Algal Conditions and the Potential for Future 

Algal Problems in the Willamette River, Oregon 

By David A. Rickert, Richard R. Petersen, Stuart W. McKenzie, 

Walter G. Hines, and Stephen A. Wille 

RIVER-QUALITY ASSESSMENT OF THE WILlAMETTE RIVER BASIN, OREGON 

G E 0 l 0 G I CAl 5 U R V E Y CIRCUlAR 715-G 

1977 
United States Department of the Interior 

THOMAS S. KLEPPE, Secretary 

Geological Survey 

V. E. McKelvey, Director 

Library of Congress Cataloging in Publication Data 

Rickert, David A., 1940-

Algal conditions and the potential for future algal problems in the Willamette River, Oregon. 

(River-quality assessment of the Willamette River Basin, Oregon) 

(Geological Survey Circular 715-G) 

Bibliography: p. 35-36. 

Supt. of Docs.: I 19.4/2:715-G 

1. Freshwater algae-Oregon-Willamette River. 2. Eutrophication-Oregon-Willamette River. 

3. Water quality-Oregon-Willamette River. 4. Willamette River. I. Rickert, David A., 

1940- II. Series. III. Series: United States Geological Survey Circular 715-G. 

QE75.C5 no. 715-G[QK571.5.07] 557.3'08s[589:39'297953] 76-608336 

Free on application to Branch of Distribution, U.S. Geological Survey, 1200 South Eads Street, Arlington, VA 22202 
FOREWORD 

The American public has identified the enhancement and protection of river 

quality as an important national goal, and recent laws have given this commitment considerable force. As a consequence, a considerable investment has been 

made in the past few years to improve the quality of the Nation's rivers. Further 

improvements will require substantial expenditures and the consumption of 

large amounts of energy. For these reasons, it is important that alternative 

plans for river-quality management be scientifically assessed in terms of their 

relative ability to produce environmental benefits. To aid this endeavor, this 

circular series presents a case history of an intensive river-quality assessment 

in the Willamette River basin, Oregon. 

The series examines approaches to and results of critical aspects of riverquality assessment. The first several circulars describe approaches for providing 

technically sound, timely information for river-basin planning and management. Specific topics include practical approaches to mathematical modeling, 

analysis of river hydrology, analysis of earth resources-river quality relations, 

and development of data-collection programs for assessing specific problems. 

The later circulars describe the application of approaches to existing or potential 

river-quality problems in the Willamette River basin. Specific topics include 

maintenance of high-level dissolved oxygen in the river, effects of reservoir 

release patterns on downstream river quality, algal growth potential, distribution of toxic metals, and the significance of erosion potential to proposed future 

land and water uses. 

Each circular is the product of a study devoted to developing resource information for general use. The circulars are written to be informative and useful to 

informed laymen, resource planners, and resource scientists. This design stems 

from the recognition that the ultimate success of river-quality assessment 

depends on the clarity and utility of approaches and results as well as their basic 

scientific validity. 

Individual circulars will be published in an alphabetical sequence in the 

Geological Survey Circular 715 series entitled uRiver-Quality Assessment of 

the Willamette River Basin, Oregon." 

J. S. Cragwall, Jr. 

Chief Hydrologist 

III 
Cover: Willamette River as it winds through Portland, Oregon. Photograph taken by 

Hugh Ackroyd. 
CONTENTS 

Page 

~bstract____________________________________________ (}1 

Introduction _ _ ______ _ _ ______ _ _ _____ ____ _ _ _______ _ _ __ 1 

The Willamette River basin ________________________ 1 

Willamette River morphology____________________ 2 

Upstream Reach---------------------------- 2 

~evvberg Pool ------------------------------ 4 

Tidal Reach-------------------------------- 4 

Reservoirs______________________________________ 4 

Methods of assessment------------------------------ 4 

Descriptive assessment__________________________ 5 

The data program ------------------------------ 5 

Use of existing data ________________________ 5 

Reconnaissance studies______________________ 5 

Intensive studies____________________________ 6 

Field and laboratory procedures__________________ 6 

Results -------------------------------------------- 7 

~utrients -------------------------------------- 7 ~ itrogen and phosphorus loadings _ _ _ _ _ _ _ _ _ _ 7 

Concentrations of nitrogen, phosphorus, and 

silica ------------------------------------ 7 

Temperature ---------------------------------- 10 

Light penetration ------------------------------ 11 

~lgal populations ------------------------------ 12 

(}eneral characteristics______________________ 12 

Page 

Results-Continued 

~lgal populations-Continued 

~ssemblages ________________________________ (}17 

A dovvnstream traverse______________________ 17 

Comparison vvith historical data ____________ 21 

Primary productivity____________________________ 21 

Light- and dark-bottle method ______________ 21 

Oxygen-curve method ______________________ 24 

Comparison vvith other rivers________________ 24 

Effect of nutrient additions---------------------- 24 

Discussion__________________________________________ 24 

Lovv-temperature limitation ____________________ 25 

Light limitation -------------------------------- 25 

Trace-nutrient limitation------------------------ 28 

Major nutrient limitation________________________ 28 

Carbon ------------------------------------ 28 ~itrogen and phosphorus____________________ 28 

Detention-time limitation ---------------------- 29 

Conceptual model of factors controlling 1 iomass 

1and the nature of algae ----------------------- 30 

Planning implications ------------------------------ 32 

Acknovvledgments ---------------------------------- 33 

(}lossary ------------------------------------------ 33 

References cited ------------------------------------ 35 

ILLUSTRATIONS 

Page 

FIGURE 1. Map and diagram representing the Willamette River, Oreg., shovving distinctive hydrologic reac~es and 

elevation profile ------------------------------------------------------------------------------ (}2 

2-5. (}raphs shovving: 

2. Typical channel cross sections of the Willamette River, at concurrent lovv-fl.ovv conditions________ 3 

3. Time and spatial variations of dissolved orthophosphate phosphorus concentrations in the Willamette River, July-~ovember 1973 ________________________________________________ ------ 8 

4. Time and spatial variations of dissolved major nutrient concentrations in the Willamette River, 

June-November 1974 _____ ------------------------------------------------------------- 9 

5. Time and spatial variations of dissolved silica concentrations in the Willamette River, June-

~ovember 1974 ------------------------------------------------------------------------ 10 

6. Hydrograph of the Willamette River at Portland, 1974 ---------------------------------------------- 11 

7. (}raph showing daily vvater temperatures at mile 7.0, Willamette River, May-September 1974---------- 12 

8. (}raph showing diel-dissolved oxygen curves, light penetration, and elevation profiles for summer bvv-fl.ow 

conditions of the Willamette River, mid-July 1973 ---------------------------------------------- 13 

9-15. (}raphs showing abundance of selected algae, by station and time, in the Willamette River, June-September 

1974: 

9. Stephanodiscus hantzschii __________________________________________________ ---------------- 14 

10. Achnanthes minutissima _____________________________________________________ ------------- __ 14 

11. Melosira distans ______________________________________________________________ ------------ 15 

12. Cymbella uentricosa ------------------------------------------------------------------------ 15 

13. Asterionella formosa ______________________________________________________________ --------__ 16 

14. (}reen algae ------------------------------------------------------------------------------ 16 

15. Anabaena SPP------------------------------------------------------------------------------ 17 

v 
FIGURE 

TABLE 

Page 

16. Graph showing abundance of selected algae in the Willamette River, August 7, 1973 ------------------ G18 

17. Diagram showing summary of the time and spatial distribution of algal populations in the Willamette 

River, ~ay-September 1974____________________________________________________________________ 19 

18. Graphs showing abundance of selected algae in the Willamette River and certain tributaries, August 5-7, 

1974 ---------------------------------------------------------------------------------------- 20 

19. Diagram showing time variation of algal types in the Willamette River, at mile 8.1, April-S<>ptember 

1963 ---------------------------------------------------------------------------------------- 21 

20. Diagram showing time variation of algal types in the Willamette River, at mile 7.0, June-Sc.ptember 

1974 ---------------------------------------------------------------------------------------- 22 

21. Diagram showing relative abundance of diatoms and blue-green algae in net plankton of the Tualatin River 

at Farmington, Oreg., ~arch-August 1973 __________________________________ -------------------- 22 

22-25. Graphs showing: 

22. The vertical distribution of primary gross productivities in the lower Willamette River, at selected 

times during summer, 1974 ------------------------------------------------------------ 23 

23. Effect of nutrient additions on algal productivity of Willamette River samples, mile 7.0, July 24, 

1973 ---------------------------------------------------------------------------------- 25 

24. Effect of nutrient additions on algal productivity ofWillamette River samples, mile 12.8, August 8, 

1974 ---------------------------------------------------------------------------------- 26 

25. Effect ofnutrient additions on algal productivity ofWillamette River samples, mile 12.8, Sc.ptember 

17, 1974 ------------------------------------------------------------------------------ 27 

26. Conceptual diagram relating algal biomass and dominant algal types to water-detention time and light 

penetration ---------------------------------------------------------------------------------- 31 

TABLES 

Page 

1. Selected physical characteristics of the main stem Willamette River, Oreg ---------------------------- G4 

2. Estimated loading of dissolved major nutrients to the Willamette River during summer low-flow conditions 7 

3. Estimated gross primary productivity at the surface of different rivers-------------------------------- 24 

4. Algal counts at mile 7.0, Willamette River, Oreg., during 1973 -------------------------------------- 38 

5. Algal counts at mile 7.0, Willamette River, Oreg., during 1974 -----------------------~-------------- 39 

CONVERSION FACTORS 

{Factors for converting English units to the Intemat10nal System of Units tSII are given below to four s1gn1ficant figures. However, in the text the metric equivalents are 

shown only to the number of significant figures cons1stent with the values for the English umts] 

English 

ft (feet) 

ft/s <feet per second) 

ft/mi (feet per mile l 

ft3/s (cubic feet per second l 

acre-ft (acre-feet) 

mi <miles) 

mi2 (square miles) 

lb/d (pounds per dayl 

Multiply by 

3.048x 10.1 

3.048x 10-1 

1.894xl0·1 

2.832x10-2 

1.233x10-3 

1.609 

2.590 

4.536x 10-1 

VI 

Metric tSII 

m (metres) 

m/s (metres per second) 

m/km (metres per kilometre) 

m3 /s (cubic metres per second) 

hm3 (cubic hectometres) 

km <kilometres) 

km2 (square kilometres) 

kg/d (kilograms per day) 
Algal Conditions and the Potential for Future Algal Problems 

in the Willamette River/ Oregon 

David A. Rickert, Richard R. Petersen, Stuart W. McKenzie, Walter G. Hines, and Stephen J. Wille 

ABSTRACT 

The summertime concentrations of nitrogen and phosphorus in the Willamette River exceed the generally accepted 

threshold levels for excessive algal growth. Nevertheless, the 

primary productivity is low for a river, and the algal community is dominated by diatoms. Bioassay tests with various additions of nitrogen and phosphorus, minor nutrients, and municipal and industrial effluents showed no marked increase in 

algal production over control samples. Results suggest that 

algal growth in the Willamette is maintained in a state of 

healthy balance by short detention times of water and possibly 

also by low light availability resulting from turbidity. 

INTRODUCTION 

In 1972, the Willamette River, Oreg., achieved 

the status of being the largest river in the United 

States for which all known waste-water sources 

(municipal and industrial) received secondary 

treatment. Although this action sharply decreased the waste loading of carbon to the river, 

the loading of nitrogen and phosphorus remained 

high because these nutrients are inefficiently removed by secondary-treatment processes. As a result, summertime concentrations of carbon in the 

Willamette are fairly low, but the concentrations 

of nitrogen and phosphorus are high. 

Despite the high nitrogen and phosphorus 

concentrations, excessive growths of algae (see 

uGlossary" for definition of technical terms) have 

not been observed. The reason might be any one 

of several, including trace-metal limitations, unfavorable water temperatures, high summertime 

turbidities, or short water-detention times. On 

the other hand, the environment in the Willamette River could possibly be approaching a 

condition in which large, problem-causing 

growths of algae might begin to occur. Recent 

work in the Upper Potomac Estuary suggests that 

the initiation of secondary treatment may cause 

ecological shifts in receiving waters and actually 

Gl 

stimulate the growth of nuisance blue-green 

algae (Jaworski and others, 1972). 

This circular characterizes the preq~nt algal 

populations of the Willamette River and attempts 

to determine which environmental factors are the 

major controls on algal growth and rroduction. 

The report also describes the implication of these 

findings to the planning and managenent of future river quality. 

THE WILLAMETTE RIVER Br'SIN 

The Willamette River basin, a watershed of 

nearly 11,500 mi2 (29,800 km2 ) (fig. 1), is located 

in northwestern Oregon between the Cascade and 

Coast Ranges. Within the basin are the State's 

three largest cities, Portland, Salem, and Eugene, 

and approximately 1.4 million people, representing 70 percent of the State's population (1970 census). The Willamette River basin supports an 

economy based on timber, agriculture, industry, 

and recreation and contains extensive fish and 

wildlife habitats. 

The basin is roughly rectangular, with a 

north-south length of about 150 mi (240 km) and 

an east-west width of 75 mi (120 km). Elevations 

vary from less than 10ft (3m) near th~ mouth of 

the Willamette River, to 450 ft (140m) on the 

valley floor near Eugene, to more than 10,000 ft 

(3,000 m) in the Cascade Range. The Coast Range 

varies in average elevation from 1,000 to 2,000 ft 

(300 to 600 m) but includes peaks higher than 

4,000 ft (1,200 m). 

The slopes and foothills of the Cascade Range 

account for more than 60 percent of the basin 

area. About 62 percent of the basin is timberland, 

located largely in the tributary basins (Gleeson, 

1972). Approximately 33 percent of the area is 

farmland, and the remaining 5 percent is urbanized and in other uses. 
(A) 

\ 

s 

( 3 135 mi (217 km) 

187 (301 km) 

{ 

\ 

0 30 MILES 

I '• 11 

0 50 KM 

300 200 100 0 

DISTANCE, IN RIVER KILOMETRES ABOVE MOUTH 

FIGURE 1.-Willamette River, Oreg. (A) Distinctive hydrologic reaches. (8) Elevation profile. 

