

3.6(25.1) 

1080(30.3) 

130(30.3) 

184(30.3) 

280(30.3) 

581(30.3) 

4.1(7.2) 

476(30.3) 

1070(30.3) 

8.0(30.3) 

0.6(30.3) 

2250(30.3) 

11.7(30.3) 

0.02(30.3) 

0.02(30.3) 

0.033(30.3) 

0.017(30.3) 

0.25(30.3) 

0.080(30.3)

Ecological summary:

Prefers extremely hard, somewhat brackish 

waters with a large sulfate but small chloride 

content; and small to medium streams (0 to 10 

ftVs) at middle elevations (2,500 to 3,500 ft). 

Substrate indifferent (tychoplanktonic?). Summer and fall (June to October) dominant.

Distribution summary:

Distributed throughout the study area. Prefers 

Armells Creek and certain tributaries of the 

Tongue River.

O

EX PLAN ATION

PERCENT RELATIVE ABUNDANCE 

EQUAL TO OR GREATER THAN 10

PERCENT RELATIVE ABUNDANCE 

LESS THAN 10

DISTRIBUTION MAP

MAJOR DIATOM ECOTYPES 33
ECOTYPE: CYCLOTELLA PSEUDOSTELLIGERA HUST.

Biotype(s):

Cyclotella pseudostelligera Hust. var. pseudostelligera

Reference:

Wujek and Rupp, 1980 (p. 10; pi. 1, fig. 10)

Herbarium slide number: 

1-2-8

Mean percent relative abundance: 

0.4

Percent occurrence: 

7.3

Abundance-occurrence index:

3.2 10

Preferred percent occurrence: 

1.4

Maximum percent relative abundance: 

49.2

Station number: 35 

Date: July 24, 1979 

Type of collection: E

Description:

Striae, 20 in 10 /on. Diameter, 5.0 /mi. A very 

small centric diatom with a central rosette that 

is morphologically similar to the marginal striae. 

Distinguished from C. stelligera Cl. et Grun. by the 

presence of marginal spines (strutted processes).

34 ECOLOGY AND DISTRIBUTION OF MAJOR DIATOM ECOTYPES IN MONTANA
Water-quality profile:

Number 

Variable of 

samples

Specific conductance (/imho/cm) 

r»TT fnnita^

Temperature ( °C) 

Turbidity (NTU)

Oxygen, dissolved (mg/L) 

Biochemical oxygen demand (mg/L) 

Hardness, total (mg/L CaCO3) 

Calcium, dissolved (mg/L) 

Magnesium, dissolved (mg/L) 

Sodium, dissolved (mg/L) 

Bicarbonate (mg/L) 

Carbonate (mg/L) 

Alkalinity, total (mg/L CaCO3)

Sulfate, dissolved (mg/L) 

Chloride, dissolved (mg/L) 

Fluoride, dissolved (mg/L) 

Dissolved solids, calculated (mg/L) 

Sediment, total suspended (mg/L) 

Nitrogen, total NO2 +NO3 (mg/L as N) 

Nitrogen, total ammonia (mg/L as N) 

Phosphorus, total (mg/L as P) 

Phosphorus, total ortho (mg/L as P) 

Iron, total recoverable (mg/L) 

1WQT"I fT Q fl £* Q £* 'fO'f Q! Vf^ftr\'\7f^'rC\\^} f* fTV*<T/T ^

23 

22 

22 

23 

15 

6 

9 

9 

9 

10 

11 

3 

11 

10 

10 

9 

9 

22 

7 

14 

18 

18 

5 

4

Range

438- 4350

7

<~lf\ O CA .70- o.oO

3.8- 24.5

O ft 1 Q9

7 en 1 9 ft

i fl °, °.

343- 1430 

at a i "7 'A

45.0- 242 

11.7- 662 

257- 611 

7.0-10.00 

211- 501

CQ OQQft

2

q i q 9

O Q ft Q

550 4020

2.9- 255 

0.02- 0.08 

0.01- 0.05 

0.020- 0.20 

0.003 0.11

0.07 0.59

0.030 0.10

Optimum (percent 

Preferred relative abundance 

range in parentheses)

942- 1400 

8.30 8.45

16.1- 23.5

8 ft 1 Q9

9 co 1 9 ft

3.0- 3.0 

424- 618

oc o fjrt FT

60.0- 111

CO A 1 AO

257- 460 

8.4-10.00 

211- 391 

308 441

4.8- 6.3

O n AC

7C.7 llQft

12.8- 255 

0.02- 0.08 

0.01- 0.03 

0.030- 0.20 

0.003 0.11

1260(49.2) 

8.39(49.2) 

23.5(49.2) 

132(49.2) 

9.52(26.5) 

3.0(18.1) 

591(49.2) 

69.4(49.2) 

101(49.2) 

75.3(49.2) 

417(49.2) 

10.00(49.2) 

359(49.2) 

345(49.2) 

6.3(49.2) 

0.6(33.7) 

1020(49.2) 

255(49.2) 

0.08(49.2) 

0.01(49.2) 

0.20(49.2) 

0.11(49.2) 

0.17(0.8) 

0.050(0.8)

Ecological summary:

Prefers pH greater than 8.00 and some carbonate ion; and medium to large streams 

(greater than 10 ft3/s) at lower elevations (less 

than 3,500 ft). Tolerates much turbidity and 

large suspended-sediment concentrations. Spring 

and summer (May to August) dominant. Tychoplanktonic.

Distribution summary:

Prefers Rosebud Creek and the upstream part 

of the Tongue River, including the Tongue River 

Reservoir.

EXPLANATION

PERCENT RELATIVE ABUNDANCE 

LESS THAN 10

DISTRIBUTION MAP

MAJOR DIATOM ECOTYPES 35
ECOTYPE: CYMBELLA AFFINIS KUTZ.

Biotype(s):

*C. affinis Kutz. var. affinis 

C. cistula (Ehr.) Kirchn. var. cistula 

C. cymbiformis Ag. var. cymbiformis 

C. cymbiformis var. nonpunctata Font.

Reference:

Patrick and Reimer, 1975 (p. 57; pi. 10, fig. 7)

Herbarium slide number: 

1-1-4

Mean percent relative abundance: 

2.8

Percent occurrence: 

54.6

Abundance-occurrence index: 

150.9

Preferred percent occurrence: 

8.6

Maximum percent relative abundance: 

54.2

Station number: 24 

Date: July 17, 1979 

Type of collection: E

10

Description:

Striae, 11 in 10 /ttm (center). Length, 23.0 /itm. 

Width, 8.0 ^m. A medium Cymbella, usually 

with an isolated stigma at the end of the middle 

stria on the ventral side. Size, shape of ends, 

and number of isolated stigmata highly variable.

36 ECOLOGY AND DISTRIBUTION OF MAJOR DIATOM ECOTYPES IN MONTANA
Water-quality profile:

Variable

pH (units) 

Temperature (°C)

Turbidity (NTU)

Oxygen, dissolved (mg/L) 

Biochemical oxygen demand (mg/L) 

Hardness, total (mg/L CaCO3) 

Calcium, dissolved (mg/L) 

Magnesium, dissolved (mg/L) 

Sodium, dissolved (mg/L) 

Bicarbonate (mg/L) 

Carbonate (mg/L) 

Alkalinity, total (mg/L CaCO3)

Sulfate, dissolved (mg/L) 

Chloride, dissolved (mg/L) 

Fluoride, dissolved (mg/L) 

Dissolved solids, calculated (mg/L) 

Sediment, total suspended (mg/L) 

Nitrogen, total NO2 +NO3 (mg/L as N) 

Nitrogen, total ammonia (mg/L as N) 

Phosphorus, total (mg/L as P) 

Phosphorus, total ortho (mg/L as P) 

Iron, total recoverable (mg/L) 

'M'nncmnpQP total vppmrovnWlo fmcr/T .^

Number 

of Range 

samples

161 

161 

160 

156 

122 

46 

96 

96 

96 

102 

107 

23 

107 

102 

102 

101 

96 

149 

84 

90 

112 

111 

68 

61

9QQ

7 en

9 A

n ^

5 99

A K

1 K A

1 Q K

Q 1

15- 

0.5-

1 Q

34-

1 Q

0.1

184

0.6- 

0.01- 

0.01- 

0.010

0.001

0.02

0.005

11000 

8.80 

30.5 

6800 

15.3 

4.2 

3490 

328 

645 

1950 

816 

38.4 

669 

6900 

51.6 

1.5 

10400 

323 

0.80 

0.22 

0.62 

0.52 

2.1 

0.37

Optimum (percent 

Preferred relative abundance 

range in parentheses)

970

7.63- 

4.9-

0

0

5.22- 

1.5- 

124- 

97 4

1 q r

Q 1

111- 

7 0

91

QX

1 Q

0.1

196- 

0.8- 

0.03- 

0.01

0.020- 

0.002

0.02- 

0.010-

6100 

8.80 

23.7 

53 

13.2 

4.2 

2020 

238 

346 

960 

661 

38.4 

542 

3350 

21.4 

1.1 

5560 

131 

0.71 

0.09 

0.16 

0.046 

2.1 

0.27

670(54.2) 

8.39(54.2) 

21.2(54.2) 

1.6(54.2) 

9.05(54.2) 

2.5(46.9) 

343(54.2) 

62.7(54.2) 

45.0(54.2) 

11.7(54.2) 

340(54.2) 

7.0(54.2) 

290(54.2) 

81(54.2) 

2.3(54.2) 

0.6(54.2) 

550(54.2) 

2.9(54.2) 

0.03(44.3) 

0.05(54.2) 

0.020(54.2) 

0.007(54.2) 

0.17(54.2) 

0.050(54.2)

Ecological summary:

Broad ecological amplitude. Seems to prefer 

fresh, calcium bicarbonate waters; small to medium streams (0.1 to 100 ft3/s) at middle elevations (2,500 to 4,000 ft); and fine gravels or 

larger (greater than 0.2 cm diameter). Tolerates 

some turbidity and suspended sediment. No 

clear seasonal preference.

Distribution summary:

Widespread. Prefers Rosebud Creek and the 

Tongue River drainages. The one sample from 

the downstream part of Armells Creek (station 

11) in which the ecotype accounted for more 

than 10 percent relative abundance (29.7) probably was affected by Yellowstone River irrigation return flows (Klarich and others, 1980).

EXPLANATION

PERCENT RELATIVE ABUNDANCE 

EQUAL TO OR GREATER THAN 10

PERCENT RELATIVE ABUNDANCE 

LESS THAN 10

DISTRIBUTION MAP

MAJOR DIATOM ECOTYPES 37
ECOTYPE: CYMBELLA MICROCEPHALA GRUN.

Biotype(s):

C. microcephala Grun. var. microcephala

Reference:

Patrick and Reimer, 1975 (p. 33; pi. 4, 

figs. 12a-13b)

Herbarium slide number: 

1-2-10

Mean percent relative abundance: 

0.5

Percent occurrence: 

24.3

Abundance-occurrence index: 

13.1

Preferred percent occurrence: 

1.4

Maximum percent relative abundance: 

38.6

10

Station number: 31 

Date: July 12, 1979 

Type of collection: E

Description:

Striae, 24-32 in 10 ^m. Length, 12.2 ^m. Width, 

3.4 ^m. A very small species of Cymbella. Distinguished from very small species of Navicula 

by the slightly eccentric raphe and subtle asymmetry on either side of the transapical axis. Distinguished from Cymbella sp. X by the much 

broader apices.

38 ECOLOGY AND DISTRIBUTION OF MAJOR DIATOM ECOTYPES IN MONTANA
Water-quality profile:

]

Variable

i

Specific conductance (/tmho/cm) 

r\f-( £/X.l. (11 \ IAXX± Tiitc^ UO/ _________________ ^^ _____ _

Tpmnprfltnrp ( °CTi

TnrhiditvfNTin

Oxygen, dissolved (mg/L) 

Biochemical oxygen demand (mg/L) 

Hardness, total (mg/L CaCO3) 

Calcium, dissolved (mg/L) 

Magnesium, dissolved (mg/L) 

Sodium, dissolved (mg/L) 

Bicarbonate (mg/L) 

Carbonate (mg/L) 

Alkalinity, total (mg/L CaCO3)

Sulfate, dissolved (mg/L) 

Chloride, dissolved (mg/L) 

Fluoride, dissolved (mg/L) 

Dissolved solids, calculated (mg/L) 

Sediment, total suspended (mg/L) 

Nitrogen, total NO2 +NO3 (mg/L as N) 

Nitrogen, total ammonia (mg/L as N) 

Phosphorus, total (mg/L as P) 

Phosphorus, total ortho (mg/L as P) 

Iron, total recoverable (mg/L) 

Ivl on cffnnfiQCk ^"/"\^~ol vcif*m7ct'v*t% r\ici (mcf/* »

dumber 

of 

samples

76 

76

7K

rr >| 74

K7

1Q-L J

/« O

4o

48 

48

52

54 

14 

54

KO

KO

K1

48 

69 

43 

48

53

KO

Of

oa

Range

292-4350 

7.62- 8.80

3 R 9^ Q

O K AQK

5 99 1 ^ fi

O .7- T o.OO C 

145 1430

33.2- 192 

15.1 242

9.5- 662 

151- 816 

0.5- 38.4

m ddQ

n 9QQfl

i 9 aa Q

0.1 1.3

254-4020 

0.2- 893 

0.01- 0.80 

0.01 0.22

0.010- 0.60 

0.001 0.38

0.02 1.1

0.005 0.23

i 

Preferred i 

range

480- 1880 

7.91- 8.63

ico 99 Q

0.8 11

8

AQ I 0 0

OOC ndA

41.8- 60.0

9Q Q 1 EC

15.8- 199 

281- 564 

18.0- 22.0

OQA /ICO

n

ai n

i a a9

0.4 1.3

389- 1550 

0.8- 22.0 

0.06- 0.41 

0.03 0.06

0.020-0.040 

0.002 0.020

O AO f\ OC

0.010 0.045

Optimum (percent 

 elative abundance 

in parentheses)

1580(38.6) 

8.55(38.6)

9fi QfIR fi\

O Q/OQ C\

10.5(38.6)

1 QfR 7^

rr/J/i/QQ C\

47.8(38.6)

1 KC^QQ C\

108(38.6) 

393(38.6) 

22.0(38.6)

OCO/'OO C\ o5o(,oo.b)

ci nfoo c\

7

C/OQ C\ .b(6o.b)

0.4(38.6)

1350(38.6) 

0.9(38.6) 

0.41(17.0) 

0.06(17.0)

0.030(38.6)

O A.flQ/'QQ c\

O CiCfOQ d\

O f\i f\foQ a\

Ecological summary:

Prefers alkaline waters containing some carbonate ion; small streams (0.1 to 10 ft8/s) at middle elevations (3,000 to 3,500 ft); and fine gravel 

(0.2- to 1-cm diameter). Sensitive to suspended 

sediment and turbidity. Summer (July and Auggust) dominant.

Distribution summary:

Distributed throughout the western part of 

the study area; conspicuously absent from downstream reaches of the Powder River drainage. 

Largest populations from small tributaries of 

the Tongue River.

EXPLANATION

PERCENT RELATIVE ABUNDANCE 

EQUAL TO OR GREATER THAN 10

PERCENT RELATIVE ABUNDANCE 

LESS THAN 10

DISTRIBUTION MAP

MAJOR DIATOM ECOTYPES 39
ECOTYPE: CYMBELLA PUSILLA GRUN.

Biotype(s):

C. pusilla Grun. var. pusilla

Reference:

Patrick and Reimer, 1975 (p. 25; pi. 3, fig. 18)

Herbarium slide number: 

1-2-11

Mean percent relative abundance: 

0.4

Percent occurrence: 

26.2

Abundance-occurrence index: 

11.7

Preferred percent occurrence: 

0.8

Maximum percent relative abundance: 

20.7

10

Station number: 30 

Date: September 30, 1979 

Type of collection: E

Description:

Striae, 16-20 in 10 urn. Length, 22.8 urn. Width, 

5.0 fim. A small species of Cymbella without setoff ends. Distinguished by the shortened central 

striae on both the dorsal and ventral sides.

40 ECOLOGY AND DISTRIBUTION OF MAJOR DIATOM ECOTYPES IN MONTANA
Water-quality profile:

Number 

Variable of Range 

samples

Specific conductance (^mho/cm) 

pH (units) 

Temperature (°C)

Turbid itv(NTTF)

Biochemical oxygen demand (mg/L) 

Hardness, total (mg/L CaCO3) 

Calcium, dissolved (mg/L) 

Magnesium, dissolved (mg/L) 

Sodium, dissolved (mg/L) 

Bicarbonate (mg/L) 

Carbonate (mg/L) 

Alkalinity, total (mg/L CaCO3)

Sulfate, dissolved (mg/L) 

Chloride, dissolved (mg/L) 

Fluoride, dissolved (mg/L) 

Dissolved solids, calculated (mg/L) 

Sediment, total suspended (mg/L) 

Nitrogen, total NO2 +NO3 (mg/L as N)

Nitrogen, total ammonia (mg/L as N) 

Phosphorus, total (mg/L as P) 

Phosphorus, total ortho (mg/L as P) 

Iron, total recoverable (mg/L) 

Manganese, total recoverable (mg/L) 

84 

84 

85 

84 

58 

14 

53 

53 

53 

57 

58 

16 

58 

57 

57 

54 

53 

77 

34 

54 

57 

58 

30 

25

1210

7 GO

1 Q

0.7

4 ^9

1 ^

i a r\

20.0-

1 QO

1 OS

0.5-

1 CO

304- orv ^

2.2- 

0.04

1130

0.4- 

0.01

0.01- 

0.010

0.001

0.02

0.005-

11000 

8.80 

30.5 

435 

19.0 

3.6 

3490 

330 

645 

1950 

913 

38.4 

748 

6900 

126 

1.7 

10400 

893 

0.71 

0.57 

0.62 

0.52 

1.1 

0.41

Optimum (percent 

Preferred relative abundance 

range in parentheses)

9QQfl

8

f\C

1.3- 

1 Q

4.52-

736- 

113- 

172- 

350- 

547-

448

1260- 

81

n ^

2450-

1 Q

0.17- 

0.010

0.008

0 1 K

0.41-

6400 

8.50 

18.0 

17 

12.3

2610 

224 

496 

949 

913

748 

3930 

29.1 

0.6 

6210 

10.7

0.17 

0.030 

0.018 

0.25 

0.41

6400(20.7) 

8.22(20.7) 

15.8(20.7) 

1.9(20.7) 

12.1(20.7) 

1.6(6.2) 

2610(20.7) 

224(20.7) 

496(20.7) 

949(20.7) 

579(20.7) 

19.0(3.6) 

475(20.7) 

3930(20.7) 

29.1(20.7) 

0.6(20.7) 

6210(20.7) 

1.3(20.7) 

0.02(6.4) 

0.17(14.0) 

0.010(20.7) 

0.008(14.0) 

0.18(20.7) 

0.41(14.0)

Ecological summary:

Prefers extremely hard, brackish water with 

large concentrations of sulfate and some chloride; and small streams (0.1 to 1 ft3/s) at lower 

to middle elevations (less than 4,000 ft). Absent 

from substrates finer than coarse sand (less 

than 0.3-mm diameter). Late summer and early 

fall (August to October) dominant.

Distribution summary:

Widespread. Prefers Mizpah Creek and downstream tributaries of the Tongue River.

O

EXPLANATION

PERCENT RELATIVE ABUNDANCE 

EQUAL TO OR GREATER THAN 10

PERCENT RELATIVE ABUNDANCE 

LESS THAN 10

DISTRIBUTION MAP

MAJOR DIATOM ECOTYPES 41
ECOTYPE: CYMBELLA SPECIES X

Biotype(s):

C. sp. X var. X

Reference:

None

Herbarium slide number: 

1-2-9

Mean percent relative abundance: 

0.1

Percent occurrence: 

3.0

Abundance-occurrence index: 

0.4

Preferred percent occurrence: 

0.8

Maximum percent relative abundance: 

18.6

Station number: 40 

Date: August 21, 1979 

Type of collection: E

10

Description:

Striae, 22-24 in 10 /urn. Length, 17.5 ^m. Width, 

4.7 jtm. This is a small Cymbella with fine striae 

and protracted, sub-capitate ends. Some specimens have a central indentation on the ventral 

margin. C. W. Reimer (Academy of Natural Sciences of Philadelphia, written commun., 1981) 

indicates that this taxon may be a variation of 

C. ruttneri Hust., distinguished from the nominate variety by the "odd shape of the ends." 

J. C. Kingston (Limnological Research Center, 

Univ. of Minnesota, written commun., 1981) 

thinks it is closer to C. fonticola Hust., and he 

proposes to name it in the near future as a new 

species or variety.

42 ECOLOGY AND DISTRIBUTION OF MAJOR DIATOM ECOTYPES IN MONTANA
Water-quality profile:

Variable

Specific conductance (jitmho/cm) 

r»T^ fnti'ii'eA

Tarrmarafnra (T^

TurhiHitv (NTTT1)

Oxygen, dissolved (mg/L) - - 

Biochemical oxygen demand (mg/L) 

Hardness, total (mg/L CaCO3) 

Calcium, dissolved (mg/L) 

Magnesium, dissolved (mg/L) 

Sodium, dissolved (mg/L) 

Bicarbonate (mg/L) 

C arbonate (mg/L) 

Alkalinity, total (mg/L CaCO3)

Sulfate, dissolved (mg/L) 

Chloride, dissolved (mg/L) 

Fluoride, dissolved (mg/L) 

Dissolved solids, calculated (mg/L) 

Sediment, total suspended (mg/L) 

Nitrogen, total NO2 +NO3 (mg/L as N)

Nitrogen, total ammonia (mg/L as N) 

Phosphorus, total (mg/L as P) 

Phosphorus, total ortho (mg/L as P) 

Iron, total recoverable (mg/L) 

Manganese, total recoverable (mg/L) 

Numbei 

of 

samples

10

10

10

10

7

0

7

7

7

1

8

7

10

7

q

8

q

9

Range

>

OCQA O7AA

7 ox Q f*f\

3

rj f)A tr

2 ft Q9

c oo 19 fi

441 1350

C A O 1 QO

79 0 91 7

/19ft £Oft

464- A f* A 608 f*f\Q

5.0- 5.0

OftT /IQft

1080- 1940 

12.0 43.1

0.5 0.8

91QO ^4SO

2.8 55.1

0.07 0.71

0.01 0.09

0.010 0.080

0.003-0.032 

0.08 0.35

0.065 0.10

< 

Preferred i 

range

9770 ^700

7 ft/1 ft Oft

 37 94. 4.

2 ft 11

5

00 1 o a

441 1350

K A O 1 QO

70 o 917

4oO- A Of\ Ooo COO

A TO £AQ

OQ7 /IQft

1110- 1940 

91 4. 4.°, 1

O /J AT

OOQ.fi Q/lQfi

2

Q 1 T K

0.43 0.62

0.02 0.04

0.010 0.020

0.005-0.006

O AQ A 00

0.10 0.10

Optimum (percent 

 elative abundance 

in parentheses)

OQK/V1 ft fi.\

8

QOY1 Q C\

24.4(18.6)

1 1 f1 Q C\

10.9(18.6)

441(18.6)

54.3(18.6)

TO QY1 Q £i\

COQ/"1 Q C\

A TO^1 Q £i\

5.0(2.7)

OQT^I Q £i\

1110(18.6) 

43.1(18.6)

O

rj/i Q /j\

990^1 ft fi.\

17.5(18.6)

0.47(18.6)

0.04(18.6)

O AO/V1 ft C"\

0.006(18.6)

O

no/1 o £*\

0

1 A/I O f*\

Ecological summary:

Prefers brackish, sodium sulfate waters with 

relatively large concentrations of chloride and 

inorganic nitrogen; gravel-size substrates or 

larger (greater than 1-cm diameter); and small 

streams (0.1 to 1.0 ft3/s). Eurythermal from 3 to 

25 °C. Indifferent to elevation. Tolerates some 

turbidity and suspended sediment. Late summer 

and early fall (August to October) dominant.

Distribution summary:

Found in the Tongue River drainage and 

Sweeney Creek (station 40). Best population development in Sweeney Creek and Bear Creek 

near Otter (station 13).

O

EXPLANATION

PERCENT RELATIVE ABUNDANCE 

EQUAL TO OR GREATER THAN 10

PERCENT RELATIVE ABUNDANCE 

LESS THAN 10

DISTRIBUTION MAP

MAJOR DIATOM ECOTYPES 43
ECOTYPE: DIATOMA TENUE AG.

Biotype(s):

*D. tenue Ag. var. tenue 

D. tenue var. elongatum Lyngb.

Reference:

Patrick and Reimer, 1966 (p. 108; pi. 2, fig. 5)

Herbarium slide number: 

1-2-12

Mean percent relative abundance: 

1.6

Percent occurrence: 

36.5

Abundance-occurrence index: 

58.3

Preferred percent occurrence: 

4.3

Maximum percent relative abundance:

74.8

10

Station number: 11 

Date: May 13, 1979 

Type of collection: E

Description:

Costae, 6-9 in 10 pm. Length, 25.0 jim. Width, 

4.0 jtm. A very slender species of Diatoma. Distinguished from D. vulgare by the narrow frustules; not more than 5 pm wide in valve view.

44 ECOLOGY AND DISTRIBUTION OF MAJOR DIATOM ECOTYPES IN MONTANA
Water-quality profile:

Variable

Specific conductance (^mho/cm) - 

rjJJ (units)

TpmnpvatnrA ( °C*}

Turbidity (NTU)

OYVCTPTI HiQQnlv^H rmtr/T A

Biochemical oxygen demand (mg/L) -- - 

Hardness, total (mg/L CaCO3) 

Calcium, dissolved (mg/L) _ 

Magnesium, dissolved (mg/L) 

Sodium, dissolved (mg/L) 

Bicarbonate (mg/L) 

Carbonate (mg/L) 

Alkalinity, total (mg/L CaCO3)

Sulfate, dissolved (mg/L) 

Chloride, dissolved (mg/L) 

Fluoride, dissolved (mg/L) 

Dissolved solids, calculated (mg/L) 

Sediment, total suspended (mg/L) 

Nitrogen, total NO2 +NO3 (mg/L as N)

Nitrogen, total ammonia (mg/L as N) 

Phosphorus, total (mg/L as P) 

Phosphorus, total ortho (mg/L as P) 

Iron, total recoverable (mg/L) 

Manganese, total recoverable (mg/L) 

Number 

of 

samples

106 

1 nc

1 0^

i nc

7ft

00

67 

an

an

79

7C

q&

7C

79

79

71

an

101

54

C<7

7C

74 

42 

37

Range

362-6400 

7 co Q on

10 °.fl 9

0.5 4200

c oo 14 q

n c xo

181-3320

QQ £ QQ.n

20.6 605

14.3 995

1C Q1 C

0.5- 38.4

1 o ccn

QQ K^Cfl

O /l ftft Q

0.1 1.2

1 ft/I 7CQH

0 9 °.99fl

0.01 0.80

0.01 0.57

0.010 2.6

0.001- 1.8 

0.04- 2.1 

0.005- 0.36

( 

Preferred i 

range

1880- 5200 

Ton ft QC.

5 1 97 °.

2 Q 1 ft

8 Aft 1 9 Q

1.0 2.5

635- 1610 

en n ooo

no f\ oc£

1 QQ ftOH

AJK 7Qn

OQQ KQft

584 2850

8 fl 9*. °.

O Q n a

1550 4760

11 44 4

0.01 0.66

0.01 0.22

0.020 0.060

0.003-0.020 

0.21- 0.36 

0.040- 0.12

Dptimum (percent 

 elative abundance 

in parentheses)

5200(74.8) 

8.05(74.8)

1 C O/T A O\ 15.o(74.oJ

1 a(n A Q\

9.40(74.8)

1 QY74 8)

1440(74.8) 

184(74.8)

f)OQf7A Q\

Qf)(\C7A Q\

a^ntn A si\

22.0(6.4)

514(74.8)

OC1 f\C7A Q.\

OK QC74 ft')

0.3(74.8)

4500(74.8)

44 4C74. ft)

0.01(74.8)

0.06(74.8)

0.030(74.8)

0.013(74.8) 

0.32(17.9) 

0.12(17.9)

Ecological summary:

Prefers extremely hard, brackish water with 

large sodium and sulfate concentrations; coarse 

sand or larger (greater than 0.3 mm); and mediumsize streams (1 to 100 ft3/s) at lower elevations 

(2,501 to 3,000 ft). Tolerates some suspended 

sediment, turbidity, and chloride. Cool season 

(October to June) dominant.

Distribution summary:

Distributed throughout the study area.

O

EXPLANATION

PERCENT RELATIVE ABUNDANCE 

EQUAL TO OR GREATER THAN 10

PERCENT RELATIVE ABUNDANCE 

LESS THAN 10

DISTRIBUTION MAP

MAJOR DIATOM ECOTYPES 45
ECOTYPE: DIATOM A VULGARE BORY

Biotype(s):

*D. vulgare Bory var. vulgare 

D. vulgare var. breve Grun. 

D. vulgare var. linearis V. H.

Reference:

Patrick and Reimer, 1966 (p. 109; pi. 2, fig. 9)

Herbarium slide number: 

1-2-13

Mean percent relative abundance: 

1.2

Percent occurrence: 

31.1

Abundance-occurrence index: 

36.5

Preferred percent occurrence: 

3.2

Maximum percent relative abundance: 

55.5

10

Station number: 52 

Date: October 21, 1975 

Type of collection: E

Description:

Costae, 6-8 in 10 /*m. Length, 47.5 /*m. Width, 

13.0 /*m. A robust species of Diatoma. Distinguished from D. tenue by the relatively broad 

valves, not less than 8 /*m wide.

46 ECOLOGY AND DISTRIBUTION OF MAJOR DIATOM ECOTYPES IN MONTANA
Water-quality profile:

Variable

Number

of 

samples

Range Preferred 

range

Optimum (percent

relative abundance

in parentheses)

Specific conductance (^mho/cm) 82 239-4350 333-1030 876(55.5)

pH (units) 81 7.70- 8.72 8.02- 8.50 8.27(55.5)

Temperature (°C) 82 1.0- 30.5 3.7- 23.5 10.1(55.5)

Turbidity (NTU) 78 0.8- 3250 2.0- 24 4.5(38.5)

Oxygen, dissolved (mg/L) 54 7.60-13.8 8.00-13.8 10.2(55.5)

Biochemical oxygen demand (mg/L) 22 0.7- 3.3 1.0- 3.3 3.3(55.5)

Hardness, total (mg/L CaCO3) 44 123-1430 181- 528 392(55.5)

Calcium, dissolved (mg/L) 44 16.0- 174 38.6- 90.0 77.0(55.5)

Magnesium, dissolved (mg/L) 44 13.5- 242 20.6- 74.0 48.5(55.5)

Sodium, dissolved (mg/L) 47 9.1- 662 13.7- 64.0 47.0(55.5)

Bicarbonate (mg/L) 53 15- 776 15- 498 289(55.5)

Carbonate (mg/L) 15 0.5-10.00 3.0(5.3)

Alkalinity, total (mg/L CaCO3) 53 13- 636 13- 408 237(55.5)

Sulfate, dissolved (mg/L) 47 34-2390 77- 320 234(55.5)

Chloride, dissolved (mg/L) 47 1.3- 88.9 2.2- 5.2 3.6(55.5)

Fluoride, dissolved (mg/L) 44 0.1- 1.2 0.2- 0.7 0.3(55.5)

Dissolved solids, calculated (mg/L) 44 184-4020 184- 844 705(55.5)

Sediment, total suspended (mg/L) 78 0.7-8260 4.2- 26.0 7.5(55.5)

Nitrogen, total NO2 +NO3 (mg/L as N) 45 0.01- 0.43 0.01- 0.25 0.01(38.5)

Nitrogen, total ammonia (mg/L as N) 43 0.01- 0.30 0.01- 0.03 0.03(55.5)

Phosphorus, total (mg/L as P) 62 0.010- 3.7 0.015-0.037 0.015(55.5)

Phosphorus, total ortho (mg/L as P) 61 0.001- 2.5 0.002-0.013 0.003(55.5)

Iron, total recoverable (mg/L) 33 0.04- 0.83 0.08- 0.33 0.12(55.5)

Manganese, total recoverable (mg/L) 29 0.019- 0.12 0.019- 0.12 0.12(55.5)

Ecological summary:

Prefers cool, fresh waters with relatively small 

concentrations of sodium and sulfate; substrate 

the size of coarse gravel or larger (greater than 

3-cm diameter); and medium to large streams 

(greater than 1 ft'/s) at middle elevations (3,000 

to 4,000 ft). Late summer to fall (July to October) dominant.

Distribution summary:

Optimum population development in the Rosebud Creek and upstream Tongue River drainages.

O

EXPLANATIO N

PERCENT RELATIVE ABUNDANCE 

EQUAL TO OR GREATER THAN 10

PERCENT RELATIVE ABUNDANCE 

LESS THAN 10

DISTRIBUTION MAP

MAJOR DIATOM ECOTYPES 47
ECOTYPE: DIPLONEIS SMITHII VAR. PUMILA (GRUN.) HUST.

Biotype(s):

D. smithii var. pumila (Grun.) Hust. 

Reference:

Patrick and Reimer, 1966 (p. 411; pi. 38, fig. 4) 

Herbarium slide number:

1-2-14

Mean percent relative abundance:

1.1 

Percent occurrence:

47.0 

Abundance-occurrence index:

51.1 

Preferred percent occurrence:

2.4 

Maximum percent relative abundance:

25.6

Station number: 3 

Date: October 7, 1978 

Type of collection: E

Description:

Costae, 14-18 in 10 /tm. Length, 12.0 /tm. 

