Long Term Resource Monitoring Program

Technical Report

98-T001

Temporal Analyses of Select

Macroinvertebrates in the 

Upper Mississippi River System,

1992–1995

April 1998
LTRMP Technical Reports provide Long Term Resource Monitoring Program

partners with scientific and technical support.

All reports in this series receive anonymous peer review.

Environmental Management

Technical Center

CENTER DIRECTOR

Robert L. Delaney

APPLIED RIVER SCIENCE

ACTING DIRECTOR

Ken Lubinski

PROGRAM OPERATIONS

ACTING DIRECTOR

Linda E. Leake

REPORT EDITOR

Deborah K. Harris

Cover graphic by Mi Ae Lipe-Butterbrodt

Mention of trade names or commercial products does not constitute endorsement

or recommendation for use by the U.S. Geological Survey, U.S. Department of the Interior.

Printed on recycled paper 
 Temporal Analyses of Select

Macroinvertebrates in the 

Upper Mississippi River System,

1992–1995

by

Jennifer S. Sauer

April 1998

U.S. Geological Survey

Environmental Management Technical Center

575 Lester Avenue

Onalaska, Wisconsin 54650
Suggested citation:

Sauer, J. 1998. Temporal analyses of select macroinvertebrates in the Upper Mississippi River System, 1992–1995. U.S.

Geological Survey, Environmental Management Technical Center, Onalaska, Wisconsin, April 1998. LTRMP 98-T001.

26 pp. + Appendix

Additional copies of this report may be obtained from the National Technical Information Service, 5285 Port Royal Road,

Springfield, VA 22161 (1-800-553-6847 or 703-487-4650). Also available to registered users from the Defense Technical

Information Center, Attn: Help Desk, 8725 Kingman Road, Suite 0944, Fort Belvoir, VA 22060-6218 (1-800-225-3842 or

703-767-9050). 
iii

Contents

Page

Preface ......................................................................... v

Abstract ........................................................................ 1

Introduction ..................................................................... 1

Methods ........................................................................ 2

Study Area and Spatial Design .................................................... 2

Sampling Methods ............................................................. 3

Site Information ............................................................... 4

Statistical Analysis ............................................................. 4

Results ......................................................................... 5

Quality Assurance ................................................................ 6

Select Macroinvertebrates .......................................................... 6

Ephemeroptera (Mayflies) ....................................................... 6

Sphaeriidae (Fingernail Clams) ................................................... 7

Chironomidae (Midges) ......................................................... 7

Corbicula fluminea (Asiatic Clam) and Dreissena polymerpha (Zebra Mussels) ............. 7

Discussion ...................................................................... 8

Acknowledgments ................................................................ 9

References ...................................................................... 9

Appendix. Macroinvertebrate Collection Sheet ........................................ A-1

Tables

Table 1. Macroinvertebrate random sample sites by study area and aquatic area—parentheses

indicate numbers of historical (fixed) sites ................................... 13

Table 2. Sampling dates for macroinvertebrate sampling ............................... 14

Table 3. Results of analysis of covariance on weighted pool/reachwide means with year, study

area, and their interactions as independent variables ............................ 14

Table 4. Estimated mean number of Corbicula fluminea and zebra mussels per square meter by

year and study area, weighted by areas of strata ............................... 15
iv

Table 5. Reachwide estimated mean number of Ephemeroptera, Sphaeriidae, and Chironomidae

per square meter by year and study area, weighted by areas of strata ............... 16

Table 6. Mean number of organisms per square meter by study area and aquatic area with all

years combined ........................................................ 17

Table 7. Mean number of organisms per square meter by study area and substrate type ........ 21

Figures

Figure 1. Long Term Resource Monitoring Program study areas for macroinvertebrate sampling . 22

Figure 2. River miles and percentage of aquatic area in each study area ..................... 22

Figure 3. Frequency of target organisms in samples, 1992–1995 .......................... 23

Figure 4. Percent composition of target organisms: 1 = Zebra mussel sampling initiated in 1995,

2 = Midge sampling initiated in 1993 ....................................... 23

Figure 5. Estimated mean number of Ephemeroptera per square meter by study area, weighted by

area of strata .......................................................... 24

Figure 6. Estimated mean number of Sphaeriidae per square meter by study area, weighted by

area of strata .......................................................... 25

Figure 7. Estimated mean number of Chironomidae per square meter by study area, weighted

by area of strata ........................................................ 26
v

Preface

The Long Term Resource Monitoring Program (LTRMP) was authorized under the

Water Resources Development Act of 1986 (Public Law 99-662) as an element of the U.S.