WILLAMETTE RIVER MORPHOLOGY 

The main stem Willamette River forms at the 

confluence of its Coast and Middle Forks near 

Eugene and flows northward for 187 mi (301 km) 

through the 3,500-mi2 (9,100-km2 ) Willamette 

Valley floor. The river bed drops from an altitude 

of 435 ft (132 m) at Eugene to slightly below 

mean sea level at Portland (fig. 1 ). The Willamette empties into the Columbia River at a 

point which is 99 mi (160 km) from the Pacific 

Ocean. 

The Willamette River comprises three distinctive reaches whose physical characteristics govern the hydraulics of flow and therefor~ the rates 

and patterns of deposition, channel scour, and 

biological activity. Pertinent data for each of the 

three reaches are included in figures 1 and 2 and 

in table 1. 

UPSTREAM REACH 

The Upstream Reach, extending for 135 mi 

(217 km) from Eugene to above Newberg, is 

characterized by a meandering channel. The river 

G2 
River mile 119 (Upstream Reach) River mile 40.8 (Newberg Pool) 0 

\~/ --~----------------------------r-,- 0 

10 

~ 5 V) 

UJ 

UJ 

UJ 20 a: 

~ u. UJ 

z ~ 

£ 

~ 30 a.. 

UJ 

0 3 Discharge== 5280 ft /s 

(150 m%1 

z 

I. 

~ 

6100 ft% 10 a.. Discharge= UJ 

(173 m%1 0 

40 

50 ~------~------~------~~------~15 

River mile 9.2 (Tidal Reach) 

0 .--..-----------------------------------------------------------------------~-0 

10 

5 

20 V) 

UJ 

~ a: UJ ~ 

UJ UJ 

u. ~ 

~ 30 z 

£ 10 £ ~ ~ a.. a.. UJ UJ 0 40 0 

Discharge== 

50 15 

0 200 400 600 800 FEET 

0 100 200 METRES 

FIGURE 2.-Typical channel cross sections of the Willamette River, at concurrent low-flow conditions. The large downstream increases in width and depth greatly affect the hydraulics of flow and, thereby, partly determine tl ':' reach-byreach potential for biological problems. 

is shallow (table 1), and the bed is composed almost entirely of cobbles and gravel which during 

summer are covered with biological growth. 

Although the U.S. Army Corps of Engineers 

has straightened the course of the river in this 

reach considerably, there are still numerous 

meanders, islands, and side channels. At low flow, 

G3 

gravel bars are visible, and, in some places, the 

river is so shallow that small pleasure boats occasionally run aground. 

During low-flow conditions, average stream 

velocity in the Upstream Reach is m'lre than 7 

times that of either of the two downstre:tm reaches 

(table 1 ). During floods, velocities are sufficiently 
TABLE 1.-Selected physical characteristics of the main stem Willamette Riuer, Oreg. 

[CharactenstJcs refer to summer low-flow conditwns of 6 ·~ 103 ft"/s at Salem] 

Representative 

Approxtmate mtdchannel A,.-erage 

Reach Length bed slope water depth velocity 1see fig. 11 IIDJI lftlmtl Bed matenal Itt! 1ftlsl 

Approxtmate 

traveltime 

m reach 

1days1 

Tidal Reach. (11 26.5 <0.1 Intermixed clay, sand, and 40 10.16 10.0 

3.9 

gravel. 

Newberg Pool. (2) 25.5 .12 Intermixed clay, sand, and 25 1.40 

gravel with some cobbles. 

Upstream Reach. (3J 135 2.8 Mostly cobbles and gravel __ 7 22.9 2.8 

'Calculated by \'Olume displacement method using channel cross-sectwnal data. 2Calculated from dye study conducted by U.S. Geological Survey 1Harns. 19681. 

high to transport large quantities of cobbles and 

gravel as bedload. Morphologically, this upstream 

section of the Willamette is an "eroding" reach. 

NEWBERG POOL 

The Newberg Pool extends from just above 

Newberg to the Willamette Falls, a distance of 

25.5 mi (41.0 km). The pool is deep (fig. 2), slowmoving, and can be characterized hydraulically 

as a large stilling basin behind a weir (Willamette Falls). The pool is a depositional reach, as 

evidenced by the elevation profile <fig. 1 ), low velocity, and the presence of fine bottom sediments. 

TIDAL REACH 

The lower 26.5 mi <42.6 km) of the river is a 

deep, slow-moving reach affected by tides and, 

during spring and early summer, by backwater 

from the Columbia River (Velz, 1961 ). The Tidal 

Reach is extensively dredged to maintain a 40-ft 

(12-m) deep navigation channel (fig. 2) from the 

mouth to about river mile (RM) 14. The subreach 

between RM's 5 and 14 is a busy shipping corridor 

known locally as Portland Harbor. 

During the summer low-flow period, net downstream movement is slow, but tidal effects cause 

flow reversals twice daily and large changes in 

velocity. Low-flow hydraulics are most complex in 

the lower 10 mi (16 km) (fig. 2) where, depending 

on hourly changes in tide- and river-stage conditions, Willamette River water may move 

downstream or Columbia River water may move 

upstream. Columbia River water has a slightly 

higher concentration of dissolved solids and is 

commonly several degrees cooler than Willamette 

water. Columbia water is, therefore, denser than 

Willamette water and during part of each day 

(during low flows) moves upstream as a distinct 

bottom wedge to the vicinity of the St. Johns 

Bridge (RM 6). The subsequent downstream 

movement of water is very complex. Depending on 1 

slight variations in tide and relative fl0ws in the 

Willamette and the Columbia, the dC'wnstream 

discharge may be out the mouth of the illamette, 

through Multnomah Channel, or a combination of 

the two. 

Owing to morphological characteristics and 

hydraulic conditions, the subreach between RM's 

10 and 3 is the primary depositional c-rea of the 

Willamette River system. 

RESERVOIRS 

There are 11 major reservoirs in the Willamette River basin, with a combined usable 

capacity of nearly 1.9 million acre-ft (2.,300 hm3 ). 

The reservoirs are designed for multipurpose use, 

but their primary legal function is tl'~ maintenance during summer of a minimum navigable 

depth in the Willamette River <Willarnette Basin 

Task Force, 1969). The required minimum flow 

for navigation is 6,000 ft3 /s ( 170 m3/s) at Salem. 

Other uses of the reservoirs and reservoir water 

include power generation, onsite recreation, flood 

protection, maintenance of adequate f'treamflow 

for anadromous fish propagation, irrigation, and 

flow augmentation for water-quality enhancement. The last use is not explicitly planned but 

occurs as a result of summertime releases made 

for the other purposes. 

METHODS OF ASSESSMENT 

Concern about the potential for algal problems 

led to a search for a suitable assessment method. 

An applied eutrophication model would have 

been ideal. At present, however, tho. complex 

eutrophication process is so poorly understood 

<Rickert and others, 1975a) that it is virtually 

impossible to develop applied models capable of 

quantitative predictions (McGauhey, 1974). Certainly, many years of fieldwork would bo, required 

to obtain data adequate to model tl'o, sources, 

sinks, and transport mechanisms of algal nutriG4 
ents. Even more data would be necessary to quantify the relationship of algal growth to nutrient 

availability and to other environmental factors. 

These considerations indicated that it would be 

virtually impossible to formulate, calibrate, and 

verify a practical eutrophication model within the 

2%-year time span of the study. 

Instead of attempting to formulate a predictive 

mathematical model, a qualitative descriptive 

study was designed to provide insight into the 

potential for nuisance algal growth. 

DESCRIPTIVE ASSESSMENT 

Many river-quality problems exist that presently cannot be assessed through modeling, 

mapping, or the use of other specific methods. 

However, resource-planning information can be 

obtained for most of these problen1s through descriptive assessment. Descriptive assessment is 

basic to all other methods because it is the fundamental basis of scientific endeavor. 

As applied in the algal study, descriptive assessment embodied problem definition, devising 

of hypotheses, collection and analysis of data, 

and exclusion of disproven hypotheses. For some 

specific problems, the cycle was repeated several 

times to refine the remaining possibilities. The 

final results are qualitative, because they provide 

no numerical predictions, but rather a general 

knowledge of the ways in which environmental 

and cultural factors combine to control riverquality phenomena. 

The working hypotheses for this algal study 

were: 

1. Nuisance algal growths are prevented by low 

water temperatures. 

2. Nuisance algal growths are prevented by high 

summertime turbidities. 

3. Nuisance algal growths are prevented by a 

scarcity of certain trace nutrients. 

4. Nuisance algal growths will develop provided 

the loading of major nutrients to the Willamette remains constant or increases and 

loading ratios remain in the present proportion. 

5. Nuisance algal growths are prevented by short 

detention times of water in the Willamette. 

The remainder of this paper is devoted primarily to an examination of these hypotheses to determine which best explain observed algal conditions. The following sections on data programs 

and results are intended for readers interested in 

the technical aspects of the study. The nontechnical reader may wish to progress c

1

irectly to 

the "Discussion." 

THE DATA PROGRAM 

Data to assess the working hypothese2 were obtained through (1) analysis of existing data, (2) a 

reconnaissance-level study, and (3) an intensive 

field study. 

USE OF EXISTING DATA 

Available data on hydrology (fig. 1; table 1) 

were analyzed to determine which reaches of the 

river are most susceptible to possible algal problems. Conditions of high temperature and slowmoving, slowly mixing water would seem to be 

most favorable to the nuisance forms of green and 

blue-green algae. Thus, should nuisance algal 

growths develop in the river, they woulc. probably 

occur in the Tidal Reach and the N ewl: erg Pool. 

Existing water-quality data were examined 

with regard to (1) nutrient loading, (2) nutrient 

concentrations in river water, (3) the types and 

numbers of algae, and (4) physical factors such as 

temperature and light availability. The data provided a good idea of what to expect for tl'c:! loading 

and, as previously noted, for the river concentrations of carbon, nitrogen, and phosphorus. No information was found on the loading and availability of trace algal nutrients. 

Excellent temperature data were available, but 

the sparse data that did exist on algal species, 

algal quantities, and light penetration were from 

the mid-1960's when the river still received some 

untreated and primary treated waste waters. The 

relevance of the data to 1973 conditions was questionable, so a reconnaissance algal-monitoring 

study was immediately devised. 

RECONNAISSANCE STt:DIES 

The reconnaissance-level work consisted of: 

1. A plankton-monitoring network of five stations with three in the Tidal Reach (RM's 

7.0, 12.8, and 21.2) and two in the Newberg 

Pool (RM's 35.0 and 50.0). The stations were 

sampled at least once every 2 weeks from 

June through September of 1973 and 1974 

and occasionally during other n1onths of 

both years. Water samples were collected for 

enumeration of suspended algae and the 

determination of plant nutrientf.. In situ 

G5 
measurements were made of dissolved oxygen (DO), pH, temperature, and light penetration. 

2. Periodic analysis o.f waste-water effluents and 

tributary inflows to determine the river 

loading of major algal nutrients. 

Information obtained from this reconnaissance 

was used to design a series of intensive studies. 

INTENSIVE STUDIES 

The intensive studies were designed to document the chemical and physical conditions associated with the onset of peak algal growth and 

the impact of this growth on river quality. The 

work included the following elements, which 

were done simultaneously: 

1. Intensive sampling at the five stations included in the reconnaissance network. Samples for analysis of algae 'and nutrients were 

collected at least once per day. Incident light 

and light penetration were measured several times a day, whereas temperature, DO, 

and pH were monitored continuously. 

2. Algal production-respiration determinations 

using the light- and dark-bottle DO and 

carbon-14 techniques (Slack and others, 

1973). These were made at several depths 

at the Tidal Reach stations on six different 

occasions. 

3. Enrichment bioassays conducted at the same 

stations and depths, and by the same techniques, as the basic production-respiration 

tests. Treatments included enrichment with 

nitrogen and phosphorus (separately and in 

combination), mixtures of trace nutrients 

(see Environmental Protection Agency, 

1971), domestic sewage effluents, and pulpand paper-mill effluents. These tests were 

run on three occasions. 

FIELD AND LABORATORY PROCEDURES 

Water samples for nutrient and algal analysis 

consisted of several subsamples taken at regular 

intervals across the river and vertically integrated 

to the approximate depth of the euphotic zone. The 

collections were made with a USDH-59 depthintegrating suspended-sediment sampler. 

Each composite euphotic-zone sample was immediately proportioned and prepared for various 

analyses. Aliquots for determination of suspended algae were prepared by the membraneG6 

filter concentration technique (American Public 

Health Association and others, 1971 ); a sample 

size of 100 ml (millilitres) was usually suitable. 

Aliquots for analysis of orthophosphate and silica 

were filtered immediately after collection using 

0.45-~.tm pore-size filters (Millipore-type HA). 1 

The orthophosphate was then extracted with 

isobutanol (Shapiro, 1973a). Aliquots for total 

nitrogen, total phosphorus, ammonia, nitrite, and 

nitrate were transferred to 1-quart pllyethylene 

bottles and kept on ice for return to the laboratory. 

Light intensity was measured at 1-m intervals 

using a Whitney Model LMD-SA underwater 

light meter without color filters. Temperature 

and DO were routinely determined with a YSI 

Model 54 Oxygen Meter. On several occasions, 

temperature, DO, and pH were monitored continuously for several days with a Martek Mark II 

Water Quality Analyzer. 

Primary productivity was measure1 on several 

occasions by the DO light- and dark-bottle 

method and once by the carbon-14- light- and 

dark-bottle method (Slack and others, 1973). 

Bioassay experiments to assess the possibility of 

nutrient limitations were conducted according to 

Vollenweider (1969). 

Total nitrogen and total phosphorus were determined by standard methods of the U.S. Geological Survey (Brown and others, 1970) and dissolved silica by the reactive-silicate method (as 

the yellow complex) (Golterman and Clymo, 

1971). Nitrate was determined by the brucine 

method and ammonia by Nesslerization following 

distillation (American Public Health Association 

and others, 1971); both analyses wer,?. run within 

24 hours of sample collection. On Feveral occasions, alkalinity was measured in the field by the 

method in Brown, Skougstad, ard Fishman 

(1970). The alkalinity results were used in conjunction with pH data to estimate total carbonate 

carbon from the nomograph of Deffeyes (1965). 