Width, 7.0 /tm. Between the costae are two rows 

of alveoli that become three rows toward the 

valve margin. This feature is readily apparent 

only under an electron microscope; under the 

best optical microscopes, certain specimens give 

the appearance of being lineate or of having a 

single row of alveoli between the costae. Our 

specimens are mostly smaller than the usual 

size range for this taxon. D. W. Blinn (Northern 

Arizona University, written commun., 1981) reports that brackish-water forms of many diatoms 

often are smaller than sizes recorded in the literature. This taxon is similar to D. minima 

Hust., except that the "striae" between the costae are not narrower than the costae. It is distinguished from D. pseudovalis Hust. and D. 

puella (Schum.) Cl., two other small species of 

Diploneis from the study area, by the fine costae, small central area, and double row of alveoli between the costae.

10

48 ECOLOGY AND DISTRIBUTION OF MAJOR DIATOM ECOTYPES IN MONTANA
Water-quality profile:

Variable

Number

of 

samples

Range Preferred 

range

Optimum (percent

relative abundance

in parentheses)

Specific conductance (^mho/cm) 157 462-11000 1670-7030 4050(25.6)

pH (units) 157 7.65- 8.80 8.08-8.62 8.10(25.6)

Temperature (°C) 156 1.0- 30.5 6.2- 23.5 12.7(25.6)

Turbidity (NTU) 155 0.7-11600 1.2- 26 5.4(25.6)

Oxygen, dissolved (mg/L) 112 5.22- 15.3 7.65- 12.0 11.6(14.6)

Biochemical oxygen demand (mg/L) 34 0.5- 8.3 2.5- 7.8 2.5(14.6)

Hardness, total (mg/L CaCO3) 97 92- 3490 586- 1410 1320(25.6)

Calcium, dissolved (mg/L) 97 16.0- 330 69.7- 192 168(25.6)

Magnesium, dissolved (mg/L) 97 5.0- 645 81.2- 238 218(25.6)

Sodium, dissolved (mg/L) 104 18.3-1950 131-1470 580(25.6)

Bicarbonate (mg/L) 107 45- 913 492- 623 547(25.6)

Carbonate (mg/L) 28 0.5- 38.4 29.0- 29.0 29.0(11.7)

Alkalinity, total (mg/L CaCO3) 107 39- 748 403- 558 449(25.6)

Sulfate, dissolved (mg/L) 104 44-6900 454-3400 2100(25.6)

Chloride, dissolved (mg/L) 104 0.4- 174 4.4- 27.8 14.1(25.6)

Fluoride, dissolved (mg/L) 101 0.04- 1.7 0.3- 1.0 0.8(25.6)

Dissolved solids, calculated (mg/L) 97 398-10400 1430- 5800 3630(25.6)

Sediment, total suspended (mg/L) 142 0.2-22600 2.3- 42.8 11.8(25.4)

Nitrogen, total NO2 +NO3 (mg/L as N) 71 0.01- 0.62 0.01- 0.06 0.01(25.6)

Nitrogen, total ammonia (mg/L as N) 97 0.01- 0.30 0.01-0.11 0.01(14.6)

Phosphorus, total (mg/L as P) 109 0.010- 0.62 0.010- 0.11 0.010(25.6)

Phosphorus, total ortho (mg/L as P) 110 0.001- 0.52 0.002-0.045 0.002(14.6)

Iron, total recoverable (mg/L) 62 0.02- 1.4 0.21- 0.44 0.21(14.6)

Manganese, total recoverable (mg/L) 57 0.005- 0.39 0.064- 0.12 0.064(14.6)

Ecological summary:

Prefers brackish waters of large pH (greater 

than 8.00); coarse sand substrates or larger 

(greater than 0.3-mm diameter); and small 

streams (0.1 to 1.0 ft3/s) at middle elevations 

(3,000 to 3,500 ft). Eurythermal over the range 

of 6.2 to 23.5 °C. Tolerates some chloride, suspended sediment, and turbidity. Summer and 

fall (July to October) dominant.

Distribution summary:

Found throughout the study area. Best population development in the upstream part of 

Hanging Woman Creek.

EXPLANATION

PERCENT RELATIVE ABUNDANCE 

EQUAL TO OR GREATER THAN 10

PERCENT RELATIVE ABUNDANCE 

LESS THAN 10

DISTRIBUTION MAP

MAJOR DIATOM ECOTYPES 49
ECOTYPE: ENTOMONEIS PALUDOSA (W. SM.) REIM.

Biotype(s):

E. paludosa (W. Sm.) Reim. var. paludosa

Reference:

Patrick and Reimer, 1975 (p. 4; pi. 1, fig. 1)

Herbarium slide number: 

1-2-15

Mean percent relative abundance: 

0.5

Percent occurrence: 

44.3

Abundance-occurrence index: 

21.1

Preferred percent occurrence: 

0.5

Maximum percent relative abundance: 

15.3

10

Station number: 2 

Date: June 17, 1978 

Type of collection: E

: ?-

Description:

Striae, 20-24 in 10 /tm. Length, 53.0 /tm. Width, 

24.5 iim. A large, elegant diatom, almost always 

appearing in girdle view. Distinguished from the 

other two Montana species in this genus [E. 

alata (Ehr.) Ehr. and E. ornata (J. W. Bail.) 

Reim.] by the apparently undifferentiated (nonpunctate) striae.

50 ECOLOGY AND DISTRIBUTION OF MAJOR DIATOM ECOTYPES IN MONTANA
Water-quality profile:

Variable

Specific conductance (/-imho/cm) 

pH (units) 

TarrmaratiTro ( °P1

Turbiditv CNTU)

Oxygen, dissolved (mg/L) 

Biochemical oxygen demand (mg/L) 

Hardness, total (mg/L CaCO3) 

Calcium, dissolved (mg/L) 

AT a crnAQinm HieenlvAH (mcr/T .^

Sodium, dissolved (mg/L) 

Bicarbonate (mg/L) 

Alkalinity, total (mg/L CaCO3) 

Sulfate, dissolved (mg/L) 

Chloride, dissolved (mg/L) 

Fluoride, dissolved (mg/L) 

Dissolved solids, calculated (mg/L) 

Sediment, total suspended (mg/L) 

Nitrogen, total NO2 +NO3 (mg/L as N)

Nitrogen, total ammonia (mg/L as N) 

Phosphorus, total (mg/L as P) 

Phosphorus, total ortho (mg/L as P) 

Iron, total recoverable (mg/L) 

l^ll 1 Y"l ITO T"l OCO ^"f~\^"ll V*O^*f~\T7OY"1 V\l O 1 YY1 f/T "\

Number 

of Range 

samples

145 

145 

146 

144 

111 

44 

84 

84 

84 

91 

94 

19 

94 

91 

91 

91 

84 

131 

69 

93 

99 

96 

53 

46

1170 11000

7

C f\ Q Qf\

1

O OA C

0.7- 3250 

4.52 19.0

0.5 8.9

m CMQfl

1 K f\ Q9Q

20.0 645

00 Q 1 QCfk

9fi1 Q1 Q

0.5 38.4

214- 748

ncri KQf\f\

2 9 ^1 fi

0.04 1.7

1 1 40 1 0400

O O QOCA

0.01 0.71

0.01 0.57

0.010- 3.7 

0.001 2.5

0 09 91

0.010 0.41

Optimum (percent 

Preferred relative abundance 

range in parentheses)

2620 4100

8

1 ft ft 91

10.5 19.0

90 93

6.15 6.15

274 274

225- 225

45.6- 45.6

0.02- 0.02 

0.020-0.020 

0.010-0.010

4100(15.3) 

8.18(15.3) 

19.0(15.3) 

20(15.3) 

6.15(15.3) 

3.3(6.3) 

1180(6.3) 

152(6.3) 

195(6.3) 

505(6.3) 

274(10.3) 

5.0(5.7) 

225(10.3) 

1760(6.3) 

12.6(6.3) 

0.9(6.3) 

3240(6.3) 

45.6(10.3) 

0.07(5.7) 

0.02(10.3) 

0.020(10.3) 

0.010(10.3) 

0.34(5.6) 

0.054(5.6)

Ecological summary:

Prefers extremely hard, brackish, sodium sulfate waters; fine to medium gravels (0.2- to 3-cm 

diameter); and medium streams (10 to 100 ft3/s) 

at lower elevations (less than 3,500 ft). Tolerates some suspended sediment and turbidity 

and relatively small concentrations of dissolved 

oxygen. Spring (May and June) dominant.

Distribution summary:

Distributed throughout the study area. Best 

population development in Hanging Woman 

Creek and Cow Creek near Colstrip (station 18).

EXPLANATION

£ PERCENT RELATIVE ABUNDANCE 

EQUAL TO OR GREATER THAN 10

Q PERCENT RELATIVE ABUNDANCE 

LESS THAN 10

DISTRIBUTION MAP

MAJOR DIATOM ECOTYPES 51
ECOTYPE: EPITHEMIA ADNATA (KUTZ.) BREB.

Biotype(s):

E. adnata (Kutz.) Breb. var. adnata 

*E. adnata var. minor (Perag. & Herib.) Pair. 

E. adnata var. porcellus (Kutz.) Pair. 

E. adnata var. proboscidea (Kutz.) Pair.

Reference:

Patrick and Reimer, 1975 (p. 180; pi. 24, 

figs. 7-8)

Herbarium slide number: 

1-2-16

Mean percent relative abundance: 

0.1

Percent occurrence: 

10.5

Abundance-occurrence index: 

1.2

Preferred percent occurrence: 

0.3

Maximum percent relative abundance: 

13.1

Station number: 23 

Date: August 24, 1978 

Type of collection: E

10

Description:

Striae, 12-14 in 10 /on. Costae, 3-5 in 10 /tin. 

Length, 34.0 /-on. Width, 9,7 /on. This species is 

extremely variable in size and in the shape of 

the ends. It is easily distinguished from E. sorex 

in that the central nodule of the raphe is no 

closer to the dorsal margin than about mid-valve, 

whereas in E. sorex the central nodule lies very 

close to the dorsal margin. Distinguished from 

E. turgida (Ehr.) Kutz. by having more rows of 

alveoli between the costae, often more than 4 

rather than 2 to 4 as in E. turgida.

52 ECOLOGY AND DISTRIBUTION OF MAJOR DIATOM ECOTYPES IN MONTANA
Water-quality profile:

Number 

Variable of Range 

samples

Specific conductance (/^mho/cm) 

pH (units) 

Temperature ( °C) ___ __________ 

TurhirHtv fNTTF)

Oxygen, dissolved (mg/L) 

Biochemical oxygen demand (mg/L) 

Hardness, total (mg/L CaCO3) 

Calcium, dissolved (mg/L) 

Magnesium, dissolved (mg/L) 

Sodium, dissolved (mg/L) 

Bicarbonate (mg/L) 

C arbonate (mg/L) 

Alkalinity, total (mg/L CaCO3) 

Sulfate, dissolved (mg/L) 

Chloride, dissolved (mg/L) 

Fluoride, dissolved (mg/L) 

Dissolved solids, calculated (mg/L) 

Sediment, total suspended (mg/L) 

Nitrogen, total NO2 +NO3 (mg/L as N) 

Nitrogen, total ammonia (mg/L as N) 

Phosphorus, total (mg/L as P) 

Phosphorus, total ortho (mg/L as P) 

Iron, total recoverable (mg/L) 

TVflQTl fTQTl f*cSf* ^~O^~<"ll V£**'»nit7'£*VQV*l f* ^TYKT/T ^

26 

26 

26 

24 

14 

3 

17 

17 

17 

17 

20 

6 

20 

17 

17 

15 

17 

24 

6 

15 

20 

21 

12 

10

480 6400

7 Q1 ft 7°.

2.5- 29.2 

07 fi4

4.52 14.3

1.5 3.6

999 3390

40.0- 330

28.3- 605 

1 P; ft 040

m 7Qft

0.5 21.0

146- 654 

17- 4040 

1.8 54.6

O q 17

OOQ coon

1.0- 135 

0.01- 0.37 

0.01- 0.57 

0.010 0.13

0.001 0.079

0.04 1.4

0.025- 0.41

Optimum (percent 

Preferred relative abundance 

range in parentheses)

6400

8 1 n

23.3- 

3.5-

3320- 

330- 

605- 

665-

KQ4

487- 

4040-

ff A f* 54.6-

0.3-

ft9QO

4.4-

0.07- 

0.014

0.010-

6400 

8.10 

23.3 

3.5

3320 

330 

605 

665 

594

487 

4040 

54.6 

0.3 

6290 

4.4

0.07 

0.014 

0.010

6400(13.1) 

8.10(13.1) 

23.3(13.1) 

3.5(13.1) 

14.3(3.9) 

3.6(3.9) 

3320(13.1) 

330(13.1) 

605(13.1) 

665(13.1) 

594(13.1) 

11.0(0.6) 

487(13.1) 

4040(13.1) 

54.6(13.1) 

0.3(13.1) 

6290(13.1) 

4.4(13.1) 

0.05(0.6) 

0.07(13.1) 

0.014(13.1) 

0.010(13.1) 

0.10(3.9) 

0.025(3.9)

Ecological summary:

Preferences sketchy, based on only one occurrence over 10 percent relative abundance. Seems 

to prefer warm, extremely hard, brackish water 

with relatively large concentrations of magnesium and sulfate; fine gravel or larger (greater 

than 0.2-cm diameter); and very small streams 

(0 to 0.1 ft3/s) at 2,500 to 3,000 ft elevation. Tolerates some chloride. Summer (June to August) 

dominant.

Distribution summary:

Recorded from all hydrologic units except 

those representing the Powder and Little Powder 

Rivers. Best population development in the East 

Fork of Armells Creek near Colstrip (station 23).

EXPL AN ATIO N

PERCENT RELATIVE ABUNDANCE 

EQUAL TO OR GREATER THAN 10

PERCENT RELATIVE ABUNDANCE 

LESS THAN 10

DISTRIBUTION MAP

MAJOR DIATOM ECOTYPES 53
ECOTYPE: EPITHEMIA SOREX KUTZ.

Biotype(s):

E. sorex Kutz. var. sorex

Reference:

Patrick and Reimer, 1975 (p. 188; pi. 27, fig. 4)

Herbarium slide number: 

1-2-17

Mean percent relative abundance: 

0.3

Percent occurrence: 

12.2

Abundance-occurrence index: 

3.8

Preferred percent occurrence: 

0.8

Maximum percent relative abundance: 

28.0

Station number: 41 

Date: September 24, 1977 

Type of collection: E

10

Description:

Striae, 12-14 in 10 ftm. Costae, 5-7 in 10 ^m. 

Length, 28.0 ^m. Width, 8.8 ^m. A relatively 

small species of Epithemia with fairly constant 

features. Easily distinguished from E. adnata 

and E. turgida in that the central nodule of the 

raphe occurs very near to the dorsal margin of 

the valve.

54 ECOLOGY AND DISTRIBUTION OF MAJOR DIATOM ECOTYPES IN MONTANA
Water-quality profile:

Variable

Specific conductance (/imho/cm) -

oH (units)

TVmnpratiirp ( °P1

m, _ _.i_ j ' 4.,, /'XTTvr T\ lurbidity (JN 1 U) 

Oxygen, dissolved (mg/L) 

Biochemical oxygen demand (mg/L) 

Hardness, total (mg/L CaCO3) 

Calcium, dissolved (mg/L) 

Magnesium, dissolved (mg/L) 

Sodium, dissolved (mg/L) 

RipflvVinnfl'l'A fin or /T A

f^aT'Vin'nal"^ fmor/T ,^

Alkalinity, total (mg/L CaCO3) ___ 

Sulfate, dissolved (mg/L) 

Chloride, dissolved (mg/L) 

Fluoride, dissolved (mg/L) 

Dissolved solids, calculated (mg/L) 

Sediment, total suspended (mg/L) 

Nitrogen, total NO2 +NO3 (mg/L as N)

Nitrogen, total ammonia (mg/L as N) 

Phosphorus, total (mg/L as P) 

Phosphorus, total ortho (mg/L as P) 

Iron, total recoverable (mg/L) 

Manganese, total recoverable (mg/L) 

Numbe: 

of 

samples

OK

oeOO

OK

34

94

1 a

1 s

18 

20

OK

25 

90

90

1 a

10

34

1 £

18

9C

28

1C

19

r 

Range

3

OOQ OO7fi

7 70 fi ^Q

3

C O/> /"I

O Q q7c

6

(7Q -I Q -I

1

O Q C

145 1100

qq 9 -MO

15.1- 206 

9.5- 396

m

ri-t o

3.0 24.0

124- 584 

43-1440

1.2 174

0.1 1.5

OK/1 OC'Tfl

0.2 741

0.01 0.20

0.01-0.11 

0.010- 0.49

0.001- 0.31 

0.04- 0.75

0 090 0 37

1 

Preferred i 

range

dfZQ QA1 f\

8 OP. P. 9Q

1 q q 14. q

q o 7 q

7 4A 7 A.t\

1100 1100

QQ ^ QQ A

206- 206 

396- 396

278 514

228- 421 

1440 1440

taa 1 a a

O R (\ a

f)d'7r\ OG r7fl

5 0 99 ^

0.01- 0.01 

0.012 0.054

0.001-0.018

Optimum (percent 

relative abundance 

in parentheses)

qm of 1 Q n\

8

fiQ/1 Q O^i

14.3(19.0)

3.6(19.0)

7.45(19.0)

2

1(0 r>\

1100(19.0)

98.4(19.0)

206(19.0) 

396(19.0) 

514(19.0)

7 OC9 71

421(19.0) 

1 440C1 Q 01

16.6(19.0)

0.6(19.0)

9R7on Q n^

5.8(19.0)

0.03(9.0)

0.01(19.0)

O

f\-t nf-t (* o\

0.001(19.0) 

01 7(9 7^

0.050(2.7)

Ecological summary:

Prefers cool, very hard waters; fine to medium 

gravels (0.2- to 3-cm diameter); and middle elevations (3,000 to 3,500 ft). Appears to be somewhat 

sensitive to suspended sediment and turbidity 

and relatively indifferent to stream size and 

total salt content within the study area. Epiphytic on Cladophora. Late summer and fall (September) dominant.

Distribution summary:

Widespread. Prefers the Tongue River drainage and Mizpah Creek.

O

EXPLANATION

PERCENT RELATIVE ABUNDANCE 

EQUAL TO OR GREATER THAN 10

PERCENT RELATIVE ABUNDANCE 

LESS THAN 10

DISTRIBUTION MAP

MAJOR DIATOM ECOTYPES 55
ECOTYPE: FRAGILARIA CAPUCINA DESM.

Biotype(s):

F. capucina Desm. var. capucina 

F. capucina var. acuta Grun. 

F. capucina var. lanceolata Grun. 

*F. capucina var. mesolepta Rabh.

Reference:

Patrick and Reimer, 1966 (p. 119; pi. 3, fig. 6)

Herbarium slide number: 

1-2-19

Mean percent relative abundance: 

0.2

Percent occurrence: 

7.6

Abundance-occurrence index: 

1.2

Preferred percent occurrence: 

0.5

Maximum percent relative abundance: 

19.1

Station number: 12 

Date: October 18, 1979 

Type of collection: E

10

Description:

Striae, 19-20 in 10 ^m. Length, 31.6 ^m. Width, 

3.7 pm. A medium Fragilaria that forms severalcelled colonies, which frequently survive the 

acid-cleaning process intact. Distinguished from 

other common Fragilaria species reported here 

by the condition that the valves of the two most 

common forms are either linear (nominate variety) or constricted in the middle (variety mesolepta), and not lanceolate or centrally inflated.

56 ECOLOGY AND DISTRIBUTION OF MAJOR DIATOM ECOTYPES IN MONTANA
Water-quality profile:

Number 

Variable of Range 

samples

Specific conductance (/imho/cm) 

Temperature (°C)

Turbidity (NTU)

Oxygen, dissolved (mg/L) 

Biochemical oxygen demand (mg/L) 

Hardness, total (mg/L CaCO3) 

Calcium, dissolved (mg/L) 

Magnesium, dissolved (mg/L) 

Sodium, dissolved (mg/L) 

Rir*nT*ViOTi ri'i"fi ("mcff\ }

f^flvVioricitp fmcr/T A

Alkalinity, total (mg/L CaCO3)

Sulfate, dissolved (mg/L) 

Chloride, dissolved (mg/L) 

Fluoride, dissolved (mg/L) 

Dissolved solids, calculated (mg/L) 

Sediment, total suspended (mg/L) 

Nitrogen, total NO2 +NO3 (mg/L as N)

Nitrogen, total ammonia (mg/L as N) 

Phosphorus, total (mg/L as P) 

Phosphorus, total ortho (mg/L as P) 

Iron, total recoverable (mg/L) 

Afln n rrnTif^Qf* ^n^nl T*f^r*mroT*riVklo finrr/T ^

22 

22 

22 

22 

18 

7 

13 

13 

13 

15 

15 

3 

15 

15 

15 

15 

13 

21 

11 

14 

16 

17 

10 

9

270- 4890

7 en Q AK

OK 94 K

0.8 42

7.45 13.1

1.4- 3.0 

124- 1100

OT A 11C

13.5- 206 

9.1- 569 

111- 816 

1.0 5.0

91- 669 

34 1 4.QO

1 Q 9.O Q

0.1- 1.2 

196- 3210 

0.2 135

0.01 0.37

0.01- 0.57 

0.010- 0.11 

0.001 0.047

O AO A. TC

0.005-0.085

Optimum (percent 

Preferred relative abundance 

range in parentheses)

270- 1590

7

QQ Q AO

U Q 1 Q K.

0.8 42

8 CO Q QA

2.2- 2.2

124- 124 

07 A 97 4.

13.5- 13.5 

9.1- 9.1 

111- 111

91- 91 

34 34

10 10

0.1- 0.1 

196- 196 

0.7 42.5

0

1 a ft i a

0.05- 0.05 

0.11- 0.11 

0.031-0.031

O TC A TC

0.080-0.080

1590(19.1) 

7.82(19.1) 

11.9(19.1) 

0.8(19.1) 

8.80(19.1) 

2.2(19.1) 

124(12.5) 

27.4(12.5) 

13.5(12.5) 

9.1(12.5) 

111(12.5) 

1.0(0.8) 

91(12.5) 

34(12.5) 

1.3(12.5) 

0.1(12.5) 

196(12.5) 

0.7(19.1) 

0.16(12.5) 

0.05(12.5) 

0.11(12.5) 

0.031(12.5) 

0.76(12.5) 

0.080(12.5)

Ecological summary:

Prefers cool, fresh to slightly brackish, and 

hard calcium magnesium bicarbonate waters; 

relatively large concentrations of inorganic nitrogen and total phosphorus; and larger streams 

(greater than 100 ft3/s) at middle elevations 

(3,000 to 4,000 ft). Substrate indifferent (tychoplanktonic?). Sensitive to large concentrations of 

suspended sediment and to turbidity. Early 

summer (June and July) and early fall (October) 

dominant.

Distribution summary:

Conspicuously absent from the Powder River 

drainage. Best population development in the 

Upper Tongue-Hanging Woman hydrologic unit.

O

EXPLANATION

PERCENT RELATIVE ABUNDANCE 

EQUAL TO OR GREATER THAN 10

PERCENT RELATIVE ABUNDANCE 

LESS THAN 10

DISTRIBUTION MAP

MAJOR DIATOM ECOTYPES 57
ECOTYPE: FRAGILARIA CONSTRUENS (EHR.) GRUN.

Biotype(s):

*F. construens (Ehr.) Grun. var. construens 

F. construens var. pumila Grun. 

F. construens var. venter (Ehr.) Grun.

Reference:

Patrick and Reimer, 1966 (p. 125; pi. 4, fig. 4)

Herbarium slide number: 

1-2-20

Mean percent relative abundance: 

0.2

Percent occurrence: _ _

__ __ 10 jtm

15.9

Abundance-occurrence index: 

2.6

Preferred percent occurrence: 

0.3

Maximum percent relative abundance: 

10.5

Station number: 26 

Date: November 6, 1979 

Type of collection: E

Description:

Striae, 16-18 in 10 jim. Length, 14.0 jim. Width, 

5.9 jtm. A small, highly variable species of Fragilaria. Patrick (Patrick and Reimer, 1966) speculates that the various varieties are really one 

continuous series and not distinct taxa. Distinguished from F. leptostauron (Ehr.) Hust. and 

varieties by the much finer striae and from the 

other common species reported here by the smaller 

size and more lanceolate rather than linear shape.

58 ECOLOGY AND DISTRIBUTION OF MAJOR DIATOM ECOTYPES IN MONTANA
Water-quality profile:

Variable

Specific conductance (/imho/cm) 

pH (units) 

TWnnpratnrp ( T^

Turbidity (NTU)

OYVCTPTI HiQQnlvoH firicr/T^

Biochemical oxygen demand (mg/L) 

Hardness, total (mg/L CaCO3) 

Calcium, dissolved (mg/L) 

Magnesium, dissolved (mg/L) 

Sodium, dissolved (mg/L) 

Bicarbonate (mg/L) 

Carbonate (mg/L) 

Alkalinity, total (mg/L CaCO3)

Sulfate, dissolved (mg/L) 

Chloride, dissolved (mg/L) 

Fluoride, dissolved (mg/L) 

Dissolved solids, calculated (mg/L) 

Sediment, total suspended (mg/L) 

Nitrogen, total NO2 +NO3 (mg/L as N)

Nitrogen, total ammonia (mg/L as N) 

Phosphorus, total (mg/L as P)

Phosphorus, total ortho (mg/L as P) 

Iron, total recoverable (mg/L) 

liflsiTl era rioco f"ni"al vof*mr£ifaV\1a ftvirr/T *\

Numbe: 

of 

samples

44

44

44

A O

43

on

9

OQ

OQ

00

25

27

c

97

OK

OK

23

OQ

41

17

23 

9Q£j\J

31

Q&

7

r 

Range

3

99.Q A^O

7 7H Q 79

1 fi 9G 9

0.9 435

6.15 13.1

1.2- 3.5 

145 1430

QO 0 1 7Q

i K i 040

9.5- 662 

148- 764

O K 79

m CO7

A-t 9QQH

1

/J -1 o/J

0.1- 12 

254 4020

O Q GQQ

0.01 0.37

0.01- 0.57 

0.010 0.60

0.001- 0.38 

004. 0 9Q

0.010 0.10

1 Preferred i 

range

1020 1020

8.40 8.40

3

K Q K

1.7 1.7

1 Q 1 1 1. 1

3.0- 3.0

55.0- 55.0 

561- 561

460 460

1 loo- CQ 1 looKQ

49 49 '-t.A i-t.£j

0.9- 0.9

1 a 1 ft

0 i K f) i K

0.020 0.020

0.012-0.012 

0.09 0.09

Optimum (percent 

relative abundance 

in parentheses)

1020(10.5)

8.40(10.5)

q K/"| o rc\

1.7(10.5)

13.1(10.5)

3.0(10.5) 

966(3.4)

1 99f°. 4.^

1 crwQ /ii

55.0(10.5) 

561(10.5)

O K(9 7^1

460(10.5)

158(10.5)

4.2(10.5) 

0.9(10.5)

OfiQfWQ A1

1.8(10.5)

0.15(10.5)

0.02(3.4)

0.020(10.5) 

0.012(10.5)

0.09(10.5)

0.10(2.7)

Ecological summary:

Prefers cold, calcium magnesium bicarbonate 

waters; small streams (0.1 to 10 fts/s) at all but 

the very highest elevations (less than 4,000 ft); 

and fine gravel or larger (greater than 0.2-cm 

diameter). Sensitive to large amounts of suspended sediment and turbidity. Spring (May 

and June) and fall (September to November) 

dominant.

Distribution summary:

Widespread. Best population development in 

Lame Deer Creek near Lame Deer (station 26).

O

EXPLANATION

PERCENT RELATIVE ABUNDANCE 

EQUAL TO OR GREATER THAN 10

PERCENT RELATIVE ABUNDANCE 

LESS THAN 10

DISTRIBUTION MAP

MAJOR DIATOM ECOTYPES 59
ECOTYPE: FRAGILARIA CROTONENSIS KITTON

Biotype(s):

F. crotonensis Kitton var. crotonensis

Reference:

Patrick and Reimer, 1966 (p. 121; pi. 3, 

figs. 11-12)

Herbarium slide number: 

1-2-4

Mean percent relative abundance: 

0.6

Percent occurrence: 

21.1

Abundance-occurrence index: 

13.4

Preferred percent occurrence: 

0.8

Maximum percent relative abundance: 

83.3

10

Station number: 51 

Date: undated 

Type of collection: A

Description:

Striae, 16-19 in 10 /mi. Length, 113.0 /mi. 

Width, 3.5 /mi. A very long, slender species of 

Fragilaria. Distinguished by the formation of 

filaments in which the frustules are attached 

only in the middle part of the valve (see drawing).

60 ECOLOGY AND DISTRIBUTION OF MAJOR DIATOM ECOTYPES IN MONTANA
Water-quality profile:

Variable

Specific conductance (/^mho/cm) 

pH (units) 

Tarn nova -hi va (°C*\

Turbidity (NTU)

Oxygen, dissolved (mg/L) 

Biochemical oxygen demand (mg/L) 

Hardness, total (mg/L CaCO3) 

Calcium, dissolved (mg/L) 

Magnesium, dissolved (mg/L) 

SnrHiim rHesesnlvprl fmcr/T,1

Bicarbonate (mg/L) 

Carbonate (mg/L) 

Alkalinity, total (mg/L CaCO3)

Sulfate, dissolved (mg/L) 

Chloride, dissolved (mg/L) 

Fluoride, dissolved (mg/L) 

Dissolved solids, calculated (mg/L) 

Sediment, total suspended (mg/L) 

Nitrogen, total NO2 +NO3 (mg/L as N)

Nitrogen, total ammonia (mg/L as N) 

Phosphorus, total (mg/L as P) 

Phosphorus, total ortho (mg/L as P) 

Iron, total recoverable (mg/L) 

ATflTi cranpeiP fritnl vckprwekvorilek fmcr/T,1

Numbei 

of 

samples

4Q

48

47

44

07

1 C

34

34

34

QC

QC

Q/J

qc

Q*^

34

34

44

00

99

QC

35

9ft

9C

r ( 

Range Preferred r 

5 range

QOQ G-t f\f\

7

c.r\ Q en

2 n ^n ^

O ft Q"7C

6

nn 1 Q Q

07 49

1 9°. 9O9O

1 C A OQQ

20.0- 346 

U K QfiO

1 K T7K.

48 29 0

1 Q CQC

1 17-ooOU <~1 OOCA -

1

0 1 f)C

0

9 13

184 5560

0 Q 741 v. */ I L ±.

0 01 0 71

0.01 0.11

0 \J ,\J 010 ±\J 0 \J,L\J 4Q

0.002-0.31 

0.04 1.1

O m Q n 9Q

Dptimum (percent 

 elative abundance 

in parentheses)

AQfW7 91

7 Qi/7 O\

1 ft QC7 9*1

2

f)(C Q\

1 9 ftf^ 1 ^

3.3(4.5)

ooc/'7 9^

49 ft^T 91

28.8(7.2)

1 ^ ft^7 91

9ft1f7 91

4.8(4.4)

9q(Y7 o\

1 7(7 91

1 ftf7 9^

i 0^7 9^

q$3Q/'7 9\

3

KfC Q\

O OCfJ f)\

0 0°.f7 91

0 O^OC7 91

0.016(7.2)

0 1 0(7 91

0.045(7.2)

Ecological summary:

Prefers fresh, calcium magnesium bicarbonate 

waters; and large streams (greater than 100 ft3/s) 

at middle elevations (3,000 to 3,500 ft). Planktonic. Sensitive to large concentrations of suspended sediment and to turbidity. Summer and 

fall (August to October) dominant.

Distribution summary:

Widespread. Best population development in 

standing waters in the Rosebud Creek and upstream Tongue River drainages. Incidental in 

streams downstream from impoundments.

EXPLANATION

PERCENT RELATIVE ABUNDANCE 

EQUAL TO OR GREATER THAN 10

PERCENT RELATIVE ABUNDANCE 

LESS THAN 10

DISTRIBUTION MAP

MAJOR DIATOM ECOTYPES 61
ECOTYPE: FRAGILARIA VAUCHERIAE (KUTZ.) PETERS.

Biotype(s):

F. vaucheriae (Kutz.) Peters, var. vaucheriae

Reference:

Patrick and Reimer, 1966 (p. 120; pi. 3, 

figs. 14-15)

Herbarium slide number: 

1-3-1

Mean percent relative abundance: 

1.4

Percent occurrence:

52.2 ^3 10

Abundance-occurrence index:

74.4

Preferred percent occurrence: 

4.3

Maximum percent relative abundance: 

45.1

Station number: 50 

Date: October 30, 1979 

Type of collection: E

Description:

Striae, 15-16 in 10 /mi. Length, 20.0 /on. Width, 

3.1 /mi. A medium Fragilaria, easily distinguished from other species by its asymmetrical, 

somewhat swollen central area.