Army Corps of Engineers’ Environmental Management Program. The LTRMP is being

implemented by the Environmental Management Technical Center, a U.S. Geological

Survey science center, in cooperation with the five Upper Mississippi River System

(UMRS) States of Illinois, Iowa, Minnesota, Missouri, and Wisconsin. The U.S. Army

Corps of Engineers provides guidance and has overall Program responsibility. The mode of

operation and respective roles of the agencies are outlined in a 1988 Memorandum of

Agreement.

The UMRS encompasses the commercially navigable reaches of the Upper Mississippi

River, as well as the Illinois River and navigable portions of the Kaskaskia, Black, St. Croix,

and Minnesota Rivers. Congress has declared the UMRS to be both a nationally significant

ecosystem and a nationally significant commercial navigation system. The mission of the

LTRMP is to provide decision makers with information for maintaining the UMRS as a

sustainable large river ecosystem given its multiple-use character. The long-term goals of

the Program are to understand the system, determine resource trends and effects, develop

management alternatives, manage information, and develop useful products.

This trend and spatial analysis report supports Task 2.2.7.6, Evaluate and Summarize 5-

Year Trends, as specified in Goal 2, Monitor Resource Change of the LTRMP Operating

Plan (U.S. Fish and Wildlife Service 1993). This report was developed with funding

provided by the Long Term Resource Monitoring Program.
Temporal Analyses of Select

Macroinvertebrates in the

Upper Mississippi River System,

1992–1995

by

Jennifer S. Sauer

Abstract

The annual variability in mayflies (Ephemeroptera), fingernail clams (Sphaeriidae), and midges (Chironomidae) in six study areas

of the Upper Mississippi River System from 1992 to 1995 was examined. Spatial distribution is also discussed for these organisms

along with the Asiatic clam (Corbicula fluminea) and the zebra mussel (Dreissena polymorpha). Sample allocation within each reach

was based on a stratified random design where strata were aquatic areas. No significant linear trends across years were found in

estimated reachwide mean number of organisms. However, the overall test for differences in intercepts among study areas was

statistically significant (P < 0.05) for mayflies, fingernail clams, and midges. No statistical difference in trend slopes among reaches

were detected. In 1993, the estimated mean density of fingernail clams in Pool 13 was 35 times that found in other study areas.

Overall, impounded aquatic areas and silt clay substrates supported higher numbers of the select macroinvertebrates. 

Introduction

 In 1986, Congress designated the Upper Mississippi River System (UMRS), which consists of the Upper

Mississippi and Illinois Rivers and several important tributaries, as both a nationally significant ecosystem

and a nationally significant navigation system. Macroinvertebrates and other aquatic organisms play a major

role in the aquatic ecosystem. Mayflies (Ephemeroptera), fingernail clams (Sphaeriidae), and midges

(Chironomidae), part of the soft-sediment substrate fauna, were chosen as target organisms for the Long

Term Resource Monitoring Program (LTRMP) because of their important ecological role in the UMRS. For

example, Thompson (1973) found that in fall, lesser scaup (Aythya affinis) gizzard contents contained

76% sphaeriids and about 13% mayflies. Thompson also found the target organisms to be important to

canvasbacks (Aythya valisneria), ring-necked ducks (Aythya collaris), and American coots (Fulica

americana) feeding in open water. A number of fish, including commercial and recreational fish, utilize the

target organisms (Hoopes 1960; Jude 1968; Ranthum 1969). Researchers have also traditionally used

macroinvertebrates as biological indicators of river water quality (Fremling 1964, 1973, 1989; Myslinski and

Ginsburg 1977; Rosenberg and Resh 1993; Steingraber and Weiner 1995). An indicator species can be

defined as a species that has particular requirements with regard to a known set of physical or chemical

parameters. Macroinvertebrates also perform an important ecological function by digesting organic material

and recycling nutrients (Reice and Wohlenberg 1992). The Asiatic clam (Corbicula fluminea) and zebra

mussel (Dreissena polymorpha), both non-native freshwater clams, were chosen for monitoring because of

possible detrimental effects they may have on the economy and biology of the UMRS (Tucker 1995a, b), and

their status is of concern to river managers.

Few long-term studies on the distribution and abundance of mayflies, fingernail clams, and midges have

been published, and the majority of information that is available is scattered in unpublished government

reports and theses. Several areas of the UMRS have been sampled sporadically for benthic

macroinvertebrates by various researchers (Fremling 1964; Carlander et al. 1967; Gale 1969; Hubert et al.