The membrane filters for analysis of algae were 

examined with a Zeiss standard phase contrast 

microscope at a magnification of 1,000 x and a 

circular counting field 0.15 mm (millimetre) in 

diameter. The reported counts were calculated 

from data on the number of times each species, 

genus, or group was observed in a standard 

'Use of names of commercial products IS for identification only and does not 

imply endorsement by the U.S. Geological Survey. 
number of fields (American Public Health Association and others, 1971). Most species occurred 

and were scored as single cells. Multicellular 

species were scored as colonies up to a maximum 

length of 0.15 mm (corresponding to the counting 

field diameter). Thus, the counts represent individual cells, or colonies, depending on the species. 

Consequently, counts are consistent within a 

species and over time but cannot be directly compared from one species to another without taking 

average cell numbers' into consideration. 

RESULTS 

NUTRIENTS 

NITROGEN AND PHOSPHORUS LOADINGS 

Data from several sources have been collated to 

estimate the daily summertime loading of inorganic (ammonia, nitrite, and nitrate) nitrogen 

and orthophosphate phosphorus (table 2). Most of 

the data were collected during July and early 

August 197 4 for purposes of studying nitrification 

and verifying a DO model. Data for small 

sewage-treatment plants and small tributaries 

were provided by the Oregon Department of Environmental Quality (DEQ ). 

The land-runoff category (table 2) was calculated by summing the nonpoint-source contributions of individual tributaries (see Hines and 

others, 1977). These contributions were calculated for each tributary by subtracting measured 

point-source loadings of nitrogen and phosphorus 

from computed in-stream loads. To provide an 

internal check, stream-nutrient concentrations 

were measured above and below each major 

municipal and industrial discharge. On the Willamette main stem, the individual inputs from 

point and land-runoff sources were mathematically flow routed and at regular intervals comparisons were made between computed and 

measured in-river loads. 

The estimates indicate that point sources contributed about 80 percent of the orthophosphorus 

and 70 percent of the inorganic nitrogen during 

the low-flow period. For orthophosphorus, municipal effluents contributed 66 percent and industrial effluents 14 percent of the point-source loading. In contrast, industrial discharges accounted 

for 55 percent and sewage-treatment plants for 14 

percent of the point-source nitrogen. An undefined but localized source contributed 24 percent of the nitrogen between RM's 120 and 114 

(vicinity of Albany, Oreg.). This source was in adTABLE 2.-Estimated loading of dissolved major nutrients to 

the Willamette River during summer low-flow conditions 1 

Source 

Land runoff ______ 

Municipal effluents __ Industrial effluents __ 

Unknown 2 ----- -----------

Total -------

Orthophosphate as 

phosphorus 

Ibid Percent 

900 20 2,900 66 600 14 

4,400 100 

Amnonia +nitrite+ 

nitrate as mtrogen 

Ibid Percent 

3,300 7 7,000 14 28,000 55 12,000 24 

50,3('0 100 

1"Dissolved" means that samples were filtered 10.45/Lm filter! p~ior to analysis. Dissolved rather than total loadings are reported to reflect the lo1.ding of soluble "biologically available" nutrients. Duplicate analysis of selected whole water I unfiltered! samples showed slightly higher concentrations, but sirrilar percentage contributiOns from the listed sources. 2See text for explanation. 

clition to the estimated input from Fourth Lake 

and was also evident in data collected between 

1972 and 1975 by the Oregon DEQ. The resultant 

nitrogen loading has been categorizei as unknown (table 2) because sufficient data were not 

collected to verify the source and the points of 

entry into the river. However, available information suggested that this nitrogen did 11 ot derive 

from normal land runoff and hence waf' a potentially controllable source. 

"Controllable" sources thus contributed about 

90 percent of the inorganic nitrogen and 80 percent of the orthophosphorus which entered the 

Willamette during the peak period of algal productivity. The noted comparison between flowrouted inputs and measured river loads indicated 

that bottom sediments did not contribute to the 

summertime in-river loads of dissolved nitrogen 

and phosphorus. 

The high percentage of phosphorus fr1m pointsource discharges compares closely with the reported values of 87 percent for the Potonac River 

basin and 73 percent for the Hudson River basin 

(Jaworski and Hetling, 1970). However, the estimated 90 percent point-source loading of nitrogen 

exceeds by a wide margin the comparative values 

of 63 percent for the Potomac and 51 percent for 

the Hudson. The difference results primarily from 

a relatively large industrial loading of ammonia 

in the Willamette River basin, together with the 

large unknown (but probably indust:--ially related) source of nitrogen in the vicinity of Albany. 

CONCENTRATIONS OF NITROGEN, 

PHOSPHORUS, AND SILICA 

The concentrations of dissolved algal nutrients 

by station and over time are shown in figures 3, 4, 

and 5. 

During the 1973 and 197 4 field seasons, the 

lowest determined concentration of orthophosG7 
UJ 

0: 

1-

:::i 

0: 

UJ 

a.. 

en 

~ 

<! 

0: 

(.!j 

:::i 

....J 

~ 

~ 

.2 

River mile 21.2 

z 

0 

i= 

<( 

.1 

~-------6 

0: 

1-

z 

UJ 

(.) 

z 

0 

(.) 

en 

~ 

0: 

0 

I 

a.. 

en 

0 

I 

a.. 

0 

.2 I I 

River mile 50.0 -

.1 :~------~.---.-----~~ 

0 r.------~------~-------.-------.------~ I JULY I AUG I SEPT l OCT I NOV 

FIGURE 3.-Time and spatial variations of dissolved orthophosphate 

phosphorus concentrations in the Willamette River, July-November 

1973. 

phate phosphorus (P04-Pl was 0.035 milligrams 

per litre (mg/l) and the highest was 0.092 mg/l. 

Most concentrations fell between 0.05 and 0.08 

mg/1 (figs. 3, 4 ), a narrow range that is consistent 

with the limited range of streamflows under 

which most of the san1ples were collected. (See fig. 

6.) Moreover, not only were the concentrations 

relatively stable, but they were at all times well 

above the concentrations of phosphorus observed 

in some highly productive natural waters (Schindler, 1971). 

The combined concentrations of ammonia 

(NH4-N) nitrite (N02-N) plus nitrate nitrogen 

(NOa-Nl (range of0.28-2.94 mg/l) were considerably more variable than the phosphorus concentrations (fig. 4, 1974 data only) but were always quite 

high relative to theoretical algal re1uirements. 

The scales in figure 4 are adjusted so that nitrogen 

and phosphorus concentrations appear equal 

when the two are present in a molar ratio of 

16N:1P (approximate ratio in algal cells) (Stumm 

and Morgan, 1970; Kramer and others, 1972). 

G8 
2.0 .3 

1.0 

-... ....... ....... .._ .............. .2 

-....._ ....... '""'() 

.1 

0 0 

2.0 .3 

w 

a: w 

a: 

1-

:J 1.0 

a: 

w 

-... ....... 1-

.............. .2 :J -... ....... .............. a: 

-""'0 w 

CL. 

.1 (J) 

CL. ~ 

(J) 

~ 

<( 0 

<( 

a: 

0 Q 

a: .J (.!) 2.0 .J 

.J 

.3 .J 

i 

~ ~ 

z z' 

z' 1.0 0 

~ 0 <( 

1-

<( 

a: 

1-

z 

w 0 () 

z 2.0 

a: 

1-

z 

w 

0 () 

z 

0 

.3 () 

0 (J) 

() ::> 

z 

w 

(.!) 

0 

a: 1.0 

!::: 

z 

............... a: 

0 ................ .2 J: 

CL. ............... a) 

"o 0 

J: 

.1 CL. 

0 0 

2.0 .3 

', ' ', .2 

,, 

'c 

.1 

-----~ 

0 

NOV 

FIGURE 4.-Time and spatial variations of dissolved major nutrient concentrations in the 

Willamette River, June-November 197 4: 0, ammonia, nitrite, and nitrate as nitrogen; a, 

orthophosphate as phosphorus. 

Plots for total-dissolved nitrogen and phosphorus 

that were prepared in the same molar ratio showed 

relationships similar to that observed in figure 4. 

G9 

The concentrations of dissolved rea~tive silica 

(fig. 5) ranged from about 4 to 10 mg/1 and thus 

were at all times above those required for diatom 
15 

River mile 7.0 

10 

5 ------~ 

0 

15 

w 

a: 

~ 10 

River mile 12.8 

:J 

a: 

w 5 ------- 0. -- C/) 

~ 0 <( 

a: 

(!) 

....J 15 ....J 

~ 10 ~ 

z' 

5 0 

River mile 21.2 

--------~ ~ 

<( 

a: 0 ~ 

z 

w 

(.) 15 

z 

0 

(.) 10 

<( 

River mile 35.0 

(.) 

:J 5 v.; 

0 

15 

10 

5 

0 

FIGURE 5.-Time and spatial variations of dissolved silica concentrations in the 

Willamette River, ,June-November 1974. 

growth (Kilham, 1971). The data show no evidence of a decrease in silica concentration from 

upstream to downstream locations. Additional 

samples collected between RM's 183 and 50 

showed similar results. Thus, there was no apparent downstream depletion of dissolved silica 

in spite of the presence of suspended diatoms 

throughout the river and extensive beds of 

periphytic diatoms above RM 52. 

TEMPERATURE 

Water temperatures in the Willamette River 

· and in all tributaries reach a maximum during 

the July-August low-flow period. T'·,~ water 

temperatures in the Newberg Pool and the Tidal 

Reach are controlled primarily by ambient air 

temperatures. Records compiled by the Willamette Basin Task Force ( 1969) indicate the average temperature during July ranges from about 

20°C (Celsius) at RM 50 to about 22°C at RM 7. 

Figure 7 shows the minim urn and maxim urn 

daily temperature for the Willamette at RM 7.0 

for the period May-September 1974. V\~ater temperature was about 10°C in mid-May and inG10 
20,000 

500,000 

10,000 

0 200,000 

z 

0 

5,000 z 

0 

0 (.) 

(.) w w 

C/) 100,000 Sampling period C/) 

a: a: w w 

a.. 2,000 a.. 

C/) 

1-

w 50,000 w 

w 

a: 

1- u. w 

(.) 1,000 ~ 

OJ (.) 

:::> OJ (.) 

20,000 

~ 

w· 

:::> 

(.) 

500 ~ 

(.9 w a: 10,000 <( 

(.9 

a: J: <( (.) 

C/) 200 J: 

(.) 

0 5.000 C/) 

Ci 

100 

2,000 

50 

DEC 

FIGURE 6.-Hydrograph of the Willamette River at Portland, 1974. 

creased to only l3°C by mid-June. From this date, 

the temperature increased rather steadily to a 

maximum of about 24°C in early August. The 

temperature stayed about 20°C through the remainder of August and early September and then 

decreased steadily through the remainder of 

September. 

LIGHT PENETRATION 

The water in the lower Willamette was relatively turbid during the study periods in 1973 and 

197 4. Extinction coefficients, calculated from the 

measurement of relative light at the 10-ft (3-m) 

depth, were between 1.4 m-1 and 2.0 m-1 . Coefficients calculated for the 3-ft {1-m) depth were 

somewhat higher owing to selective wavelength 

absorption. 

The euphotic zone of a water body is the thickness of the surface layer that receives sufficient 

light to permit algal photosynthesis to equal or 

exceed algal respiration. This thickness is approximately equal to the depth to whin.h 1 percent 

of the surface light penetrates. The determined 

range of extinction coefficients implies a 

euphotic-zone thickness between 7.5 to 11.5 ft 

(2.3 to 3.5 m) along the course of the Willamette 

River (fig. 8). 

Only a small part of the high light extinction 

results from the presence of suspended algal cells. 

Tailing (1960) reported that a growth of Asterionella in Lake Windermere produced an increase in the extinction coefficient of 0.02 to 

0.05 m-1 /109 cells/m3 . Diatoms don1inated the 

algal populations in the Willamette (see ~tAlgal 

Populations"), and observed counts were on the 

order of 3 to 4 x 109 cells/m3 . Thus, at most, about 

10 percent of the observed extinction coefficient of 

1.5 to 2.0 m-1 in the Willamette can be ascribed to 

self-shading. 

Gll 
25 

(/) 

:::> 

(i) 

_, 

L.U 

u 

(/) 

L.U 

L.U 

a: 20 

(!) 

L.U 

Cl 

~ 

L.U. 

a: 

:::> 

1-

<( 15 

cc 

L.U 

a. 

~ 

L.U 

1-

a: 

L.U 

1-

<( 

3: 10 

FIGURE 7.-Daily water temperatures at mile 7.0, Willamette River, MaySeptember 1974. 

Light-microscope examination of the nonalgal 

suspended matter showed it was composed of both 

organic and inorganic particles. However, the 

exact natures and sources of these particles have 

not been determined. 

ALGAL POPULATIONS 

GENERAL CHARACTERISTICS 

Diatoms dominated the suspended-algae populations at all sites during both 1973 and 1974. 

(Examples of results are presented in tables 4 

and 5, at the end of the report.) The most common 

diatom genera were Melosira, Stephanodiscus, 

Cymbella, Achnanthes, Nitzschia, andFragilaria. 

Some blue-green algae and a variety of colonial 

green algae also appeared but were less abundant 

than the diatoms. 

Densities of diatoms were rather high, with individual species present in abundances of 102 to 

103 cells/mi. During both years, the diatom populations were remarkably stable. The same species 

persisted, and there were no major changes in the 

total abundance of cells with location (sampling 

station). However, minor changes in algal populations did occur, as can be seen in figures 9-15 

and in the ensuing discussion of assemblages. 

Of the 40 some genera, species, and groups of 

identified algae (see tables 4 and 5), the seven 

presented in figures 9-15 provide a summary picture of phytoplankton populations in the deep, 

slow-velocity reaches (table 1) of the Willamette 

River. Stephanodiscus hantzschii (fig. 9) and 

Achnanthes minutissima (fig. 10) were the most 

abundant organisms at all five statior. s during 

the 1974 sampling period. Both species are widely 

distributed in rivers throughout the United 

States, with Stephanodiscus hantzschii found 

primarily in eutrophic waters (Hustedt, 1930; 

Huber-Pestalozzi, 1942) andAchnanthes minutissima occurring under a wide range of c-:mditions 

(Patrick and Reimer, 1966). 

Melosira distans (fig. 11) was prominent at 

RM's 7.0 and 12.8 in late summer but was less 

abundant at these stations in June and July and 

throughout the sampling period at RM's 21.2, 

35.0, and 50.0. This species is especially abundant 

in Southeastern rivers (Weber, 1971), eo the increasing counts in the lower Willamette during 

June through mid-August may be related to increasing water temperatures. 