62 ECOLOGY AND DISTRIBUTION OF MAJOR DIATOM ECOTYPES IN MONTANA
Water-quality profile:

Variable

Specific conductance (jttmho/cm) 

pH (units) 

T'omnovafiivo ( °C*\

Turbidity (NTU)

Oxygen, dissolved (mg/L) 

Biochemical oxygen demand (mg/L) 

Hardness, total (mg/L CaCO3) 

Calcium, dissolved (mg/L) 

Magnesium, dissolved (mg/L) 

Sodium, dissolved (mg/L) 

Bicarbonate (mg/L) 

Carbonate (mg/L) 

Alkalinity, total (mg/L CaCO3) 

Sulfate, dissolved (mg/L) 

Chloride, dissolved (mg/L) 

Fluoride, dissolved (mg/L) 

Dissolved solids, calculated (mg/L) 

Sediment, total suspended (mg/L) 

Nitrogen, total NO2 +NO3 (mg/L as N)

Nitrogen, total ammonia (mg/L as N) 

Phosphorus, total (mg/L as P) 

Phosphorus, total ortho (mg/L as P) 

Iron, total recoverable (mg/L) 

Manganese, total recoverable (mg/L) 

Number 

of 

samples

148

148

147

143

109 

45 

85 

85

otr

Q4

100

1 ft

100 

94 

94 

90

OKoo 

134

7C

ft7

103 

103 

60 

49

Range

270 5080

7

CA O Q A .50- o.oO

1.0 30.5

0.5 435

5.40- 15.0 

0.5- 8.3 

123-2400 

16.0- 187

1 O K. AC'7

9

1 CCO

1 K. HHC

0.5 38.4

13- 636 

17-3150 

0.4- 174 

0.1- 1.5 

184 4650

O o fiQQ

0.01 0.80

0.01 0.30

0.010- 0.60 

0.001- 0.38 

0.02- 2.1 

0.005- 0.39

( 

Preferred i 

range

QQQ OQAA

8

AO Q AQ

2

f\ 1 C 1

1 7 QA

10.00- 13.8 

1.7- 3.0 

424- 635 

70.7- 125 

60.0 81.0

56.0 480

OK7 CAQ

211- 498 

308- 1290 

4.8- 31.1 

0.3- 0.6

7C7 oq70

1.1 310

O AQ A CO

0.01 0.05

0.010- 0.25 

0.002- 0.15 

0.08- 0.32 

0.070-0.090

Optimum (percent 

 elative abundance 

in parentheses)

1000(45.1)

8.38(45.1)

10.00(45.1)

1.7(45.1)

13.8(36.6) 

1.8(19.5) 

468(36.6) 

83.2(36.6)

/JO A/QC d\

RA A/QC K\

301(45.1)

38.4(8.4)

247(45.1) 

320(36.6) 

5.2(36.6) 

0.3(36.6)

QA 1 C^R R\

K n(AK. 1 \

0.08(45.1)

0.01(19.5)

0.020(36.6) 

0.002(36.6) 

0.21(19.5) 

0.090(19.5)

Ecological summary:

Prefers cool, fresh to slightly brackish, welloxygenated waters; fine gravels or larger (greater 

than 0.2-cm diameter) and larger streams (greater 

than 1 ft3/s) at lower elevations (less than 3,500 ft). 

Tolerates some suspended sediment and turbidity. Tychoplanktonic. Spring (February to March) 

and fall (October to November) dominant; 

winter(?).

Distribution summary:

Widespread. Best population development in 

western part of the study area.

EXPLANATION

PERCENT RELATIVE ABUNDANCE 

EQUAL TO OR GREATER THAN 10

PERCENT RELATIVE ABUNDANCE 

LESS THAN 10

DISTRIBUTION MAP

MAJOR DIATOM ECOTYPES 63
ECOTYPE: FRAGILARIA SPECIES X

Biotype(s):

F. sp. X var. X

Reference: 

None

Herbarium slide number: 

1-2-18

Mean percent relative abundance: 

0.1

Percent occurrence: 

1.4

Abundance-occurrence index: 

0.1

Preferred percent occurrence: 

0.3

Maximum percent relative abundance: 

10.7

Station number: 35 

Date: October 28, 1979 

Type of collection: F

Description:

Striae, 15-17 in 10 jan. Length, 17.0 jim. Width, 

4.0 jim. A small, highly variable species of Fragilaria with narrow, subcapitate ends and offset 

striae. A unilateral central area, occurring almost to the valve margin, may be present on 

one or both valves or be entirely absent. Sometimes "ghost striae" are present in the central 

area. It is distinguished from F. vaucheriae and 

varieties principally in that the central area, 

when present, is not swollen and does not extend to the valve margin. It is very similar to F. 

construens var.javanica Hust., except in its frequent formation of a central area. A search 

through the Iconograph Reference File, the 

Diatom Herbarium, and pertinent literature at 

the Academy of Natural Sciences of Philadelphia failed to reveal the identity of this diatom. 

It is therefore assumed to be new to science.

10

64 ECOLOGY AND DISTRIBUTION OF MAJOR DIATOM ECOTYPES IN MONTANA
Water-quality profile:

Number 

Variable of Range 

samples

Specific conductance (/^mho/cm) -

pH (units) 

Tpmnprntnrp ( °P1

Tiirhiditv (NTTD

Oxygen, dissolved (mg/L) 

Biochemical oxygen demand (mg/L) 

Hardness, total (mg/L CaCO3) 

Calcium, dissolved (mg/L) 

Magnesium, dissolved (mg/L) 

Sodium, dissolved (mg/L) 

Bicarbonate (mg/L) 

C arbonate (mg/L) 

Alkalinity, total (mg/L CaCO3)

Snlfn1"p HiGcnlvpH (mcrfl J\

Chloride, dissolved (mg/L) 

Fluoride, dissolved (mg/L) 

Dissolved solids, calculated (mg/L) 

Sediment, total suspended (mg/L) 

Nitrogen, total NO2 +NO3 (mg/L as N)

Nitrogen, total ammonia (mg/L as N) 

Phosphorus, total (mg/L as P) 

Phosphorus, total ortho (mg/L as P) 

Iron, total recoverable (mg/L) 

ATflncrji'npQp total vppnvpvnVilp ^mcr/I,^

2 

2 

2 

2 

0 

0 

0 

0 

0 

0 

2 

2 

2 

0 

0 

0 

0 

2 

2 

2 

2 

2 

0 

0

QQ8

a 40

10.5-

3

c

one

0.0

242-

C A

0.00

0.00

0.000

0.005-

1500 

8.49 

12.0 

9.8

514 

0.0 

421

 

18.8 

0.00 

0.02 

0.020 

0.008

Optimum (percent 

Preferred relative abundance 

range in parentheses)

1500

Q 4.9

If) C

9

Q

514

0.0

421-

18.8- 

0.00

0.02

0.020

0.008-

1500 

8.42 

10.5 

9.8

_____

514 

0.0 

421

_____

18.8 

0.00 

0.02 

0.020 

0.008

1500(10 

8.42(10 

10.5(10 

9.8(10

514(10 

0.0(10 

421(10

______

18.8(10 

0.00(10 

0.02(10 

0.020(10 

0.008(10

.7) 

.7) 

.7) 

.7)

.7) 

.7) 

.7)

.7) 

.7) 

.7) 

.7) 

.7)

Ecological summary:

Prefers cool, slightly brackish waters of pH 

greater than 8.00 (alkalibiontic), and larger 

streams (10 to 100 ft3/s). Tolerates some suspended sediment and turbidity. Fall (October) 

dominant. Limited environmental information.

Distribution summary:

Found only in Rosebud Creek near Colstrip 

(station 35) and the Tongue River near Brandenburg (station 47). Dominant in Rosebud Creek.

EXPLANATION

PERCENT RELATIVE ABUNDANCE 

EQUAL TO OR GREATER THAN 10

PERCENT RELATIVE ABUNDANCE 

LESS THAN 10

DISTRIBUTION MAP

MAJOR DIATOM ECOTYPES 65
ECOTYPE: GOMPHONEMA ANGUSTATUM (KUTZ.) RABH.

Biotype(s):

*G. angustatum (Kutz.) Rabh. var. angustatum 

G. angustatum var. citera (Hohn and Hellerm.)

Patr.

G. angustatum var. intermedia Grun. 

G. angustatum var. obtusatum (Kutz.) Grun. 

G. angustatum var. sarcophagus (Greg.) Grun.

Reference:

Patrick and Reimer, 1975 (p. 125; pi. 17, 

figs. 17-19)

Herbarium slide number: 

1-3-2

Mean percent relative abundance: 

0.4

Percent occurrence: 

34.3

Abundance-occurrence index: 

14.7

Preferred percent occurrence: 

0.8

Maximum percent relative abundance: 

18.0

Station number: 37 

Date: May 13, 1979 

Type of collection: E

10 (Jim

Description:

Striae, 12-14 in 10 /-tin. Length, 24.8 ^m. Width,

6.0 /nm. Distinguished by the somewhat protracted, 

often rostrate apices and by a single isolated 

punctum in the central area. Patrick (Patrick 

and Reimer, 1975) speculates that further study 

may indicate that the varieties of this species 

intergrade with the nominate variety and are 

not distinct.

66 ECOLOGY AND DISTRIBUTION OF MAJOR DIATOM ECOTYPES IN MONTANA
Water-quality profile:

Variable

Specific conductance (^mho/cm) 

r»TT Ainife^

TV^mnovof nvo ( °C*\

Turbidity (NTU) __ ____________ 

Oxygen, dissolved (mg/L) - _ 

Biochemical oxygen demand (mg/L) 

Hardness, total (mg/L CaCO3) 

Calcium, dissolved (mg/L) 

Magnesium, dissolved (mg/L) 

Sodium, dissolved (mg/L) 

Bicarbonate (mg/L) 

Carbonate (mg/L) 

Alkalinity, total (mg/L CaCO3) _______ 

Sulfate, dissolved (mg/L) 

Chloride, dissolved (mg/L) 

Fluoride, dissolved (mg/L) 

Dissolved solids, calculated (mg/L) 

Sediment, total suspended (mg/L) 

Nitrogen, total NO2 +NO3 (mg/L as N)

Nitrogen, total ammonia (mg/L as N) 

Phosphorus, total (mg/L as P) 

Phosphorus, total ortho (mg/L as P) 

Iron, total recoverable (mg/L) 

A/1 o T"i rro nf* of* 4"^if"ol T*rto^rtTrtT*o V\lf* iTnir/T ^

Number 

of Range 

samples

107 

107 

108 

107 

77 

27 

73 

73 

73 

76 

77 

17 

77 

76 

76 

71 

73 

97 

58 

72 

80 

82 

47 

45

oqn fiinn

7 efl Q <7Q

1.7- 30.2

0.7-11600 

500 1 Q n

0.8- 7.8 

qo 9400

017 A OQQ

5.0- 467

9

1 1 9QO

m Q1 K.

1.0- 22.0 

91- 669 

34- 3350 

0.4 126

0.1- 1.7 

196 5560

O

o oo/;nn

0.01- 0.71 

0.01 0.22

0.010 3.7

0.001 2.5

0.02- 2.1 

0.005 0.37

Optimum (percent 

Preferred relative abundance 

range in parentheses)

1210 6100

8.00 8.50

13.3- 18.3 

14- 46 

9.30- 10.2 

2.6- 4.2 

1 090 9090

124- 238 

173- 346 

410- 960

KQ7 fi47

481- 530 

1370- 3350 

14.0 15.2

0.3- 0.6

OC'7r» K.K.df\

94 9 fi4 9

0.01- 0.01 

0.02 0.02

0.050 0.090

0.009 0.041

0.51- 0.79 

0.18 0.20

3090(18.0) 

8.12(18.0) 

13.3(18.0) 

24(18.0) 

10.2(18.0) 

2.6(18.0) 

1020(18.0) 

124(18.0) 

173(18.0) 

410(18.0) 

587(18.0) 

5.0(6.1) 

481(18.0) 

1370(18.0) 

14.0(18.0) 

0.3(18.0) 

2670(18.0) 

64.2(18.0) 

0.01(18.0) 

0.02(18.0) 

0.050(18.0) 

0.021(18.0) 

0.79(18.0) 

0.18(18.0)

Ecological summary:

Prefers cool, brackish, extremely hard, sodium 

sulfate waters; fine gravels or larger (greater 

than 0.2-cm diameter); and all but the very 

largest streams (less than 100 ft3/s) at lower and 

middle elevations (less than 4,000 ft). Somewhat 

sensitive to suspended sediment and turbidity. 

Spring (May) and fall (October) dominant.

Distribution summary:

Widespread. Best population development in 

Sarpy Creek and tributaries to the Tongue River.

O

EXPLANATION

PERCENT RELATIVE ABUNDANCE 

EQUAL TO OR GREATER THAN 10

PERCENT RELATIVE ABUNDANCE 

LESS THAN 10

DISTRIBUTION MAP

MAJOR DIATOM ECOTYPES 67
ECOTYPE: GOMPHONEMA OLIVACEUM (LYNGB.) KUTZ.

Biotype(s):

*G. olivaceum (Lyngb.) Kutz. var. olivaceum 

G. olivaceum var. calcarea (Cl.) Cl.

Reference:

Patrick and Reimer, 1975 (p. 139; pi. 18, 

figs. 13-14)

Herbarium slide number: 

1-3-3

Mean percent relative abundance: 

2.1

Percent occurrence: 

58.1

Abundance-occurrence index: 

121.5

Preferred percent occurrence: 

6.2

Maximum percent relative abundance: 

49.7

10 (Jim

Station number: 7 

Date: May 20, 1979 

Type of collection: E

Description:

Striae, 11-13 in 10 pm. Length, 21.8 /*m. Width, 

7.0 jum. The only common Gomphonema in the 

study area without an isolated punctum in the 

central area.

68 ECOLOGY AND DISTRIBUTION OF MAJOR DIATOM ECOTYPES IN MONTANA
Water-quality profile:

Variable

Specific conductance (/^mho/cm) 

pH (units) 

Tprrmpratnrp ( °fM

Turbiditv fNTTD

Oxygen, dissolved (mg/L) 

Biochemical oxygen demand (mg/L) 

Hardness, total (mg/L CaCO3) 

Calcium, dissolved (mg/L) 

Magnesium, dissolved (mg/L) 

Sodium, dissolved (mg/L) 

Bicarbonate (mg/L) 

Carbonate (mg/L) 

Alkalinity, total (mg/L CaCO3 )

Sulfate, dissolved (mg/L) 

Chloride, dissolved (mg/L) 

Fluor ide, dissolved (mg/L) 

Dissolved solids, calculated (mg/L) 

Sediment, total suspended (mg/L) 

Nitrogen, total NO2 +NO3 (mg/L as N)

Nitrogen, total ammonia (mg/L as N) 

Phosphorus, total (mg/L as P) 

Phosphorus, total ortho (mg/L as P) 

Iron, total recoverable (mg/L) 

Ivl Q n CTQ YIOCO ^~ni"al vof*fnrovo rtlo iYYirr/T ^

Number 

of Range 

samples

166 

166 

166 

161 

127 

53 

105 

105 

105 

111 

116 

24 

116 

111 

111 

108 

105 

154 

91 

95 

118 

123 

71 

64

9QQ

7.50- 

1.7

n P»

4

Pi9

0.5- 

124- 

97 4

1 Q K

Q 1

1 Pi

1.0

1 *3

34

0.4- 

0.1- 

184- 

0.2- 

0.01

0.01

0.010

0.001

0.02

0.005

11000 

8.80 

27.3 

4200 

15.3 

8.9 

3490 

328 

645 

1950 

764 

38.4 

627 

6900 

88.9 

1.7 

10400 

8260 

0.80 

0.22 

3.7 

2.5 

2.1 

0.41

Optimum (percent 

Preferred relative abundance 

range in parentheses)

292- 

7 QO

3.5- 

1.7

7.60- 

1.0- 

145- 

33.2- 

i ^ i

9.5- 

i Pii

i 94

43- A O

1.6- 

0.1- 

254- 

1.1- 

0.01- 

0.01

0.020

0.002

0.09

O nPiPi

3520 

8.40 

21.0 

24 

13.8 

3.0 

1120 

151 

183 

502 

730

598 

1690 

14.0 

0.9 

3030 

64.2 

0.66 

0.22 

0.099 

0.021 

0.83 

0.18

818(49 

8.28(49 

12.9(49 

17(49 

9.33(49 

1.4(49 

456(49 

81.3(49 

61.0(49 

17.2(49 

402(49 

7.0(6 

330(49 

156(49 

2.5(49 

0.5(49 

721(49 

51.2(49 

0.07(44 

0.01(44 

0.060(49 

0.017(49 

0.31(38 

0.055(38

.7) 

.7) 

.7) 

.7) 

.7) 

.7) 

.7) 

.7) 

.7) 

.7) 

.7) 

.7) 

.7) 

.7) 

.7) 

.7) 

.7) 

.7) 

.1) 

.1) 

.7) 

.7) 

.0) 

.0)

Ecological summary:

Prefers cool, fresh to slightly brackish, calciummagnesium bicarbonate waters; fine gravel or 

larger (greater than 0.2-cm diameter); and medium to large streams (greater than 1 ft3/s) at 

the middle elevations (2,500 to 4,000 ft). Tolerates some suspended sediment and turbidity. 

Fall to winter(?) to spring (October-?-June) 

dominant.

Distribution summary:

Widespread. Best population development in 

the western part of the study area.

O

EXPLAN ATIO N

PERCENT RELATIVE ABUNDANCE 

EQUAL TO OR GREATER THAN 10

PERCENT RELATIVE ABUNDANCE 

LESS THAN 10

DISTRIBUTION MAP

MAJOR DIATOM ECOTYPES 69
ECOTYPE: GOMPHONEMA TENELLUM KUTZ.

Biotype(s):

G. tenellum Kutz. var. tenellum

Reference:

Patrick and Reimer, 1975 (p. 124; pi. 17, 

figs. 16a-b)

Herbarium slide number: 

1-3-4

Mean percent relative abundance: 

0.5

Percent occurrence: 

20.8

Abundance-occurrence index: 

10.6

Preferred percent occurrence: 

1.1

Maximum percent relative abundance: 

17.0

10

Station number: 9 

Date: August 27, 1978 

Type of collection: C

Description:

Striae, 11-13 in 10 /mi. Length, 17.6 /mi. Width, 

4.0 /mi. Distinguished from the other two common species of Gomphonema from the study 

area by having an isolated punctum in the central area and ends that are not protracted.

70 ECOLOGY AND DISTRIBUTION OF MAJOR DIATOM ECOTYPES IN MONTANA
Water-quality profile:

Variable

Number

of 

samples

Range Preferred 

range

Optimum (percent

relative abundance

in parentheses)

Specific conductance (/miho/cm) 71 292-4350 610- 882 610(17.0)

pH (units) 71 7.70-8.80 8.00-8.37 8.20(17.0)

Temperature (°C) 72 2.0-30.5 18.1- 20.0 18.1(17.0)

Turbidity (NTU) 71 0.5- 190 1.4- 12 2.2(17.0)

Oxygen, dissolved (mg/L) 49 5.22-13.2 7.70- 9.10 7.70(14.2)

Biochemical oxygen demand (mg/L) 15 1.0- 3.5 1.0- 2.2 2.2(14.2)

Hardness, total (mg/L CaCO3) 44 123-1430 288- 375 288(17.0)

Calcium, dissolved (mg/L) 44 16.0-183 58.4-69.6 58.4(17.0)

Magnesium, dissolved (mg/L) 44 15.1- 242 34.5- 48.9 34.5(17.0)

Sodium, dissolved (mg/L) 46 9.5- 662 12.8- 31.1 26.9(17.0)

Bicarbonate (mg/L) 47 15- 776 222- 392 222(17.0)

Carbonate (mg/L) 18 0.5-38.4 7.0(6.7)

Alkalinity, total (mg/L CaCO3) 47 13-636 182- 321 182(17.0)

Sulfate, dissolved (mg/L) 46 43-2390 69- 163 149(17.0)

Chloride, dissolved (mg/L) 46 0.4-21.4 2.4- 3.4 3.1(17.0)

Fluoride, dissolved (mg/L) 45 0.1- 1.2 0.3- 0.6 0.3(17.0)

Dissolved solids, calculated (mg/L) 44 184-4020 494- 596 494(17.0)

Sediment, total suspended (mg/L) 68 0.8- 413 2.9- 67.4 3.5(17.0)

Nitrogen, total NO2 +NO3 (mg/L as N) 38 0.01-0.80 0.08- 0.08 0.08(14.2)

Nitrogen, total ammonia (mg/L as N) 41 0.01-0.05 0.01-0.02 0.01(17.0)

Phosphorus, total (mg/L as P) 49 0.010-0.25 0.014-0.064 0.014(17.0)

Phosphorus, total ortho (mg/L as P) 51 0.001-0.15 0.006-0.023 0.006(17.0)

Iron, total recoverable (mg/L) 38 0.02- 1.4 0.59- 0.59 0.59(14.2)

Manganese, total recoverable (mg/L) 35 0.005-0.15 0.095-0.095 0.095(14.2)

Ecological summary:

Prefers fresh, calcium-magnesium bicarbonate 

waters; fine to medium gravels (0.2- to 3-cm diameter); and larger streams (greater than 10 ft3/s) 

at middle elevations (3,000 to 4,000 ft). Stenothermal between 18 and 20 °C. Sensitive to 

large amounts of suspended sediment and turbidity. Summer (July to September) dominant.

Distribution summary:

Found in all areas except the Middle Powder 

and Lower Powder hydrologic units. Best population development in the upstream Tongue 

River and Rosebud Creek drainages.

EXPLANATION

PERCENT RELATIVE ABUNDANCE 

EQUAL TO OR GREATER THAN 10

PERCENT RELATIVE ABUNDANCE 

LESS THAN 10

DISTRIBUTION MAP

MAJOR DIATOM ECOTYPES 71
ECOTYPE: MELOSIRA VARIANS C. A. AG.

Biotype(s):

M. varians C. A. Ag. var. varians

Reference:

Hustedt, 1930b (p. 85; fig. 41)

Herbarium slide number: 

1-3-5

Mean percent relative abundance: 

0.3

Percent occurrence: 

22.7

Abundance-occurrence index: 

6.2

Preferred percent occurrence: 

0.8

Maximum percent relative abundance: 

30.4

10

Station number: 29 

Date: September 8, 1978 

Type of collection: E

Description:

Diameter, 13.3 /tm. Length of frustule (girdle 

view), 25.3 /im. A large species of Melosira, most 

frequently found in girdle view. Distinguished 

from other species of this genus by the absence 

of visibly distinctive ornamentation.

72 ECOLOGY AND DISTRIBUTION OF MAJOR DIATOM ECOTYPES IN MONTANA
Water-quality profile:

Variable

pH (units) 

Temperature (°C)

Turbidity (NTU)

Oxygen, dissolved (mg/L) 

Biochemical oxygen demand (mg/L) 

Hardness, total (mg/L CaCO,) 

7 \ O O'

Calcium, dissolved (mg/L) 

ATacmpsriiTm Hissssnlv^H (mcr/T ,^

Sodium, dissolved (mg/L) 

Bicarbonate (mg/L) 

Carbonate (mg/L) 

Alkalinity, total (mg/L CaCO3) 

Sulfate, dissolved (mg/L) 

Chloride, dissolved (mg/L) 

Fluoride, dissolved (mg/L) 

Dissolved solids, calculated (mg/L) 

Sediment, total suspended (mg/L) 

Nitrogen, total NO2 +NO3 (mg/L as N)

Nitrogen, total ammonia (mg/L as N) 

Phosphorus, total (mg/L as P) 

Phosphorus, total ortho (mg/L as P) 

Iron, total recoverable (mg/L) 

Manganese, total recoverable (mg/L) 

Numbej 

of 

samples

70

70

70

cc

C1

99

41

41

41

47 

49*±^

q^

49

47

47

47

41

CQ

44

41 

57 

57 

41

QC

Range

5

OQQ A99fl

7

CA o cn .50- 0.59

2

ft OK Q

0.5 190

6

rro 1 Q 7

O f^ ^ ^

124 1080

97 4. 1 ^4

i Q c 1 q4.

9.1- 385 

111 754

90 94 0

91- 618 

34 1070

1.2 51.6

0.1 1.5

1 QK 9^inn

0.2 413

0.01 0.38

0.01- 0.07 

0.010- 0.11 

0.001- 0.12 

0.04- 0.76 

0.005 0.39

<

Preferred i 

range

OOO 1 COA 666- 15oO

8 fl9 ft OQ

1 ft o 9n Q

0.5 24

8

f\r\ 100

1.4 1.4

CRTI 7ftf4

71 7 ft7 O

-1 -1 Q -1 Q>7

100- 118

ci T ccn

424- 467 

436 498

4.9 5.7

0.7 0.7

1250 1410

0.6 3.4

0.02 0.06

0.04- 0.04 

0.030-0.030 

0.007-0.015 

0.13- 0.18 

0.040 0.058

Dptimum (percent 

 elative abundance 

in parentheses)

1580(30.4)

8.08(30.4)

20.3(30.4)

1.7(30.4)

8.00(14.9)

1 4(1 4 q^

7QA/OA A\

ft7 OfQfi A\

137(30.4)

118(30.4) 

569(30.4)

24.0(0.9)

467(30.4) 

498(30.4)

4.9(30.4)

0.7(30.4)

1410(30.4)

3.4(30.4)

0.06(30.4)

0.04(30.4) 

0.030(30.4) 

0.015(30.4) 

0.18(30.4) 

0.058(30.4)

Ecological summary:

Prefers fresh to slightly brackish, magnesium 

sulfate bicarbonate waters; pH between 8.00 and 

8.30; fine sand or larger (greater than 0.05-mm 

diameter); and larger streams (greater than 1 

ft3/s) at middle elevations (3,000 to 3,500 ft). 

Stenothermal between 18 and 21 °C. Sensitive 

to small amounts of suspended sediment and 

chloride. Summer dominant (June to September).

Distribution summary:

Conspicuously absent from the Powder River 

drainage. Best population development in Muddy 

Creek near Busby (station 29) and the upstream 

part of the Tongue River.

O

EXPLANATION

PERCENT RELATIVE ABUNDANCE 

EQUAL TO OR GREATER THAN 10

PERCENT RELATIVE ABUNDANCE 

LESS THAN 10

DISTRIBUTION MAP

MAJOR DIATOM ECOTYPES 73
ECOTYPE: NAVICULA CINCTA (EHR.) RALFS VAR. CINCTA

Biotype(s):

N. cincta (Ehr.) Ralfs var. cincta

Reference:

Patrick and Reimer, 1966 (p. 516; pi. 49, fig. 8)

Herbarium slide number: 

1-3-6

Mean percent relative abundance: 

1.9

Percent occurrence: 

51.9

Abundance-occurrence index: 

100.4

Preferred percent occurrence: 

6.2

Maximum percent relative abundance: 

43.1

Station number: 5 

Date: August 7, 1979 

Type of collection: E

10 (Am

Description:

Striae, 10-14 in 10 /mi. Length, 30.2 /mi. Width, 

6.6 /mi. Distinguished from similar species of 

Nauicula by the characteristic transverse central area. Patrick and Reimer (1966, p. 516) describe the central area as "sometimes formed by 

the striae at the center of the valve being shorter 

than the others and more distant from each 

other; at other times the two central striae reach 

almost to the central nodule while those on each 

side are much shorter, thus giving the central 

area an irregular appearance." In our specimens, 

the striae at the valve ends are not as dense as 

stated by Patrick and Reimer (". . . to 17 in 10 

/mi at the ends"). However, our specimens do 

have the characteristic central area, which sets 

them apart from N. heufleri Grun. and varieties.

74 ECOLOGY AND DISTRIBUTION OF MAJOR DIATOM ECOTYPES IN MONTANA
Water-quality profile:

Variable

Specific conductance (/imho/cm) 

nPoTTirkovQf ii-ro ( °C( \

Turhiditv CNTTT^

Oxygen, dissolved (mg/L) 

Biochemical oxygen demand (mg/L) 

Hardness, total (mg/L CaCO3) 

Calcium, dissolved (mg/L) 

Magnesium, dissolved (mg/L) 

Sodium, dissolved (mg/L) 

Bicarbonate (mg/L) 

Carbonate (mg/L) 

Alkalinity, total (mg/L CaCO3)

Sulfate, dissolved (mg/L) 

Chloride, dissolved (mg/L) 

Fluoride, dissolved (mg/L) 

Dissolved solids, calculated (mg/L) 

Sediment, total suspended (mg/L) 

Nitrogen, total NO2 +NO3 (mg/L as N) 

Nitrogen, total ammonia (mg/L as N) 

Phosphorus, total (mg/L as P) 

Phosphorus, total ortho (mg/L as P) 

TvfiTI tfltll V£l^*fnrovo r\l f\ iTmrtl* *

Manganese, total recoverable (mg/L) 

Number 

of Range 

samples

165 

165 

164 

163 

117 

39 

93 

93 

93 

99 

103 

21 

103 

99 

99 

95 

93 

145 

70 

100 

113 

111 

47 

44

480

7.41- 

1 3

0.7

0.80-

O c

92- 

16.0- 

5.0- 

15.8- 

171-

O c

146- 

17

0.4- 

0.1- 

389- 

0 4 '

0.01- 

0.01- 

0.010

0.001

0.04- 

0.005

11000 

8.73 

30.5 

11600 

19.0 

8.3 

3490 

328 

645 

1950 

913 

36.0 

748 

6900 

174 

1.7 

10400 

22600 

0.71 

0.57 

3.7 

2.5 

2.1 

0.41

Optimum (percent 

Preferred relative abundance 

range in parentheses)

900

7 R9

If) C

9 A.

5.40

5 9

92- 

16.0- 

5.0- 

1 33

261- 

2.4

214

3RH

2 2

0.6- 

992-

3

C

0.02- 

0.01

0.020

0.005

O

n A .34-

0.054

3810 

8.73 

30.5 

11600 

12.1 

5.2 

1250 

179 

204 

835 

776 

26.0 

636 

1560 

24.0 

0.8 

3260 

22600 

0.12 

0.08 

0.25 

0.22 

2.1 

0.27

3270(43.1) 

8.46(43.1) 

25.9(43.1) 

26(43.1) 

8.48(43.1) 

5.2(26.9) 

981(27.8) 

85.6(27.8) 

186(27.8) 

390(27.8) 

630(27.8) 

2.4(27.8) 

521(27.8) 

1230(27.8) 

10.4(27.8) 

0.7(27.8) 

2540(27.8) 

46.6(43.1) 

0.02(43.1) 

0.02(43.1) 

0.080(43.1) 

0.031(43.1) 

0.46(14.3) 

0.095(14.3)

Ecological summary:

Prefers somewhat brackish, moderately hard 

to extremely hard sodium sulfate waters; fine 

gravels or larger (greater than 0.2-cm diameter); 

and lower elevations (less than 3,500 ft). Apparently indifferent to stream size, large concentrations of suspended sediment, and turbidity. 

Eurythermal between 10 and 31°C. Summer 

(June to August) dominant.

Distribution summary:

Found throughout the study area. A dominant 

in all but the Little Powder and Lower Powder 

hydrologic units.

O

EXPL AN ATI ON

PERCENT RELATIVE ABUNDANCE 

EQUAL TO OR GREATER THAN 10

PERCENT RELATIVE ABUNDANCE 

LESS THAN 10

DISTRIBUTION MAP

MAJOR DIATOM ECOTYPES 75
ECOTYPE: NAVICULA CINCTA VAR. ROSTRATA REIM.

Biotype(s):

N. cincta var. rostrata Reim.

Reference:

Reimer, 1961 (p. 314; pi. 1, fig. 1)

Herbarium slide number: 

1-3-7

Mean percent relative abundance: 

2.2

Percent occurrence: 

76.5

Abundance-occurrence index: 

167.6

Preferred percent occurrence: 

5.4

Maximum percent relative abundance: 

25.3

Station number: 23 

Date: October 28, 1979 

Type of collection: E

10

Description:

Striae, 15-16 in 10 /mi. Length, 24.3 /mi. Width, 

5.5 /mi. This variety has rostrate ends, which 

make it easily distinguishable from the nominate variety in which the ends are attenuate 

and not set off from the valve body. Other features are very similar to those of the nominate 

variety, including the typically transverse central area.

76 ECOLOGY AND DISTRIBUTION OF MAJOR DIATOM ECOTYPES IN MONTANA
Water-quality profile:

Variable

Specific conductance (/imho/cm) 

nTT ^/j.A fnnitcA \ U.J.J.J. VO/ ______ __ __________ ^. . .^ .^^ . _ _

Temperature ( °C) _____ ___ __ 

Turbidity (NTU)

Oxygen, dissolved (mg/L) 

Biochemical oxygen demand (mg/L) 

Hardness, total (mg/L CaCO3) 

Calcium, dissolved (mg/L) 

Magnesium, dissolved (mg/L) 

Sodium, dissolved (mg/L) 

Bicarbonate (mg/L) 

Carbonate (mg/L) 

Alkalinity, total (mg/L CaCO3) ____ 

Sulfate, dissolved (mg/L) 

Chloride, dissolved (mg/L) 

Fluoride, dissolved (mg/L) 

Dissolved solids, calculated (mg/L) 

Sediment, total suspended (mg/L) 

Nitrogen, total NO2 +NO3 (mg/L as N)

Nitrogen, total ammonia (mg/L as N) 

Phosphorus, total (mg/L as P) 

Phosphorus, total ortho (mg/L as P) 

Iron, total recoverable (mg/L) 

Manganese, total recoverable (mg/L) 

Number 

of 

samples

243 

242 

241 

242 

176 

65 

144 

144 

144 

156 

162 

33 

162 

156 

156 

151 

144 

221 

118 

147 

170 

173 

101 

89

Range

239-11000 

7.50- 8.80 

1.0- 30.5 

0.5 11600

3 Qo ion

0.8- 8.9

Q9 3AQH

1 a f\ QQA

c o CAK.

11.5 1950

1 4ft Q1 Q

0.5- 38.4 

133- 748 

17- 6900 

0.4- 174 

0.04- 1.7 

389-10400 

0.2-22600 

0.01 0.80

0.01 0.57

0.010 3.7

0.001 2.5

0.02 1.4

0.005 0.41

Optimum (percent 

Preferred relative abundance 

range in parentheses)

958- 6100 

7.70- 8.50 

1.3- 26.7 

0.7- 23 

4.52 14.3

1.5- 3.6 

402 2300

KA Q 9^7

55.0- 416

cc I ftTft

979 Q1 3

8.4- 14.0 

225- 748 

248- 3770 

4.0- 43.1 

0.2- 1.7 

781- 5560 

1.0- 45.6 

0.05 0.71

0.01 0.57

0.010 0.070

0.003 0.047

O AQ fk QC

0.025- 0.41

5550(24.4) 

8.12(24.4) 

22.0(24.4) 

5.9(24.4) 

11.0(24.4) 

3.5(21.9) 

2080(22.3) 

220(22.3) 

373(22.3) 

878(22.3) 

272(22.3) 

8.4(22.3) 

237(22.3) 

3770(22.3) 

33.5(22.3) 

0.2(22.3) 

5560(22.3) 

6.9(22.3) 

0.10(21.9) 

0.03(22.3) 

0.030(22.3) 

0.006(22.3) 

0.08(21.9) 

0.41(19.2)

Ecological summary:

Prefers brackish, extremely hard, sodium sulfate waters; fine sand or larger (greater than 

0.015-mm diameter); and small streams (less 

than 10 ft3/s) at all elevations in the study area. 