1983; Eckblad and Lehtinen 1991; Brewer 1992; Hornbach et al. 1993). Although these studies contain

valuable information, they were collected by different methods and over relatively short periods, making it

impossible to evaluate long-term trends. Long-term monitoring is needed to detect population trends and

local changes to direct management actions or measure the effectiveness of management actions. 
2

The objective of this report is to document spatial and temporal patterns in select benthic

macroinvertebrates from samples collected from the UMRS by field stations of the LTRMP. This

documentation will provide baseline data for future reference on the distribution and abundance of select

macroinvertebrates in the UMRS and provide data for other analyses (e.g., synthesis among LTRMP

components). Also, these first years of monitoring will be used to establish a scientifically acceptable

procedure, using consistent protocols, for the long-term collection of macroinvertebrates in the UMRS.

The publicly available data and annual status reports (Sauer 1996, 1997aSd) are the most basic LTRMP

products. Annual status reports provide more detailed summaries of macroinvertebrate data than are included

in this trend report, but they lack analyses or syntheses. The trend report and the status reports are best used

as information sources for the assessment of background variation (Lubinski 1993), identification of

management problems, and formulation of hypotheses. The ultimate goal of the LTRMP is not simply to

report status and trends, but to improve the understanding and management of the UMRS. That goal can best

be achieved by the integration of routine monitoring with experimental research directed at identifying the

causes of and solutions to specific problems. Future LTRMP efforts will integrate more narrowly focused

analyses of data from all LTRMP monitoring components (limnology, bathymetry, sediments, aquatic plants,

and fisheries) with the results of experimental studies to identify causes of problems and opportunities for

improved management. 

Methods

Study Area and Spatial Design

In 1992, macroinvertebrate sampling was initiated in six study areas on the UMRS. The six LTRMP study

areas represent the variety of aquatic areas within the UMRS. They range in size (calculated from geographic

information system coverage; Lowenberg 1993) from Pool 8 (19,000 ha) to the Open River (107,000 ha).

Long Term Resource Monitoring Program study areas are referred to herein by the navigation pool

designations according to the U.S. Army Corps of Engineers lock and dam system and include: Pools 4 (river

mile 752 to 797), 8 (679 to 703), 13 (523 to 557), and 26 (202 to 242); the Open River Reach (29 to 80) of the

Mississippi River; and La Grange Pool (80 to 158) of the Illinois River (Figure 1). The choice of these

study areas was based on several criteria (Jackson et al. 1981):

1. Monitoring locations were either representative of major UMRS habitat types or capable of influencing

a significant portion of the system.

2. A historical database was available.

3. Selected pools or reaches were recognized as important fish and wildlife resources.

4. Monitoring locations were established with regard to availability of workers and facilities.

The first year of macroinvertebrate sampling was used to refine the sampling design, and changes have

been documented in the Procedures Manual for the LTRMP (Thiel and Sauer 1995). Initially, mayflies,

fingernail clams, and C. fluminea were selected for monitoring. Midges were added to monitoring in 1993,

and zebra mussels were added in 1995.

Sampling was conducted yearly at about 125 sites per study area. Sample allocation was based on a

stratified random design, where strata were aquatic areas (Figure 2) as defined by Wilcox (1993): 
3

C contiguous backwaters (BWC), which are areas having apparent surface-water connection with the rest

of the river; 

C main channel borders (MCB), the area between the navigational buoys and the riverbank (not including

revetments and channel-training structures); 

C impounded areas (IMP), the large, mostly open water areas located in the downstream portion of the

navigational pools; 

C side channels (SC), which are channels that carry less flow than the navigational channel; and

C tributary delta lake (TDL), which in Pool 4 is Lake Pepin, an impounded area formed by the Chippewa

River.

A spatial database of aquatic areas was developed at the Environmental Management Technical Center

(Owens and Ruhser 1996) based on aerial photography made in 1989; this database is used for randomized

selection of sampling sites and the quantification of sampling strata reported herein. This database is updated

at appropriate intervals. Sampling maps are updated, as needed, from direct observations made by the

sampling crews.

Sample sites also included some historical (fixed) sites, where benthic samples were collected by previous

researchers (Paloumpis and Starrett 1960; Fremling 1973; Emge et al. 1974; Colbert et al. 1975; Anderson

1977; Elstad 1977; Hubert et al. 1983; Brewer 1992).

In 1992, stratified random sampling sites were distributed equally in each aquatic area. After analysis of

the 1992 data—where 57% of the samples contained no target organisms—it was decided to more heavily

sample the particular habitat of the target organisms (i.e., soft-sediment substrate; Table 1). All sites were

sampled in spring to characterize the benthic community before mayfly emergence (Table 2).