Throughout the 1974 sampling per~0d Gymbella ventricosa (fig. 12) was present in counts 

ranging from 10 to 102 cells/ml at RM's 7.0 and 

12.8 and in counts exceeding 102 cells/ml at the 

three upstream stations. This species grows attached to surfaces such as river bottom rocks 

(periphytic or benthic) rather than suspended 

G12 
0 

~ 

~ 

(A) 

(B) 

(C) 

z' 

~CI) 

>-~w x<Ccx: 

ocx:f- (.!)-

~:i~ >-w 

...J~Il. 

£z 

Cl)-

0 

tucx: wW u..f-W 

10 

5 

<(U 

~~ ~ 2.5 

:£~a: 

f-0:::> 

c.....JCI) 

ww 

am 

River mile 161.0 

~Gross productivity 

3.7 (g02fm2)fd 

River mile 86.5 

10 .------L----, 

Gross productivity 

2.7 (g02fm2)/d 

River mile 7.0 

10 .----....1.----, 

Gross productivity 

1.7 (g02fm2)fd 

L---~------~--------------------5L-----------~-------------------------- 0 2400 O I 2400 2400 

TIME, IN HOURS 

I 

0 .----_._----:::a'"'\ 

2.5 

40f> > ; ; ; ; ; ; > > ,q 

0 100 

LIGHT PENETRATION, IN PERCENT 

FEETr-------t---------------------1--------------------------------------------4---, METRES 

120 

300 

Sea 

Level 

300 

180 160 140 120 100 80 

DISTANCE, IN RIVER MILES ABOVE MOUTH 

200 100 

DISTANCE, IN RIVER KILOMETRES ABOVE MOUTH 

80 

40 

Sea ~'------jr--r Level 

0 

FIGURE 8.--(A) Diel dissolved-oxygen curves and calculated gross productivities, (B) light penetration as a function of water depth, and (C) elevation profiles for summer 

low-flow conditions of the Willamette River, mid-July 1973. 
1000 

100 

10 

1000 

w 

a: 100 

1-

:; 

:; 10 ...J 

~ 

a: 

w 

a.. 

a: 1000 w 

co 

~ 

:::> 100 

z 

z 

10 River mile 21.2 ~--~ 

z 

:::> 

0 

u 

~ 

VJ 1000 

z 

<( 

t:) 100 a: 

0 

10 

1000 1 I I I 

~~-----~- 100 ~ ~ 

10 t- - River mile 50.0 

l JUNE I JULY I AUG I SEPT 

FIGURE 9.-Abundance of Stephanodiscus hantzschii, by 

station and time, in the Willamette River, JuneSeptember 1974. 

(planktonic) in water (Huber-Pestalozzi, 1942). 

The greater abundance at upstream sites is consistent with the presence of extensive beds of 

periphyton in the Willamette above RM 52 (in the 

Upstream Reach). 

In contrast, Asterionella formosa (fig. 13), a 

classic planktonic diatom (Huber-Pestalozzi, 

1942; Patrick and Reimer, 1966), was more persistent and abundant at RM's 7.0 and 12.8 than 

farther upstream. This species is described as a 

widely distributed diatom (Weber, 1971), espe1000 I I l.r.. ~ 

100 J'\. t-u- -v - w 

a: 

1- 10 1- :; River mile 12.8 

:; 

...J I I I I 

~ 

a: 

w 1000 a.. I I I I 

- a: 

w 

co 100 

~ 

:::> 

z 10 f-. River mile 21.2 - z 

~--~ I I I I 

z 

:::> 

0 

u 1000 

~ 

VJ 100 z 

<( 

t:) 

a: 10 

0 

1000 r~~------.--------.-------,------~ "'o--1-o-- ~ 

_...:___ ___ ~ 

100 10---d -

10 1- - River mile 50.0 

1 JUNE I JULY I AUG SEPT 

FIGURE 10.-Abundance of Achnanthes minutissima, by 

station and time, in the Willamette River, JuneSeptember 1974. 

cially common in eutrophic waters (Hustedt, 

1930; Huber-Pestalozzi, 1942). 

The green-algae group (fig. 14) waP dominated 

by a colonial form but also included unidentified 

single-cell and filamentous forms and occasional 

observations of Scenedesmus and Pediastrum. 

The group was most persistent and abundant at 

RM 7.0. At each successive upstream station, its 

occurrence became increasingly sporadic. 

Anabaena (fig. 15) was the only blue-green 

genus identified in the study. Like the green alG14 
1000 

w 100 

a: 

1-

:::i 10 

:::i 

...J 

~ 

a: 

w 

0.. 1000 

a: 

w 

co 100 ::;E 

::::> 

z 10 ~ River mile 21.2 

~--

z 

::::> 

0 

u 1000 

::;E 

~ 

z 100 <{ 

(!) 

a: 

0 10 

1000 ~.------~,------~,r-------r-,------. 

100 

~-----~-

10 ~ - River mile 50.0 

I JUNE I JULY I AUG I SEPT 

FIGURE 11.-Abundance of Melosira distans, by station 

and time, in the Willamette River, June-September 1974. 

gae, Anabaena was most persistent and abundant 

at RM 7.0. 

Figure 16 shows the abundance of selected 

algae during early August 1973. With the exception of Anabaena, the counts and relative location 

shifts are similar to those noted for the same time 

period during 1974 (figs. 9-15). 

The common species of diatoms observed in the 

Willamette can be characterized as cosmopolitan 

and eutrophic. No species appeared that would 

indicate highly polluted conditions, although 

w 

a: 

1-

:::i 

:::i 

...J 

~ 

a: 

w 

0.. 

a: 

w 

co 

~ 

::::> 

z 

~ 

~--

z 

::::> 

0 

u 

~ 

~ 

z 

<{ 

(!) 

a: 

0 

1000 

100 ~ 

10 

1000 

100 

10 

1000 

100 

10 

1000 rT-------.,--------.-,------.-,------. 

~-----~ 100 -

10 ~ River mile 50.0 -

I JUNE I JULY I AUG I SEPT 

FIGURE 12.-Abundance ofCymbella uentricosa, by station 

and time, in the Willamette River, June-September 

1974. 

some of the common diatoms are moderately tolerant of organic enrichment (Palmer, 1969). Although short filaments of Anabaena were observed in some samples, no Hblooms'~ occurred 

during the course of study. Collectively, the composition of all suspended algae suggests that the 

lower two reaches of the Willamette were nutrient enriched but not grossly polluted. 

Only a few of the diatom species observed in the 

lower river can be regarded as une,1uivocally 

planktonic. Melosira granulata and Melosira 

G15 
1000 

w 100 a: 

1-

:J 10 

:J 

...1 

~ 

a: 

w 

a.. 1000 I I I I 

a: 

w River mile 21.2 co 

~ 100 1- - ;:) 

z 10 1- - z 

1-. I I I I 

z 

;:) 

0 

(.) 1000 

~ 

~ 

z 100 

<( 

(.!) 

a: 

0 10 

FIGURE 13.-Abundance ofAsterionellaforrnosa, by station 

and time, in the Willamette River, June-September 

1974. 

italica were present at all sampling stations in 

moderate abundance and can be regarded as truly 

planktonic types. Asterionella formosa and 

Fragilaria crotonensis also appeared, but generally in low abundance. In contrast, a number of 

commonly observed diatoms were probably derived chiefly from upstream periphyton; these 

included Rhiocosphenia curvata, Cymbella ventricosa (as previously noted), other species of Gymbella, and several species of Nitzschia. In addiw 

a: 

1-

:J 

:J 

...1 

~ 

a: 

w 

a.. 

a: 

w 

co 

~ 

;:) 

z 

z 

1-. 

z 

;:) 

0 

(.) 

~ 

en 

z 

<( 

(.!) 

a: 

0 

100 

10 

1000 

100 

10 

1000 

100 

10 

1000 

100 

10 

1000 ~~-------,--------~~------~,----~ 

River mile 50.0 

100 ~ -

10 ~ 

JULy I AUG I SEPT 

FIGURE 14.-Abundance of green algae, by station and 

time, in the Willamette River, June-Septerber 1974. 

tion, a third category of diatoms included species 

that possibly were derived from ups~ream periphyton but that are frequently observed in the 

suspended plankton of rivers (Williams, 1964, 

1972). These facultative planktonic types included Achnanthes minutissima, Melosira distans, and Synedra ulna. 

The aggregate nature of diatoms in the lower 

Willamette indicates that the population resulted 

from both in-river growth of planktonic forms 

Gl6 
1000 

w 100 a: 

t-

::i 10 ::i 

...J 

~ 

a: 

w 

a.. 1000 a: I I I I 

w 

co River mile 21.2 

~ 100 - -

::> 

z 

~ 10 - -

t-' I z I 

::> 

0 

u 1000 ~ 

~ 

z 100 <3: 

(.!) 

a: 

0 10 

FIGURE 15.-Abundance of Anabaena spp., by station and 

time, in the Willamette River, June-September 1974. 

(see ''A Downstream Traverse") and the exportation of cells from upstream (above RM 52) benthic 

communities. 

ASSEMBLAGES 

The algal-count data were analyzed according 

to a cluster analysis procedure (Hartigan, 1975) 

to determine if there was any evidence of identifiable subgroups or population assemblages. By 

using a K-means algorithm, the counts were first 

assigned to the two groups that gave the minimum variance. By the same technique, the counts 

were assigned to the best three, fo•1r, and five 

groups in succession. The clusterirg based on 

three groups produced three compact assemblages related to both sampling time and location (fig. 17). Clusters of four and five were also 

readily identified but added relatively little 

information. 

The three clusters shown in figure 17 represent (1) all the early samples, from l\fay through 

June, (2) most of the lower three stations from 

July through mid-September, and (3) upstream 

stations from July through mid-September and 

some of the samples at RM's 12.8 and 21.2 in 

September. 

The clustering of the three groups resulted 

from the abundance of the commoner species together with the relative abundance of some ofthe 

less common species. The samples from early in 

the year <Group 1) consisted of moderate abundances of Achnanthes minutissimc:, Nitzschia 

spp., and Stephanodiscus hantzschii, with occasional moderate counts of other species. The second cluster, from the three downstream stations 

and from July-September, consisted of relatively 

high abundances of Stephanodiscus hantzschii, 

Achnanthes minutissima, Nitzschia spp., and 

some Cymbella ventricosa. The third cluster, representing the more upstream sa1nples from 

July-September (fig. 17), was disting·1ished from 

the other two primarily by the presence of additional species (Cymbella spp., Stephanodiscus astrae, and others) which occurred in moderate 

abundance. Thus, this third cluster represented a 

somewhat more diverse assemblage than the 

other two. 

Overall, the cluster analysis shows that from 

mid-July through mid-September, there was 

some evidence for a downstream progression in 

species composition. The changes were not pronounced, however, and consisted principally of 

some of the moderately abundant species becoming less significant. 

A DOWNSTREAM TRAVERSE 

During the period August 5-7, 1 97 4, water 

samples were collected for suspended-plankton 

analysis during a raft traverse of the entire Willamette main stem. Figure 18 presents selected 

results for 17 sites on the Willamette, with additional data on the McKenzie, Santiam, and 

Yamhill Rivers. Data shown for RM 35.0 are inG17 
DISTANCE, IN RIVER KILOMETRES ABOVE MOUTH 

80.4 56.3 34.1 20.6 11.2 

1000 ). _}., -.,_, 

100 1-v- -

10 t- Stephanodiscus hantzschii 

1000 

~ ~ 

l~ l 100 

10 

w 

~l a: 1000 

[ Achnanthes minutissima : 

1-

:::i ~ ~ 100 ::i 

...J 

~ 10 

a: 

w 

a.. 

a: 1000 

f~mbel/a ventricosa 

~ ~ : :l w 

co 

~ 100 :::> 

z 10 z 

t-' 

z 

:::> 

L ~l 0 1000 

[ Asterione/1~ formosa : (.) 

~ 100 en 

z 10 

<( 

(!) 

a: 

0 

1000 

l~'""" algae 

= ~ ~l 100 

10 

1000 

: j 100 

10 

50.0 35.0 21.2 12.8 7.0 

DISTANCE, IN RIVER MILES ABOVE MOUTH 

FIGURE 16.-Abundance of selected algae in the Willamette River, August 7, 1973. 

eluded from July 23, when flow and water temperatures were nearly identical to those of August 5--7. 

The plots show that Achnanthes minutissima is 

the only diatom species that occurs in high abundance over the entire main stem. Stephanodiscus 

hantzschii was not observed at RM 169 

downstream from the McKenzie River but increased gradually thereafter to reach maximum 

counts in the Tidal Reach. Melosira distans was 

not observed above RM 60, but below this location 

it increased gradually to maximum abundance at 

RM 7.0. The periphytic Cymbella ventricosa occurred sporadically above RM 131 anrl then inG18 
50.0 P().4 

35.0} fs6.3 I 

.... I ::> 

.... 0 

::> ~ 

0 w ~ > w 21.21 {~.1 0 

> lXI 

0 <( 

lXI (/) 

<( w (/) a: w .... 

12B} {W.6 

w ..J 

~ ~ 

0 

a: ..J 

w ~ 

~ a: a: w 

> 

a: 

7.0 11.2 

MAY JUNE JULY AUG SEPT 

FIGURE 17 .-Summary of the time and spatial distribution of algal populations in the Willamette River, MaySeptember 1974. (Numbered groups are explained in text.) 

creased to levels on the order of 102 cells/ml 

throughout the remainder of the Upstream Reach. 

This general abundance was fairly well maintained throughout the Newberg Pool down to RM 

12.8. The planktonic Asterionella formosa occurred sporadically over the entire river but was 

most abundant at the lower four stations, beginning at RM 35.0. The spatial distribution of both 

Asterionella formosa and Melosira distans (and 

perhaps even Stephanodiscus hantzschii) suggests 

that these algae were actively growing below RM 

35.0 rather than merely derived from growth in 

upstream reaches or reservoirs. 

Green algae were not observed above RM 78, 

and the highest counts were from the Tidal 

Reach. In contrast, Anabaena was observed in low 

abundance in three distinct pockets located at the 

beginning of the main stem to RM 169, at RM's 90 

and 78, and in the Tidal Reach. The patchy occurrence of Anabaena spp. is suggestive of derivation 

from outside the river rather than growth within 

the river. The Anabaena spp. at the upper end of 

the Willamette may have originated in upstream 

reservoirs, whereas the filaments observed at RM 

21.2 possibly entered from the Tualatin River. 