Sensitive to large concentrations of suspended 

sediment and turbidity. Eurythermal between 1 

and 27 °C. Apparently without a seasonal preference. This taxon differs ecologically from the 

nominate variety in that it prefers somewhat 

cooler, more brackish, and less turbid water.

Distribution summary:

Found throughout the study area. A dominant 

in all hydrologic units except those representing 

the Powder and Little Powder Rivers.

O

EXPLANATION

PERCENT RELATIVE ABUNDANCE 

EQUAL TO OR GREATER THAN 10

PERCENT RELATIVE ABUNDANCE 

LESS THAN 10

DISTRIBUTION MAP

MAJOR DIATOM ECOTYPES 77
ECOTYPE: NAVICULA CRYPTOCEPHALA VAR. VENETA (KUTZ.) RABH.

Biotype(s):

N. cryptocephala var. veneta (Kutz.) Rabh.

Reference:

Patrick and Reimer, 1966 (p. 504; pi. 48, fig. 5)

Herbarium slide number: 

1-3-10

Mean percent relative abundance: 

1.1

Percent occurrence:

75.4

Abundance-occurrence index:

85.7

Preferred percent occurrence: 

0.5

Maximum percent relative abundance: 

20.9

Station number: 22 

Date: June 10, 1976 

Type of collection: F

10 urn

Description:

Striae, 15-17 in 10 /*m. Length, 14.6 ^m. Width, 

5.0 ^m. A small, lanceolate Navicula with an irregular and sometimes indistinct central area. 

Distinguished from N. radiosa var. tenella by 

the slightly protracted ends and from N. cincta 

var. rostrata by the inconspicuous central area. 

N. gregaria has striae that are more nearly parallel and a central area that is more distinct.

78 ECOLOGY AND DISTRIBUTION OF MAJOR DIATOM ECOTYPES IN MONTANA
Water-quality profile:

Variable

Specific conductance (jimho/cm) 

pH (units) 

Ternneratiirp ( °C,}

Turhiditv fNTID

Oxygen, dissolved (mg/L) 

Biochemical oxygen demand (mg/L) 

Hardness, total (mg/L CaCO3) 

Calcium, dissolved (mg/L) 

Magnesium, dissolved (mg/L) 

Sodium, dissolved (mg/L) 

Bicarbonate (mg/L) 

Carbonate (mg/L) 

Alkalinity, total (mg/L CaCO3 ) 

Sulfate, dissolved (mg/L) 

Chloride, dissolved (mg/L) 

T^lnnviHp HicsnlvpH ffnor/T,^

Til Qc/tl \7O/"i c/tli/ic f*d 1 r*n 1 Q^~O/I i TYI f^T i

Sediment, total suspended (mg/L) 

Nitrogen, total NO2 +NO3 (mg/L as N)

Nitrogen, total ammonia (mg/L as N) 

Phosphorus, total (mg/L as P) 

Phosphorus, total ortho (mg/L as P) 

Iron, total recoverable (mg/L) 

Manganese, total recoverable (mg/L) 

Number Optimum (percent 

of Range Preferred relative abundance 

samples range in parentheses)

224 

224 

226 

219 

168 

63 

137 

137 

137 

146 

152 

34 

152 

146 

146 

144 

137 

203 

107 

129 

152 

152 

93 

83

OOQ i i AAA

7 .50- C A o.i Q TO 6 

10 °,0 *>

n K 1 1 cnn

0.80 19.0

O er Q Q

QO Q/lQfl

1 R. (\ QQO

5.0- 645 

9.1 1950

45 816

0.5- 29.0 

39- 669 

34 6900

0.4 174

0 04 17

1 Qfi 1 04.00

O O OOCA.A.

0 01 071

0.01- 0.57 

0.010- 3.7 

0.001 2.5

0 09 91

0.010 0.39

6000(7.2) 

8.20(7.2) 

22.0(7.2) 

15(7.2) 

12.0(7.0) 

1.8(5.8) 

1400(7.2) 

190(7.2) 

226(7.2) 

1040(7.2) 

651(7.2) 

14.0(3.0) 

534(7.2) 

3170(7.2) 

23.8(7.2) 

0.04(7.2) 

5300(7.2) 

26.6(7.2) 

0.03(7.0) 

0.01(7.2) 

0.032(7.2) 

0.008(7.2) 

0.08(7.0) 

0.030(7.0)

Ecological summary:

There is a limited amount of chemical and 

physical data associated with populations having a relative abundance of 10 percent or greater. 

Seems to prefer brackish waters with some carbonate ion and relatively large concentrations of 

sulfate and sodium; fine sand or larger (greater 

than 0.05-mm diameter); and middle elevations 

(2,500 to 4,000 ft). Tolerates small concentrations of chloride, suspended sediment, and turbidity. Seems to be indifferent to stream size 

and season of the year.

Distribution summary:

Widespread, but rarely found in abundance. 

Best population development in the upstream 

Tongue River drainage.

EXPLANATION

PERCENT RELATIVE ABUNDANCE 

EQUAL TO OR GREATER THAN 10

PERCENT RELATIVE ABUNDANCE 

LESS THAN 10

DISTRIBUTION MAP

MAJOR DIATOM ECOTYPES 79
ECOTYPE: NAVICULA GOERSH BAHLS

Biotype(s):

N. goersii Bahls var. goersii

Reference:

Bahls, 1983 (p. 1; fig. 1)

Herbarium slide number: 

1-3-17

Mean percent relative abundance: 

0.2

Percent occurrence: 

22.2

Abundance-occurrence index: 

4.6

Preferred percent occurrence: 

0.3

Maximum percent relative abundance: 

10.5

Station number: 21 

Date: August 24, 1979 

Type of collection: E

10

Description:

Striae, 14-16 in 10 /on. Length, 11.0 /tin. Width, 

3.5 /on. This taxon could not be identified using 

references immediately available to the principal author. After a search through the Iconograph Reference File, the Diatom Herbarium, 

and pertinent literature at the Academy of Natural Sciences of Philadelphia, it was concluded 

that this taxon is new to science. It was named 

and described in a recent paper (Bahls, 1983). 

Navicula goersii is closely related to N. dulcis 

Patr., which was not found in the study area 

but which has very similar morphological and 

ecological attributes. It is distinguished from N. 

dulcis principally by the subrostrate rather 

than rounded ends.

80 ECOLOGY AND DISTRIBUTION OF MAJOR DIATOM ECOTYPES IN MONTANA
Water-quality profile:

Variable

pH (units) 

TVmnprature (°C1

TurbirHtv CNTTH

Oxygen, dissolved (mg/L) 

Biochemical oxygen demand (mg/L) 

Hardness, total (mg/L CaCO3) 

Calcium, dissolved (mg/L) 

Magnesium, dissolved (mg/L) 

Sodium, dissolved (mg/L) 

Ri Cft vVjnn ft tp (m or/T ,^

Carbonate (mg/L) 

Alkalinity, total (mg/L CaCO3)

Sulfate, dissolved (mg/L) 

Chloride, dissolved (mg/L) 

Fluoride, dissolved (mg/L) 

Dissolved solids, calculated (mg/L) 

Sediment, total suspended (mg/L) 

Nitrogen, total NO2 +NO3 (mg/L as N) 

Nitrogen, total ammonia (mg/L as N) 

Phosphorus, total (mg/L as P) 

Phosphorus, total ortho (mg/L as P) 

Iron, total recoverable (mg/L) 

Ivicin fTon oco i~/"ii~il T*OO/^TTOT*O rilo iTYir*/! ^

Numbei 

of 

samples

rr/;

76

7C

7K

KK

17

KO

53 

53

K.A

K.a

14

KC

K<1

54

51 

53 

68

Q1

47

KG

K.a

97

9fi

Range

5

576 11000

8.00- 8.73 

2K. on o

0 f* 4^^

0.80- 19.0

O C Q O

OOQ CMQA

40.0- 328 

33.5- 645 

UK 1QPJO

1 rvQ TEC

1 n 9Q n

1 CO /Jl Q

QO fionn

1

0 -I OC

0.1- 1.5 

568-10400 

0.2- 893 

0.01 0.64

0.01 0.57

0.010 0.62

0.002 0.52

0.04 0.75

0.005 0.39

( 

Preferred i 

range

9070 9070

8.12- 8.12 

17.0 17.0

79 79

6

QQ R. QQ

700 7fi9

84.6- 84.6 

138- 138 

909 909

7ic 7iK

CO£J KOC

604 604

1 a a 1 a a

0.3- 0.3 

1760- 1760 

28.4- 28.4

0.03 0.03

0.060-0.060

019 019

0.50 0.50

O OQ n QQ

Dptimum (percent 

 elative abundance 

in parentheses)

9070(1 0 ^

8.12(10.5) 

17.0(10.5)

7 9(i n *{\

6

OQ/'i n K^

9 9(9 Q^

rroo/i f\ e\

84.6(10.5) 

138(10.5) 

202(10.5)

715(10.5)

8.4(4.7)

586(10.5)

604(10.5)

16.6(10.5)

0.3(10.5) 

1760(10.5) 

28.4(10.5) 

0.37(5.2)

0.03(10.5)

0.060(10.5)

0.12(10.5)

0.50(10.5)

0.39(10.5)

Ecological summary:

Prefers slightly brackish water; pH greater 

than 8.00 (alkalibiontic); substrate the size of 

fine gravel (0.2- to 1-cm diameter); and small 

streams (less than 1 fta/s) at all but the highest 

elevations (less than 4,000 ft) in the study area. 

Tolerates small amounts of suspended sediment, 

turbidity, and chloride. Summer (August) dominant but occurs in all seasons.

Distribution summary:

Widespread; found in 82 collections from 31 

sites in the study area. Best population development in Davis Creek near Busby (station 21).

O

EXPL AN ATI ON

PERCENT RELATIVE ABUNDANCE 

EQUAL TO OR GREATER THAN 10

PERCENT RELATIVE ABUNDANCE 

LESS THAN 10

DISTRIBUTION MAP

MAJOR DIATOM ECOTYPES 81
ECOTYPE: NAVICULA GREGARIA DONK.

Biotype(s):

*N. gregaria Donk. var. gregaria 

N. secreta var. apiculata Patr.

Reference:

Patrick and Reimer, 1966 (p. 467; pi. 44, fig. 6)

Herbarium slide number: 

1-3-11

Mean percent relative abundance: 

1.8

Percent occurrence: 

78.6

Abundance-occurrence index: 

144.6

Preferred percent occurrence: 

3.2

Maximum percent relative abundance: 

35.5

Station number: 8 

Date: June 19, 1980 

Type of collection: E

10 jim

Description:

Striae, 19-21 in 10 /mi. Length, 23.8 /mi. Width, 

6.0 /mi. The ecotype is distinguished by nearly 

parallel striae and protracted ends. In our material we have forms spanning both biotypes, 

often in one collection. Valve shape varies from 

lanceolate to linear-lanceolate; ends vary from 

protracted-rostrate to somewhat capitate; and 

central areas range from a slight broadening of 

the axial area to one that is distinctly transverse and rectangular, though often asymmetrical. The principal author believes that the two 

biotypes are different expressions of the same 

genome.

82 ECOLOGY AND DISTRIBUTION OF MAJOR DIATOM ECOTYPES IN MONTANA
Water-quality profile:

Variable

Number

of 

samples

Range Preferred 

range

Optimum (percent

relative abundance

in parentheses)

Specific conductance (/^mho/cm) 241 239-11000 1300-2450 1410(26.2)

pH (units) 240 7.50- 8.73 8.10-8.35 8.30(26.2)

Temperature (°C) 240 1.7- 30.5 12.3- 16.4 16.4(26.2)

Turbidity (NTU) 241 0.5- 3250 1.8- 16 7.0(26.2)

Oxygen, dissolved (mg/L) 175 3.82- 19.0 7.92- 12.6 12.6(26.2)

Biochemical oxygen demand (mg/L) 69 0.8- 8.3 1.4- 2.3 1.5(26.2)

Hardness, total (mg/L CaCO3) 145 123- 3490 506-1070 719(26.2)

Calcium, dissolved (mg/L) 145 16.0- 330 81.7- 110 85.1(26.2)

Magnesium, dissolved (mg/L) 145 15.1- 645 71.0- 194 123(26.2)

Sodium, dissolved (mg/L) 154 9.5- 1950 77.8- 238 77.8(26.2)

Bicarbonate (mg/L) 161 45- 816 473- 754 488(26.2)

Carbonate (mg/L) 34 0.5- 29.0 4.1- 4.1 4.1(19.5)

Alkalinity, total (mg/L CaCO3) 161 39- 669 388- 618 400(26.2)

Sulfate, dissolved (mg/L) 154 38-6900 267- 875 475(26.2)

Chloride, dissolved (mg/L) 154 0.4- 174 0.4- 6.4 3.8(26.2)

Fluoride, dissolved (mg/L) 149 0.04- 1.7 0.4- 1.2 0.5(26.2)

Dissolved solids, calculated (mg/L) 145 254-10400 1140-2180 1250(26.2)

Sediment, total suspended (mg/L) 219 0.2- 8260 1.9- 37.4 16.1(26.2)

Nitrogen, total NO2 +NO3 (mg/L as N) 114 0.01- 0.71 0.01- 0.39 0.01(26.2)

Nitrogen, total ammonia (mg/L as N) 139 0.01- 0.57 0.01-0.02 0.01(26.2)

Phosphorus, total (mg/L as P) 165 0.010- 3.7 0.020-0.068 0.020(26.2)

Phosphorus, total ortho (mg/L as P) 166 0.001- 2.5 0.004-0.064 0.004(26.2)

Iron, total recoverable (mg/L) 94 0.02- 2.1 0.02- 0.60 0.21(26.2)

Manganese, total recoverable (mg/L) 84 0.005- 0.41 0.025- 0.24 0.065(26.2)

Ecological summary:

Prefers cool, extremely hard, slightly brackish 

waters; pH of 8.10 to 8.35; fine sand or larger 

(greater than 0.05-mm diameter); and medium 

streams (1 to 100 fts/s) at middle elevations 

(3,000 to 4,000 ft). Tolerates some suspended 

sediment and turbidity. Spring (May and June) 

dominant.

Distribution summary:

Found throughout the study area. Best population development in certain tributaries of 

Rosebud Creek and the Tongue River.

O

EXPLANATION

PERCENT RELATIVE ABUNDANCE 

EQUAL TO OR GREATER THAN 10

PERCENT RELATIVE ABUNDANCE 

LESS THAN 10

DISTRIBUTION MAP

MAJOR DIATOM ECOTYPES 83
ECOTYPE: NAVICULA ODIOSA WALLACE

Biotype(s):

N. odiosa Wallace var. odiosa

Reference:

Patrick and Reimer, 1966 (p. 510; pi. 48, fig. 18)

Herbarium slide number: 

1-3-13

Mean percent relative abundance: 

0.6

Percent occurrence: 

34.3

Abundance-occurrence index: 

19.5

Preferred percent occurrence: 

1.6

Maximum percent relative abundance: 

20.2

10

Station number: 46 

Date: July 24, 1979 

Type of collection: F

Description:

Striae, 22-24 in 10 pm. Length, 14.8 pm. Width, 

3.0 fim. A small Navicula with fine, radiate to 

parallel striae and a central area that is only a 

bit wider than the axial area. Our specimens 

are somewhat less linear and more lanceolate 

than those described by Patrick and Reimer 

(1966); otherwise, the features are the same.

84 ECOLOGY AND DISTRIBUTION OF MAJOR DIATOM ECOTYPES IN MONTANA
Water-quality profile:

Variable

Specific conductance (/imho/cm) 

pH (units) 

Tptnnpraturp f°C}

Turbidity (NTU)

Oxygen, dissolved (mg/L) ~ 

Biochemical oxygen demand (mg/L) 

Hardness, total (mg/L CaCO3) 

Calcium, dissolved (mg/L) 

Magnesium, dissolved (mg/L) 

Sodium, dissolved (mg/L) 

Bicarbonate (mg/L) 

PI jjvV»n'na'J"p fmcr/T ,^

Alkalinity, total (mg/L CaCO3)

Sulfate, dissolved (mg/L) -

Chloride, dissolved (mg/L) 

Fluoride, dissolved (mg/L) 

Dissolved solids, calculated (mg/L) 

Sediment, total suspended (mg/L) 

Nitrogen, total NO2 +NO3 (mg/L as N)

Nitrogen, total ammonia (mg/L as N) 

Phosphorus, total (mg/L as P) 

Phosphorus, total ortho (mg/L as P) 

Iron, total recoverable (mg/L) 

l\^c*i"i (TC*T"i£*Qr* ^Tii~c*l vr*nm7£*vo Vil F* frYirT/T ^

Number 

of Range 

samples

117 

117 

115 

117 

76 

28 

72 

72 

72 

76 

78 

22 

78 

76 

76 

72 

72 

111 

52 

78 

90 

87 

37 

34

462 11000

7.50- 8.73

1

0 QA K

0.7 4200

0.80- 19.0 

0.8- 8.3 

123- 3490

1 d A QQn

 I Q Q C/| C

loq iQKn

1 /IP. Q1 °.

AC OQ A

1 QQ 7 /IP.

41 6900

1.2 174

0.04- 1.7 

398-10400 

0.7- 8260 

0.01 0.66

0.01 0.57

0.010- 3.7 

0.001- 2.5 

0.07- 2.1 

0.010 0.41

Optimum (percent 

Preferred relative abundance 

range in parentheses)

1690 6100

8.08 8.40

10.5 24.0

2

O A OC

9.50- 10.7 

1.5- 1.5

eec cqo

iqo 1/iQ

51.0- 69.5 

170- 298

1 QQ OC1

162- 214

£*1 17 QQK

88.9- 174 

1.5- 1.5 

1260-1700 

1.7- 893 

0.05 0.32

0.01 0.11

0.040 0.60

0.016- 0.38 

0.36- 0.36 

0.10- 0.10

1690(20.2) 

8.14(20.2) 

24.0(20.2) 

435(20.2) 

9.50(16.9) 

1.5(16.9) 

556(20.2) 

138(20.2) 

51.0(20.2) 

170(20.2) 

198(20.2) 

18.0(4.7) 

162(20.2) 

617(20.2) 

88.9(20.2) 

1.5(12.6) 

1260(20.2) 

893(20.2) 

0.32(20.2) 

0.01(20.2) 

0.60(20.2) 

0.38(20.2) 

0.36(11.8) 

0.10(11.8)

Ecological summary:

Prefers very hard, brackish water with relatively large amounts of chloride (88 to 174 

mg/L); and a pH of 8.00 to 8.40; but is apparently indifferent to substrate particle size, stream 

size, and elevation. Eurythermal between 10 to 

24 °C. Tolerates considerable suspended sediment and turbidity. Summer and fall (July to 

October) dominant.

Distribution summary:

Widespread. Best population development in 

Mizpah Creek, the Powder River, and Deer 

Creek near Decker (station 22).

EXPLAN ATIO N

PERCENT RELATIVE ABUNDANCE 

EQUAL TO OR GREATER THAN 10

PERCENT RELATIVE ABUNDANCE 

LESS THAN 10

DISTRIBUTION MAP

MAJOR DIATOM ECOTYPES 85
ECOTYPE: NAVICULA PAVILLARDH HUST.

Biotype(s):

N. pavillardii Hust. var. pavillardii

Reference:

Hustedt, 1939 (p. 635; figs. 86-90)

Herbarium slide number: 

1-1-2

Mean percent relative abundance: 

0.2

Percent occurrence: 

3.5

Abundance-occurrence index: 

0.7

Preferred percent occurrence: 

0.8

Maximum percent relative abundance: 

19.3

10

Station number: 6 

Date: August 9, 1979 

Type of collection: E

Description:

Striae, 14-17 in 10 /*m. Length, 37.3 fim. Width, 

5.0 urn. A very delicate and lightly silicified 

Navicula. Not easily confused with any other 

diatom in the study area.

86 ECOLOGY AND DISTRIBUTION OF MAJOR DIATOM ECOTYPES IN MONTANA
Water-quality profile:

Number 

Variable of Range 

samples

Specific conductance (^mho/cm) 

pH (units) 

Tpmnpraturp ( °C~)

Turbidity (NTU)

Oxygen, dissolved (mg/L) 

Biochemical oxygen demand (mg/L) 

Hardness, total (mg/L CaCO3) 

Calcium, dissolved (mg/L) 

Magnesium, dissolved (mg/L) 

Bicarbonate (mg/L) 

Carbonate (mg/L) 

Alkalinity, total (mg/L CaCO3) 

Sulfate, dissolved (mg/L) 

Chloride, dissolved (mg/L) 

Fluoride, dissolved (mg/L) 

Dissolved solids, calculated (mg/L) 

Sediment, total suspended (mg/L) 

Nitrogen, total NO2 +NO3 (mg/L as N)

Nitrogen, total ammonia (mg/L as N) 

Phosphorus, total (mg/L as P) 

Phosphorus, total ortho (mg/L as P) 

Iron, total recoverable (mg/L) 

Manganese, total recoverable (mg/L) 

13 

13 

13 

13 

10 

2 

10 

10 

10 

11 

11 

8 

11 

11 

11 

10 

10 

13 

5 

10 

11 

10 

5 

5

CT1 TAOA

8

1 ft ft 7Q.

4

ft oft O

1

r i QO

8 1 ft 1 Q ft

99 97

190-2040 

35.7- 254

1 ft Q QA9

56.5 1470

148- 755

79 9Q 0

133- 619 

165 5450

2 O 9ft ft

O Q f\ C

448 7680

1 A. 9^

0.01 0.11

0.01 0.21

0.010 0.20

0.003-0.11 

0.16-0.46 

0.035- 0.36

Optimum (percent 

Preferred relative abundance 

range in parentheses)

3080 6000

8

CC Q TO

91 A 9Q 9

10.0- 35

n

O 1Q ft

238- 829 

35.7- 78.6

oo.o- oo e i looco

654 1230

531- 597 

19.0- 26.0 

470- 533

1 1 9ft 97ftft

1 K. O Oft ft

0.5 0.6

OAOft AftOft

22.4- 55.5

0.03- 0.21 

0.030 0.070

0.021-0.032 

0.46- 0.46 

0.095-0.095

6000(19.3) 

8.55(19.3) 

27.5(19.3) 

10.0(19.3) 

19.0(19.3) 

2.2(1.2) 

829(19.3) 

78.6(19.3) 

153(19.3) 

1230(19.3) 

541(19.3) 

19.0(19.3) 

475(19.3) 

2780(19.3) 

19.8(19.3) 

0.5(19.3) 

4820(19.3) 

22.4(19.3) 

0.04(1.9) 

0.21(19.3) 

0.030(19.3) 

0.021(19.3) 

0.46(16.8) 

0.095(16.8)

Ecological summary:

Prefers brackish, sodium sulfate waters; warm 

temperatures (mesothermal between 21 and 

30 °C); pH greater than 8.10 (alkalibiontic); 

dissolved-oxygen content greater than 8.10 mg/L; 

coarse sand substrates or larger (greater than 

0.3-mm diameter); and small streams (0 to 1 

fts/s) at lower elevations (less than 2,500 ft) in 

the study area. Tolerates some suspended sediment, turbidity, and chloride. Summer (August) 

dominant.

Distribution summary:

Found only in the downstream reaches of 

Rosebud Creek, Armells Creek, Pumpkin Creek, 

and Mizpah Creek, with good population development (greater than 10 percent relative abundance) in the last two streams. Elsewhere in 

eastern Montana, this taxon achieves greater 

abundance.

O

EXPLANATIO N

PERCENT RELATIVE ABUNDANCE 

EQUAL TO OR GREATER THAN 10

PERCENT RELATIVE ABUNDANCE 

LESS THAN 10

DISTRIBUTION MAP

MAJOR DIATOM ECOTYPES 87
ECOTYPE: NAVICULA PEREGRINA VAR. LANCEOLATA SKVORTZOW

Biotype(s):

N. peregrina var. lanceolata Skvortzow

Reference:

Skvortzow, 1929 (p. 22; figs. 14-15)

Herbarium slide number: 

1-3-12

Mean percent relative abundance: 

0.2

Percent occurrence: 

1.4

Abundance-occurrence index: 

0.3

Preferred percent occurrence: 

0.5

Maximum percent relative abundance: 

49.1

Station number: 21 

Date: September 8, 1978 

Type of collection: E

10

Description:

Striae, 10-13 in 10 /mi. Length, 36.5 /mi. Width, 

7.5 /im. Distinguished from the nominate variety by its smaller size and finer striae. Distinguished from N. viridula var. avenacea by the 

transverse rather than rounded central area.

ECOLOGY AND DISTRIBUTION OF MAJOR DIATOM ECOTYPES IN MONTANA
Water-quality profile:

Number 

Variable of Range 

samples

Specific conductance (^mho/cm) -

r»T"T ^iTni^C!^

TVrrmprfltnrp ( °P1

Turbidity (NTU)

Oxygen, dissolved (mg/L) 

Biochemical oxygen demand (mg/L) 

Hardness, total (mg/L CaCO3) 

Calcium, dissolved (mg/L) 

Magnesium, dissolved (mg/L) 

Sodium, dissolved (mg/L) 

Bicarbonate (mg/L) 

Carbonate (mg/L) 

Alkalinity, total (mg/L CaCO3)

Snl'fsit^ Hiocmlir^H fmcr/T ,^

Chloride, dissolved (mg/L) 

T^lnnviHp HiccnlvpH fmcr/TA

Dissolved solids, calculated (mg/L) 

Sediment, total suspended (mg/L) 

Nitrogen, total NO2 +NO3 (mg/L as N)

Nitrogen, total ammonia (mg/L as N) 

Phosphorus, total (mg/L as P) 

Phosphorus, total ortho (mg/L as P) 

Iron, total recoverable (mg/L) 

Ivl *"in iron oco "1~ /^"1~ *"i 1 v&r*f\'\7&vi r\\ o iTYir^/T i

5 

5 

5 

5 

4 

1 

5 

5 

5 

5 

5 

0 

5 

5 

5 

5 

5 

5 

3 

5 

5 

5 

4 

4

1530

8 1 9

16.4

1 9

6

QQ

7 a

CQC

83.2- 

ai 9

117

409

403

440

4.4

O Q

1 ^7O

9 Q

0.03

0.02- 

0.011

0.004

0 99

0.090

2460 

8.20 

21.2 

7.2 

12.0 

7.8 

1070 

110 

194 

356 

754

618 

899 

18.6 

0.5 

2180 

28.4 

0.12 

0.11 

0.084 

0.12 

0.50 

0.39

Optimum (percent 

Preferred relative abundance 

range in parentheses)

9070

8 1 9

-\ f* A

16.4-

1 fi

6

QQ

7fi9

84.6-

1 Qft

202-

71 ^

FQ/I

604

6

0

0.3- 

1760-

Q C

012

0.02- 

0.060

0.028- 

0.47

0.24-

2450 

8.20 

17.0 

7.2 

6.88

1070 

110 

194 

238 

754

618 

875 

16.6 

0.4 

2180 

28.4 

0.12 

0.03 

0.060 

0.12 

0.50 

0.39

2450(49. 

8.20(49. 

16.4(49. 

1.8(49. 

6.88(31. 

7.8(3. 

1070(49. 

110(49. 

194(49. 

238(49. 

754(49.

618(49. 

875(49. 

6.2(49. 

0.4(49. 

2180(49. 

3.5(49. 

0.12(49. 

0.02(49. 

0.060(49. 

0.028(49. 

0.47(49. 

0.24(49.

1) 

1) 

1) 

1) 

0) 

0) 

1) 

1) 

1) 

1) 

1)

1) 

1) 

1) 

1) 

1) 

1) 

1) 

1) 

1) 

1) 

1) 

1)

Ecological summary:

Prefers cool, extremely hard, slightly brackish 

waters; pH of 8.10 to 8.20 (alkalibiontic); fine 

gravels (0.2- to 1-cm diameter); and small streams 

(0.1 to 1 ft3/s) at middle elevations (3,000 to 

3,500 ft) in the study area. Tolerates small concentrations of chloride, suspended sediment, and 

turbidity. Late summer (August and September) 

dominant.

Distribution summary:

Found to date only in Davis Creek near Busby 

(station 21). N. peregrina var. peregrina (Ehr.) 

Kutz. occurs frequently throughout the study 

area, but never in large numbers.

O

EXPLAN ATI ON

PERCENT RELATIVE ABUNDANCE 

EQUAL TO OR GREATER THAN 10

PERCENT RELATIVE ABUNDANCE 

LESS THAN 10

DISTRIBUTION MAP

MAJOR DIATOM ECOTYPES 89
ECOTYPE: NAVICULA RADIOSA VAR. TENELLA (BREB. EX KUTZ.) GRUN.

Biotype(s):

N. radiosa var. tenella (Breb. ex Kutz.) Grun.

Reference:

Patrick and Reimer, 1966 (p. 510; pi. 48, fig. 17)

Herbarium slide number: 

1-3-9

Mean percent relative abundance:

1.1 

Percent occurrence:

51.1 

Abundance-occurrence index:

55.4 

Preferred percent occurrence:

1.4 

Maximum percent relative abundance:

25.0

Station number: 7 

Date: August 3, 1978 

Type of collection: E

Description:

Striae, 13-17 in 10 jan. Length, 23.0 jim. Width, 

5.0 jttm. A small, highly variable Navicula. Valve 

shape may range from linear-lanceolate to lanceolate to elliptical-lanceolate. The ends may be 

acute or slightly apiculate. The axial area in 

our specimens is not thickly silicified, as it is in 

N. radiosa Kutz. The central area occasionally 

is formed by the median striae being longer 

than the rest and extending almost to the central nodule (as in N. salinarum var. intermedia), 

but more often it is formed by one or two irregularly shortened striae. The striae count may 

range from 11 to 18 in 10 jttm, depending on the 

population and the individual frustule selected. 

The principal author can find no convincing evidence why this taxon should be included under 

N. radiosa and believes it is more closely related to N. salinarum var. intermedia, with 

which it is frequently associated in nature. See 

description of N. salinarum var. intermedia.

10

90 ECOLOGY AND DISTRIBUTION OF MAJOR DIATOM ECOTYPES IN MONTANA
Water-quality profile:

Variable

Specific conductance (^mho/cm) 

nTT fnni'l'cA

Tprrmprfltiirp ( °P^

TiirbiHitvfNTTFl

Oxygen, dissolved (mg/L) 

Biochemical oxygen demand (mg/L) 

Hardness, total (mg/L CaCO3) 

Calcium, dissolved (mg/L) 

Magnesium, dissolved (mg/L) 

Sodium, dissolved (mg/L) 

Bicarbonate (mg/L) 

Alkalinity, total (mg/L CaCO3) _________ 

Sulfate, dissolved (mg/L) 

Chloride, dissolved (mg/L) 

Fluoride, dissolved (mg/L) 

Sediment, total suspended (mg/L) 

Nitrogen, total NO2 +NO3 (mg/L as N)

Nitrogen, total ammonia (mg/L as N) 

Phosphorus, total (mg/L as P) 

Phosphorus, total ortho (mg/L as P) 

Iron, total recoverable (mg/L) 

Manganese, total recoverable (mg/L) 

Number 

of Range 

samples

150 

150 

149 

147 

105 

38 

93 

93 

93 

96 

103 

25 

103 

96 

96 

93 

93 

140 

80 

88 

113 

114 

57 

55

239-

7.70

1.0

0.5- 

6 on

1.0- 

123- 

16.0-

1 q K

9.1-

AK

0 K

39- 

34- 

1.3- 

0.1- 

IQfi -LC/vJ

0 9

0.01

0.01

0.010- 

0.001- 

0.02

0.005-

11000 

8.73 

30.5 

3250 

15.3 

8.9 

3490 

328 

645 

1950 

913 

21.0 

748 

6900 

174 

1.5 

10400 

8260 

0.71 

0.30 

3.7 

2.5 

1.4 

0.26

Optimum (percent 

Preferred relative abundance 

range in parentheses)

239- 890

7 Q7 ft Qft

190 91 9

U Q4

7 7H Q 1 O

1.0- 2.2 

375- 484 

69.6- 77.0

AQ Q 71 A

12.8- 43.2 

9Q9 441

90 90

321- 362 

69- 181 

94 37

0.6- 0.9 

KQR 777

91 9 1QQ

0.08- 0.08 

0.02 0.02

0.064-0.064 

0.023-0.023 

0.59 0.59

0.095-0.095

818(25.0) 

8.30(25.0) 

15.0(25.0) 

11(25.0) 

9.10(20.2) 

1.0(20.2) 

484(25.0) 

77.0(25.0) 

71.0(25.0) 

19.9(25.0) 

441(25.0) 

2.0(11.7) 

362(25.0) 

165(25.0) 

2.5(25.0) 

0.6(25.0) 

777(25.0) 

21.2(25.0) 

0.08(18.4) 

0.02(18.4) 

0.064(18.4) 

0.023(18.4) 

0.59(18.4) 

0.095(18.4)

Ecological summary:

Prefers cool, fresh, very hard waters with relatively small concentrations of sodium and sulfate; fine to medium gravels (0.2- to 3-cm diameter); and larger streams (10 to 100 fts/s) at 

higher elevations in the study area (3,500 to 

4,000 ft). Tolerates some suspended sediment 

and turbidity. Sensitive to small concentrations 

of chloride. Summer (July to September) dominant.

Distribution summary:

Found in all except the Little Powder and 

Lower Powder hydrologic units. Best population 

development in the western part of the study 

area.

O

EXPLANATION

PERCENT RELATIVE ABUNDANCE 

EQUAL TO OR GREATER THAN 10

PERCENT RELATIVE ABUNDANCE 

LESS THAN 10

DISTRIBUTION MAP

MAJOR DIATOM ECOTYPES 91
ECOTYPE: NAVICULA RHYNCHOCEPHALA KUTZ.

Biotype(s):

N. rhynchocephala Kutz. var. rhynchocephala 

N. rhynchocephala var. amphiceros (Kutz.) Grun. 

*N. rhynchocephala var. germainii (Wallace) Pair.

Reference:

Patrick and Reimer, 1966 (p. 506; pi. 48, fig. 8)

Herbarium slide number: 

1-3-14

Mean percent relative abundance: 

0.2

Percent occurrence: 

19.7

Abundance-occurrence index: 

4.3

Preferred percent occurrence: 

0.3

Maximum percent relative abundance: 

31.2

Station number: 21 

Date: July 25, 1978 

Type of collection: E

10

Description:

Striae, 13-16 in 10 /on. Length, 37.2 /on. Width, 

8.0 fim. A medium Navicula with protracted 

ends, coarse striae, and a large, rounded central 

area. Axial area and central nodule more thickly 

silicified than the rest of the valve. Differs from 

N. cincta var. rostrata by having a larger central area and a larger overall size. Distinguished 

from N. gregaria by its larger size and coarser 

striae. Distinguished from N. salinarum var. intermedia by its rounded rather than irregular 

central area and from N. viridula var. avenacea 

by its protracted rather than rounded ends.

92 ECOLOGY AND DISTRIBUTION OF MAJOR DIATOM ECOTYPES IN MONTANA
Water-quality profile:

Variable

Specific conductance (/^mho/cm) 

nTT fiTnifcA

Temperature (°C) 

Turbiditv (NTtn

Oxygen, dissolved (mg/L) 

Biochemical oxygen demand (mg/L) 

Hardness, total (mg/L CaCO3) 

Calcium, dissolved (mg/L) 

Magnesium, dissolved (mg/L) 

Sodium, dissolved (mg/L) 

Bicarbonate (mg/L) 

Alkalinity, total (mg/L CaCO3) 

Sulfate, dissolved (mg/L) 

Chloride, dissolved (mg/L) 

Fluoride, dissolved (mg/L) 

T")iQQnlvpH QrtliHci r*dlpiil af o/l fmcr/T ^

Sediment, total suspended (mg/L) 

Nitrogen, total NO2 +NO3 (mg/L as N)

Nitrogen, total ammonia (mg/L as N) 

Phosphorus, total (mg/L as P) 

Phosphorus, total ortho (mg/L as P) 

Iron, total recoverable (mg/L) 

Manganese, total recoverable (mg/L) 

Numbei 

of 

samples

at

at

61

CQoo 

44 

15 

97

97

97

9Q

35 

11

35

9Q

29 

oc

97

cc

9Q

QC

42 

44

91

1Q

Range

s

oqq 7030

7

Q/1 Q rrq

1.3- 29.2 

o Q d.^

5.40- 15.0 

0.5- 7.8 

190 1250

OK 7 -tCK

1 Q q 904.

31.1 1470

148- 913 

0.5 29.0

133- 748 

116 3400

1.2- 88.9

O q 19

416 5800

1 K. ftQO.

0.01 0.32

0.01 0.11

0.010- 0.60 

0/1/10 n OQ

0.04 2.1

0.015 0.39

(

Preferred r 

range

1 Cr7f» 1 Cr7f»

S on Q on

21.2- 21.2 

19 19

7.65- 7.65

7.8- 7.8

7KO 7KO

QO O ftq O

1 00 1 00

m i q-i

623- 623

511- 511 

454 454

4.4- 4.4 

n q n ^

1430 1430

2

q o q

0.03 0.03

0.02 0.02

0.078-0.078 

0.045 0.045

0 99 0 99

A 19 019

Dptimum (percent 

 elative abundance 

in parentheses)

1 CTA/'OI f)\

8

OfV9.1 9\

21.2(31.2)

1 9(31 9^

7.65(31.2) 

7.8(31.2) 

7^9(31 91

oq o/'oi o^

1 39(31 91

iqifqi 9^1

623(31.2)

on fi/o o\

511(31.2) 

454(31.2)

4.4(31.2)

O q(qi 9\

i,iqnrqi 9"»

2

q/-qi 9\

O rjqrqi 91

0 09C31 91

0.078(31.2) 

0.045(31.2)

0 99(31 91

0 19(31 91

Ecological summary:

Prefers very hard, slightly brackish waters; 

sand substrates (0.05- to 2-mm diameter); and 

small streams (0.1 to 1 ft3/s) at middle elevations 

(3,000 to 3,500 ft) in the study area. Appears to 

be sensitive to small amounts of suspended sediment, turbidity, and chloride. Summer (July to 

September) dominant.

Distribution summary:

Found in all hydrologic units except those representing the downstream drainage of the Powder 

River and the Little Powder River. Best population development in Davis Creek near Busby 

(station 21).

O

EXPLANATION

PERCENT RELATIVE ABUNDANCE 

EQUAL TO OR GREATER THAN 10

PERCENT RELATIVE ABUNDANCE 

LESS THAN 10

DISTRIBUTION MAP

MAJOR DIATOM ECOTYPES 93
ECOTYPE: NAVICULA SALINARUM VAR. INTERMEDIA (GRUN.) CL.

Biotype(s):

N. salinarum var. intermedia (Grun.) Cl.

Reference:

Patrick and Reimer, 1966 (p. 503; pi. 48, fig. 2)

Herbarium slide number: 

1-3-8

Mean percent relative abundance: 

1.4

Percent occurrence: 

47.3

Abundance-occurrence index: 

66.3

Preferred percent occurrence: 

3.2

Maximum percent relative abundance: 

31.0

Station number: 8 

Date: August 26, 1978 

Type of collection: E

10

Description:

Striae, 13-15 in 10 pm. Length, 35.0 ^m. Width, 

7.4 /um. Distinguished from other varieties of 

Navicula by the protracted, subcapitate to capitate ends and the irregular central area formed 

by striae being alternately longer and shorter. 

The principal author questions the association 

of this taxon with N. salinarum Grun., which 

has a lanceolate-elliptical central area and a 

largely exclusive ecological amplitude. This 

taxon may belong more appropriately with N. 

radiosa var. tenella by virtue of its similar habitus and frequent association. See description of 

N. radiosa var. tenella.

94 ECOLOGY AND DISTRIBUTION OF MAJOR DIATOM ECOTYPES IN MONTANA
Water-quality profile:

Variable

Specific conductance (jimho/cm) -

r»PT (unite! ^

Temperature ( °C) 

Turbiditv CNTTR

Oxygen, dissolved (mg/L) 

Biochemical oxygen demand (mg/L) 

Hardness, total (mg/L CaCO3) 

Calcium, dissolved (mg/L) 

Magnesium, dissolved (mg/L) 

Sodium, dissolved (mg/L) 

Bicarbonate (mg/L) 

Carbonate (mg/L) 

Alkalinity, total (mg/L CaCO3)

Sulfate, dissolved (mg/L) 

Chloride, dissolved (mg/L) 

Fluoride, dissolved (mg/L) 

Dissolved solids, calculated (mg/L) 

Sediment, total suspended (mg/L) 

Nitrogen, total NO2 +NO3 (mg/L as N)

Nitrogen, total ammonia (mg/L as N) 

Phosphorus, total (mg/L as P) 

Phosphorus, total ortho (mg/L as P) 

Iron, total recoverable (mg/L) 

n/t r*-r% ffrt-m r\nr\ i"/^4"ol VO^*/"fcT7OVO Vll A iTrv^rr/l I

Number 

of 

samples

1OQ

1 9fl

131

1 9*i

93

QQ

74

74

74 

79

QC

OQ

ocoo 

79 

79 

76

74

199

71

74

97 

97& i

K7

K1

Range

oqn CQI rj

7

nr\ o 70

1.7- 30.5 

0.5 4200

7.00- 15.0

0 7 ft Q

123 1430

1 £5 f\ 1 QO

13.5- 242 

9.1- 662

m

(7(7C

O c 94 n

O1 AQC

34-2390 

1.2- 174 

0.1- 1.7 

196-4020

O d QO9fi

0.01 0.53

0.01 0.15

0.010- 2.6 

0.001 1.8

0.04 1.4

0.010 0.26

i 

Preferred i 

range

CCO OQKfk

8.10 8.40

13.3- 20.5 

1.0 60

7.60- 9.42 

1.0 1.0

0171 QftO

57. IT'7 D- C l^D1 OC 

45.7- 180 

12.8- 188

QQK AQQ

6

7 7 O

m 41 9

67- 918 

2.4- 51.0 

0.5- 0.9

K.GQ 1 QQH

17 1 9Q

0.02 0.17

0.01 0.05

0.017- 0.15 

0.007 0.080

n n? n ft^

0.015 0.11

Optimum (percent 

 elative abundance 

in parentheses)

2140(31.0)

8.40(31.0)

19.8(31.0)

3

C/Q1 f\\

8.38(29.3) 

i nroc R\

QfiAfQI f\\

no nroi n\

180(31.0) 

188(31.0) 

488(31.0)

7 9f91 (Vl

412(31.0)

918(31.0) 

4.9(31.0)

0.5(31.0) 

i aftfWQi n\

8 irQi r\\

0.05(31.0)

0.02(31.0)

0.020(31.0) 

0.007(31.0)

0.16(31.0)

0.055(31.0)

Ecological summary:

Prefers cool, fresh to slightly brackish waters 

relatively rich in magnesium and bicarbonate 

ions; fine gravels or larger (greater than 0.2-cm 

diameter); and medium streams (0.1 to 100 ft3/s) 

at higher elevations (3,500 to 4,000 ft). Tolerates some suspended sediment, turbidity, and 

chloride. Summer (June to September) dominant.

Distribution summary:

Widespread. Best population development in 

the Rosebud Creek and Tongue River drainages.

EXPLANATION

PERCENT RELATIVE ABUNDANCE 

EQUAL TO OR GREATER THAN 10

PERCENT RELATIVE ABUNDANCE 

LESS THAN 10

DISTRIBUTION MAP

MAJOR DIATOM ECOTYPES 95
ECOTYPE: NAVICULA SYMMETRICA PATR.

Biotype(s):

N. schroeteri var. escambia Patr. 

*AT. symmetrica Patr. var. symmetrica

Reference:

Patrick and Reimer, 1966 (p. 513; pi. 49, fig. 2)

Herbarium slide number: 

1-3-15

Mean percent relative abundance: 

0.4

Percent occurrence: 

22.7

Abundance-occurrence index: 

9.8

Preferred percent occurrence: 

0.8

Maximum percent relative abundance: 

31.5

10

Station number: 28 

Date: August 16, 1978 

Type of collection: E

Description:

Striae, 13-17 in 10 /mi. Length, 33.0 /im. Width, 

6.6 /mi. Distinguished by striae that are radiate 

throughout the valve. Specimens matching the 

descriptions for each biotype often are found together in our collections; consequently we believe that they are different expressions of the 

same genome.

96 ECOLOGY AND DISTRIBUTION OF MAJOR DIATOM ECOTYPES IN MONTANA
Water-quality profile:

Variable

Specific conductance 0-imho/cm) 

nTT fnnitcA

TpTrmprntiirp f 0(Tl

Turhiditv (NTTD

Oxygen, dissolved (mg/L) 

Biochemical oxygen demand (mg/L) 

Hardness, total (mg/L CaCO3) 

Calcium, dissolved (mg/L) 

Magnesium, dissolved (mg/L) 

Sodium, dissolved (mg/L) 

Bicarbonate (mg/L) 

Carbonate (mg/L) 

Alkalinity, total (mg/L CaCO3)

Sulfate, dissolved (mg/L) 

Chloride, dissolved (mg/L) 

Fluoride, dissolved (mg/L) 

Dissolved solids, calculated (mg/L) 

Sediment, total suspended (mg/L) 

Nitrogen, total NO2 +NO3 (mg/L as N) __ 

Nitrogen, total ammonia (mg/L as N) 

Phosphorus, total (mg/L as P) 

Phosphorus, total ortho (mg/L as P) 

Iron, total recoverable (mg/L) 

TvlQ T"I rr^T"! AGA i~/"^i~dl yA/^/^TAYTiril A (imrfl* ^

Numbei 

of 

samples

71 

71

70

£Q

j rf 47

1 C

4.9

42 

42 

43

48 

1 a

48

43

43

40

42

CO

34 

43

KO

KO

01

90

Range

239-6400

7

QC Q 170

2.4 30.5

0.7-4200

6

170 1 C A

0 1 ft Q

1 9Q QQ9O

16.0- 330 

15.1- 605

9

C CCC. .5- boo

22- 776 

10 94. 0

QO. COG

43 4040

0.4 174

0.1 1.7

254-6290 

1 9 Q990

0.01- 0.42 

0.01- 0.15

O A1 O O G

0.001 1.8

0.04 1.4

0.015 0.39

(

Preferred r 

range

838- 1450

8

00 Q Af)

1CC O1 (\

IK KO

9

1 A Q 1 A

404 617

57.6- 63.2 

61.0- 112

CC A 1 QQ

460- 481 

7.0 7.0

QftQ QCM

116 481

3 9 70

0.6 1.0

782- 1260

1C 1? 1 AO

0.01- 0.02 

0.01- 0.03 

0.040 0.078

0.008 0.012

0.36 0.47

0.015 0.085

Dptimum (percent 

 elative abundance 

in parentheses)

838(31.5) 

8.40(31.5)

1 a Kfoi K.\

1 T/OI C\ 1/Col.O) 

9.10(31.5)

3

d( A f)\

406(31.5)

57.6(31.5) 

64.0(31.5)

KK f)(<)-\ K\

481(31.5)

7

A/-I A Q\

394(31.5)

1 1 GfQ1 K"\

7

A/O1 C\

O Q/-qi c\

782(31.5)

1 C "7/O1 C\

0.02(31.5) 

0.03(12.3) 

0.040(31.5)

0.012(31.5)

O OC/O1 C\

0.015(31.5)

Ecological summary:

Prefers cool, fresh to slightly brackish waters 

with relatively small concentrations of sodium 

and sulfate; pH of 8.20 to 8.50 (alkalibiontic); 

sand substrates (0.05- to 2-mm diameter); and 

small streams (0.1 to 10 ft3/s) at lower elevations 

(less than 3,000 ft) in the study area. Tolerates 

some suspended sediment and turbidity and 

small concentrations of chloride. Summer (August 

and September) dominant.

Distribution summary:

Widespread. Best population development in 

Logging Creek (station 28) and the downstream 

part of Rosebud Creek.

O

EXPLAN ATIO N

PERCENT RELATIVE ABUNDANCE 

EQUAL TO OR GREATER THAN 10

PERCENT RELATIVE ABUNDANCE 

LESS THAN 10

DISTRIBUTION MAP

MAJOR DIATOM ECOTYPES 97
ECOTYPE: NAVICULA TRIPUNCTATA (O. F. MULL.) BORY

Biotype(s):

N. tripunctata (O. F. Mull.) Bory var. tripunctata 

N. tripunctata var. schizonemoides (V. H.) Patr.

Reference:

Patrick and Reimer, 1966 (p. 513; pi. 49, fig. 3)

Herbarium slide number: 

1-1-14

Mean percent relative abundance: 

1.0

Percent occurrence: 

42.2

Abundance-occurrence index: 

41.2

Preferred percent occurrence: 

2.4

Maximum percent relative abundance: 

32.6

10

J[JJJ5P

Station number: 48 

Date: June 1, 1979 

Type of collection: E

Description:

Striae, 10-12 in 10 /mi. Length, 43.6 ^m. Width, 

8.4 fim. Distinguished from other species of Navicula by the obtuse ends, the large rectangular 

central area, and the almost parallel striae.

98 ECOLOGY AND DISTRIBUTION OF MAJOR DIATOM ECOTYPES IN MONTANA
Water-quality profile:

Variable

Number

of 

samples

Range Preferred 

range

Optimum (percent

relative abundance

in parentheses)

Specific conductance (^mho/cm) 116 239-6100 506- 868 662(21.6)

pH (units) 116 7.70-8.72 8.21-8.40 8.40(21.6)

Temperature (°C) 118 1.0-26.0 14.5- 19.0 19.0(21.6)

Turbidity (NTU) 110 0.5-3250 2.0- 7.5 2.0(21.6)

Oxygen, dissolved (mg/L) 83 7.02-13.8 8.70- 9.45 8.70(21.6)

Biochemical oxygen demand (mg/L) 31 0.5- 3.6 1.4(4.9)

Hardness, total (mg/L CaCO3) 75 124-2040 239- 475 371(21.6)

Calcium, dissolved (mg/L) 75 27 A- 254 52.1-79.6 68.0(21.6)

Magnesium, dissolved (mg/L) 75 13.5- 342 26.4- 67.0 48.9(21.6)

Sodium, dissolved (mg/L) 79 9.1- 995 12.8- 22.3 12.8(21.6)

Bicarbonate (mg/L) 86 15- 671 283- 447 359(21.6)

Carbonate (mg/L) 21 0.5-24.0 6.7- 6.7 6.7(21.6)

Alkalinity, total (mg/L CaCO3) 86 13-557 232- 367 306(21.6)

Sulfate, dissolved (mg/L) 79 34-5450 41- 124 70(21.6)

Chloride, dissolved (mg/L) 79 0.4-51.6 2.2- 3.0 2.4(21.6)

Fluoride, dissolved (mg/L) 78 0.1- 1.2 0.6- 1.2 0.6(21.6)

Dissolved solids, calculated (mg/L) 75 184-7680 425- 744 569(21.6)

Sediment, total suspended (mg/L) 108 0.4-8260 4.0- 18.0 4.0(21.6)

Nitrogen, total NO2 +NO3 (mg/L as N) 67 0.01-0.53 0.03- 0.07 0.04(21.6)

Nitrogen, total ammonia (mg/L as N) 63 0.01-0.30 0.01-0.03 0.01(21.6)

Phosphorus, total (mg/L as P) 88 0.010- 3.7 0.017-0.040 0.017(21.6)

Phosphorus, total ortho (mg/L as P) 89 0.001- 2.5 0.004-0.029 0.010(21.6)

Iron, total recoverable (mg/L) 58 0.02- 1.4 0.14- 0.33 0.14(21.6)

Manganese, total recoverable (mg/L) 54 0.005-0.36 0.025-0.055 0.025(21.6)

Ecological summary:

Prefers cool, fresh, calcium-magnesium bicarbonate waters with relatively small concentrations 

of sodium, sulfate, chloride, suspended sediment, 

and turbidity; pH of 8.20 to 8.40 (alkalibiontic); 

gravel substrates (greater than 0.2-cm diameter); and medium streams (0.1 to 100 ft3/s) at 

higher elevations (3,500 to 4,000 ft).

Distribution summary:

Distribution limited to relatively good-quality 

(little dissolved solids) waters in the study area, 

with best population development in Cow Creek 

near Fort Howe (station 19), Indian Creek (station 24), Rosebud Creek, and the Tongue River 

downstream from Hanging Woman Creek.

O

EXPLANATION

PERCENT RELATIVE ABUNDANCE 

EQUAL TO OR GREATER THAN 10

PERCENT RELATIVE ABUNDANCE 

LESS THAN 10

DISTRIBUTION MAP

MAJOR DIATOM ECOTYPES 99
ECOTYPE: NAVICULA VIRIDULA VAR. AVENACEA (BREB. EX GRUN.) V. H.

Biotype(s):

N. viridula var. avenacea (Breb. ex Grun.) V. H.

Reference:

Patrick and Reimer, 1966 (p. 507; pi. 48, fig. 10)

Herbarium slide number: 

1-3-16

Mean percent relative abundance: 

2.8

Percent occurrence:

45.7

Abundance-occurrence index:

127.7

Preferred percent occurrence: 

8.9

Maximum percent relative abundance: 

49.3

Station number: 12 

Date: June 10, 1978 

Type of collection: E

10

Description:

Striae, 12-14 in 10 /on. Length, 47.8 /*m. Width, 

10.4 /im. A large, lanceolate Navicula with a 

large, rounded central area. Distinguished from 

N. lanceolata (Ag.) Kutz. and from other varieties of N. viridula in that the ends are not set 

off from the valve body.

100 ECOLOGY AND DISTRIBUTION OF MAJOR DIATOM ECOTYPES IN MONTANA
Water-quality profile:

Variable

Specific conductance (/-imho/cm) -

TAmnm-fltnrpi ( °C*~\

Turbidity (NTU)

Oxygen, dissolved (mg/L) 

Biochemical oxygen demand (mg/L) 

Hardness, total (mg/L CaCO3) 

Calcium, dissolved (mg/L) 

Magnesium, dissolved (mg/L) 

Sodium, dissolved (mg/L) 

Bicarbonate (mg/L) 

Carbonate (mg/L) 

Alkalinity, total (mg/L CaCO3 ) 

Sulfate, dissolved (mg/L) 

Chloride, dissolved (mg/L) 

Fluoride, dissolved (mg/L) 

Dissolved solids, calculated (mg/L) 

Sediment, total suspended (mg/L) 

Nitrogen, total NO2 +NO3 (mg/L as N)

Nitrogen, total ammonia (mg/L as N) 

Phosphorus, total (mg/L as P) 

Phosphorus, total ortho (mg/L as P) 

Iron, total recoverable (mg/L) 

Manganese, total recoverable (mg/L) 

Number 

of Range 

samples

142 

142 

141 

140 

108 

43 

86 

86 

86 

92 

94 

20 

94 

92 

92 

90 

86 

131 

77 

86 

100 

105 

63 

56

239-7030

7

CA Q TO

1.0 30.5

O R QOKA

5.40 19.0

0.5 8.9

123-1430 

16.0- 190

1 O C O/l O

Q 1 1470 ^. -L J.^ f w

1 K T7C

0.5- 29.0 

13- 636 

34 3400

0.4 174

0.04 1.5

184 5800

0.2-8260 

0.01 0.53

0.01- 0.57 

0.010 3.7

0.001 2.5

0 09 91

0.005- 0.27

Optimum (percent 

Preferred relative abundance 

range in parentheses)

782- 2550 

81 n. ft AO

17 91 ft

17 IQft

8.10 14.0

1

A O CT .4- 3.5

379- 967 

65.6- 121

CO A 1 C1

n

o 14.A

QI7A CQC

1.0- 4.1

310- 521 

m77ft

2 c 140

0.1 1.1

C"7O 1 "7QA

1.8- 413 

0.01- 0.34 

0.01- 0.07 

0.020 0.079

0.004 0.058

0.02 0.75

0.020- 0.17

1280(49.3) 

8.42(49.3) 

15.0(49.3) 

6.7(49.3) 

9.55(49.3) 

1.4(32.2) 

764(32.2) 

107(32.2) 

121(32.2) 

93.8(32.2) 

473(32.2) 

1.0(22.1) 

388(32.2) 

565(32.2) 

2.9(32.2) 

0.4(32.2) 

1360(32.2) 

9.6(49.3) 

0.32(29.1) 

0.04(29.1) 

0.050(32.2) 

0.028(32.2) 

0.60(32.2) 

0.17(32.2)

Ecological summary:

Prefers fresh to slightly brackish waters with 

relatively small concentrations of sodium; gravel 

substrates (0.6- to 3-cm diameter); and medium 

streams (0.1 to 100 ft»/s) at all but the highest 

elevations (less than 4,000 ft) in the study area. 

Eurythermal between 1 and 22 °C. Tolerates 

some suspended sediment and turbidity. Spring 

(April to June) dominant.

Distribution summary:

Found throughout the study area. Best population development in the Rosebud Creek and 

upstream Tongue River drainages.

O

EXPLANATION

PERCENT RELATIVE ABUNDANCE 

EQUAL TO OR GREATER THAN 10

PERCENT RELATIVE ABUNDANCE 

LESS THAN 10

DISTRIBUTION MAP

MAJOR DIATOM ECOTYPES 101
ECOTYPE: NITZSCHIA ACICULARIS W. SMITH

Biotype(s):

N. acicularis W. Smith var. acicularis

Reference:

Hustedt, 1930b (p. 423; fig. 821)

Herbarium slide number: 

1-3-18

Mean percent relative abundance: 

0.6

Percent occurrence: 

47.6

Abundance-occurrence index: 

30.9

Preferred percent occurrence: 

0.8

Maximum percent relative abundance: 

29.3

10

Station number: 32 

Date: October 29, 1979 

Type of collection: E

Description:

Keel puncta 17-23 in 10 /mi. Length, 48.0 /tin. 

Width, 4.0 /on. A very slender Nitzschia with 

long, protracted ends. Striae extremely fine, 

hardly if at all visible under most optical microscopes. Similar to N. closterium, except that the 

ends are straight and not curved.

102 ECOLOGY AND DISTRIBUTION OF MAJOR DIATOM ECOTYPES IN MONTANA
Water-quality profile:

Variable

Specific conductance (/tmho/cm) 

Temperature (°C) 

Turbidity (NTU) ____ 

Oxygen, dissolved (mg/L) 

Biochemical oxygen demand (mg/L) 

Hardness, total (mg/L CaCO3) 

Calcium, dissolved (mg/L) 

Magnesium, dissolved (mg/L) 

Sodium, dissolved (mg/L) 

RiPflvVinnsii"^ (mcfff A

Carbonate (mg/L) 

Alkalinity, total (mg/L CaCO3)

Sulfate, dissolved (mg/L) 

Chloride, dissolved (mg/L) 

T^liKYPiHci rli ccnl^rcirl (mcrfl ,}

Dissolved solids, calculated (mg/L) 

Sediment, total suspended (mg/L) 

Nitrogen, total NO2 +NO3 (mg/L as N) 

Nitrogen, total ammonia (mg/L as N) 

Phosphorus, total (mg/L as P) 

Phosphorus, total ortho (mg/L as P) 

Iron, total recoverable (mg/L) 

Manganese, total recoverable (mg/L) 

Number 

of Range 

samples

162 

161 

163 

157 

119 

47 

91 

91 

91 

102 

109 

25 

109 

102 

102 

99 

91 

145 

70 

86 

107 

107 

64 

51

270- 

7.50- 

1 3

0.5-] 

4.52- 

0.5

Q9

i £ n

5

n

Q 1

45

O c

QQ

OA

1 9

0.1

IQfi

0.2-S 

0.01- 

0.01- 

0.010

0.001- 

0.02- 

0.015-

8700 

8.80 

30.5 

L1600 

19.0 

4.9 

3320 

360 

605 

1770 

913 

38.4 

748 

5450 

126 

1.5 

7680 

52600 

0.80 

0.21 

0.60 

0.38 

1.1 

0.41

Optimum (percent 

Preferred relative abundance 

range in parentheses)

798-: 

8.21-

8

0

1.7- 

11.7-

1 R

359-

R^ 9

Arr rr 47.7-

46.2- 

970

4.8

ooc

A 9

0.4

CCQ

0.9- 

0.02- 

0.01- 

0.010 0

0.010-0 

0.05- 

0.019-0

2620 

8.45 

10.5 

23 

11.7 

1.8 

359 

65.2 

47.7 

46.2 

274 

4.8 

232 

211 

4.2 

0.4 

653 

45.6 

0.02 

0.02 

.020 

.010 

0.05 

.019

2620(29.3) 

8.21(29.3) 

10.5(29.3) 

23(29.3) 

11.7(10.9) 

1.8(10.9) 

359(10.9) 

65.2(10.9) 

47.7(10.9) 

46.2(10.9) 

274(29.3) 

4.8(10.9) 

225(29.3) 

211(10.9) 

4.2(10.9) 

0.4(10.9) 

653(10.9) 

45.6(29.3) 

0.02(10.9) 

0.02(29.3) 

0.020(29.3) 

0.010(29.3) 

0.05(10.9) 

0.019(10.9)

Ecological summary:

Prefers fresh to somewhat brackish waters; 

pH greater than 8.00; cold temperatures (8.0 to 

10.5 °C); sand substrates (0.05- to 2-mm diameter); and larger streams (10 to 100 fts/s) at 

lower elevations (less than 2,500 ft). Fall (October and November) dominant. Tolerates considerable amounts of suspended sediment and turbidity, but does best at smaller concentrations.

Distribution summary:

Found throughout the study area. Best population development in the Little Powder River 

and the downstream part of the Powder River.

O

EXPLAN ATI ON

PERCENT RELATIVE ABUNDANCE 

EQUAL TO OR GREATER THAN 10

PERCENT RELATIVE ABUNDANCE 

LESS THAN 10

DISTRIBUTION MAP

MAJOR DIATOM ECOTYPES 103
ECOTYPE: NITZSCHIA AMPHIBIA GRUN.

Biotype(s):

N. amphibia Grun. var. amphibia

Reference:

Hustedt, 1930b (p. 414; fig. 793)

Herbarium slide number: 

1-3-19

Mean percent relative abundance: 

0.3

Percent occurrence: ___ 10

42.4

Abundance-occurrence index: 

13.1

Preferred percent occurrence: 

0.3

Maximum percent relative abundance:

15.7

* «> * « ! 

» . * I 1

I !» » 

Station number: 4 

Date: June 16, 1978 

Type of collection: F

Description:

Striae, 17-18 in 10 jim. Keel puncta, 9-10 in 

10 fim. Length, 17.5 ^m. Width, 3.8 jim. A relatively small Nitzschia with coarse striae and keel 

puncta. Easily distinguished on this basis from 

the other species of Nitzschia in the study area.

104 ECOLOGY AND DISTRIBUTION OF MAJOR DIATOM ECOTYPES IN MONTANA
Water-quality profile:

Variable

Specific conductance (/^mho/cm) 

Tpmnpratiirp (°C,}

Turbiditv CNTU)

OwcTfin HiccnlvfiH fmcr/T/l

Biochemical oxygen demand (mg/L) 

Hardness, total (mg/L CaCO3) 

Calcium, dissolved (mg/L) 

Magnesium, dissolved (mg/L) 

Sodium, dissolved (mg/L) 

Bicarbonate (mg/L) 

Carbonate (mg/L) 

Alkalinity, total (mg/L CaCO3) 

Sulfate, dissolved (mg/L) 

Chloride, dissolved (mg/L) 

PMiinviHp Hiccnl vpH fmcr/T .^

Dissolved solids, calculated (mg/L) 

Sediment, total suspended (mg/L) 

Nitrogen, total NO2 +NO3 (mg/L as N)

Nitrogen, total ammonia (mg/L as N) 

Phosphorus, total (mg/L as P) 

Phosphorus, total ortho (mg/L as P) 

Iron, total recoverable (mg/L) 

Manganese, total recoverable (mg/L) 

Number 

of 

samples

140

140

1 QQ

1 QQ

1 0*.

40

87

ft7

87 

96 

Qfi w 

99

96 

Q6

96 

95

C7

129

en

Q1

101

100

CO

KO

(

Range Preferred r 

range

270 6400 2410 2410

7.62- 8.80 8.52-8.52 

1.3 30.5 25.5 25.5

O K 11 finn OQ OQ

0.80 19.0 8.00 8.00

10 83

92- 3320 

i a c\ QQn

5.0- 605 

9.1- 1230 

4.K Q1 Q

0.5 38.4

39_ 748 

n4.04.fl

0.4- 54.6 

n i 17

i oft soon

0.4-22600 

0.01 0.80

0.01 0.57

0.010 0.15

0.001 0.080

0 02 14

0.010 0.41

)ptimum (percent 

elative abundance 

in parentheses)

2410(15.7)

8.52(15.7)

OK K/'l K I7\

OQ/1 K rf\

8

f\f\fi K I7\

3

/VK -I \

1230(5.1) 

i ^fir^ i ^

203(5.1) 

740(5.1)

cc-t (c i \

U on Q^

542(5.1) 

91 lor*, i^

10.9(5.1) 

0 4-C^ 1 ^

QOOA/K i N\

27.6(6.4)

O OfVO C^

0.02(6.4)

0.090(6.4)

0.041(6.4)

1 1(9 9^

0 99/9 9^

Ecological summary:

Prefers warm, brackish, sodium sulfate waters; 

pH greater than 8.00; fine to medium gravels 

(0.2- to 3-cm diameter); and larger streams (10 

to 100 fta/s) at lower elevations (less than 2,500 ft). 

Tolerates some suspended sediment and turbidity. Spring and early summer (May to July) 

dominant.

Distribution summary:

Distributed throughout the western part of 

study area. Best population development in Mizpah Creek.

O

EXPLANATION

PERCENT RELATIVE ABUNDANCE 

EQUAL TO OR GREATER THAN 10

PERCENT RELATIVE ABUNDANCE 

LESS THAN 10

DISTRIBUTION MAP

MAJOR DIATOM ECOTYPES 105
ECOTYPE: NITZSCHIA CLOSTERIUM (EHR.) W. SMITH

Biotype(s):

N. closterium (Ehr.) W. Smith var. closterium

Reference:

Hustedt, 1930b (p. 424; fig. 822)

Herbarium slide number: 

1-4-7

Mean percent relative abundance: 

1.5

Percent occurrence: 

40.8

Abundance-occurrence index: 

61.9

Preferred percent occurrence: 

3.8

Maximum percent relative abundance: 

52.3

Station number: 8 

Date: September 5, 1979 

Type of collection: C

Description:

Keel puncta, 12-18 in 10 ^m. Length, 75.0 ^m. 

Width, 4.8 jton. A seemingly transparent Nitzschia with extremely fine striae that are practically invisible under all but the best quality 

optical microscopes. Similar to N. acicularis, except that the ends are curved instead of straight. 

This taxon often has been called N. longissima 

var. reversa Grun. by American workers. N. longissima (Breb.) Ralfs is an extremely large and 

robust marine diatom. N. closterium is much 

smaller and finer in detail and apparently restricted to inland waters. Hustedt (1930b) writes 

that the ends of N. closterium can be bent either 

in the same direction or in opposite directions; 

the latter is the most common form in our collections. Distinguished from N. reversa W. Sm., 

which is not found in the study area, by the 

presence of a median gap in the row of keel puncta.