Total algal counts from the traver;;oe (fig. 18) 

increased from the uppermost sampling points to 

the four lowermost stations, with a peak abundance at RM 50.0. Specifically, the counts were 

between about 1,000 and 1,200 at RM's 183 to 

169, between 1,600 and 2,100 at RM's 152 to 131, 

between 2,300 and 2,900 at RM's 120 to 60, more 

than 3,200 at RM 50.0, and then back c0wn to the 

2,300-2,900 level below RM 35. 

Figure 18 shows interesting contrasts of algal 

populations in the McKenzie, Santiam, and 

Yam hill Rivers to those in the Willamette. Of the 

seven groups presented in the plots, only Achnanthes minutissima and Asterionella formosa were 

observed in the McKenzie, and the total count 

was 500 cells/mi. At the time of sanpling, the 

McKenzie was adding about 3,400 ft3 /s (96 m3/s) 

to a mainstem flow of 2,100 ft3/s (59 m3/s). The 

dilution effects of the McKenzie are no~able in the 

downstream counts. Of the seven groups noted in 

figure 18, only Achnanthes minutissima and 

G19 
w 

1000 

100 

10 

300 

1000 

1 

~ t1:;stans 

DISTANCE, IN RIVER KILOMETRES ABOVE MOUTH 

200 100 0 

~l ~1000~~: ~~~~ ~~~ ~ :~ t ~-,:.~Vss-;m_a_ l_____l j a. 

ffi 1000 

6 

~ z 

1000 

~~=--i~~-~-------ll 

i ~~ f l 

0 

McKenz1e 

River 

Santiam Yamhill 

River River 

DISTANCE, IN RIVER MILES ABOVE MOUTH 

TABLE 18.-Abundance of selected algae in the Willamette River and certain tributaries, August 5-7, 1974. (Values at 

river mile 35.0 are from July 23. l 

Cymbella venticosa were observed in the Santiam 

River, and the total count was about 2,000 cells/ 

ml. The flow in the Santiam was about 1,500 ft3/s 

(42 m3/s). 

During summer, the McKenzie and Santiam 

are swift-flowing, large-volume, low-tmnperature 

rivers that originate in the Cascade Fange and 

are augmented by reservoir releases. Ir contrast, 

the Yamhill River during summer has low flows, 

long detention times, and high terrperatures 

G20 
1-

z 

w 

u 

cr: 

w 

"-

z 

t-' 

z 

::J 50 

0 

u 

~ 

(J) 

z 

<! 

l? 

cr: 

0 

FIGURE 20.-Time variation of algal types in the Willamette River, at mile 7.0, 

June-September 197 4. 

1-

z 

w 

u 

cr: 

w 

"-

z 

t-' 

z 

::J 

0 

u 

~ (J) 

z 

<! 

l? 

cr: 

0 

FIGURE 21.-Relative abundance of diatoms and blue-green algae in net plankton of the Tualatin River at Farmington, 

Oreg., March-August 1973 (Carter, 1975). 

light- and dark-bottle method (Slack and others, 

1973). Vertical distributions of the gross productivities are presented in figure 22. The values 

plotted for September 19 were determined by 

measuring the uptake of carbon-14 and converting the data to equivalent units of oxygen. Values 

plotted for the other dates were determined by 

direct measurement of oxygen production. For 

G22 
1-

z 

w 

u 

a: 

w 

a. 

~ 50 

1-. 

z 

:::> 

0 

u 

~ 

Ul 

z 

<( 

(.:J 

a: 

0 

0 

FIGURE 19.-Time variation of algal types in the Willamette River and certain tributaries, at mile 8.1, April-September 

1963 (U.S. Public Health Service, 1964). 

(Willamette Basin Task Force, 1969). The Yamhill algal assemblage reflected the river's character. The total algal count exceeded 6,000 cells/ml, 

and the dominant forms were a variety of colonial 

green algae and Stephanodiscus hantzschii. The 

discharge of the Yamhill on the date of sampling 

was about 100 ft3/s (3 m3Js). 

COM PARISO N WITH HISTORICAL DATA 

Figures 19 and 20 compare the relative abundances during 1963 (U.S. Public Health Service, 

1964) and 1974 of diatoms, green algae, and 

blue-green algae in the lower Willamette River. 

Differences in methodology between the two 

studies could well account for the observed higher 

abundance of green algae during 1963 (Williams, 

1964, 1972). However, the point of major importance is that the suspended algal population in 

the lower river was dominated by diatoms in 

1963, just as it was during 1973 and 1974. This 

observation is significant, because the lower Willamette was polluted with sewage and pulp-mill 

wastes in 1963 (Velz, 1961; Gleeson, 1972) but 

now is relatively free of such organic pollution 

(Rickert and others, 1975b). Unfortunately, no 

1963 data are available on nitrogen and phosphorus concentrations to provide a comparison of 

nutrient availability. 

The Public Health Service report (U.S. Public 

Health Service, 1964) also noted that the dominant spring and autumn diatoms were Stephanodiscus hantzchii and Synedra ulna. The 1973 

and 1974 data show that Stephanodiscus hantzschii was the dominant late spring and summer 

species in the lower Willamette; however, 

Synedra ulna counts were very low or nil during 

the summer and early fall. 

Figure 21 shows the relative abundance of 

diatoms and blue-green algae in net plankton 

from the Tualatin River. The illustrated data 

(Carter, 1975) indicate that the eutrophic but not 

heavily polluted reach at Farmington was dominated by blue-green algae during July-August 

1973. During this period, streamflow in the 

Tualatin was low, at about 10 fP/s (0.3 m3/s). The 

Tualatin enters the Willamette at RM 28.6, and, 

as previously noted (see "A Downstream Traverse"), this tributary inflow may account for the 

low counts of Anabaena sometimes observed m 

the Tidal Reach. (See figs. 15, 18.) 

PRIMARY PRODUCTIVITY 

LIGHT- AND DARK-BOTTLE METHOD 

Phytoplankton productivity was measured on 

several occasions at RM's 7.0 and 12.8 by the 

G21 
RIVER Ml LE 7.0 

0 0 0 0 

9/17/74 9/19/74 

1- en 

w w a: w 1- u. 5 5 w 

~ 2 2 ~ 

£ Gross productivity Gross productivity ~ 

1- £ a.. 4.4(g0 2/m2)/d 2.0(g0 2fm2)/d w 1-

0 a.. 

10 10 w 

0 

4 4 

0 2 3 0 2 3 

RIVER MILE 12.8 

0 0 

7/5/74 

5 

2 

Gross productivity 

1.8(g02/m2)/d 

10 

1-

w 

w 4 u. 0 2 3 

z 

£ 

1- 0 a.. 

w 8/6/74 

0 

5 

2 

Gross productivity 

1.6(g02/m2)/d 

10 

4 

0 2 3 

0 

8/5/74 

5 

10 

0 

0 

9/19/74 

5 

10 

Gross productivity 

1.9(g02/m2)/d 

2 

Gross productivity 

1.7(g02fm2)/d 

3 

2 

4 

0 

2 

~--------~----------~---------4-4 

0 2 3 

en 

w 

a: 

1-

w 

~ 

z 

r.' 

1-

a.. 

w 

0 

DISSOLVED OXYGEN, PRODUCED IN LIGHT-DARK BOTTLES TESTS, IN MILLIGRAMS PER LITRE PER DAY 

FIGURE 22.-Vertical distribution of primary gross productivities in the lower Willamette River, at sel('ded times 

during summer, 1974. The gross productivity for each euphotic zone, reported as (g02 /m2 )/d, was calculated according to Slack, Averett, Greeson, and Lipscomb (1973). 

each plot in figure 22, the area enclosed by the 

smooth curve has been integrated to obtain a 

total gross productivity for the euphotic zone. (See 

~~Light Penetration.") These results, which represent the productivity of a vertical column of water 

1m2 in cross section, ranged from 1.6 to 4.4 

(g02 /m2)/d (grams DO per square metre per day). 

The measured rates of productivity are low 

but, nevertheless, indicate that the suspended 

algae in the lower Willamette were metabolically 

active rather than dead cells transpor+ed from the 

periphytic beds above RM 52. 

The vertical distributions show that gross 

productivity decreased rapidly with depth, a result consistent with the low light t-:-ansmission 

properties of the water. The clarity of the water 

varied over the summer, but the depth of the 

euphotic zone at the two stations was usually 

G23 
within the range of 8 to 11.5 ft (2.4 to 3.5 m). In 

contrast, the depth of the total water columns was 

42ft (12.8 m) at RM 7.0 and 37ft (11.2 m) at RM 

12.8 (fig. 8). 

Net productivity was determined from gross 

productivity by subtracting community respiration as calculated from the results of extensive 

BOD (biochemical oxygen demand) tests (Hines 

and others, 1977). This approach for calculating 

respiration was used so that net production could 

be estimated for the entire water column as well 

as for the euphotic zone. At RM 7.0, the resultant 

net productivities were 1.3 and 3. 7 (g02 /m2 )/d for 

the euphotic zone and -1.7 and +0. 7 (g02 /m2 )/d 

for the water column. At RM 12.8, the net productivity values were 1.3, 1.4, 1.5, and 1.7 (g02 / 

m2 )/d for the euphotic zone and 0.1, 0.2, 0.3, and 

0.4 (g02 /m2 )/d for the water column. 

The total water-column values indicate that for 

RM 12.8 oxygen produced by algal photosynthesis 

approximately balanced the oxygen consumed by 

community respiration on each of the 4 days. In 

contrast, at RM 7.0, the oxygen produced exceeded that consumed by a small amount on September 17, but oxygen consumption exceeded 

production by a considerable margin on the 19th. 

These reported values for water column net productivity are based on several assumptions and 

can be considered only as estimates. N evertheless, the values are in general accord with the DO 

regimen of the W illamette as described by Hines, 

McKenzie, Rickert, and Rinella (1977). 

OXYGEN-CURVE J\1ETHOD 

Primary production has also been estimated by 

graphical analysis (Slack and others, 1973) of diel 

oxygen curves obtained by continuous recording 

monitors. Figure 8 presents the DO curves, lighttransmission plots, and estimated gross productivities at three stations, for virtually cloudless 

days, during mid-July 1973. The stations at RM's 

161 and 86.5 were shallow and dominated by 

periphyton. The entire water column at these 

sites was illuminated, a condition characteristic 

of most of the Upstream Reach. The gross productivities observed under these conditions were 3. 7 

(g02 /m2 )/d at RM 161 and 2. 7 (g02 /m2 )/d at 

RM 86.5 

The gross productivity estimated at RM 7.0 in 

the deep Tidal Reach was 1. 7 (g02 /m2 )/d. This 

smaller value suggests that primary production 

in the Willamette occurs at higher rates where 

periphyton predominate. This result ag":"ees with 

the nature of numerous DO curves obi;ained at 

sites throughout the Willamette River. (See 

Hines and others, 1977). All curves from the shallow Upstream Reach showed considerably larger 

day-to-night DO fluctuations than those from the 

Newberg Pool and the Tidal Reach. 

Although differences in sampling dates and locations preclude direct comparison, the gross 

productivities determined by the oxygen-curve 

method are similar to those obtained by the lightand dark-bottle method. 

COMPARISON WITH OTHER RIVERS 

Dvihally (1974) has compiled data on the rates 

of gross primary productivity in rivers. Her information, compared with the present Fi;udy (table 3 ), suggests that primary productivity in the 

Willamette is low to moderate for a river. 

EFFECT OF NUTRIENT ADDITIONS 

The bioassay results (figs. 23, 24, and 25) 

suggest that nutrient availabilities were not 

limiting to algal productivity in the kwer Willamette River. In no case did the productivity of 

treated samples exceed that in control samples. In 

fact, certain additions, such as the trace nutrients 

and the waste-water effluents, seem to have 

caused slight reductions in productivity (figs. 24 

and 25). 

DISCUSSION 

In the section entitled "Descriptive Assessment," five hypotheses were listed as to why nuisance algal growths have not occurred ir the Willamette River. The remainder of this p~per will 

TABLE 3.-Estimated gross primary productivity at the surface 

of different rivers 

[<g02 /m2>/d corrected for average depth (after Dvihally, 1974>) 

River 

Minimummaximum 

Raritan <N.J. U.S.A.l ____________ 2.5-25.1 

Klyazma (U.S.S.R.l -------------------------- Volga at Saratov (U.S.S.R.) ------------------

Orinoco !Venezuela)--------------------------

Wisla estuary !Poland) ---------------------- Mosel (dammedl <Germany) _________________ _ 

Ivel <Great Britainl ______________ 3.2-17.6 

Silver Springs <Fla., U.S.A.)------ 8-35 

White River <Ind., U.S.A.)--------------------

Itchen River <Great Britain)______ .4-14.0 

River Lark !Great Britain) ______ .5-39 

German Danube ________________ 5-7 

Hungarian Danube ______________ 1-15 

Willamette ______ _ _____ ________ _ _ 1.6-4.4 

Average 

4.7-11.6 

2.4 

1.01 

.20 

5.27 

20-30 

.24-57 

G24 
Q 

w 

Q 

Q 

<( 

Cl) 

.... 

z 

w 

[[ 

.... 

:::> 

z 

0 

I 

Phosphorus 

0.2 mg/1 P04-P 

I 

Ammonia 

3.3 mg/1 NH4-N 

I 

Nitrate 

3.3 mg/1 N03-N 

I 

Phosphorus + Ammonia + Nit rate 

0.2 mg/1 P04-P, 3.3 mg/1 NH4-N, 3.3 mg/1 N03-N 

I 

Micro-nutrients 

B,Mn,Zn,Co,Cu,Mo,Fe 

I 

Control 

I 

I 

I 

I 

I 

I 

I 

I 

2 3 

DISSOLVED OXYGEN PRODUCED, IN MILLIGRAMS PER LITRE PER DAY 

FIGURE 23.-Effect of nutrient additions on algal productivity ofWillamette River samples, mile 7.0, 1July 24, 1973. 

assess each hypothesis by relating data collected 

and collated in this study to published findings on 

river and lake limnology. 