10

106 ECOLOGY AND DISTRIBUTION OF MAJOR DIATOM ECOTYPES IN MONTANA
Water-quality profile:

Variable

Specific conductance (/^mho/cm) 

pH (units) 

TWrm*»rat nr*» ( °P^

Turbidity (NTU) 

Oxygen, dissolved (mg/L) 

Biochemical oxygen demand (mg/L) 

Hardness, total (mg/L CaCO3) 

Calcium, dissolved (mg/L) 

Magnesium, dissolved (mg/L) 

Sodium, dissolved (mg/L) 

Bicarbonate (mg/L) 

Alkalinity, total (mg/L CaCO3) 

Sulfate, dissolved (mg/L) 

Chloride, dissolved (mg/L) 

Fluoride, dissolved (mg/L) 

Dissolved solids, calculated (mg/L) 

Sediment, total suspended (mg/L) 

Nitrogen, total NO2 +NO3 (mg/L as N)

Nitrogen, total ammonia (mg/L as N) 

PVinorkVinviiQ irvfal fmcr/T, a a ~P\

Phosphorus, total ortho (mg/L as P) 

Iron, total recoverable (mg/L) 

Number 

of 

samples

10K

1 9^

125 

88 

26

GH

GH

en

70

76 

10

76 

73 

73 

71

en

1 1 ^

48

81

on

87

35 

on

Range

478 11000

7

C(\ Q I7O

I

Q on K

0.7-11600 

0.80- 19.0 

1.5- 8.3 

no Q/ton

1 R. n QQn

5.0 645

qi i 1QKO

171- 913

O K. QG n

146- 748 

138- 6900 

2.2- 174 

0.04 1.7

416 10400

0

0 oocnn

0.01 0.71

0.01- 0.57 

0.010 3.7

0.001- 2.5 

0.04- 0.75 

0.020 0.41

< 

Preferred i 

range

1 Qfin Q7nn

8

1O Q CK

3

O OT K

3.3- 29 

5.65- 19.0 

3.6- 4.9 

243 1400

qe n i nn

07 i O9C

1 07 1 770

449- 739

inn 9Q fl

368- 606 

507- 5290 

6.8- 27.8 

0.04 1.5

1 con conn

4.0 45.6

0.03 0.10

0.01- 0.21 

0.011 0.11

0.004-0.024 

0.23- 0.75

0 07°. 0 °,7

Optimum (percent 

'elative abundance 

in parentheses)

onqn/co o\

8.32(52.3)

19.4(52.3)

16(52.3) 

11.7(52.3) 

3.6(35.0) 

1400(28.1)

1 QiV9ft 1 1

226(28.1)

1 T7(\(A(\ G\

739(40.6) 

on n/"i K. a\

606(40.6) 

5290(40.6) 

24.4(40.6) 

0.4(40.6)

KOfl/VOQ 1 \

40.1(52.3)

0 04C4.0 fi)

0.17(40.6) 

0.080(40.6)

0.012(40.6) 

0.23(40.6) 

0.11(16.6)

Ecological summary:

Prefers brackish, sodium sulfate waters; fine 

to medium gravels (0.2- to 3-cm diameter); and 

smaller streams (0 to 10 ft3/s) at less than 4,000 ft 

elevation. Tolerates some suspended sediment 

and turbidity. Eurythermal over the range 3 to 

28 °C. Late summer and fall (August to November) dominant.

Distribution summary:

Found throughout the study area. Best population development in Squirrel Creek near Decker 

(station 8).

O

EXPLANATION

PERCENT RELATIVE ABUNDANCE 

EQUAL TO OR GREATER THAN 10

PERCENT RELATIVE ABUNDANCE 

LESS THAN 10

DISTRIBUTION MAP

MAJOR DIATOM ECOTYPES 107
ECOTYPE: NITZSCHIA COMMUNIS RABH.

Biotype(s):

N. bergii A. Cl. var. bergii 

*N. communis Rabh. var. communis

Reference:

Hustedt, 1930b (p. 417; fig. 798)

Herbarium slide number: 

1-3-20

Mean percent relative abundance: 

0.6

Percent occurrence: 

53.0

Abundance-occurrence index: 

31.4

Preferred percent occurrence: 

0.3

Maximum percent relative abundance: 

13.7

Station number: 6 

Date: September 6, 1978 

Type of collection: E

10

Description:

Keel puncta, 14-17 in 10 /on. Length, 26.3 /on. 

Width, 4.2 jim. A small, transparent Nitzschia 

with blunt ends. Striae are so fine as to be practically invisible under most optical microscopes. 

Distinguished from N. palea and other transparent Nitzschias by the broadly rounded rather 

than pointed or protracted ends.

108 ECOLOGY AND DISTRIBUTION OF MAJOR DIATOM ECOTYPES IN MONTANA
Water-quality profile:

Variable

Specific conductance (/tmho/cm) 

pH (units) 

Temperature ( °C)

Turbidity (NTU) ___ _____ _____ 

Oxygen, dissolved (mg/L) 

Biochemical oxygen demand (mg/L) 

Hardness, total (mg/L CaCO3) 

Calcium, dissolved (mg/L) 

Magnesium, dissolved (mg/L) 

Sodium, dissolved (mg/L) 

flovl'wnjii'P fVncr/TA

Alkalinity, total (mg/L CaCO3) 

Sulfate, dissolved (mg/L) 

Fluoride, dissolved (mg/L) 

Dissolved solids, calculated (mg/L) 

Sediment, total suspended (mg/L) 

Nitrogen, total NO2 +NO3 (mg/L as N)-

Nitrogen, total ammonia (mg/L as N) 

Phosphorus, total (mg/L as P) 

Pnn*2TVhrn*ii*2 i"Ai"fil nv4"Vin fTYirr/T . C*G "P^

Iron, total recoverable (mg/L) 

ivl cm frciYiOGO ^f^cil T*o/*fnroY*cir\lo iTYifYM i

Number 

of 

samples

164 

164 j. \j^

IfiK

162 

122 

43 

Q7

Q7

97

1 rvfj

110

97

110

1 rvfj

1 f\fi

in'?

97

 ten

fin

100

11C

iic

64\j^

KC

1

Range Preferred i 

range

438-11000 1250- 1250 

7.41 8.80 8.44 8.44

1

0 orv c

0.5- 4200 67- 67 

0.80- 19.0 9.52- 9.52 

0.5- 8.9 

199. Q4.QO

1 K ft QOQ

18.3- 645 

U K lORH

14.fi Q19

0 5 ^fi 4.

1 33 74fi j.tjtj 1 'xO

Qfi fionn

04 19fi

0 04 17

398-10400 

O O QOCfl 1 O7 1 01?

0.01 0.71 0.02 0.02

0.01 0.57 0.03 0.03

0.010 3.7 0.050 0.050

0.001 2.5 0.052 0.052

0 09 91

0

00*1 0 4.1

Optimum (percent 

 elative abundance 

in parentheses)

1250(14.2) 

8.44(14.2)

1 Q ti(1 Q\

67(14.2) 

9.52(14.2) 

3.3(5.2)

QOO/TT c\

Qfi Qf7 d\

144(7.6)

qc9/7 e\

GOftffJ fi\

O K.C7 K\ .o(,/.b;

C1 Off7 C\ oloi/.b)

1 AK/VT C^

3

tf7 Ct\

O df7 (t\

2270(7.6) 

1 97(1 4. 9>

0.02(14.2)

0.03(14.2)

0.050(14.2)

0.052(14.2)

O Qf*C7 Q\

0 1 Af 7 ft"k

Ecological summary:

Prefers somewhat brackish, sodium sulfate 

waters; gravel bottoms (0.2- to 3-cm diameter); 

and lower elevations (less than 3,000 ft). Indifferent to stream size and season of the year. 

Tolerates considerable amounts of suspended 

sediment and turbidity.

Distribution summary:

Widespread. Best population development in 

Pumpkin Creek.

O

EXPLANATION

PERCENT RELATIVE ABUNDANCE 

EQUAL TO OR GREATER THAN 10

PERCENT RELATIVE ABUNDANCE 

LESS THAN 10

DISTRIBUTION MAP

MAJOR DIATOM ECOTYPES 109
ECOTYPE: NITZSCHIA DISSIPATA (KUTZ.) GRUN.

Biotype(s):

N. dissipata (Kutz.) Grun. var. dissipata

Reference:

Hustedt, 1930b (p. 412; fig. 789)

Herbarium slide number: 

1-4-1

Mean percent relative abundance: 

2.8

Percent occurrence:

74.1

Abundance-occurrence index: 

210.3

Preferred percent occurrence: 

9.5

Maximum percent relative abundance: 

23.4

10

Station number: 24 

Date: July 25, 1978 

Type of collection: E

Description:

Keel puncta, 9-11 in 10 /mi. Length, 21.3 /xm. 

Width, 4.0 fim. A small transparent Nitzschia 

with coarse keel puncta and protracted ends. 

Keel slightly eccentric. Striae extremely fine 

and invisible under most optical microscopes. 

The only member of the Dissipatae group found 

in the study area.

110 ECOLOGY AND DISTRIBUTION OF MAJOR DIATOM ECOTYPES IN MONTANA
Water-quality profile:

Variable

Specific conductance (/tmho/cm) 

pH (units) 

Temperature (°C) - _____________ 

Turbiditv (NTTF)

OYVcrpn HiQQnlvpfl fmcr/T,^

Biochemical oxygen demand (mg/L) 

Hardness, total (mg/L CaCO3) 

Calcium, dissolved (mg/L) 

Magnesium, dissolved (mg/L) 

Sodium, dissolved (mg/L) 

Bicarbonate (mg/L) 

Carbonafp (m&f\ /I

Alkalinity, total (mg/L CaCO3) __________ 

Sulfate, dissolved (mg/L) 

Chloride, dissolved (mg/L) 

Fluoride, dissolved (mg/L) 

Dissolved solids, calculated (mg/L) 

Sediment, total suspended (mg/L) 

Nitrogen, total NO2 +NO3 (mg/L as N) ________ 

Nitrogen, total ammonia (mg/L as N) 

Phosphorus, total ortho (mg/L as P) 

Iron, total recoverable (mg/L) 

IvT cm frcmoco i~/"i4~cil vo^*rtT7o>ioril'* (w\ctf\ i

Number 

of Range 

samples

219 

218 

218 

213 

153 

63

133 

133 

139 

148 

33 

148 

139 

139 

135 

133 

205 

114 

131 

162 

163 

86 

80

239-6100 

7.50- 8.73 

1.0- 30.5 

0.5-3250 

5.40- 15.0 

0.5 8.9

123-2040 

16.0- 254 

13.5- 346 

9.1- 995 

15- 798 

0.5- 24.0 

13- 654 

34-5450 

0.4- 174 

0.1- 1.7 

184-7680 

0.2-8260 

0.01- 0.66 

0.01 0.30

0.010 3.7

0.001 2.5

0 O9 9 1

0.005 0.39

Optimum (percent 

Preferred relative abundance 

range in parentheses)

362- 4350 

8.19- 8.50 

4.3- 23.5 

1.6- 190 

7.70- 14.0

1 fl °. K

181- 1430 

38.6- 174 

20.6- 242 

11.5- 662 

15- 586 

2.0- 8.4 

13- 481 

67- 2390 

2.2- 12.6 

0.2- 1.2 

184- 4020 

0.9- 413 

0.01- 0.19 

0.01 0.05

0.010- 0.13 

0.002 0.079

0.05 1.4

0.019 0.15

690(23.4) 

8.19(23.4) 

19.5(23.4) 

11(23.4) 

7.70(23.4) 

2.2(23.4) 

375(23.4) 

69.6(23.4) 

48.9(23.4) 

12.8(23.4) 

392(23.4) 

2.0(22.0) 

321(23.4) 

69(23.4) 

2.4(23.4) 

0.6(23.4) 

596(23.4) 

67.4(23.4) 

0.08(23.4) 

0.02(23.4) 

0.064(23.4) 

0.023(23.4) 

0.59(23.4) 

0.095(23.4)

Ecological summary:

Prefers fresh to brackish, calcium magnesium 

bicarbonate waters; fine to medium gravels (0.2- 

to 3-cm diameter); and larger streams (greater 

than 10 fts/s) at all but the highest elevations 

(less than 4,000 ft). Eurythermal over a range of 

4 to 24 °C. Tolerates large amounts of suspended 

sediment and turbidity. Summer and fall (June 

to October) dominant.

Distribution summary:

Widespread. Best population development in 

the western part of the study area.

EXPLANATION

PERCENT RELATIVE ABUNDANCE 

EQUAL TO OR GREATER THAN 10

PERCENT RELATIVE ABUNDANCE 

LESS THAN 10

DISTRIBUTION MAP

MAJOR DIATOM ECOTYPES 111
ECOTYPE: NITZSCHIA FILIFORMIS (W. SM.) HUST.

Biotype(s):

N. filiformis (W. Sm.) Hust. var. filiformis

Reference:

Hustedt, 1930b (p. 422; fig. 818)

Herbarium slide number: 

1-4-2

Mean percent relative abundance: 

0.8

Percent occurrence: 

33.2

Abundance-occurrence index: 

27.1

Preferred percent occurrence: 

1.9

Maximum percent relative abundance: 

29.1

10

Station number: 8 

Date: November 1, 1979 

Type of collection: C

Description:

Striae, 35-37 in 10 /im. Keel puncta, 8-10 in 

10 /mi. Length, 107.5 /im. Width, 5.0 /im. A 

long, slender Nitzschia with very fine striae and 

ends that are not set off from the body of the 

valve. Distinguished from N. obtusa by the finer 

striae, smaller size, and narrower valve. Distinguished from N. ignorata Krasske by being 

much less sigmoid in outline.

112 ECOLOGY AND DISTRIBUTION OF MAJOR DIATOM ECOTYPES IN MONTANA
Water-quality profile:

Variable

Specific conductance (^mho/cm) -

r»TT fnni't'C!^

TprrmArntnrp (°C*}

Turbiditv CNTU)

Oxygen, dissolved (mg/L) 

Biochemical oxygen demand (mg/L) 

Hardness, total (mg/L CaCO3) 

Calcium, dissolved (mg/L) 

Magnesium, dissolved (mg/L) 

Sodium, dissolved (mg/L) 

RipavVinnatp fmcr/T ,^

Carbonate (mg/L) 

Alkalinity, total (mg/L CaCO3)

Sulfate, dissolved (mg/L) 

Chloride, dissolved (mg/L) 

Fluoride, dissolved (mg/L) 

Dissolved solids, calculated (mg/L) 

Sediment, total suspended (mg/L) 

Nitrogen, total NO2 +NO3 (mg/L as N) - 

Nitrogen, total ammonia (mg/L as N) 

Phosphorus, total (mg/L as P) 

Phosphorus, total ortho (mg/L as P) 

Iron, total recoverable (mg/L) 

Manganese, total recoverable (mg/L) 

Number 

of Range 

samples

102 

102 

102 

100 

75 

31 

53 

53 

53 

56 

59 

17 

59 

56 

56 

55 

53 

94 

41 

62 

72 

70 

29 

27

540-7030

7

/jc o rjn

1

O OA C

0.8 1500

5.40 19.0

O C Q Q

m t d"\ A

t C A OOO

18.3- 256 

13.7 1470

45 913

O C OC A

QQ 7/1 Q

77 °,4.flfl

1

O 1 OC

0.1 1.5

448-5800 

0.2- 741 

0.01- 0.66 

0.01- 0.22 

0.010- 0.49 

0.001 0.31

0.04 2.1

0.015 0.27

Optimum (percent 

Preferred relative abundance 

range in parentheses)

540- 4800

8 97 ft C.Q

2 ft QO. 9

5

1 /jrp

Q KO 1 Q 7

2

0 o Q

273- 868

rrj c on c

31.4- 160 

19.0- 937 

226- 495

8 9 99 fi

199- 442 

1 no 9Qcn

3 1 9ft n

0.3- 0.4 

448- 4090 

8.6- 127 

0.01- 0.07 

0.01 0.03

0.030-0.057 

n D99 n 0^9

2150(29.1) 

8.27(29.1) 

2.8(29.1) 

14(29.1) 

13.7(29.1) 

2.8(29.1) 

273(15.2) 

57.6(15.2) 

31.4(15.2) 

19.0(15.2) 

226(15.2) 

8.2(15.2) 

199(15.2) 

102(15.2) 

3.1(15.2) 

0.3(15.2) 

448(15.2) 

21.6(29.1) 

0.07(29.1) 

0.03(29.1) 

0.030(29.1) 

0.022(29.1) 

0.36(7.5) 

0.10(7.5)

Ecological summary:

Prefers fresh to brackish waters; coarse sand 

to fine gravel substrates (0.03- to 1-cm diameter); and medium streams (0.1 to 100 fVYs) at all 

but the highest elevations (less than 4,000 ft). 

Tolerates some suspended sediment and turbidity. 

Fall and winter (October and March) dominant.

Distribution summary:

Widespread. Best population development in 

Armells Creek and certain tributaries of the 

Tongue River.

O

EXPLANATION

PERCENT RELATIVE ABUNDANCE 

EQUAL TO OR GREATER THAN 10

PERCENT RELATIVE ABUNDANCE 

LESS THAN 10

DISTRIBUTION MAP

MAJOR DIATOM ECOTYPES 113
ECOTYPE: NITZSCHIA FRUSTULUM (KUTZ.) GRUN.

Biotype(s):

N. frustulum (Kutz.) Grun. var. frustulum 

1N. frustulum var. perminuta Grun. 

2N. frustulum var. perpusilla (Rabh.) Grun. 

N. frustulum var. subsalina Hust.

Reference:

^ustedt, 1930b (p. 415); 2Hustedt, 1930b (p. 415)

Herbarium slide number: 

il_4_3; '1-4-4

Mean percent relative abundance: 

9.1

Percent occurrence: 

93.0

Abundance-occurrence index: 

844.2

Preferred percent occurrence: 

31.1

Maximum percent relative abundance: 

69.7

10

N. frustulum var. perminuta

Station number: 6 

Date: July 31, 1978 

Type of collection: E

Description:

Striae, 28-32 in 10 /mi. Keel puncta, 11-14 in 

10 /mi. Length, 22.3 /on. Width, 3.0 /mi. 2Striae, 

24-26 in 10 /mi. Keel puncta, 7-8 in 10 /mi. 

Length, 7.6 /mi. Width, 2.6 /mi. The Nitzschia 

frustulum complex is the most taxonomically 

perplexing ecotype in the southern Fort Union 

coal region. The two most common and morphologically distinct forms are illustrated and described. Intermediate between the nominate 

variety and variety perpusilla is a seemingly infinite number of variations on the Nitzschia 

frustulum theme, many of them often occurring 

together in a single collection. The median gap 

in each row of keel puncta seems to be a common denominator of all varieties. This complex 

needs a rigorous taxonomic analysis.

N. frustulum var. perpusilla

114 ECOLOGY AND DISTRIBUTION OF MAJOR DIATOM ECOTYPES IN MONTANA
Water-quality profile:

Variable

Specific conductance (^tmho/cm) 

pH (units) 

Temperature (°C)

TnrhiHitvfNTTD J. til UL\JLl\jjf V^-^ * U ) 

Oxygen, dissolved (mg/L) 

Biochemical oxygen demand (mg/L) 

Hardness, total (mg/L CaCO3) 

Calcium, dissolved (mg/L) 

Magnesium, dissolved (mg/L) 

Sodium, dissolved (mg/L) 

Bicarbonate (mg/L) 

C arbonate (mg/L) 

Alkalinity, total (mg/L CaCO3)

Sulfate, dissolved (mg/L) 

Chloride, dissolved (mg/L) 

Fluoride, dissolved (mg/L) 

Dissolved solids, calculated (mg/L) 

Sediment, total suspended (mg/L) 

Nitrogen, total NO2 +NO3 (mg/L as N) 

Nitrogen, total ammonia (mg/L as N) 

Phosphorus, total (mg/L as P) 

Phosphorus, total ortho (mg/L as P) 

Iron, total recoverable (mg/L) 

Manganese, total recoverable (mg/L) 

Number 

of Range 

samples

289 

289 

289 

282 

209 

78 

172 

172 

172 

185 

194 

47 

194 

185 

185 

180 

172 

260 

135 

167 

200 

201 

116 

101

9QQ

7.41

1.0

ft P»

0.80-

O c

92- 

16.0- 

5.0- 

9.1-

1C

O K

1 °«

17

0.4

0.04

184- 

0.2-: 

0.01- 

0.01- 

0.010- 

0.001- 

0.02

0.005-

11000 

8.80 

30.5 

11600 

19.0 

8.9 

3490 

360 

645 

1950 

913 

38.4 

748 

6900 

174 

1.7 

10400 

22600 

0.80 

0.57 

3.7 

2.5 

2.1 

0.41

Optimum (percent 

Preferred relative abundance 

range in parentheses)

480

7.41

1.7

0.7-: 

0.80- 

1 P»

92-

28.8- 

5.0- 

15.8- 

45

ft P»

on

17

i o

ft 9

389- 

0.9-5 

0.01- 

0.01- 

0.010- 

0.001- 

0.04

0.010-

7030 

8.73 

30.2 

L1600 

14.3 

8.9 

3320 

330 

605 

1470 

816 

36.0 

669 

5450 

54.6 

1.5 

7680 

22600 

0.64 

0.57 

3.7 

2.5 

1.4 

0.41

1880(69.7) 

8.41(69.7) 

25.5(69.7) 

22(69.7) 

0.80(69.7) 

6.0(68.8) 

339(69.7) 

65.0(69.7) 

42.9(69.7) 

350(69.7) 

354(69.7) 

12.0(69.7) 

310(69.7) 

782(69.7) 

5.9(69.7) 

0.4(69.7) 

1610(69.7) 

25.8(69.7) 

0.43(64.2) 

0.19(64.2) 

3.7(64.2) 

2.5(64.2) 

0.75(51.4) 

0.086(51.4)

Ecological summary:

Very broad ecological amplitude. Tolerates 

large amounts of suspended sediment and turbidity but does best at smaller concentrations. 

Does well on coarse sand particles or larger 

(greater than 0.3-mm diameter). Present in 

abundance in all size streams, at all elevations, 

and during all seasons. The several biotypes in 

this ecotype may represent several narrower 

and therefore more useful ecological amplitudes; 

however, great care and discipline are required 

to distinguish between them in most collections 

from the study area.

Distribution summary:

Present and abundant in all hydrologic units 

except the Little Powder and Lower Powder. 

This is the most common diatom ecotype in the 

southern Fort Union coal region.

 

O

EXPLANATION

PERCENT RELATIVE ABUNDANCE 

EQUAL TO OR GREATER THAN 10

PERCENT RELATIVE ABUNDANCE 

LESS THAN 10

DISTRIBUTION MAP

MAJOR DIATOM ECOTYPES 115
ECOTYPE: NITZSCHIA LINEARIS W. SMITH

Biotype(s):

N. linearis W. Smith var. linearis

Reference:

Hustedt, 1930b (p. 409; fig. 784)

Herbarium slide number: 

1-4-6

Mean percent relative abundance: 

0.5

Percent occurrence: 

49.2

Abundance-occurrence index: 

22.3

Preferred percent occurrence: 

0.3

Maximum percent relative abundance: 

11.0

Station number: 1 

Date: May 19, 1979 

Type of collection: E

Description:

Striae, 28-30 in 10 /*m. Keel puncta, 8-13 in 

10 urn. Length, 128.0 /xm. Width, 6.5 /*m. A 

long, slender, parallel-sided Nitzschia with very 

fine striae and a shallow notch on one margin 

at midvalve. It does not closely resemble any of 

the other common Nitzschia species in the study 

area. Distinguished from N. intermedia Hantzsch, 

which is not common in the study area, by the 

central notch and much finer striae.

10

116 ECOLOGY AND DISTRIBUTION OF MAJOR DIATOM ECOTYPES IN MONTANA
Water-quality profile:

Variable

Specific conductance (/^mho/cm) 

tVPT fiTni'fe^

Temneraturp ( °C])

TiirhiHitvfNTTD

Ovvcrpn HicjcjnlvpH (mcrff t *\

Biochemical oxygen demand (mg/L) 

Hardness, total (mg/L CaCO3) 

Calcium, dissolved (mg/L) 

Magnesium, dissolved (mg/L) 

Sodium, dissolved (mg/L) 

Bicarbonate (mg/L) 

Carbonate (mg/L) 

Alkalinity, total (mg/L CaCO3) 

Sulfate, dissolved (mg/L) 

Chloride, dissolved (mg/L) 

Fluoride, dissolved (mg/L) 

Dissolved solids, calculated (mg/L) 

Sediment, total suspended (mg/L) 

Nitrogen, total NO2 +NO3 (mg/L as N)

Nitrogen, total ammonia (mg/L as N) 

Phosphorus, total (mg/L as P) 

Phosphorus, total ortho (mg/L as P) 

Iron, total recoverable (mg/L) 

11/1 Tn fTOYl OCO 4~^l4~ll t*O^*^^7Ol*O r^l ^ (imff!* 1

Number 

of Range 

samples

148 

148 

148 

143 

112 

46 

94 

94 

94 

102 

106 

26 

106 

102 

102 

100 

94 

136 

74 

72 

96 

101 

71 

61

oqq cvfin

7

CA Q CA

I

rr Q/J f\

O K OOC

4. co 14 o

0.5 8.9

145 2880

33.2- 360 

15.1 482

9.5 740

22- 816 

0.5- 28.0 

124 669

oo OCOA oo-o5oO

0.4 51.6

0.1 1.7

254 5500

0.2 413

0.01 0.71

0.01 0.17

0.010 0.20

0.001 0.11

0.02 1.1

0.005 0.41

Optimum (percent 

Preferred relative abundance 

range in parentheses)

1300 1300

8

Ofl Q Ofl

ICO 15.O- ICO lo.o

7.0 7.0

9.85- 9.85

2

0 00

en? K.07

86.4- 86.4 

71.0 71.0

126- 126 

548- 548

449- 449 

304 304

4.0 4.0

1.1- 1.1 

1140 1140

i o a i o c

0.01 0.01

0.01 0.01

0.030 0.030

0.013 0.013

0.02 0.02

0.025-0.025

1300(11.0) 

8.20(11.0) 

15.8(11.0) 

7.0(11.0) 

9.85(11.0) 

2.3(11.0) 

507(11.0) 

86.4(11.0) 

71.0(11.0) 

126(11.0) 

548(11.0) 

1.0(5.0) 

449(11.0) 

304(11.0) 

4.0(11.0) 

1.1(11.0) 

1140(11.0) 

12.6(11.0) 

0.01(11.0) 

0.01(11.0) 

0.030(11.0) 

0.013(11.0) 

0.02(11.0) 

0.025(11.0)

Ecological summary:

Prefers cool, slightly brackish waters; relatively small amounts of suspended sediment and 

chloride; coarse sand substrates (0.3- to 2-mm 

diameter); and small streams (0.1 to 1 ft3/s) at 

middle elevations (3,000 to 3,500 ft) in the study 

area. Spring (March to May) dominant.

Distribution summary:

Found in all hydrologic units except those representing the Powder River drainage. Seldom 

occurs in abundance. Best population development in the East Fork of Hanging Woman Creek.

O

EXPLANATION

PERCENT RELATIVE ABUNDANCE 

EQUAL TO OR GREATER THAN 10

PERCENT RELATIVE ABUNDANCE 

LESS THAN 10

DISTRIBUTION MAP

MAJOR DIATOM ECOTYPES 117
ECOTYPE: NITZSCHIA MICROCEPHALA GRUN.

Biotype(s):

N. microcephala Grun. var. microcephala

Reference:

Hustedt, 1930b (p. 414; fig. 791)

Herbarium slide number: 

1-4-8

Mean percent relative abundance: 

1.0

Percent occurrence: 

37.6

Abundance-occurrence index: 

38.4

Preferred percent occurrence: 

2.4

Maximum percent relative abundance: 

40.0

10 (Jim

Station number: 11 

Date: September 21, 1979 

Type of collection: E

Description:

Striae, 33-35 in 10 /mi. Keel puncta, 12-13 in 

10 /mi. Length, 12.4 /mi. Width, 3.6 /mi. A very 

small Nitzschia with protracted and somewhat 

capitate ends. Similar in outline to Cymbella 

microcephala.

118 ECOLOGY AND DISTRIBUTION OF MAJOR DIATOM ECOTYPES IN MONTANA
Water-quality profile:

Variable

Specific conductance (^mho/cm) 

r»TT Tnni'fs^

Tprrmpratnrp ( °P1

rrv...,JL J 'j.__ /XTT'T'r\

Oxygen, dissolved (mg/L) 

Biochemical oxygen demand (mg/L) 

Hardness, total (mg/L CaCO3) 

Calcium, dissolved (mg/L) 

Magnesium, dissolved (mg/L) 

Sodium, dissolved (mg/L) 

Bicarbonate (mg/L) 

Carbonate (mg/L) 

Alkalinity, total (mg/L CaCO3) 

Sulfate, dissolved (mg/L) 

Chloride, dissolved (mg/L) 

Fluoride, dissolved (mg/L) 

Sediment, total suspended (mg/L) 

Nitrogen, total NO2 +NO3 (mg/L as N)

Nitrogen, total ammonia (mg/L as N) 

Phosphorus, total (mg/L as P) 

Phosphorus, total ortho (mg/L as P) 

Iron, total recoverable (mg/L) 

IV/To "n fro "n oco ^"o^ol T*o/*r\T7OT* -a V\l o fiYicfi* *

Number 

of Range 

samples

130 

130 

129 

129 

96 

30 

86 

86 

86 

93 

93 

21 

93 

93 

93 

89 

86 

121 

53 

81 

88 

85 

51 

45

506-

7 CO

1 3

O K

0.80

1 9

1 oq

1 £ n

20.0

19.5

1 Qft

O K

162- 

41

0.4

0.04

49 c

0 9

0.01

0.01

0.010

0.001

0.02

0.005

11000 

8.80 

30.5 

435 

19.0 

8.3 

3490 

330 

645 

1950 

913 

38.4 

748 

6900 

174 

1.7 

10400 

893 

0.80 

0.57 

0.62 

0.52 

1.1 

0.41

Optimum (percent 

Preferred relative abundance 

range in parentheses)

2670- 

7 Qft

3.5- 

0.7

8 fin

1

C

441

54 3 t-F^.O

7Q ft

qc9

AAQ

O K

368- 

1050

q -1

O c

997ft

1.0

0.11

0.01

0.010

O nna

0 1 ^

0.020

4890 

8.70 

24.4 

14 

14.8 

2.7 

1040 

120 

179 

855 

755 

14.0 

619 

1920 

43.1 

1.7 

2880 

46.4 

0.47 

0.07 

0.050 

0.016 

0.34 

0.10

4300(40.0) 

8.70(40.0) 

24.3(40.0) 

1.5(40.0) 

14.8(40.0) 

2.7(40.0) 

808(22.6) 

96.8(22.6) 

137(22.6) 

855(25.2) 

755(25.2) 

14.0(22.6) 

619(25.2) 

1920(25.2) 

17.2(25.2) 

0.6(25.2) 

2510(22.6) 

1.4(40.0) 

0.11(25.2) 

0.07(40.0) 

0.010(40.0) 

0.010(25.2) 

0.34(25.2) 

0.060(25.2)

Ecological summary:

Prefers brackish, sodium sulfate waters; relatively large concentrations of inorganic nitrogen; fine to medium gravels (0.2- to 3-cm diameter); and small streams (0.1 to 1 fts/s) below 

4,000 ft in the study area. Eurythermal between 

3 and 25 °C. Tolerates some suspended sediment, 

turbidity, and chloride. Summer and fall (July 

to October) dominant.

Distribution summary:

Found throughout the study area. Best population development in Armells Creek near Forsyth (station 11).

O

EXPLANATION

PERCENT RELATIVE ABUNDANCE 

EQUAL TO OR GREATER THAN 10

PERCENT RELATIVE ABUNDANCE 

LESS THAN 10

DISTRIBUTION MAP

MAJOR DIATOM ECOTYPES 119
ECOTYPE: NITZSCHIA OBTUSA W. SMITH

Biotype(s):

*N. obtusa W. Smith var. obtusa 

N. obtusa var. scalpelliformis Grun.

Reference:

Hustedt, 1930b (p. 422; fig. 817 a-c)

Herbarium slide number: 

1-2-11

Mean percent relative abundance: 

0.4

Percent occurrence: 

7.0

Abundance-occurrence index:

2.7

Preferred percent occurrence: 

1.6

Maximum percent relative abundance: 

39.6

Station number: 30 

Date: September 30, 1979 

Type of collection: E

Description:

Striae, 30 in 10 /tin. Keel puncta, 5-6 in 10 /on. 

Length, 293.0 /tin. Width, 7.6 /tin. An extremely 

large Nitzschia and one of the longest diatoms 

in the study area. Very similar in appearance to 

N. filiformis but much larger. Hustedt (1930b) 

gives the size range for N. obtusa var. obtusa as 

120 to 350 /tin, whereas N. filiformis var. filiformis is listed as 20 to 100 /mi long.

10

120 ECOLOGY AND DISTRIBUTION OF MAJOR DIATOM ECOTYPES IN MONTANA
Water-quality profile:

Variable

Specific conductance (/^mho/cm) 

T\TT flTm+eA

Temperature ( °C) ___ ___

Tnrhiditv TNTTD

Oxygen, dissolved (mg/L) 

Biochemical oxygen demand (mg/L) 

Hardness, total (mg/L CaCO3) 

Calcium, dissolved (mg/L) 

Magnesium, dissolved (mg/L) 

Sodium, dissolved (mg/L) 

Bicarbonate (mg/L) 

Carbonate (mg/L) 

Alkalinity, total (mg/L CaCO3)

Sulfate, dissolved (mg/L) 

Chloride, dissolved (mg/L) 

Fluoride, dissolved (mg/L) 

Dissolved solids, calculated (mg/L) 

Sediment, total suspended (mg/L) 

Nitrogen, total NO2 +NO3 (mg/L as N) 

Nitrogen, total ammonia (mg/L as N) 

Phosphorus, total (mg/L as P) 

Phosphorus, total ortho (mg/L as P) 

Iron, total recoverable (mg/L) 

Ivl in (Tin oco i"oi"ol vofifHT^Y*o V\l o iiYif'T i

Numbei 

of 

samples

99

99

99

99

18

12 

19

12

1 /;

1 £ 

1 c

 I C

16

1 c

19

90

4 

10

1 *\

1 3

q

Range

i

478 6400

7

Cf\ a 70

1 Q 9Q 9

0.7 11600

6.00- 19.0

 ic q o

92- 2880

OQ Q Q£A

5.0- 496

1 Q A 1 OOA

99fi Q1 ^

5.0 21.0

1 QQ 7Aft

1 fl9 ^Q3A

2.2- 29.1 

0.04 1.7

448 6210

O O 99CAA

0.01- 0.15 

0.01 0.21

0.010 0.080

0.006 0.052

0.04 0.34

0.020- 0.060

(

Preferred r 

range

1020 6400

7 Qft ft *>*>

3 ^ 9Q ft

0.7 17

7.04- 13.1

1

C Q A

824- 2610

1 03 994

137- 496

KK A Q/1Q

KC1 7KK

460 619

1 CO OOOA loo- oyoO

4.2- 29.1

O R 17

OKOA CO1A

1.2 46.4

0.11- 0.15 

0.06 0.06

0.010 0.030

0.010 0.016

0.09 0.34

0.020 0.060

Dptimum (percent 

 elative abundance 

in parentheses)

6400(39.6)

8

99/OQ c\

1 c a/on c\ lo.o(oy.b)

1 QfQQ &}

12.1(39.6) 

Icft "7 a\

2610(39.6)

oo/l/qq f>\

496(39.6)

Q/KV-QQ c\

K7Q/qQ C\

14.0(3.6)

475(39.6)

qcjOA/qa c\

29.1(39.6)

O CfOQ C\

cn-t A/qo c\

1 'V^Q fi">

0.15(11.0) 

0.06(32.4)

OO1 Of^Q R"!

0.016(32.4)

0 1 ftfqo <?"»

0.020(32.4)

Ecological summary:

Prefers extremely hard, brackish waters; relatively large concentrations of inorganic nitrogen; small amounts of suspended sediment and 

turbidity; fine to coarse gravels (0.2- to 6-cm diameter); and small streams (0.1 to 1 fts/s) at 

higher elevations (greater than 3,000 ft) in the 

study area. Eurythermal between 3 and 24 °C. 

Fall (September to November) dominant.

Distribution summary:

Found in all hydrologic units except those representing the Powder and Little Powder Rivers. 

Best population development in Stroud Creek 

(station 39) and the upstream part of Otter Creek 

near the Wyoming border.

EXPLANATION

PERCENT RELATIVE ABUNDANCE 

EQUAL TO OR GREATER THAN 10

PERCENT RELATIVE ABUNDANCE 

LESS THAN 10

DISTRIBUTION MAP

MAJOR DIATOM ECOTYPES 121
ECOTYPE: NITZSCHIA PALEA (KUTZ.) W. SMITH

Biotype(s):

N. kutzingiana Hilse var. kutzingiana 

*N. palea (Kutz.) W. Smith var. palea 

N. palea var. tenuirostris Grun. 

N. paleacea Grun. var. paleacea

Reference:

Hustedt, 1930b (p. 416; fig. 801)

Herbarium slide number: 

1-4-10

Mean percent relative abundance: 

4.5

Percent occurrence: 

91.6

Abundance-occurrence index: 

411.9

Preferred percent occurrence: 

11.6

Maximum percent relative abundance: 

56.6

Station number: 4 

Date: May 12, 1979 

Type of collection: F

Description:

Keel puncta, 12-14 in 10 /*m. Length, 35.5 /an. 

Width, 3.8 /an. The striae are extremely fine 

(35-40 in 10 /an), giving the appearance of transparency under most optical microscopes. The 

shape of the valve varies from linear to narrowly 

lanceolate. The ends are attenuated and somewhat capitate; they are never extremely protracted as in N. acicularis or blunt as in N. communis. Specimens matching the descriptions of 

the four biotypes often are found in the same 

collection, along with any number of intermediate forms. This complex, like the Nitzschia frustulum complex, begs rigorous taxonomic scrutiny.

10

122 ECOLOGY AND DISTRIBUTION OF MAJOR DIATOM ECOTYPES IN MONTANA
Water-quality profile:

Variable

"nTT fnnil'Q^

Tprrmpratnrp ( °P"l

rrv.,,-L J'j_w _ /"\TTvrT\

Oxygen, dissolved (mg/L) 

Biochemical oxygen demand (mg/L) 

Hardness, total (mg/L CaCO3) 

Calcium, dissolved (mg/L) 

Magnesium, dissolved (mg/L) 

Sodium, dissolved (mg/L) 

Bicarbonate (mg/L) 

Carbonate (mg/L) 

Alkalinity, total (mg/L CaCO3) 

Sulfate, dissolved (mg/L) 

Chloride, dissolved (mg/L) 

Fluoride, dissolved (mg/L) 

Dissolved solids, calculated (mg/L) 

Sediment, total suspended (mg/L) 

Nitrogen, total NO2 +NO3 (mg/L as N)

Nitrogen, total ammonia (mg/L as N) 

Phosphorus, total (mg/L as P) 

Phosphorus, total ortho (mg/L as P) 

Iron, total recoverable (mg/L) 

Manganese, total recoverable (mg/L) 

Number 

of Range 

samples

283 

282 

283 

276 

204 

78 

169 

169 

169 

182 

191 

46 

191 

182 

182 

177 

169 

256 

133 

164 

196 

198 

117 

102

OOQ 1 i nnn

7

Cf\ Q Qf\

1

.6- 0 oO.o or» K 

0.5 11600

0.80- 19.0 

0.5- 8.9 

GO QAon

1 a c\ Q£n

5.0- 645

Q 1 IQftO

22- 913 

0.5 38.4

39- 748 

17 6900

0.4- 174 

0.04 1.7

196 10400

0 9 99fiOO

0.01 0.80

0.01 0.57

0.010- 3.7 

0.001- 2.5 

0.02- 2.1 

0.005- 0.41

Optimum (percent 

Preferred relative abundance 

range in parentheses)

478 6100

7 on Q 170

3 f\ 9Q 9

1

O A OCT .0- 4o5

6.00- 19.0 

1.6- 8.9

nr\C f)f\Af\

QC 7 OK4.

25.7- 342

90 0 1 9^0

198- 816 

0.5 26.0

162- 669 

38 5450

1.2- 174 

0.3 1.5

441-7680

1

0 QQQ

0.01 0.42

0.01 0.21

0.010- 0.60 

0.002- 0.38 

0.04- 0.79 

0.025- 0.37

3280(56.6) 

8.30(56.6) 

15.0(56.6) 

22(56.6) 

9.84(56.6) 

2.7(56.6) 

776(56.6) 

123(56.6) 

114(56.6) 

540(56.6) 

495(56.6) 

0.5(24.1) 

406(56.6) 

1450(56.6) 

9.0(56.6) 

0.3(56.6) 

2730(56.6) 

45.1(56.6) 

0.08(18.3) 

0.02(56.6) 

0.040(56.6) 

0.014(56.6) 

0.22(24.1) 

0.10(24.1)

Ecological summary:

Very broad ecological amplitude. Prefers fresh 

to brackish, very hard to extremely hard waters; 

all substrates larger than clay and silt (greater 

than 0.05-mm diameter); and all stream sizes (0 

to greater than 100 fts/s) at middle and lower 

elevations (less than 4,000 ft). Indifferent to 

moderate amounts of suspended sediment, turbidity, and chloride. Spring to fall (May to October) dominant.

Distribution summary:

A dominant ecotype in all hydrologic units of 

the study area. This is the third most common 

ecotype in the southern Fort Union coal region.

O

EXPLANATION

PERCENT RELATIVE ABUNDANCE 

EQUAL TO OR GREATER THAN 10

PERCENT RELATIVE ABUNDANCE 

LESS THAN 10

DISTRIBUTION MAP

MAJOR DIATOM ECOTYPES 123
ECOTYPE: NITZSCHIA SUPRALITOREA LANGE-BERTALOT

Biotype(s):

N. supralitorea Lange-Bertalot var. supralitorea

Reference:

Lange-Bertalot, 1979 (p. 199; figs. 25-27, 76-78)

Herbarium slide number: 

1-4-12

Mean percent relative abundance: 

0.1

Percent occurrence: 

1.4

Abundance-occurrence index: 

0.1

Preferred percent occurrence: 

0.3

Maximum percent relative abundance: 

16.5

10 n,m

 umiimiil

llllllltlUllfl

iiiiiimiiinr,

'" u?,'k j 

... «!.,, 

Station number: 31 

Date: August 18, 1979 

Type of collection: E

Description:

Striae, 24-25 in 10 jim. Keel puncta, 12-13 in 

10 ^m. Length, 20.0 ^m. Width, 4.0 jim. A medium Nitzschia with finely punctate striae, parallel sides and somewhat capitate ends. Closely 

resembles at least three other species that are 

not known to occur in the study area: striae 

and stria puncta are finer than in N. bulnheimiana var. capitata Reimer; sides are parallel 

rather than convex and ends are capitate rather 

than beaked as in N. desertorum Hust.; ends are 

capitate rather than short and beak-like as in 

N. legleri Hust.

124 ECOLOGY AND DISTRIBUTION OF MAJOR DIATOM ECOTYPES IN MONTANA
Water-quality profile:

Number 

Variable of Range 

samples

Specific conductance (/-imho/cm) 

r»TT rnnii'Q^

TWrmpratiirpk ( °P1

Turbidity (NTU) 

Biochemical oxygen demand (mg/L) 

Hardness, total (mg/L CaCO3) 

Calcium, dissolved (mg/L) 

Magnesium, dissolved (mg/L) 

SnHinm HiQcinl vdH (mcrfl ,^

Bicarbonate (mg/L) 

C arbonate (mg/L) 

Alkalinity, total (mg/L CaCO3)

Sulfate, dissolved (mg/L) 

Chloride, dissolved (mg/L) 

PMnni*ifl*i rlicionl \7Arl fmcrft ^\

Dissolved solids, calculated (mg/L) 

Sediment, total suspended (mg/L) 

Nitrogen, total NO2 +NO3 (mg/L as N) 

Nitrogen, total ammonia (mg/L as N) 

Phosphorus, total (mg/L as P) 

Phosphorus, total ortho (mg/L as P) 

Iron, total recoverable (mg/L) 

A^flTl CT flTl AQA i"oi"ol VP^n^f^VO Vl1 P* ^TYl fT/T ^

4 

4 

3 

4 

3 

0 

2 

2 

2 

2 

2 

0 

2 

2 

2 

1 

2 

3 

3 

3 

3 

3 

1 

1

1250-

7.77-

1 K 7

1.3- 

7 04 f »\j^

K.K.C

QQ K

51.0-

1 KfJ

198-

162-

K^Q

8.2- 

1.0-

1 OCA

2.2- 

0.02- 

0.01- 

0.010- 

0.006- 

0.12- 

0.035 (

3290 

8.44 

24.0 

435 

9.52

709 

138 

115 

170 

503

412 

617 

88.9 

1.0 

1410 

893 

0.38 

0.03 

0.60 

0.38 

0.12 

3.035

Optimum (percent 

Preferred relative abundance 

range in parentheses)

1750-

7.77

15.7- 

1.3-

8 A Q

709

no K

115- 

1 ^fl

SOS412

c^q

8.2- 

1.0-

1410 :

9 9

O

oo

0.01- 

0.010 0

0.006-0 

0.12- 

0.035 0

1750 

7.77 

15.7 

1.3 

8.48

709 

93.5 

115 

150 

503

412 

543 

8.2 

1.0 

1410 

2.2 

0.38 

0.01 

.010 

.006 

0.12 

.035

1750(16 

7.77(16 

15.7(16 

1.3(16 

8.48(16

709(16 

93.5(16 

115(16 

150(16 

503(16

412(16 

543(16 

8.2(16 

1.0(16 

1410(16 

2.2(16 

0.38(16 

0.01(16 

0.010(16 

0.006(16 

0.12(16 

0.035(16

.5)

.5) 

.5) 

.5) 

.5)

.5) 

.5) 

.5) 

.5) 

.5)

.5) 

.5) 

.5) 

.5) 

.5) 

.5) 

.5) 

.5) 

.5) 

.5) 

.5) 

.5)

Ecological summary:

Prefers brackish waters; relatively large concentrations of inorganic nitrogen; small streams 

at middle elevations (3,000 to 3,500 ft); and 

small amounts of suspended sediment and turbidity. Summer (August) dominant.

Distribution summary:

Rare. Prairie Dog Creek near Birney (station 

31) and the Powder River near Broadus (station 

46) produced the only populations in the study area.

O

EXPLANATION

PERCENT RELATIVE ABUNDANCE 

EQUAL TO OR GREATER THAN 10

PERCENT RELATIVE ABUNDANCE 

LESS THAN 10

DISTRIBUTION MAP

MAJOR DIATOM ECOTYPES 125
ECOTYPE: NITZSCHIA VALDESTRIATA ALEEM & HUST.

Biotype(s):

N. valdestriata Aleem & Hust. var. valdestriata

Reference:

Foged, 1978 (p. 112; pi. 46, fig. 24)

Herbarium slide number: 

1-4-11

Mean percent relative abundance: 

0.2

Percent occurrence: 

19.2

Abundance-occurrence index: 

3.2

Preferred percent occurrence: 

0.3

Maximum percent relative abundance: 

13.3

S (ATI

Station number: 4 

Date: July 31, 1978 

Type of collection: F

Description:

Striae, 7-8 in 10 ftm. Keel puncta, 4-5 in 10 

lim. Length, 8.5 fim. Width, 2.5 fim. This is a 

very small Nitzschia with blunt ends and very 

coarse striae and keel puncta.

126 ECOLOGY AND DISTRIBUTION OF MAJOR DIATOM ECOTYPES IN MONTANA
Water-quality profile:

Number 

Variable of Range 

samples

Specific conductance (/imho/cm) 

r»PT fnn'ii'C^

Torn nor a til ro ( °C*\

Turbidity (NTU)

Oxygen, dissolved (mg/L) 

Biochemical oxygen demand (mg/L) 

Hardness, total (mg/L CaCO3) 

Calcium, dissolved (mg/L) 

Magnesium, dissolved (mg/L) 

Sodium, dissolved (mg/L) 

Bicarbonate (mg/L) 

Carbonate (mg/L) 

Alkalinity, total (mg/L CaCO3)

Sulfate, dissolved (mg/L) 

Chloride, dissolved (mg/L) 

Fluoride, dissolved (mg/L) 

Dissolved solids, calculated (mg/L) 

Sediment, total suspended (mg/L) 

Nitrogen, total NO2 +NO3 (mg/L as N)

Nitrogen, total ammonia (mg/L as N) 

Phosphorus, total (mg/L as P) 

Phosphorus, total ortho (mg/L as P) 

Iron, total recoverable (mg/L) 

Manganese, total recoverable (mg/L) 

57 

57 

57 

56 

37 

16 

34 

34 

34 

34 

37 

5 

37 

34 

34 

33 

34 

51 

18 

33 

37 

37 

14 

14

542 6100

7 UK. Q Cfl

2 .0- f\ oO.O ork c 

0.8-11600 

0.80- 13.4

O

r Q Q

92- 2110

ic n 9^7

5

ft ^p.?

31.1- 1040

m TJC

0.5 12.0

1 AC CQC

1 1 C QQKfl

2 9 ^1 fi

0.04- 1.1 

416- 5560 

0.7-22600 

0.01- 0.64 

0.01- 0.11 

0.010- 0.25 

0.001- 0.15 

0.08- 0.51 

0.015- 0.26

Optimum (percent 

Preferred relative abundance 

range in parentheses)

Q10

7 89

99 ft

11600-1 

6.90

92-

9ft ft

c n

205- 

37ft

qnq

Qftn

9 9

0.6- 

992- 

22600-2

______

910 

7.82 

22.0 

1600 

6.90

92 

28.8 

5.0 

205 

370

303 

380 

2.2 

0.6 

992 

2600

 

910(13.3) 

7.82(13.3) 

22.0(13.3) 

11600(13.3) 

6.90(13.3) 

1.5(1.1) 

92(13.3) 

28.8(13.3) 

5.0(13.3) 

205(13.3) 

370(13.3) 

12.0(0.6) 

303(13.3) 

380(13.3) 

2.2(13.3) 

0.6(13.3) 

992(13.3) 

22600(13.3) 

0.01(6.3) 

0.03(2.7) 

0.010(6.3) 

0.005(2.7) 

0.34(2.7) 

0.054(2.7)

Ecological summary:

Prefers fresh, moderately hard water of large 

sodium concentration; fine to medium gravels 

(0.2- to 3-cm diameter); and larger streams (10 

to 100 ft3/s) at lower elevations (less than 2,500 ft). 

Tolerates very large amounts of suspended sediment and turbidity. Summer (July) dominant.

Distribution summary:

Widespread but rarely found in abundance. 

Best population development in Mizpah Creek.

EXPLANATION

PERCENT RELATIVE ABUNDANCE 

EQUAL TO OR GREATER THAN 10

PERCENT RELATIVE ABUNDANCE 

LESS THAN 10

DISTRIBUTION MAP

MAJOR DIATOM ECOTYPES 127
ECOTYPE: PLEUROSIGMA DELICATULUM W. SM.

Biotype(s):

P. delicatulum W. Sm. var. delicatulum

Reference:

Patrick and Reimer, 1966 (p. 336; pi. 28, 

figs. 4a-b)

Herbarium slide number: 

1-4-13

Mean percent relative abundance: 

0.7

Percent occurrence: 

51.1

Abundance-occurrence index: 

34.3

Preferred percent occurrence: 

0.8

Maximum percent relative abundance: 

13.4

10

Station number: 14; 30

Date: October 9, 1978; August 29, 1978

Type of collection: F; E

Description:

Striae, 19-22 in 10 /mi. Length, 200.0 /tm. Width, 

14.3 /tm. A very large diatom with a sigmoid 

outline. This is the only species of Pleurosigma 

found to date in the study area. Distinguished 

from species of Gyrosigma in that the striae run 

diagonally across the valve rather than at right 

angles to the transverse and apical axes.

128 ECOLOGY AND DISTRIBUTION OF MAJOR DIATOM ECOTYPES IN MONTANA
Water-quality profile:

Variable

Specific conductance (^mho/cm) 

nTT ^/ i.-L fnnii"Q^ \ V41J.J. UO/ _________________ _ _

Temperature ( °C) 

Turbiditv fNTID

Oxygen, dissolved (mg/L) 

Biochemical oxygen demand (mg/L) 

Hardness, total (mg/L CaCO3) 

Calcium, dissolved (mg/L) 

Magnesium, dissolved (mg/L) 

Sodium, dissolved (mg/L) 

Bicarbonate (mg/L) 

Carbonate (mg/L) 

Alkalinity, total (mg/L CaCO3)

Sulfate, dissolved (mg/L) 

Chloride, dissolved (mg/L) 

T^lnnviHp HiQQnlvpH fmcr/TA

Dissolved solids, calculated (mg/L) 

Sediment, total suspended (mg/L) 

Nitrogen, total NO2 +NO3 (mg/L as N) 

Nitrogen, total ammonia (mg/L as N) 

Phosphorus, total (mg/L as P) 

Phosphorus, total ortho (mg/L as P) 

Iron, total recoverable (mg/L) 

Manganese, total recoverable (mg/L) 

Number 

of 

samples

160 

160 

160

1 tt

122

A /"> 46

Q4 ^*±

Q4 ^*±

Q4 ^*±

QQ77 

1 ft3

90

1 03

QQ^^

QQ77

Q7 7 I

Q4 7*±

145 

69 

91 

103 

104

C-l

55

Range

540-11000 

7.41- 8.73 

2.0- 30.5 

0.6 11600

1.85- 19.0

O .5- C o.o Q O 

Q9 QAQA

1 a f\ Qcn

5.0 645

19.0 1950

ix Q QAQ

O C OC A

1 QQ G.QA

102 6900

1

0 1 nc

0.04 1.7

448 10400

0.2-22600 

0.01- 0.71 

0.01- 0.57 

0.010- 0.62 

0.001- 0.52 

ft ft9 91

0.005- 0.41

(

Preferred r 

range

540- 3160 

8.20- 8.59 

7.2- 21.9 

44 19

10.9- 10.9

O7Q 1 1 Qf)

CT C 1 A Q

31.4 200

19.0 405

99£ 7QR

8

0 Q 9

1 QQ 654

1 ft9 1 44ft

3 1 19^

O Q f\ a

448 2690

10.1- 13.3 

0.01- 0.22 

0.01- 0.04 

0.020-0.057 

0.005-0.033 

0.34 0.39

0.12- 0.14

Dptimum (percent 

 elative abundance 

in parentheses)

3160(13.4) 

8.20(13.4) 

17.8(13.4) 

4.4(13.4)

10.9(13.4)

2

Q(Q f)\

1180(13.4)

143(13.4)

200(13.4)

Q7ftf1 Q A}

498(13.4)

8 9^1 1 Q1

408(13.4)

1 440H 3 4^

12.5(13.4)

0.6(13.4)

OCr7fW1 Q A\

10.1(13.4) 

0.22(13.4) 

0.04(13.4) 

0.020(13.4) 

0.005(13.4) 

0.34(13.4)

0.14(13.4)

Ecological summary:

Prefers fresh to brackish waters with small 

amounts of suspended sediment and turbidity; 

coarse sand to fine gravel substrates (0.03- to 

1-cm diameter); and small to medium streams 

(0.1 to 10 ft3/s) at all but the highest elevations 

(less than 4,000 ft) in the study area. Late summer and fall (August to October) dominant.

Distribution summary:

Widespread and commonly found in the study 

area, but seldom in abundance. Best population 

development in certain tributaries of the Tongue 

River.

EXPLANATION

PERCENT RELATIVE ABUNDANCE 

EQUAL TO OR GREATER THAN 10

PERCENT RELATIVE ABUNDANCE 

LESS THAN 10

DISTRIBUTION MAP

MAJOR DIATOM ECOTYPES 129
ECOTYPE: RHOICOSPHENIA CURVATA (KUTZ.) GRUN. EX RABH.

Biotype(s):

R. curvata (Kutz.) Grun. ex Rabh. var. curvata

Reference:

Patrick and Reimer, 1966 (p. 282; pi. 20, 

figs. 1-5)

Herbarium slide number: 

1-4-14

Mean percent relative abundance: 

2.2

Percent occurrence: 

74.3

Abundance-occurrence index: 

162.1

Preferred percent occurrence: 

4.6

Maximum percent relative abundance: 

67.6

Station number: 8 

Date: June 19, 1980 

Type of collection: E

10

Rudimentary 

raphe valve

Raphe 

valve

Description:

Striae, 12-18 in 10 ^m on raphe valve and 

14-18 in 10 fim on rudimentary raphe valve. 

Length, 26.0 ^m. Width, 6.0 ^m. Like species of 

Achnanthes and Cocconeis, Rhoicosphenia curvata has a fully developed raphe on one valve 

only and is arched in girdle view. Unlike members of these other two genera, R. curvata is heteropolar and has a well-developed pseudoseptum at each end of both valves. It attaches to 

the substrate by a stalk. This is the only species 

of this genus found in the study area.

130 ECOLOGY AND DISTRIBUTION OF MAJOR DIATOM ECOTYPES IN MONTANA
Water-quality profile:

Variable

Specific conductance (/^mho/cm) 

pH (units) 

Temperature (°C)

Turbidity (NTU)

Oxygen, dissolved (mg/L) 

Biochemical oxygen demand (mg/L) 

Hardness, total (mg/L CaCO3) 

Calcium, dissolved (mg/L) 

Magnesium, dissolved (mg/L) 

Sodium, dissolved (mg/L) 

Carbonate (mg/L) 

Alkalinity, total (mg/L CaCO3 )

Sulfate, dissolved (mg/L) 

Chloride, dissolved (mg/L) 

Fluoride, dissolved (mg/L) 

Dissolved solids, calculated (mg/L) 

Sediment, total suspended (mg/L) 

Nitrogen, total NO2 +NO3 (mg/L as N) 

Nitrogen, total ammonia (mg/L as N) 

Phosphorus, total (mg/L as P) 

Phosphorus, total ortho (mg/L as P) 

Iron, total recoverable (mg/L) 

Manganese, total recoverable (mg/L) 

Number 

of Range 

samples

219 

219 

218 

214 

159 

63 

133 

133 

133 

138 

145 

32 

145 

138 

138 

134 

133 

201 

108 

123 

153 

152 

88 

82

9QQ

7 CO

1.7

O K

A CO

0 *»

124-

97 4.

1 Q f\

9.1- 

1 f\

f) C

13- 

17- 

0.4- 

0.1

184- 

0 9

0.01- 

0.01

0.010

0.001

0.02

0.005

11000 

8.72 

30.2 

435 

19.0 

8.9 

3490 

330 

645 

1950 

816 

36.0 

669 

6900 

126 

1.7 

10400 

893 

0.71 

0.57 

0.62 

0.52 

2.1 

0.41

Optimum (percent 

Preferred relative abundance 

range in parentheses)

cin

8.00- 

60

1.4

6 on

0 c

273-

c.7 o

01 A

19.0-

00

8.2- 

180- 

102- 

2.8-

0

0

290-

0 Q

0.01- 

0.01

0.020

0.002

0.21- 

0.064

4200 

8.59 

25.5 

67 

12.7 

3.2 

1400 

192 

224 

622 

576 

36.0 

524 

2200 

15.0 

1.0 

3830 

127 

0.06 

0.03 

0.12 

0.069 

0.21 

0.064

2810(27 

8.29(27 

19.2(27 

25(27 

6.80(27 

3.2(27 

1050(17 

88.0(17 

202(17 

404(17 

566(17 

36.0(17 

524(17 

1270(17 

9.9(17 

0.7(17 

2580(17 

26.8(17 

0.02(15 

0.03(15 

0.050(15 

0.052(15 

0.21(10 

0.064(10

.3) 

.3) 

.3) 

.3) 

.3) 

.3) 

.5) 

.5) 

.5) 

.5) 

.5) 

.5) 

.5) 

.5) 

.5) 

.5) 

.5) 

.5) 

.0) 

.0) 

.0) 

.0) 

.7) 

.7)

Ecological summary:

Prefers fresh to brackish waters; fine to coarse 

gravels (0.2- to 6-cm diameter); and middle elevations (2,500 to 4,000 ft). Tolerates some suspended sediment and turbidity. Apparently 

indifferent to season and stream size. Eurythermal 

between 6 and 26 °C. Requires stable attachment sites.

Distribution summary:

Widespread. Best population development in 

the Tongue River drainage.

O

EXPLANATION

PERCENT RELATIVE ABUNDANCE 

EQUAL TO OR GREATER THAN 10

PERCENT RELATIVE ABUNDANCE 

LESS THAN 10

DISTRIBUTION MAP

MAJOR DIATOM ECOTYPES 131
ECOTYPE: RHOPALODIA GIBBA (EHR.) O. MULL.

Biotype(s):

*R. gibba (Ehr.) O. Mull. var. gibba 

R. gibba var. ventricosa (Kutz.) H. & M. Perag.

Reference:

Patrick and Reimer, 1975 (p. 189; pi. 28, fig. 1)

Herbarium slide number: 

1-4-5

Mean percent relative abundance: 

0.3

Percent occurrence: 

35.9

Abundance-occurrence index: 

10.4

Preferred percent occurrence: 

0.3

Maximum percent relative abundance: 

11.0

Station number: 14 

Date: July 18, 1979 

Type of collection: E

Description:

Costae, 7-8 in 10 /mi. Rows of alveoli, 13-16 

in 10 /mi. Length, 100.0 /mi. Width (frustule in 

valve-girdle view), 27.5 /mi. A large diatom of 

complex structure, generally found in valvegirdle view. Distinguished from the other two 

species of Rhopalodia from the study area R. 

gibberula (Ehr.) O. Mull, and R. musculus (Kutz.) 

O. Mull. by its large size, characteristic shape, 

and median notch on the margin of each valve. 

The two biotypes of R. gibba frequently compose 

a size and morphological continuum in our collections, and the principal author questions 

whether they warrant varietal distinction.

10

132 ECOLOGY AND DISTRIBUTION OF MAJOR DIATOM ECOTYPES IN MONTANA
Water-quality profile:

Variable

Specific conductance (/^mho/cm) - 

 pjj (units)

TVmnpratnrp ( °C\~\

Turbidity (NTU)

Oxygen, dissolved (mg/L) 

Biochemical oxygen demand (mg/L) 

Hardness, total (mg/L CaCO3) 

Calcium, dissolved (mg/L) 

Sodium, dissolved (mg/L) -

Bicarbonate (mg/L) 

fIm*'KnTifi1"o fmcr/T A

Alkalinity, total (mg/L CaCO3) 

Snlfa'fp fllQQnlvPfl ^TTlOr/TA

Chloride, dissolved (mg/L) 

Fluoride, dissolved (mg/L) 

Dissolved solids, calculated (mg/L) 

Sediment, total suspended (mg/L) 

Nitrogen, total NO2 +NO3 (mg/L as N)

Nitrogen, total ammonia (mg/L as N) 

Phosphorus, total (mg/L as P) 

Phosphorus, total ortho (mg/L as P) 

Iron, total recoverable (mg/L) 

A/I 51Y1 CTOT1ACO 4"/"l4" rll yo^rtTTOVl r\l O I TYl {* 

Number Optimum (percent 

of Range Preferred relative abundance 

samples range in parentheses)

115 

115 

116 

111 

74 

28 

75 

75 

75 

80 

86 

24 

86 

80 

80 

78 

75 

108 

43 

63 

83 

82 

53 

45

462-7030 

7 en Q on

1

0 Q/1 C

0.7 150

4.52 19.0

0.5- 8.3 

m QQOfl

16.0- 360 

i o Q cnc

199 14.70

14.fi QIQ

0.5 38.4

133_ 748 _______ 

17 4040

04. ^4. fi

0 04 17

qfiO coon

0 9 Q.9Q.

0 01 0 fi4

0.01-0.57 - 

0.010 0.25

0 001 0 99

0.02 0.75

0.010 0.41

5200(8.3) 

8.02(8.3) 

27.3(8.3) 

15(8.3) 

9.40(8.3) 

1.8(8.3) 

1610(8.3) 

222(8.3) 

256(8.3) 

820(8.3) 

588(8.3) 

21.0(2.0) 

482(8.3) 

2850(8.3) 

23.8(8.3) 

0.4(8.3) 

4760(8.3) 

24.6(8.3) 

0.06(4.5) 

0.17(5.8) 

0.030(8.3) 

0.006(8.3) 

0.32(8.3) 

0.12(8.3)

Ecological summary:

Prefers warm, brackish, sodium sulfate waters; 

fine to medium gravels (0.2- to 3-cm diameter); 

and small streams (0 to 1 ft3/s) at middle elevations (2,500 to 3,000 ft). Summer (June to August) dominant.

Distribution summary:

Widespread but rarely abundant. Best population development in Beaver Creek near Ashland 

(station 14).

EXPL AN ATI ON

A PERCENT RELATIVE ABUNDANCE 

EQUAL TO OR GREATER THAN 10

O

PERCENT RELATIVE ABUNDANCE 

LESS THAN 10

DISTRIBUTION MAP

MAJOR DIATOM ECOTYPES 133
ECOTYPE: STEPHANODISCUS ASTRAEA VAR. MINUTULA (KUTZ.) GRUN.

Biotype(s):

S. astraea var. minutula (Kutz.) Grun.

Reference:

Hustedt, 1930a (p. 369; figs. 193d-e)

Herbarium slide number: 

1-4-16

Mean percent relative abundance: 

0.4

Percent occurrence: 

18.6

Abundance-occurrence index: 

8.0

Preferred percent occurrence: 

0.8

Maximum percent relative abundance: 

35.6

Station number: 51 

Date: May 29, 1976 

Type of collection: A

Description:

Striae, 18-20 in 10 jim. Diameter, 19.0 fim. A 

small to medium Stephanodiscus, ranging in 

size from less than 10 to nearly 30 fim in diameter. Several features distinguish this diatom 

from S. niagarae: The spines are smaller, more 

regularly spaced, and inserted closer to the 

valve margin; no striae are visible on the valve 

mantle; no central strutted processes are present; the striae and the puncta composing the 

striae are finer; and the overall size is generally 

smaller. The principal author considers S. astraea 

var. minutula to be synonymous with S. minutus 

Cleve and Moller. Only in the plankton in water 

from the Tongue River Reservoir do specimens 

of this taxon get larger than 15 fim. in diameter; 

elsewhere in the study area, in stream collections, they are generally in the range of 8 to 12 

im. in diameter.