LOW-TEMPERATURE LIMITATION 

Water temperatures in the Willamette River 

reflect the moderate air temperatures of the basin 

and usually peak in August at about 25°C. (See 

fig. 7.) The recorded temperatures are lower than 

those observed in many lakes and rivers that experience nuisance algal growths. Cairns (1956) 

noted that diatoms generally are favored at temperatures below 25°C, green algae between 30° to 

35°C, and blue-green algae above 35°C. Hutchinson (1967) concluded that blue-green algae may 

dominate in mid-to-late summer because they 

outcompete other forms by growing faster at low 

inorganic nutrient levels and at high temperatures. However, in the Willamette River basin, 

blooms of Anabaena occur under the quiescent 

conditions in certain headwater reservoirs at 

water temperatures below l8°C (Douglas Larson, 

Oregon Dept. of Environmental Quality, written 

commun., 1974). 

In spite of this occurrence, the moderate summer temperatures in the lower reacres of the 

Willamette could well be one factor that helps 

maintain suspended algal growth in its present 

desirable state. 

LIGHT LIMITATION 

As previously noted, the euphotic zone comprises only a small part of the water column in 

the Newberg Pool and the Tidal Rea~h (fig. 8, 

table 1). In these reaches, both the watE.r and suspended matter are completely mixed to the bottom (unstratified) in most locations. Consequently, only part of the suspended algae is 

G25 
c 

w 

c 

c 

<{ 

~ z 

w 

a: 

1-

::::> 

z 

·:,· 

0 

I 

Phosphorus 

0.2 mg/1 P04-P 

I 

Ammonia 

3.3 mg/1 NH4-N 

I 

Nit rate 

3.3 mg/1 N03-N 

I 

Phosphorus+ Ammonia+ Nitrate 

0.2 mg/1 P04-P, 3.3 mg/1 NH4-N, 3.3 mg/1 N03-N 

I 

Micro-nutrients 

B,Mn,Zn,Co,Cu,Mo,Fe 

I 

Sewage Effluent 

1:300 dilution 

J 

Pulp Mill Effluent l 1:300 dilution 

I 

Control 

·,: 

I 

J 

( I 

2 3 

DISSOLVED OXYGEN PRODUCED, IN MILLIGRAMS PER LITRE PER DAY 

FIGURE 24 .. -Effect of nutrient additions on algal productivity ofWillamette River samples, mile 12.8, Augus~ 8, 1974. 

capable of photosynthesis at any moment, but 

algae and all other organisms are respiring 

throughout the entire water column. 

Talling ( 1971) described the significance of 

light as a controlling factor in the ecology of 

freshwater phytoplankton. He pointed out that a 

high ratio of mixed depth to euphotic depth will 

act to dilute light income per unit area over a 

deeper population, until respiration losses exceed 

photosynthetic gains. The depth at which respiration over the entire mixed layer exceeds oxygen 

production in the euphotic part of the 1nixed layer 

is called the ''critical depth" (Sverd':"up, 1953). 

Talling (1971) stated that one case in which critical depth is likely to be exceeded is slowly flowing 

river water of high light extinction not due to 

algae. 

In the Willamette River, this case appears to 

apply at RM 7.0. This finding is es:t:~cially significant to the DO regimen of the lower river because the subreach below RM 10 is the primary 

depositional zone of the Willamette. (See HTidal 

G26 
0 

w 

0 

0 

~ 

(/) 

1-

z 

w 

a: 

1-

::> 

z 

0 

I 

Phosphorus 

0.2 mg/1 P04-P 

I 

Ammonia 

3.3 mg/1 NH4-N 

I .. ______.... 

Nitrate 

3.3 mg/1 NOJ"N 

I 

Phosphorus+ Ammonia+ Nitrate 

0.2 mg/1 P04-P, 3.3 mg/1 N03-N, 3.3 mg/1 NH4-N 

I 

Micro-nutrients 

I B,Mn,Zn,Co,Cu,Mo,Fe 

I 

Sewage Effluent 

1:300 dilution 

l 

Pulp Mill Effluent 

1:300 dilution 

I 

Control 

I 

2 3 

DISSOLVED OXYGEN PRODUCED, IN MILLIGRAMS PER LITRE PER DAY 

FIGURE 25.-Effect of nutrient additions on algal productivity of Willamette River samples, mile 12.8, Septemb~r 17, 1974. 

Reach.") Thus, not only is there the possibility of 

a critical-depth respiration excess from living algae, but there is the distinct probability that dead 

algal cells and other organic particles deposit in 

this zone and thereafter create an oxygen demand 

(Rickert and others, 1975b; Hines and others, 

1977). 

Results of the light- and dark-bottle tests lend 

further support to the possibility of light limitation in the lower Willamette. As shown in figure 

22, gross productivity falls off rapidly with depth 

and is nil below 10 ft (3 m). 

The combined evidence suggests that low light 

availability restricts primary production in the 

Tidal Reach and the Newberg Pool. From a management standpoint, there are two important 

questions concerning the light limitation: 

(1) what are the natures and sources of the materials causing the high light extinctior. and (2) if 

turbidity were decreased, would the increased 

G27 
light availabilities result in greater prin1ary 

production and possibly cause undesirable shifts 

in algal populations? Unfortunately, at present, 

there is insufficient information to answer either 

question. Until such time that definite answers 

are available, it may be prudent to assume that 

measures aimed at decreasing summertime turbidities <if this is indeed possible) might cause 

undesirable changes in algal-growth dynamics. 

TRACE-NUTRIENT LIMITATION 

The bioassay results <figs. 23-25) provide evidence that availability of key trace elements is 

not a limitation on algal growth and possible development of nuisance algal conditions. Trace 

nutrients in addition to those tested are necessary 

for algal growth. However, the Willamette receives secondary effluents from many sewage 

treatment plants and urban runoff from several 

large cities along its 187-mi (301-km) course. For 

example, the slow-moving Tidal Reach receives 

combined-sewer overflows below RM 17, sewage 

effluents upstream from RM 18, and urban drainage along its entire length. With so many sources 

of trace elements and the presence of numerous 

metals in bottom sediments (Rickert and others, 

1976) it seems unlikely that minor nutrient limitation could occur. 

MAJOR-NUTRIENT LIMITATION 

CARBON 

The Willamette is a low-alkalinity (15--25 mg/l 

as CaC03 ) river <U.S. Geological Survey, 1974); 

so the possibility of a carbon limitation on algal 

production needs to be considered. In assessing 

this topic, there are two relevant questions: ( 1) 

are carbon concentrations possibly limiting to 

gross production of phytoplankton and (2) how 

does the distribution of carbon an1ong the inorganic forms affect the qualitative nature of the 

phytoplankton? 

The first question can be assessed by comparing 

the ratios of total carbonate carbon to inorganic 

nitrogen to orthophosphorus in Willamette River 

water to reported ratios of carbon:nitrogen:phosphorus (C:N:P) in algal protoplasm. During July 

and August 1974, the C:N:P ratios at RM 7.0 in 

the Willamette ranged from 185:21:1 to 285:60:1. 

In contrast, the commonly quoted ratio of these 

elements in algae is 106:16:1 (Stumm and Morgan, 1970; Kramer and others, 1972), and a ratio 

reported as typical for blue-green algae is 40:7:1 

<James and Lee, 1974l. 

Comparison of the two sets of ratios shows that 

on a relative basis carbon in the Willamette was 

more abundant than the phosphorus needed for 

algal growth and equal to or more abundant than 

the required nitrogen. These findings suggest 

that carbon was not limiting to algal production 

in the lower Willamette River. 

The second question can be assessed by examining diel records of pH values. During July and 

August of 1973 and 1974, continuous 3-day pH 

traces were obtained at RM's 7.0 (depths of 3 and 

20ft, or 1 and 6 m) and 12.8 (depth of::' ft, or 1m). 

During each of six measurement p~riods, the 

maximum daily variation in pH was from 6.8 to 

7.1. Data collected by the Oregon DEQ under its 

water-quality monitoring program were within 

the same range. The stability of pH near neutrality indicates that free carbon dioxide (C02 ) was 

not depleted by algal production to the point 

where extensive bicarbonate carbon was utilized. 

Such a condition is favorable to maintenance of 

diatom and green-algae populations. In contrast, 

blue-green algae tend to dominate under conditions of high pH, because their advantageous uptake kinetics allow them to compete better for 

bicarbonate C02 once free C02 is depleted (King, 

1970, 1972; Shapiro, 1973b). In the lower Willamette River, there apparently was a maintenance of sufficient free C02 to prevent conditions 

where blue-green algae would have a competitive 

advantage over diatoms and green algae. 

NITROGEN AND PHOSPHORU~ 

The concentrations of nitrogen and phosphorus 

in the lower Willamette River (figs. 3 and 4) are 

higher than those reported as sufficient to cause 

nuisance algal blooms in lakes (Sa¥ryer, 1954; 

Schindler, 1971) but lower than concentrations 

observed in certain rivers and estuarie~ that have 

nuisance algal problems (Shane and others, 1971; 

Jaworski and others, 1972; Clark ~nd others, 

1973). 

The observed nitrogen and phosphorus concentrations seem sufficient to support higher levels of 

primary production than those measured in the 

river. This deduction is supported by tl'~ bioassay 

tests (figs. 23-25) which indicate that neither nitrogen nor phosphorus was limiting to algal productivity at RM's 7.0 and 12.8. 

G28 
Comparison of N:P ratios in Willamette River 

water (fig. 4) to the commonly reported ratio for 

algal tissue (16:1) indicates that nitrogen was 

relatively more abundant than phosphorus by a 

wide margin during 1974. Thus, if algal production were greatly increased and nutrient loading 

remained constant, phosphorus (not nitrogen or 

carbon) would probably become the limiting 

major nutrient. However, the 1973 and 1974 concentrations of phosphorus were far from being depleted to the point where limitation of productivity was even a remote possibility. 

Qualitatively, the diatom populations that 

dominate the Willamette are consistent with the 

moderately enriched levels of nitrogen and phosphorus. Limnologists are now piecing together 

several hypotheses that interrelate broad types of 

algal populations with observed levels of major 

nutrients (Hutchinson, 1967; Bush and others, 

1972; King, 1972; Shapiro, 1973b). In general, the 

hypotheses suggest that (1) diatoms predominate 

in low to moderately enriched waters when concentrations of the major nutrients remain high 

and at about the initially observed ratios, (2l 

green algae dominate in moderately to greatly 

enriched waters, again when nutrient concentrations remain high and in proportion, and (3 l 

blue-green algae dominate in enriched waters, 

but specifically during periods when prior productivity has depleted the concentration of one or 

more major nutrients. Under the condition of depleted nutrient concentrations, and especially at 

high temperatures, blue-green algae apparently 

have a competitive advantage resulting from 

favorable kinetics of carbon and phosphorus uptake (Shapiro, 1973b) and the ability of certain 

species to fix atmospheric nitrogen. 

DETENTION-TIME LIMITATION 

As in the Willa~nette, the suspended-algae 

populations of most rivers in the United States 

(Williams, 1964, 1972l and throughout the world 

(Hynes, 1970; Prowse and Talling, 1958; Villegas 

and de Giner, 1973) are dominated by diatoms. In 

a study covering more than 50 United States rivers, Williams (1964) found that diatoms comprised about 80 percent of the algal biomass. 

Hynes (1970) found from a worldwide review that 

the plankton of large rivers are almost everywhere dominated by diatoms. 

Exceptions to the general pattern of diatom 

dominance do occur, however, and are usually observed in parts of river systems having long detention times (slow rates of water exchange). In 

recent years, blooms of Anacystis, a blue-green 

alga, have appeared in the slow-moving Anacostia and Upper Potomac River Estuaries near 

Washington, D.C. (Jaworski and others, 1972). 

Another example is the White Nile near Khartoum, where Anabaena appears yearly as the 

dominant alga after the closure of a dam creates a 

"river lake" (Prowse and Talling, 1958). 

Detention time has been noted by several authors as an important factor in algal productivity 

and succession in lakes and reserve irs. Welch 

(1968b) suggested that the failure of blue-green 

algae to develop in Tennessee Valley reservoirs in 

spite of high nutrient concentrations c-nd productivity might be partly due to the high exchange 

rates of water. The detention times in main-stem 

impoundments were too short (several days) for 

development of species succession leading to 

blue-green blooms. Dickman (1969) found that 

the potential of algal production in a Pritish Columbia lake was not realized because of a high 

rate of water exchange. He also found that the 

water-exchange rate exerted a selective pressure 

in determining the species composition of the 

phytoplankton. In a study of Moses Lake, Wash., 

Bush, Welch, and Buchanan (1972) found that 

water-detention time was an important factor in 

determining the stability of diatom :r;opulations. 

The entire lake was enriched, but diatoms dominated throughout the summer in an arm of the 

lake having high water-exchange rates, whereas 

algal succession to green and blue-gr1~en populations occurred in arms having longer detention 

times. Dillon (1975) found in Cameron Lake, Ontario, that high hydraulic-flushing rates diluted 

high phosphorus loadings to produce 2 low degree 

of eutrophy. 

In a study on the enriched Duwamirh River Estuary, Welch (1968a, 1969) noted that hydrographic conditions, rather than nutrient content, 

apparently controlled the occurrence of blooms. 

He concluded that there was probably a minimum 

of water-retention time and stability b:~low which 

phytoplankton development is limited (Welch, 

1968a). 

As previously noted, summer low flows in the 

Willamette River are augmented by reservoir 

releases to maintain a minimum of 6,000 ft3/s 

(170 m3/s) at Salem. At this discharge, waterdetention times are short, with volumetric disG29 
placement tin1es of 3.9 days for the Newberg Pool 

and 7.5 days for the Tidal Reach down to RM 5 

(point of mixing with the Columbia River). The 

water at this discharge is confined within welldefined banks (very few sloughs and side channels) and in most locations is mixed to depth. 

Thus, in the lower Willamette, the total detention 

time of water during the period having the 

slowest flow velocities and the highest water 

temperatures is about 11 days. 

In contrast to the Willamette, low-flow detention time in the 35-mi (56-km) Upper Potomac 

Estuary (freshwater only) would be 50 days at the 

60-day, 2-year low flow of about 2,000 ft3 /s 

(57 m3/s) (Walker, 1971). Thus, under low-flow 

conditions, detention time in the freshwater 

reach of the Potomac Estuary (where algal 

blooms occur) is four to five times greater than 

that observed in the Willamette River between 

RM's 52 and 5. 

On the basis of the results and the noted comparisons, we believe that short detention time is 

the primary reason productivity is low in the Willamette and that diatoms dominate in spite of the 

high availability of nitrogen and phosphorus. 

However, based on published results (Fogg, 

1965), the 11-day, low-flow detention time seems 

long enough to permit significant growth of 

planktonic blue-green algae. Thus, the absence of 

nuisance blooms in the Willamette apparently results from the influence of detention time (and 

associated variables such as local velocities and 

rates of mixing) on other factors which control 

algal growth. The following section examines 

several relationships which could be prominent in 

the Willamette and in many other rivers. 

CONCEPTUAL MODEL OF FACTORS CONTROLLING 

BIOMASS AND THE NATURE OF ALGAE 

Figure 26 schematically portrays the relationship of algal biomass and dominant algal types to 

water-detention time and light penetration. The 

schematic is based on observations made in waters of the Willamette system but is presented as 

a conceptual model to be considered for all river 

basins. 

The schematic was devised to generalize the locations and stream-current conditions under 

which nuisance algal growths are likely to occur. 

Nuisance algal conditions include problems of 

esthetics, DO depletion, and increased watertreatment costs. In this context, the occurrence of 

nuisance conditions depends on the type and 

amount of biomass (weight of algal cells per unit 

volume of water) that can develop and accumulate in the water. 

The relationships depicted in figure 26 are 

based on the assumption that initial nutrient 

concentrations are identical in all areas of the 

basin. However, this does not preclude the possibility that nutrient concentrations can be altered 

by subsequent algal growth. Indeed, alteration of 

nutrient concentrations is probably a prerequisite 

for the occurrence of algal succession. 

In the diagram, water-detention time increases 

toward the right and biomass toward tbe top. The 

figure body is divided into three hydraulicecological habitats. The habitat at the left is representative of fast-moving shallow rivers in 

which the photosynthetic zone extends to the bottom. Under such conditions, periphyti~ diatoms 

are typically the dominant algal type and both 

primary production and biomass are high. However, biomass concentrations level at th~ extreme 

left because high flow velocities scour the riverbottom substrate. For the same reason, the 

biomass in this general hydraulic regin1e is probably lower than that which can accumulate in 

sluggish and standing waters (far right of 

diagram). 

The habitat at the center of the scl,~matic is 

typical of moderate-velocity rivers in which average depth is high relative to the penetration of 

light. This habitat characteristically occurs 

downstream from the regime at the left of the 

figure and is commonly the condition found over 

long reaches of most large rivers. In such waters, 

the dominant algae are planktonic diatoms. 

Biomass is relatively low because of lower productivity and the dispersion and transprwt of cells 

by the current. A second curve could b€ drawn in 

the middle section of figure 26 to represent shallow, moderate-velocity rivers. However, this 

hydraulic-ecological habitat was not considered 

separately because it probably is similar to that 

existing in shallow, high-velocity rivers. 

The hydraulic-ecological habitat at the center 

of figure 26 can also occur in tidal rivers (such as 

the Willamette Tidal Reach) where net downstream velocities are low, but the waters are well 

mixed owing to tidally induced currents. 

The habitat at the right of the diagram is representative of sluggish and standing waters such 

G30 
HYDRAULIC-ECOLOGICAL HABITATS 

HIGH-VELOCITY RIVERS MODERATE-VELOCITY RIVERS SLUGGISH AND STANDING WATERS 

A. Shallow A. Deep A. Deep 

UJ 

z 

0 

N Periphytic diatoms Planktonic diatoms Planktonic diatoms, 

greens, and blue rreens u 

i= 

0 

:r: 

a. 

::> 

UJ 

LL 

0 

UJ 

~ 

::> 

_j 

0 

> 

!:: 

z 

::> 

0::: 

UJ 

a. 

vi 

(/) 

<( 

~ 

0 

co 

_j 

<( 

c.:; 

_j 

<( 

B. Shallow 

Planktonic diatom~ 

greens, and blue rreens; 

Periphytic diatom~ and 

FIGURE 26.-Conceptual diagram relating algal biomass and dominant algal types to water-detention tine and light 

penetration. Shallow implies that the euphotic zone extends to the bottom; deep implies the euphotic z')ne does not 

reach the bottom. 

as pooled rivers, lakes, reservoirs, and poorly 

mixed estuaries. Primary productivity is often 

high in the euphotic zones of these waters, and 

biomass accumulation can be great, leading to 

nuisance conditions. The deep waters of this hydraulic regime are commonly poorly mixed, or 

stratified. It is at the surface of such waters that 

seasonal planktonic blue-green blooms are most 

likely to occur, sometimes as the result of a seasonal succession beginning with diatoms and 

green algae. 

Productivity and biomass are also high in many 

sluggish, shallow waters. In rivers having these 

physical characteristics, the site-to-site environmental conditions tend to be diverse. Consequently, the dominant algal types include a broad spectrum ranging from planktonic diatoms, greens, 

and blue greens to periphytic diatoms and 

filamentous greens. Occasionally, periphytic 

blue-green growths also occur (K. V. Slack, U.S. 

Geol. Survey, oral commun., 1976). The same 

broad spectrum of algal types inhabit and can 

also dominate the shallow areas of lakes, reservoirs, and estuaries. 

For either the planktonic or periphytic mode of 

growth, biomass concentrations gener;:~lly level at 

the extreme right of the diagram. This results 

primarily from exhaustion of available nutrients, 

but sometimes from self-shading effects. 

Waters in the Willamette River br~in provide 

examples of most of the hydraulic-ecological 

habitats delineated in the diagran1. The Upstream Reach (figs. 1 and 2; table 1) is an example of a high-velocity shallow river in which the 

algal population is dominated by periphytic diatoms. The Newberg Pool fits the crtegory of a 

moderate-velocity deep river doninated by 

planktonic diatoms, and the Tidal Reach fits into 

the same category because it is well mixed owing 

to tidally induced currents. 

The Tualatin is a sluggish shallow river in 

which the dominant algal type vari€~ with locaG31 
tion and tin1e, and certain reaches are sometimes 

dominated by nuisance growths of filamentous 

greens (McHugh, 1967) and planktonic blue 

greens (McHugh, 1967; Carter, 1975). 

Upstream reservoirs on the Middle Fork Willamette represent a pooled, open-water habitat in 

which the dominant algal type changes with time 

of year with blue-green blooms occurring during 

summer. 

Shallow stagnant pools along the banks of the 

Willamette are another type of habitat implicit in 

the diagram. During late summer, some of these 

pools are dominated by profuse growths of 

filamentous green algae. It is well documented 

(Hynes, 1970; Whitton, 1975) that different algal 

assemblages grow in quiet waters along the 

banks of rivers than in the main current. Indeed, 

Hynes (1970) believes that most river plankters 

originate in still or gently flowing waters and 

subsequently enter rivers where they may or n1ay 

not reproduce significantly. The combined evidence indicates that green and blue-green algae 

do grow along the banks of the Willamette and in 

certain tributaries but do not reproduce significantly after entering the main-stem current. 

Two conditions covered in figure 26 but not 

found in the Willamette River basin are the nuisance algal growths that occur in certain estuaries and along the edges of some lakes and 

reservoirs. However, many examples of these 

conditions exist in the United States, and two of 

the more prominent are the aforementioned 

blooms of A nacystis in the freshwater Upper 

Potomac Estuary (Jaworski and others, 1972) and 

the severe nuisance problems with Cladophora 

aegogropila in Lake Erie (International Joint 

Commission, 1969). Cladophora spp. is a filamentous green algae that grows attached to rocky 

shorelines and shoals in nutrient-enriched waters. Unlike the common nuisance forms of bluegreen algae (for example, Anabaena, Anacystis, 

Aphanizomenon, Oscillatoria ), the periphytic, 

filamentous green algae seem to be favored by 

high concentrations of nutrients, especially phosphorus (International Joint Commission, 1969). 

Also, it is important to note that filamentous 

green algae apparently are not part of a natural 

succession to blue-green algae. 

With figure 26 for perspective, we can hypothesize why significant growth of blue-green 

algae does not occur in the Willamette nor in 

most large rivers (as represented by the middle 

regime). The exact relationship betwEen waterdetention time, biomass, and the qualitative nature of plankton depends on a large number of 

factors. Foremost among these are nutrient 

availability, water temperature, light penetration, and perhaps sin1ply the requirement of some 

algae for a period of adjustment to new environmental conditions. However, the crux of the conceptual model (fig. 26) is that in free-flowing rivers detention time largely controls these factors 

in a manner that prevents the onset of conditions 

conducive to the growth of planktonic blue-green 

algae. 

Perhaps most importantly, flowing water provides a constant chemical influx that prevents 

depletion of major nutrients to concentrations at 

which blue-green algae would enjoy a competitive 

advantage. In addition, most flowing waters remain unstratified (except estuaries), and temperatures do not reach the same levels that would 

occur in stratified standing water under identical 

climatic conditions. Moreover, because flowing 

water carries suspended sedin1ent, rivers are 

usually n1ore turbid and permit less light penetration than standing water. Also, in fl'1wing water, turbulent mixing negates the buoyancy advantage that blue-green algae enjoy in standing 

water because of their unique possesE"ion of gas 

vacuoles (Walsby, 1970). 

All these factors may be important in various 

combinations and degrees in different rivers. In 

the Willamette River, the most important factor 

is probably the maintenance of a balance in nutrient concentrations by flow and mixing, but low 

light availability resulting from turl'idity also 

plays a role. 

PLANNING IMPLICATIONf 

The key to keeping algal growth in the Willamette River at its present balance app~ars to be 

control of those factors that maximize summertime flow and thus minimize time of passage. 

Such control would require maintenance of present levels of flow augmentation and avoidance of 

large increases in summertime diverfions. The 

high observed concentrations of nitrogen and 

phosphorus result primarily from point-source 

loading but, under the present physical conditions, do not stimulate nuisance growths of green 

and blue-green algae. It appears that treatment 

to remove nitrogen and phosphorus from point 

G32 
sources is not needed to control nuisance algal 

growths provided summer low flows are maintained in the range of 6,000 to 7,000 ft3/s (170 to 

200 m3/s) at Salem. However, future decreases in 

summer low flows or turbidity levels would cause 

an increase in the potential for nuisance algal 

growths; if such decreases are significant, further 

study will be needed to determine the possible 

benefits of nutrient removal. 

The results of this study indicate that arbitrary 

standards for permissible nitrogen and phosphorus concentrations in rivers may bear little 

relationship to primary productivity and to 

algal-growth dynamics. This means that the need 

for advanced waste-treatment removal of phosphorus and nitrogen must be assessed on a riverby-river or reach-by-reach basis. The environmental benefits that will result from different 

pollution-control measures can only be determined by conducting sound river-quality assessments that are keyed to local conditions. 

ACKNOWLEDGMENTS 

We wish to acknowledge the aid and encouragement of the Non-Federal Advisory Committee 

on Water Data for Public Use. Our special thanks 

go to the members of the Advisory Committee's 

Ad Hoc Working Group on River Quality Assessment. During the Willamette Study, the group 

included Howard B. Brown, Robert A. Canham, 

Edward J. Cleary, Laurence R. Jahn, John E. 

Kinney, Walter A. Lyon, John A. Roller, and 

Clarence J. Velz. The authors also acknowledge 

the helpful suggestions of Glen D. Carter, Lolita 

M. Carter, Keith V. Slack, Robert C. Averett, and 

Eugene B. Welch. 

GLOSSARY 

[Many definitions were obtained or modified from Slack and others 119731 or Bntton and others 119751] 

Alga, algae (n), algal (adj). Simple plants, many 

microscopic, containing chlorophyll. Most algae 

are aquatic and may produce a nuisance when 

conditions are suitable for prolific growth and 

subsequent death and decay. 

Algal bloom (n). A large number of a particular 

algal species, frequently amounting to 0.5 to 1 

million cells per litre. Sometimes defined as a 

readily visible concentrated growth or aggregation of algae. 

Aliquot (n, adj). A known exact part of a whole 

sample. 

Aquatic (adj). Pertaining to water; aquatic organisms such as algae or fish live in water. 

Benthos (n), benthic (adj). The community of 

organisms living in or on the bottom of an 

aquatic environment. 

Bioassay (n). The use of living organisms to test 

the effects of a substance. 

Biomass (n). The weight of living matter present 

in a unit area or volume at a given time. 

Blue-green algae (n). A group of algae with a 

blue pigment in addition to green cl'lorophyll. 

Members of this group often cause nuisance 

conditions in water. 

Compensation depth (n). The depth of water at 

which oxygen production by photosynthesis 

balances oxygen uptake by respiration of plants 

and animals. 

Diatom (n). A unicellular or colonial alga having 

a siliceous shell. 

Diel (adj). Relating to a 24-hour period that usually includes a day and the adjoining night. 

Diurnal (adj). Relating to daytime or something 

recurring every day, often used as a synonym 

for diel. 

Dissolved oxygen (n). The oxygen dissolved in 

water, waste water, or other liquid, usually expressed in milligrams per litre or percent of 

saturation. Abbreviated DO. 

Ecology (n), ecological (adj)~ The science or 

study of the relation of organisms or groups of 

organisms to their environment. 

Enrichment (n). Addition or accumulation of 

plant nutrients within a body of water. 

Euphotic zone (n). That part of the aquatic environment in which the light is sufficient for 

photosynthesis; commonly considered to be that 

part of a water body in which the intensity of 

underwater light equals or exceeds 1 percent of 

the intensity of surface light. 

Eutrophication (n), eutrophic (adj). The 

natural process of enrichment and aging of a 

body of water that may be accelerated by the 

activities of man. 

Eutrophic waters (n). Waters with c good supply of nutrients. These waters may s11pport rich 

organic production such as algal blooms. 

Genus, genera (n). The taxonomic category 

below family, consisting of specief: the first 

part of the scientific name of organisms. 

Green algae (n). Algae that have pignents simiG33 
lar in color to those of higher green plants. 

Some forms produce algal mats or floating 

"moss" in lakes. 

Gross primary productivity (n). The total rate 

at which organic matter is formed by photosynthesis, including the organic matter used up in 

respiration by plants and animals. The term is 

synonymous with total photosynthesis. 

Growth (n). The increase in biomass by synthesis 

of living matter. 