10

134 ECOLOGY AND DISTRIBUTION OF MAJOR DIATOM ECOTYPES IN MONTANA
Water-quality profile:

Number 

Variable of Range 

samples

Specific conductance (/^mho/cm) 

pH (units) 

Tpmnpraf nrA ( °P1

Turbidity (NTU)

OYVCTPTI HiQQn1v£*H fmcr/TA

Biochemical oxygen demand (mg/L) 

Hardness, total (mg/L CaCO3) 

Calcium, dissolved (mg/L) _

Magnesium, dissolved (mg/L) 

Sodium, dissolved (mg/L) _

Bicarbonate (mg/L) 

Carbonate (mg/L) 

Alkalinity, total (mg/L CaCO3) __________

Sulfate, dissolved (mg/L) 

Chloride, dissolved (mg/L) 

Fluoride, dissolved (mg/L) 

Til QQnl'VAfi Qnlis^Q n*"i 1 pnl t\\r*f\ (~mcff\ .}

Sediment, total suspended (mg/L) 

Nitrogen, total NO2 +NO3 (mg/L as N) 

Nitrogen, total ammonia (mg/L as N) 

Phosphorus, total (mg/L as P) 

Phosphorus, total ortho (mg/L as P) -

Iron, total recoverable (mg/L) - 

Manganese, total recoverable (mg/L) 

44 

43 

42 

38 

31 

13 

22 

22 

22 

22 

28 

6 

28 

22 

22 

21 

22 

42 

17 

17 

32 

32 

13 

11

9QQ qq-in

7

ork o en .80- O.50

2 n 9*3 n

1.2 150

7 04 138

O c no

m i ion

97 A IOQ

1 q c OfkQ

9.1 540

15- 661

q fl 7 n

13- 542 

°,4 14^0

1.3- 16.8 

0.1 1.1

i ft/i oftftn

0.9- 323 

0.01- 0.29 

0.01 0.06

0.010- 0.25 

0.001- 0.15 

0.04- 0.83 

0.019- 0.12

Optimum (percent 

Preferred relative abundance 

range in parentheses)

099 l9Kfk

8.44 8.44

7

n <57

9.52- 9.52

_______

13.1- 127 

0.02- 0.02 

0.03 0.03

0.050-0.050 

0.052-0.052

1250(10.1) 

8.44(10.1) 

9.3(9.6) 

67(10.1) 

9.52(10.1) 

0.5(9.6) 

758(9.6) 

114(9.6) 

115(9.6) 

385(9.6) 

616(9.6) 

5.0(8.6) 

505(9.6) 

1040(9.6) 

12.2(9.6) 

1.1(9.6) 

2300(9.6) 

127(10.1) 

0.02(10.1) 

0.03(10.1) 

0.050(10.1) 

0.052(10.1) 

0.28(9.6) 

0.050(9.6)

Ecological summary:

Prefers cool, fresh to somewhat brackish waters; 

fine to medium gravels (0.2- to 3-cm diameter); 

and larger streams (greater than 1 ft3/s) at all 

but the highest elevations (less than 4,000 ft). 

Tolerates some suspended sediment and turbidity. Spring (May) dominant. Euplanktonic and 

tychoplanktonic.

Distribution summary:

Found in all hydrologic units except those representing the Powder River and the Little Powder River. Best population development (and the 

largest specimens) in the Tongue River Reservoir.

 

O

EX PL AN ATIO N

PERCENT RELATIVE ABUNDANCE 

EQUAL TO OR GREATER THAN 10

PERCENT RELATIVE ABUNDANCE 

LESS THAN 10

DISTRIBUTION MAP

MAJOR DIATOM ECOTYPES 135
ECOTYPE: STEPHANODISCUS NIAGARAE EHR.

Biotype(s):

S. niagarae Ehr. var. niagarae

Reference:

Collins and Kalinsky, 1977 (p. 21; pi. VIII, fig. 9)

Herbarium slide number: 

1-4-15

Mean percent relative abundance: 

0.2

Percent occurrence: 

10.5

Abundance-occurrence index:

1.7

Preferred percent occurrence: 

0.3

Maximum percent relative abundance: 

31.3

Station number: 51 

Date: October 16, 1976 

Type of collection: A

10

Description:

Striae, 14 in 10 /mi. Diameter, 38.0 /mi. This 

is the largest of the common centric diatoms in 

the study area. (Biddulphia laevis Ehr. is considerably larger but rare.) Distinguished from S. 

astraea (Ehr.) Grun. in that the spines are larger 

and inserted submarginally, finely punctate 

striae are visible on the valve mantle, and a variable number of central strutted processes (not 

illustrated) are present.

136 ECOLOGY AND DISTRIBUTION OF MAJOR DIATOM ECOTYPES IN MONTANA
Water-quality profile:

Variable

pH (units) 

Tpmnpratnrp ( °ri l

Turbiditv (NTLH

OYVCTOTI rliccnlvf^ fmcr/T,^

Biochemical oxygen demand (mg/L) 

Hardness, total (mg/L CaCO3) 

Calcium, dissolved (mg/L) 

Magnesium, dissolved (mg/L) 

Sodium, dissolved (mg/L) 

Carbonate (mg/L) 

Alkalinity, total (mg/L CaCO3)

Sulfate, dissolved (mg/L) 

Chloride, dissolved (mg/L) 

Fluoride, dissolved (mg/L) 

Dissolved solids, calculated (mg/L) 

Sediment, total suspended (mg/L) 

Nitrogen, total NO2 +NO3 (mg/L as N)

Nitrogen, total ammonia (mg/L as N) 

Phosphorus, total (mg/L as P) 

Phosphorus, total ortho (mg/L as P) 

Iron, total recoverable (mg/L) 

Ivlon crQY"i oco ir^i'ol vo^r^T7OvoV\lo iTvirf^T ^

Number 

of 

samples

90

1Q

10

14

14

Q&

1Q

1 q

13 

1 3

14

c

14

1 q

1 Q

19

1 q

1Q

1 ^

14

Q\j

(

Range Preferred r 

s range

K4.0 Q9QO

7 .oO- QA o.oU Q CA -

2 A OC A

14. Q4.

7 A/I 1 Q Q

O r Q Q

999 7^8

4.9 i 114.

28.3- 115 

9C Q QQK

99 filfi iiii -" VI J. vl

Q A fi A

146 505

116 1040

97 199

0.3 1.1

9QA 9QOO

O Q Q1 fi

0.01 0.29

0.01 0.06

0.010 0.25

0.002 0.15

0.04 0.60

0.015 0.12

)ptimum (percent 

elative abundance 

in parentheses)

oncfc n\

8

nrj(c n\

1 A 1 (R. 9^

7.0(4.8)

1 A 9fC 9^»

3

ofc o^

qoo/fi o^v

77 f\ffi 9^

48.5(6.2) 

47.0(6.2)

OQQ/'fi ON

6.0(0.9)

9Q7fC 9N

OQ/l/'C 9"v

S C/'C 9N

O Q/'C 9N

rT/-vc//5 n\

7

C//5 Q\ .O(D. Z)

0 09(9 1}

O AQ/'C 9N

0.015(6.2)

O AAQfC 9N

0

1 9^C f)\

0

1 9/'fI 9^

Ecological summary:

Prefers cool, fresh waters with small amounts 

of suspended sediment and turbidity; and large 

streams (greater than 100 fts/s) at lower elevations (2,500 to 3,000 ft). Euplanktonic. Fall (October) dominant.

Distribution summary:

Found in the Tongue River Reservoir and incidental to the Tongue River downstream from 

the reservoir.

EXPLANATION

^ PERCENT RELATIVE ABUNDANCE 

* EQUAL TO OR GREATER THAN 10

~ PERCENT RELATIVE ABUNDANCE 

(J LESS THAN 10

DISTRIBUTION MAP

MAJOR DIATOM ECOTYPES 137
ECOTYPE: STEPHANODISCUS SUBTILIS VAN GOOR

Biotype(s):

S. subtilis Van Goor var. subtilis

Reference:

Bradbury, 1975 (p. 58; pi. 1, figs. 5-6; pi. 4, fig. 3)

Herbarium slide number: 

1-4-17

Mean percent relative abundance: 

0.6

Percent occurrence: 

16.5

Abundance-occurrence index: 

9.8

Preferred percent occurrence: 

1.6

Maximum percent relative abundance: 

80.0

Station number: 51 

Date: May 14, 1976 

Type of collection: A

Description:

Striae, 20 in 10 /*m. Diameter, 7.0 /*m. A small, 

very delicately ornamented Stephanodiscus with 

very subtle spines at the valve margin between 

the striae. Striae composed of one and two rows 

of very fine puncta, which are not visible under 

most optical microscopes. Distinguished from 

other common species of this genus by the very 

fine features and from Cyclotella pseudostelligera by the absence of a central rosette.

138 ECOLOGY AND DISTRIBUTION OF MAJOR DIATOM ECOTYPES IN MONTANA
Water-quality profile:

Variable

Number

of 

samples

Range Preferred 

range

Optimum (percent

relative abundance

in parentheses)

Specific conductance (/tmho/cm) 49 239- 4890 822- 1460 822(80.0)

pH (units) 48 7.70- 8.72 8.28- 8.50 8.50(19.9)

Temperature (°C) 46 3.3- 26.0 3.3- 21.9 3.3(19.9)

Turbidity (NTU) - 49 0.8- 435 7.0- 150 7.0(80.0)

Oxygen, dissolved (mg/L) 32 7.04-13.1 8.21- 12.8 12.8(19.9)

Biochemical oxygen demand (mg/L) 9 1.4- 3.3 3.3(2.5)

Hardness, total (mg/L CaCO3) 28 124- 900 561- 617 617(14.6)

Calcium, dissolved (mg/L) 28 27.4- 143 63.2- 68.9 63.2(14.6)

Magnesium, dissolved (mg/L) 28 13.5- 147 94.0- 112 112(14.6)

Sodium, dissolved (mg/L) 30 9.1- 384 71.0- 133 133(14.6)

Bicarbonate (mg/L) 32 45- 561 429- 460 460(14.6)

Carbonate (mg/L) 15 1.0-10.00 7.0- 7.0 7.0(14.6)

Alkalinity, total (mg/L CaCO3) 32 39- 460 364- 389 389(14.6)

Sulfate, dissolved (mg/L) 30 34-1200 314- 481 481(14.6)

Chloride, dissolved (mg/L) 30 1.3- 174 5.5- 5.6 5.5(14.6)

Fluoride, dissolved (mg/L) 26 0.1- 1.5 0.6- 0.6 0.6(14.6)

Dissolved solids, calculated (mg/L) 28 196-2390 990-1260 1260(14.6)

Sediment, total suspended (mg/L) 45 0.9- 893 13.1- 323 13.1(80.0)

Nitrogen, total NO2 +NO3 (mg/L as N) 19 0.01- 0.32 0.02- 0.02 0.02(10.1)

Nitrogen, total ammonia (mg/L as N) 25 0.01- 0.11 0.01- 0.03 0.01(14.6)

Phosphorus, total (mg/L as P) 36 0.010- 0.60 0.040-0.078 0.040(19.9)

Phosphorus, total ortho (mg/L as P) 36 0.002- 0.38 0.008-0.052 0.015(19.9)

Iron, total recoverable (mg/L) 17 0.05- 1.4 0.08(7.9)

Manganese, total recoverable (mg/L) 14 0.019- 0.15 0.019(7.9)

Ecological summary:

Prefers fresh to slightly brackish waters; fine 

gravels or larger (greater than 0.2-cm diameter); and medium streams (10 to 100 ft*/s) at 

lower elevations (less than 3,000 ft). Eurythermal between 3 and 22 °C. Tolerates large amounts 

of suspended sediment and turbidity. Spring (May) 

dominant. Euplanktonic and tychoplanktonic.

Distribution summary:

Widespread. Best population development in 

the Tongue River Reservoir and the downstream 

part of Rosebud Creek.

O

EXPLANATION

PERCENT RELATIVE ABUNDANCE 

EQUAL TO OR GREATER THAN 10

PERCENT RELATIVE ABUNDANCE 

LESS THAN 10

DISTRIBUTION MAP

MAJOR DIATOM ECOTYPES 139
ECOTYPE: SURIRELLA OVATA KUTZ.

Biotype(s):

*S. ovata Kutz. var. ovata 

S. ovata var. pinnata (W. Sm.) Hust.

Reference:

Hustedt, 1930b (p. 442; figs. 863-864)

Herbarium slide number: 

1-4-18

Mean percent relative abundance:

Percent occurrence: 

67.6

Abundance-occurrence index: 

91.2

Preferred percent occurrence: 

2.4

Maximum percent relative abundance: 

28.1

Station number: 34 

Date: May 28, 1978 

Type of collection: E

Description:

Striae, 16-18 in 10 /mi. Ribs, 4-5 in 10 /*m. 

Length, 28.4 /mi. Width, 13.8 /mi. A small eggshaped diatom; this is the smallest and most 

common species of Surirella in the study area.

140 ECOLOGY AND DISTRIBUTION OF MAJOR DIATOM ECOTYPES IN MONTANA
Water-quality profile:

Variable

Specific conductance (/^mho/cm) 

r»TT fiTni'f'Q^

Tpmnpratiirp ( °C}

TurhiditvCNTTTI

Biochemical oxygen demand (mg/L) 

Hardness, total (mg/L CaCO3) - - 

Calcium, dissolved (mg/L) 

Magnesium, dissolved (mg/L) 

Sodium, dissolved (mg/L) 

Bicarbonate (mg/L) 

Carbonate (mg/L) 

Alkalinity, total (mg/L CaCO3) 

Sulfate, dissolved (mg/L) 

Chloride, dissolved (mg/L) 

Dissolved solids, calculated (mg/L) 

Sediment, total suspended (mg/L) 

Nitrogen, total NO2 +NO3 (mg/L as N)

Nitrogen, total ammonia (mg/L as N) 

Phosphorus, total (mg/L as P) 

Phosphorus, total ortho (mg/L as P) 

Tvnn total yffwvfval'ilp fmcr/T ,^

Manganese, total recoverable (mg/L) 

Number 

of Range 

samples

208 

207 

209 

206 

156 

62 

125 

125 

125 

134 

138 

30 

138 

134 

134 

131 

125 

189 

107 

122 

143 

147 

85 

76

239-8700

7

c A o OA

in QA o

0.5-4200 

5.40 15.0

0.5 8.9

m OQQA

O7 A QCA

1 0 C AftO

Q i 1770

m Q1 Q

0.5 38.4

91- 748 

34-5290 

0.4- 174 

0.1 1.5

196 5560

n 9 3990

0.01 0.71

0.01 0.57

0.010- 2.6 

0.001- 1.8

0 09 91

0.005- 0.39

Optimum (percent 

Preferred relative abundance 

range in parentheses)

1280- 2100

8

1 A Q AC)

A i 91 9

0.9- 11

9

CK 100

2.4- 2.4 

496- 967 

82.8- 121

7A A 1 d"\

100- 138 

393- 636 

1.0- 1.0 

322- 521 

285- 770 

3.5- 51.6 

0.5- 1.0 

1050 1780

4-9 93 9

0.03- 0.13 

0.01 0.04

0.010-0.020 

0.005-0.010 

0.08 0.10

0.030-0.030

2080(28.1) 

8.33(28.1) 

20.0(28.1) 

6.6(28.1) 

10.4(28.1) 

2.4(14.1) 

496(16.1) 

82.8(16.1) 

70.0(16.1) 

124(16.1) 

478(16.1) 

1.0(16.1) 

394(16.1) 

285(16.1) 

4.9(16.1) 

1.0(16.1) 

1050(16.1) 

9.6(18.7) 

0.13(14.1) 

0.01(16.1) 

0.020(14.1) 

0.005(16.1) 

0.10(14.1) 

0.030(11.7)

Ecological summary:

Prefers slightly brackish waters; sand substrates (0.05- to 2-mm diameter); and small 

streams (0.1 to 10 ft*/s) at middle elevations 

(2,500 to 4,000 ft). Eurythermal between 4 and 

22 °C. Tolerates small amounts of suspended 

sediment and turbidity. Spring (March to June) 

dominant.

Distribution summary:

Found throughout the study area; best population development in the western part.

O

EXPLANATION

PERCENT RELATIVE ABUNDANCE 

EQUAL TO OR GREATER THAN 10

PERCENT RELATIVE ABUNDANCE 

LESS THAN 10

DISTRIBUTION MAP

MAJOR DIATOM ECOTYPES 141
ECOTYPE: SYNEDRA FAMELICA KUTZ.

Biotype(s):

S. famelica Kutz. var. famelica

Reference:

Patrick and Reimer, 1966 (p. 139; pi. 5, fig. 9)

Herbarium slide number: 

1-4-19

Mean percent relative abundance: 

0.8

Percent occurrence: 

35.4

Abundance-occurrence index: 

27.1

Preferred percent occurrence: 

2.2

Maximum percent relative abundance: 

30.9

10

Station number: 18 

Date: May 20, 1979 

Type of collection: E

Description:

Striae, 20-21 in 10 /mi. Length, 21.6 /mi. Width, 

2.8 /mi. Distinguished from other species of 

Synedra by its small size, linear shape, fine 

striae, and a central area that is small or absent.

142 ECOLOGY AND DISTRIBUTION OF MAJOR DIATOM ECOTYPES IN MONTANA
Water-quality profile:

Variable

Specific conductance (/tmho/cm) 

pH (units) 

TWnnp»ratnrp» ( °P"l

Turbidity (NTU) ________ 

Oxygen, dissolved (mg/L) 

Biochemical oxygen demand (mg/L) 

Hardness, total (mg/L CaCO3) 

Calcium, dissolved (mg/L) 

Magnesium, dissolved (mg/L) 

Sodium, dissolved (mg/L) 

Bicarbonate (mg/L) 

Carbonate (mg/L) 

Alkalinity, total (mg/L CaCO3)

Sulfate, dissolved (mg/L) 

Chloride, dissolved (mg/L) 

Fluoride, dissolved (mg/L) 

Dissolved solids, calculated (mg/L) 

Sediment, total suspended (mg/L) 

Nitrogen, total NO2 +NO3 (mg/L as N) 

Nitrogen, total ammonia (mg/L as N) 

Phosphorus, total (mg/L as P) 

Phosphorus, total ortho (mg/L as P) 

Iron, total recoverable (mg/L) 

ATflncmn^Q^ fnfal vo^nvovaVilfi fmcr/T ^

Number 

of Range 

samples

115 

115 

116 

115 

98 

36 

79 

79 

79 

86 

86 

14 

86 

86 

86 

85 

79 

103 

48 

70 

76 

76 

54 

45

438-] 

7 ^n

2.4- 

0.5- 

4.52- 

0.8- 

402-

49.3- 

cc n

KK 1

ocfi

O K

91 3

1 134- O A

0.4- 

0.1- 

781-] 

0.2- 

0.01- 

0 01 v/.v/X

0.010- 

0.001

0.02

0.005

L1000 

8.80 

30.2 

60 

15.3 

7.8 

3490 

360 

645 

1950 

816 

38.4 

669 

6900 

54.6 

1.7 

10400 

139 

0.80 

0.17 

0.62 

0.52 

2.1 

0.41

Optimum (percent 

Preferred relative abundance 

range in parentheses)

Qnon

7 ftft

10 Q

0.9- 

7.02- 

1.8- 

1020- 

124- 

143

410

547

14.0

AK.Q

1 9.70

2.2- 

0.3-

O£J7fi

1.0- 

0.01- 

0.01

0.020

0.003

0

1 a

0.035

5760 

8.28 

29.7 

60 

13.6 

2.6 

2880 

360 

482 

930 

764 

14.0 

627 

3530 

24.0 

0.6 

5500 

64.2 

0.03 

0.02 

0.25 

0.22 

0.79 

0.18

5760(30.9) 

8.05(30.9) 

25.3(30.9) 

4.0(30.9) 

10.9(25.9) 

2.2(25.9) 

2880(30.9) 

360(30.9) 

482(30.9) 

545(30.9) 

572(30.9) 

14.0(16.6) 

469(30.9) 

3530(30.9) 

19.2(30.9) 

0.5(30.9) 

5500(30.9) 

5.2(30.9) 

0.03(25.9) 

0.01(25.9) 

0.020(25.9) 

0.003(25.9) 

0.18(30.9) 

0.035(25.9)

Ecological summary:

Prefers warm, brackish, extremely hard waters 

with large concentrations of sulfate; and small 

amounts of suspended sediment and turbidity. 

Apparently indifferent to substrate, stream size, 

and elevation. Tychoplanktonic? Spring and 

summer (May to August) dominant.

Distribution summary:

Widespread. Best population development in 

the western part of the study area.

O

EXPLAN ATIO N

PERCENT RELATIVE ABUNDANCE 

EQUAL TO OR GREATER THAN 10

PERCENT RELATIVE ABUNDANCE 

LESS THAN 10

DISTRIBUTION MAP

MAJOR DIATOM ECOTYPES 143
ECOTYPE: SYNEDRA FASCICULATA (AG.) KUTZ.

Biotype(s):

S. fasciculata (Ag.) Kutz. var. fasciculata 

*S. fasciculata var. truncata (Grev.) Patr.

Reference:

Patrick and Reimer, 1966 (p. 142; pi. 5, fig. 16)

Herbarium slide number: 

1-4-20

Mean percent relative abundance: 

0.8

Percent occurrence: 

42.2

Abundance-occurrence index: 

34.3

Preferred percent occurrence: 

1.4

Maximum percent relative abundance: 

21.6

10

Station number: 3 

Date: November 4, 1978 

Type of collection: E

Description:

Striae, 12-14 in 10 /tin. Length, 69.0 /tin. Width, 

4.6 fim. Distinguished from other species of 

Synedra by the clear ends, broad pseudoraphe, 

coarse striae, and a distinct jelly pore at one 

end of the valve. The two biotypes of this species are distinguished only by the shape of the 

pseudoraphe, the size of the valve, and the lengthto-breadth ratio. Almost all our material from 

the southern Fort Union coal region fits the description for variety truncata.

144 ECOLOGY AND DISTRIBUTION OF MAJOR DIATOM ECOTYPES IN MONTANA
Water-quality profile:

Variable

Specific conductance (/imho/cm) 

TWnnpratnrp f°P1

Turbidity (NTU)

Owcrpn HiQQnlvpH fm cr/T A

Biochemical oxygen demand (mg/L) 

Hardness, total (mg/L CaCO3) 

Calcium, dissolved (mg/L) 

Magnesium, dissolved (mg/L) 

Sodium, dissolved (mg/L) 

Bicarbonate (mg/L) 

f!avV»r»'na+-p fmcr/T ,}

Alkalinity, total (mg/L CaCO3)

Sulfate, dissolved (mg/L) 

Chloride, dissolved (mg/L) 

Fluoride, dissolved (mg/L) 

Dissolved solids, calculated (mg/L) 

Sediment, total suspended (mg/L) 

Nitrogen, total NO2 +NO3 (mg/L as N) 

Nitrogen, total ammonia (mg/L as N) 

PVir»Qr>Vir»vnQ total fmcP/T. aa P^

Phosphorus, total ortho (mg/L as P) 

Iron, total recoverable (mg/L) 

Number 

of Range 

samples

135 

135 

135 

135 

105 

43 

78 

78 

78 

85 

86 

15 

86 

85 

85 

84 

78 

122 

63 

81 

89 

89 

48 

40

4.R9

7

Cf\ .50-

O A

ft ^

4.52-

0

0

907

41.8-

97 3

18.3- 

226- 

ft f\

199- 

44- 

0.4- 

0.04- 

398- 

0.2- 

0.01- 

0.01

0.010

0.001- 

0.02- 

0.010

11000 

8.70 

30.2 

60 

19.0 

8.9 

3490 

360 

645 

1950 

816 

36.0 

669 

6900 

54.6 

1.7 

10400 

135 

0.71 

0.57 

0.62 

0.52 

2.1 

0.41

Optimum (percent 

Preferred relative abundance 

range in parentheses)

1590

7.82- 

60

0

0

6.20- 

o o

1400

187- 

994

537- 

260-

213- 

2200- 

15.0- 

1.0- 

3830- 

0.7- 

0.06- 

0.01

0.020

0.002- 

0.21- 

0.064

5910 

8.19 

24.0 

23 

11.6 

3.2 

2400 

192 

467 

622 

576

472 

3150 

45.6 

1.0 

4650 

5.8 

0.06 

0.05 

0.040 

0.008 

0.21 

0.064

4200(21 

8.10(21 

6.2(21 

4.8(21 

11.6(21 

2.5(21 

1400(21 

192(21 

224(21 

622(21 

576(21 

5.0(4 

472(21 

2200(21 

15.0(21 

1.0(21 

3830(21 

5.3(21 

0.06(21 

0.01(21 

0.020(21 

0.002(21 

0.21(21 

0.064(21

.6) 

.6) 

.6) 

.6) 

.6) 

.6) 

.6) 

.6) 

.6) 

.6) 

.6) 

.5) 

.6) 

.6) 

.6) 

.6) 

.6) 

.6) 

.6) 

.6) 

.6) 

.6) 

.6) 

.6)

Ecological summary:

Prefers cool, brackish, extremely hard, sodium 

sulfate waters; gravel substrates (0.6- to 6-cm 

diameter); and small streams (0.1 to 10 ft3/s) at 

middle elevations (2,500 to 4,000 ft). Sensitive 

to increased levels of suspended sediment and 

turbidity. Summer and fall (July to November) 

dominant.

Distribution summary:

Not found in the Powder River drainage. Best 

population development in Hanging Woman 

Creek and Armells Creek.

O

EXPLANATION

PERCENT RELATIVE ABUNDANCE 

EQUAL TO OR GREATER THAN 10

PERCENT RELATIVE ABUNDANCE 

LESS THAN 10

DISTRIBUTION MAP

MAJOR DIATOM ECOTYPES 145
ECOTYPE: SYNEDRA ULNA (NITZ.) EHR.

Biotype(s):

*S. ulna (Nitz.) Ehr. var. ulna 

S. ulna var. contracta Ostr. 

S. ulna var. danica (Kutz.) V. H. 

S. ulna var. ramesi (Herib.) Hust. 

S. ulna var. spathulifera (Grun.) V. H. 

S. ulna var. subaequalis (Grun.) V. H.

Reference:

Patrick and Reimer, 1966 (p. 148; pi. 7, 

figs. 1-2)

Herbarium slide number: 

1-5-1

Mean percent relative abundance: 

0.8

Percent occurrence: 

53.2

Abundance-occurrence index: 

41.6

Preferred percent occurrence: 

1.9

Maximum percent relative abundance: 

35.6

10

Station number: 48 

Date: April 14, 1979 

Type of collection: E

Description:

Striae, 12-14 in 10 jon. Length, 122.0 jon. Width, 

6.3 (im. A large, highly variable Synedra. Distinguished from other species of this genus by 

the shape of the ends and the shape of the central area.

146 ECOLOGY AND DISTRIBUTION OF MAJOR DIATOM ECOTYPES IN MONTANA
Water-quality profile:

Variable

Specific conductance (/tmho/cm) 

pH (units) 

Temperature ( °C)

Turbidity (NTU)

Oxygen, dissolved (mg/L) 

Biochemical oxygen demand (mg/L) 

Hardness, total (mg/L CaCO3) 

Calcium, dissolved (mg/L) 

Magnesium, dissolved (mg/L) 

Sodium, dissolved (mg/L) 

Bicarbonate (mg/L) 

Carbonate (mg/L) 

Alkalinity, total (mg/L CaCO3) 

Sulfate, dissolved (mg/L) 

Chloride, dissolved (mg/L) 

Fluoride, dissolved (mg/L) 

Dissolved solids, calculated (mg/L) 

Sediment, total suspended (mg/L) 

Nitrogen, total NO2 +NO3 (mg/L as N) _ 

Nitrogen, total ammonia (mg/L as N) 

Phosphorus, total (mg/L as P) 

Phosphorus, total ortho (mg/L as P) 

Iron, total recoverable (mg/L) 

Ivi *"l n iron oca 4~/"&4~ol vo/^/^TTOfO Vila ^TYirv/T "\

Number 

of Range 

samples

161 

161 

164 

155 

123 

48 

105 

105 

105 

114 

120 

24 

120 

114 

114 

111 

105 

149 

85 

94 

116 

119 

76 

65

OQQ

7 ^ft

1.0

ft ^

4.52- 

0.5- 

123- 

16.0-

1 q c

Q 1 & J~

15-

O c

13- 

34- 

0.4

0.1

184 J.O^

ft 9

0.01- 

0.01

0.010

0.001

0.02

0.005

11000 

8.80 

30.5 

1500 

15.3 

7.8 

3490 

328 

645 

1950 

816 

38.4 

669 

6900 

174 

1.7 

10400 

893 

0.80 

0.30 

0.62 

0.52 

2.1 

0.41

Optimum (percent 

Preferred relative abundance 

range in parentheses)

1030

8 Oft

5.0- 

9 ft

9.55-

468-

83.2- 

CQ n

64.0- 

305-

250- 

320- 

5.2-

0

0

841

4 9

0.25-

0.020

0.002

1280 

8.42 

15.0 

6.7 

13.8

468 

83.2 

63.0 

64.0 

305

250 

320 

5.2 

0.3 

841 

9.6 

0.25

0.020 

0.002

1280(13.4) 

8.42(13.4) 

15.0(13.4) 

6.7(13.4) 

9.55(13.4) 

1.5(9.4) 

468(11.9) 

83.2(11.9) 

63.0(11.9) 

64.0(11.9) 

305(11.9) 

4.8(3.2) 

250(11.9) 

320(11.9) 

5.2(11.9) 

0.3(11.9) 

841(11.9) 

9.6(13.4) 

0.25(11.9) 

0.01(9.4) 

0.020(11.9) 

0.002(11.9) 

0.21(9.4) 

0.065(9.4)

Ecological summary:

Prefers cool, fresh waters of large mineral content; relatively large concentrations of inorganic 

nitrogen; coarse gravel substrates or larger 

(greater than 3-cm diameter); and large streams 

(greater than 100 ft3/s) at middle elevations 

(3,000 to 4,000 ft). Sensitive to suspended sediment and turbidity. Spring and fall (March to 

June and October) dominant.

Distribution summary:

Found throughout the study area except in 

the downstream part of the Powder River. Best 

population development is in the Tongue River.

O

EXPLANATION

PERCENT RELATIVE ABUNDANCE 

EQUAL TO OR GREATER THAN 10

PERCENT RELATIVE ABUNDANCE 

LESS THAN 10

DISTRIBUTION MAP

MAJOR DIATOM ECOTYPES 147
ECOTYPE: THALASSIOSIRA PSEUDONANA (HUST.) HASLE & HEIMDAL

Biotype(s):

T. pseudonana (Hust.) Hasle & Heimdal var. 

pseudonana

Reference:

Lowe and Busch, 1975 (p. 121; figs. 1-4)

Herbarium slide number: 

1-1-17

10 

Mean percent relative abundance:

0.5

Valve view 

Percent occurrence:

17.0

Abundance-occurrence index:

9.2 Girdle view

Preferred percent occurrence: 

1.1

Maximum percent relative abundance: 

31.4

Station number: 45 

Date: June 21, 1978 

Type of collection: E

Description:

Striae, (not visible under optical microscopes), 

about 50 in 10 /*m. Marginal fultoportulae (strutted processes), about 11 in 10 fim. Diameter, 3.5 

fim. An extremely small centric diatom; very 

lightly silicified and barely visible, except under 

optimum conditions using the best quality optical microscopes. Distinguished from other centric diatoms by its very small size and the absence of visible ornamentation, except for the 

very faint marginal fultoportulae. In girdle view 

it tends to be relatively thick in relation to its 

width when compared to species of Cyclotella 

and Stephanodiscus (see drawing).

148 ECOLOGY AND DISTRIBUTION OF MAJOR DIATOM ECOTYPES IN MONTANA
Water-quality profile:

Variable

Specific conductance (/^mho/cm) 

pH (units) 

Temperature (°C)

Turbidity (NTU)

Oxygen, dissolved (mg/L) 

Biochemical oxygen demand (mg/L) 

Hardness, total (mg/L CaCO3) 

Calcium, dissolved (mg/L) 

Magnesium, dissolved (mg/L) 

Sodium, dissolved (mg/L) - Bicarbonate (mg/L) 

Carbonate (mg/L) -

Alkalinity, total (mg/L CaCO3)

Sulfate, dissolved (mg/L) -

Chloride, dissolved (mg/L) -

Fluoride, dissolved (mg/L) - Dissolved solids, calculated (mg/L) -

Sediment, total suspended (mg/L) -

Nitrogen, total NO2 +NO3 (mg/L as N)

Nitrogen, total ammonia (mg/L as N) -

Phosphorus, total (mg/L as P) -

Phosphorus, total ortho (mg/L as P) -

Iron, total recoverable (mg/L) -

Number 

of Range 

samples

cc

cc

cc

f)A

QT

1 <=;

QO

09

QO

QQ

QC

4

QP;

QQ

QQ

01

Q9

48

1Q

o/j

0^

QC

10

10-LV/

478 11000

7

R(\ Q TO

47 94 0

1.4-11600

K Aft 1 K Q

O f Q Q

qo 04QO

Oft ft QOft

5.0- 645 

1 o ft 1 Q^O

AK. TCC

1.0- 7.2

QQ ft1 Q

70- 6900 

99 174

0.1 1.5

448 10400

2 Q 99fiOO

0.01 0.32

0.01 0.11

0.010- 0.62 

0.002 0.52

O

f\f* 0 -1

n 09(:; o 9.7

Optimum (percent 

Preferred relative abundance 

range in parentheses)

onon 0.0.10

8 no ft 90

194 189

4 c 94

Q 10 109

2.4- 2.6

Q(2(2 1 1 OH

106 124

1 ac\ one

410 440

COG <?<?1

433 542

1370 1450

10.4 16.8

0.3 1.1

2670- 2880 

9.4- 64.2 

0.01 0.01

0.02 0.02

0.020-0.060 

0.007 0.021

O TQ n TO

0.18- 0.18

3200(23.1) 

8.09(23.1) 

12.4(23.1) 

4.5(23.1) 

9.58(23.1) 

2.4(22.5) 

966(23.1) 

122(23.1) 

160(23.1) 

433(23.1) 

528(23.1) 

1.0(1.4) 

433(23.1) 

1430(23.1) 

16.8(23.1) 

1.1(23.1) 

2690(23.1) 

9.4(23.1) 

0.01(11.9) 

0.02(23.1) 

0.020(23.1) 

0.007(23.1) 

0.79(11.9) 

0.18(11.9)

Ecological summary:

Prefers cool, brackish, extremely hard, sodium 

sulfate waters; fine to medium gravels (0.2- to 

3-cm diameter); and medium streams (1 to 100 

ft3/s) at middle elevations (2,500 to 3,000 ft). Tolerates some suspended sediment, turbidity, and 

chloride. Spring and summer (May to September) dominant.

Distribution summary:

Present in all hydrologic units of the study 

area. Best population development in the downstream reaches of Sarpy Creek, Hanging Woman 

Creek, Otter Creek, and the Little Powder River.

O

EXPLANATION

PERCENT RELATIVE ABUNDANCE 

EQUAL TO OR GREATER THAN 10

PERCENT RELATIVE ABUNDANCE 

LESS THAN 10

DISTRIBUTION MAP

MAJOR DIATOM ECOTYPES 149
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