Habitat (n). The place where an organism lives. 

Interpretative (adj). A type of sampling program or study designed to collect information 

useful in describing a system, and cause and 

effect relationships within the system. 

Limnology (n). The science or study of the physical, chemical, and biological aspects of inland 

waters. 

Loading (n). The amount of a given substance or 

type of material discharged or otherwise entering a water body in a given unit of time. 

Membrane filter (n). A thin, microporous material of specific pore size used to filter bacteria, 

algae, and other very small particles from 

water. 

Net primary productivity (n). The rate of storage of photosynthetically produced organic 

matter in plant tissues in excess of the respiratory utilization by plants and animals. The 

term is synonymous with net photosynthesis. 

Nuisance (n, adj). Pertaining to the waterquality conditions caused by algal blooms. 

Blooms are often esthetically objectionable because they create floating green mats, cause 

foul odors, and cover beaches and shorelines. 

Blooms also reduce dissolved-oxygen concentrations in water through the respiration of living cells and the decay of dead cells. Algal cells 

also can clog the intakes of water-supply systems and interfere with water treatment. 

Nutrient (n). Any chemical element, ion, or compound that is required by an organism for the 

continuation of growth, for reproduction, and 

for other life processes. Trace nutrients are 

substances required by an organism in very 

small amounts. 

Organic (n). Pertaining or relating to a compound containing carbon. 

Organism (n). Any living entity. 

Periphyton (n), periphytic (adj). The community of micro-organisms that is attached to or 

lives upon submerged surfaces. 

pH (n). The reciprocal of the logarithm of the 

hydrogen-ion concentration. The pH value of 

water is a measure of the degree of its acid or 

alkaline reaction. 

Photosynthesis (n), photosynthetic (adj). The 

process by which simple sugars and starches 

are produced from carbon dioxide and water by 

living plant cells, with the aid of chlorophyll 

and in the presence of light. In the process, carbon dioxide is consumed and oxygen is released. 

Phytoplankter (n). An individual phytoplanktonic organis1n. 

Phytoplankton (n), phytoplanktonic (adj). 

The plant part of the plankton. 

Plankton (n), planktonic (adj). The community 

of suspended or floating organismE that drifts 

passively with water currents. The organisms 

are mostly microscopic and include both plants 

and animals. 

Primary production (n). The weight_ of new organic material created by photosynthesis, or 

the energy it represents. 

Primary productivity (n). The rate of primary 

production, expressed as grams of organic matter per metre squared per day. 

Reconnaissance (n, adj). A type of sample or 

sampling program designed to determine the 

present status of something; a preliminary 

survey. 

Respiration (n). A life process in which carbon 

compounds are oxidized to carbon dioxide and 

water. The liberated energy is used in the 

metabolic processes of living organisms. 

Sediment (n). Fragmental materiaL both mineral and organic, that is in suspE.nsion or is 

being transported by the water n1ass or has 

been deposited on the bottom of the aquatic 

environment. 

Sedimentation (n). The deposition of suspended 

material by water, wind, or gravity transport. 

Species (n, sing. and pl.). The basic unit for the 

classification of organisms; the taxonomic 

category below genus, and the second part of 

the scientific name of an organism. 

Substrate (n). The physical surface upon which 

something lives. 

Suspended sediment (n). Fragmental material, 

both mineral and organic, that is maintained in 

suspension in water. 

Turbidity (n), turbid (adj). The ability of materials suspended in water to reduce the penetration of light. 

G34 
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---1969, Factors initiating phytoplankton Hooms andresulting effects on dissolved oxygen in Duwamish River 

estuary, Seattle, Washington: U.S. Geol. E'•1rvey WaterSupply Paper 1873--A, 62 p. 

Whitton, B. A., 1975, Algae, in Whitton, B. A., ed., River 

ecology: Berkeley, California Univ. Press, 725 p. 

Willamette Basin Task Force, 1969, The Willamette Basin 

comprehensive study of water and related land resources, 

Appendix B, Hydrology: Pacific Northwest River Basins 

Comm. rept. 163 p. 

Williams, L. G., 1964, Possible relationships between 

plankton-diatoms species numbers and water-quality estimates: Ecology, v. 45, no. 4, p. 809-823. 

---1972, Plankton diatom species biomass and the quality 

of American rivers and the Great Lakes: Ecology, v. 53, 

no.6, p. 1038-1050. 

G36 
TABLES 4 AND 5 
TABLE 4.-Algal counts at mile 7.0, Willamette River, Oreg., during 1973 

[Counts, in number per millilitre] 

Diatoms: 

Algal groups and species 

Meloszra distans ______________ _ granulata _________________ _ 

ztalica ____________________ _ vanans ___________________ _ 

spp ------------------------ Achnanthes mmuttsszmn __ lanceolata _________________ _ 

lewiszana ___________ _ 

spp ------------------------ Stephanodiscus hantzschu ___ _ 

astraea -------------------- spp -------------- ---------- Cymbella uentncosa ___________ _ 

smuata -------------------- tumida ___________________ _ 

spp ------------------------ Nit.zschw spp __ _ Nauzcula spp ________________ _ 

Svnedra ulna · Cunnmgtonu _____________ _ 

mazamaenszs 

spp --------------- Cocconeis spp _______________ _ Cyclotella stelligera ___________ _ Meneghiniana _____________ _ 

spp -------- Rhozcosphenza curuata ______ _ Diatoma hezmale _______________ _ t•ulgare ___________________ _ 

spp ------------------------ Asterionella formosa ___ _ Hannaea arcus _________________ _ 

Gomphoneis/Gomphonema _____ _ Fragzlarza crotonenszs _________ _ 

Gree~!sc~~~~~~~~~~~~~~~~~~~======== Blue Greens _____________________ _ 

Anabaena spp _ 

Totals: Diatoms __________________ _ Greens ___________________ _ Blue greens _______________ _ 

Total 

4-17 

0 

0 

90 

15 

0 155 

0 

0 

0 175 

110 

175 

50 

15 

0 

0 155 0 

15 

0 

35 

0 

50 

0 

0 

0 

15 

0 

0 

0 

70 

0 

15 

0 

35 

300 

0 

0 

1,470 

0 

0 

1,470 

5--01 

0 

0 

50 

0 

0 

175 

0 

0 

0 380 

90 

130 

35 

0 

0 

0 380 0 

0 

0 

0 

0 

0 

15 

0 

0 

50 

0 

0 

0 110 

0 

0 

15 

0 240 0 

0 

1,670 

0 

0 

1,670 

5--15 

0 

0 

50 

0 

0 200 

0 

0 

0 200 

70 

130 

70 

0 

0 

15 

225 

50 

0 

15 

0 

70 

0 

0 

50 

0 

35 

0 

0 

0 

70 

0 

0 

35 

0 175 

0 

0 

1,460 

0 

0 

1,460 

5--30 

35 

70 

130 0 

0 175 

0 

0 

0 345 

35 

35 

50 

0 

0 

15 

455 

15 

15 

50 

0 

70 

0 

0 

0 

0 

0 

0 

0 

0 110 0 

0 

0 

70 

135 

0 

0 

1,800 0 

0 

1,800 

6-21 

90 

130 

15 

0 

0 

200 

0 

0 

15 

345 

90 

70 

15 

0 

0 

15 

110 

15 

35 

0 

0 

35 

15 

0 

50 

0 

50 

0 

0 

0 110 0 

0 

0 

0 

255 

50 

0 

1.660 50 

0 

1,710 

G38 

Month-day 

7-06 

90 

90 

285 0 

0 315 

0 

0 

0 

285 

130 

70 

35 

0 

0 

15 

315 0 

15 

0 

0 

0 

15 

0 

0 

0 

35 

0 

0 

0 

70 

0 

0 

0 

50 

145 

70 

0 

1,950 70 

0 

2,020 

7-17 

455 

315 

600 0 

0 

90 

0 

0 

15 

550 

130 

50 

0 

0 

0 

15 

155 

15 

0 

15 

0 

0 

0 

0 

90 

0 

15 

0 

0 

0 130 

0 

35 

15 

0 250 

35 

0 

2,935 35 

0 

2,985 

7-31 

735 

300 

285 

15 

0 110 

0 

0 

0 225 

70 

15 

35 

0 

0 

15 

345 

90 

0 

0 

0 

15 

35 

0 

35 

0 

0 

0 

0 

0 

70 

0 

0 

0 

15 

255 

15 

0 

2,565 

15 

0 

2,580 

8-21 

1,010 

175 

415 0 

0 130 

0 

0 

15 

415 

15 

50 

50 

0 

0 

35 

200 0 

0 

0 

0 

15 

15 

0 

0 

0 

35 

0 

0 

0 

50 

0 

0 

15 

0 

35 

225 

0 

2,625 

225 0 

2,850 

8-28 

345 

175 

345 0 

0 

200' 

0 

0 

0 345 

70 

0 

70 

0 

0 

15 

175 

15 

0 

0 

0 

50 

35 

0 

0 

0 

0 

0 

0 

0 

35 

0 

0 

0 

0 110 

50 

0 

1,985 50 

0 

2,035 

~27 

130 

15 

50 

0 

0 455 

0 

0 

0 380 

15 

50 

35 

0 

0 

35 

255 

50 

0 

0 

0 

50 

0 

15 

35 

0 

0 

0 

0 

0 

15 

0 

15 

0 

0 330 

0 

0 

1,910 

0 

0 

1,910 

10-20 

15 

0 225 

15 

0 

380 

0 

0 

0 225 

15 

15 

130 0 

0 

50 

315 

50 

0 

0 

0 

0 

50 

0 

0 

0 

90 

0 

0 

0 

35 

0 

15 

0 

15 

130 

35 

0 

1,770 35 

0 

1,805 
TABLE 5.-Algal counts at mile 7.0, Willamette River, Oreg., during 1974 

[Counts, in number per millilitre] 

Algal groups and species 

Diatoms: Melosira distans _______________________ _ 

f!ai':c~ varzans ~'::_- ___________________________ == = = === == = = = = == = = == == ===== _ 

spp -------------------------------- Achnanthes mznutzssima _______________ _ lanceolata _________________________ _ 

lewiszana ___ ------------- _________ _ 

spp -------------------------------- Stephanodiscus hantzschzi _____________ _ 

astraea _____ -----------------------

spp -------------------------------- Cymbella ventricosa ___________________ _ sinuata ___________________________ _ tum ida ___________________________ _ 

spp -------------------------------- Nitzschza spp _________________________ _ 

Navicula spp -------------------------- Synedra ulna _________________________ _ 

Cunningtonzi ------------ _________ _ mazamaenszs _____________________ _ 

spp -------------------------------- Cocconeis spp ______ -------------------- Cyclotella stelligera ___________________ _ 

Meneghiniana ------------ _________ _ 

spp -------------------------------- Rhoicosphenia curvata _________________ _ 

Diatoma hezmale _ ----------------------- uulgare ___________________________ _ 

spp -------------------------------- Asterionella formosa ---------- _________ _ Hannaea arcus _________________________ _ 

Gomphoneis/Gomphonema _____________ _ Fragilaria crotonensis _________________ _ 

spp -------------------------------- Miscellaneous diatom spp ___ ------------- Greens: Scenedesmus _________________________ _ Pediastrum ___________________________ _ Single cell _____________________________ _ 

Coloma! ___________________ -------------

Filamentous------------------------- __ _ Blue greens: 

Anabaena spp _________________________ _ 

Totals Diatoms ___________________________ _ Greens ___________________________ _ Blue greens _______________________ _ 

Total ________ --------------------

6-12 

0 

0 

0 

0 

0 

90 

0 

0 

0 155 

70 

0 

50 

15 

0 

70 

735 

50 

15 

15 

0 

0 

0 

0 

0 

0 

0 

0 

0 

0 

15 

0 

50 

70 

35 

175 

0 

0 

0 

15 

0 

15 

1,605 15 

15 

1,635 

6-25 

35 

0 

50 

0 

0 

50 

0 

0 

0 285 

200 

70 

15 

15 

0 

35 

285 

70 

15 

90 

0 

0 

0 

0 

0 

0 

0 

0 

0 

0 

50 

0 

0 

15 

0 

35 

0 

0 

0 

15 

0 

0 

1,315 

15 

0 

1,330 

7-09 

50 

0 

90 

0 

0 

90 

0 

0 

0 805 

315 

50 

35 

0 

0 

50 

315 

50 

0 

0 

0 

0 

35 

15 

50 

0 

0 

0 

0 

0 110 0 

50 

50 

0 

70 

0 

0 

0 

35 

0 

50 

2,215 35 

50 

2,300 

G39 

Month-day 

7-22 

15 

35 

70 

0 

0 175 0 

0 

70 

660 

380 

70 

0 

0 

0 

70 

175 

110 

15 

0 

0 

0 

0 

50 

0 

15 

0 

0 

0 

0 

50 

0 

30 

0 

15 

90 

15 

0 

0 

50 

0 

35 

2,065 65 

35 

2,165 

8--07 

315 

15 

35 

0 

0 130 0 

0 

0 805 

35 

90 

0 

0 

0 

35 

200 

15 

0 

15 

0 

0 

0 

15 

35 

0 

0 

0 

0 

0 

50 

0 

0 

15 

0 

15 

0 

0 

0 

50 

0 

35 

1,820 

50 

35 

1,905 

8--20 

735 

70 

15 

0 

0 175 0 

0 

35 

660 

175 

70 

35 

0 

0 

70 

315 

50 

50 

0 

0 

0 

15 

35 

70 

35 

0 

0 

0 

0 

35 

0 

0 

0 

0 

15 

0 

0 

90 

15 

15 

50 

2,650 

120 

50 

2,820 

9--04 

255 

70 

155 0 

0 315 0 

0 

50 

805 

110 

50 

35 

35 

0 

35 

415 

90 

35 

0 

0 

0 

15 

50 

110 

35 

15 

0 

0 

0 

15 

0 

15 

0 

0 

35 

0 

0 

15 

130 

0 

0 

2,890 

9--18 

200 

345 

90 

0 

0 315 0 

0 

15 

805 

455 

70 

50 

0 

0 

70 

380 0 

35 

15 

0 

0 

35 

70 

15 

0 

0 

0 

0 

0 

50 

0 

50 

15 

0 

35 

0 

0 

0 

15 

0 

15 

3,110 

15 

15 

3,140