Sampling Methods

Macroinvertebrate sampling procedures are described in detail in the LTRMP Procedures Manual (Thiel

and Sauer 1995). Benthic samples were collected with a winch-mounted 0.052-m standard Ponar grab

2

sampler (Ponar Grab Dredge, Wildlife Supply Company, Saginaw, Michigan). The wash frame sieve size was

changed from a U.S. Standard Sieve no. 30 (595 Fm), used in 1992, to a U.S. Standard Sieve no. 16

(1.18 mm) in 1993 to increase sorting efficiency in the field. Thus, inferences in macroinvertebrate numbers

made from these data are restricted to the larger organisms of the population whole (Dukerschein et al. 1996).

Mayflies, fingernail clams, midges, C. fluminea, and zebra mussels were picked and counted in the field.

After the picking process was complete, leaving only detritus and organisms other than the target organisms,

it was determined by random draw whether the sample would be brought back to the laboratory for quality

assurance (Norris and Georges 1992). A total of 10% of the sites sampled within each aquatic area were

brought back to the laboratory to evaluate field-picking efficiency without the aid of magnification or

 staining.
y ̄st '

1

N j

L

h ' 1 Nh

y ̄h

s

2

(y ̄st) '

1

N

2j

L

h' 1 Nh

Nh& nh

s

2

h

nh

s

2

h

'

j

nh

i' 1

(y

hi& y ̄h

)

2

nh& 1

(DS)

DS

DS

y ̄st

y ̄h

y ̄st

y ̄st s( y ̄st)

4

(1)

(2)

Site Information

At each site, substrate composition was noted according to subjective characterization. Six categories of

substrate composition were used: hard clay, silt clay, silt clay with sand, sand with silt clay, sand, and gravel

rock. The absence or percentage of submersed and floating-leaved aquatic vegetation in the column of water

and sediment through which the Ponar dredge fell was estimated. The type and percentage of vegetation and

open water in a 15-m radius from the boat were qualitatively characterized. Water depth was measured at

each site (Appendix).

Statistical Analysis

Density was recorded for each target taxa from individual Ponarsamples. Whenever a taxa was not caught

in a sample, the catch for that taxa in that sample is zero.

Analyses of densities (DS) were based on estimates of mean densities obtained by pooling data over all

strata. In this way, the analyses track the broadest possible spatial scale for trends in relative densities. The

pooling probably presents a truer image of reachwide trends in densities because it does not rely only on

particularly favorable habitats. If the quantity of preferred habitat declines through time while densities in

those preferred habitats remains constant, then these pooled estimated mean densities statistics should

also reflect that decline, whereas mean density statistics from only the preferred habitats would not. If the

quantity of that aquatic area class preferred by a particular species declines through time while the

abundances within each aquatic area remain constant, then the pooled statistics should also reflect the

resulting decline in reachwide abundance, whereas mean density statistics from only the preferred aquatic

area would not. 

The estimates of pooled reachwide were obtained from the conventional design-based estimator for

stratified random samples (Cochran 1977). For an arbitrary random variable denoted y (for this report y is

DS), the pooled mean, denoted (st represents stratified) is given by

where N is the number of sampling units within stratum h, N = E N , and denotes the estimator of the h h=1 h

L

simple mean of y for stratum h. The estimator of the variance of is

where

is the usual estimator of the variance of yh and nh is the number of samples taken in stratum h (Cochran

1977). The standard error of is therefore . For LTRMP macroinvertebrate monitoring, random

sample sites are selected from grids whose cells are 50 m .

2
DS rt ' J0

% $1t

r

% J0r% $1rt

r

% ,rt ,

DS rt

DS rt

s

&2

( y ̄st) DS rt

DS rt

DS rt

DS rt

DS rt

5

(3)

Equation (1) is used to obtain estimates of overall mean densities of 1992–95 random sampling. In random

samples, equation (1) yields unbiased estimates of the pooled meansregardless of the probability distribution

of y (Cochran 1977). 

For this report, the presence of differences among LTRMP study areas and simple linear trends was tested.

Because only the first 4 years of data obtained by the LTRMP were examined in this report, it is impossible

to perform sophisticated time-series and trend analyses because the existing series are still too short.

However, under some simplifying assumptions, it is possible to test for simple linear trends (straight-line

increases or decreases) over the 4-year period and also to make useful comparisons of these trends among

the six LTRMP study areas. 

To place inference in terms of the reachwide estimates of mean densities, the observed obtained

from equation (1) to make inferences about the unknown true values of reachwide mean densities statistical

tests were constructed assuming the general linear model given by

where denotes reachwide mean abundance for reach r during year t, J is the parameter for the overall 0

intercept for all reaches combined, $ is the parameter for the overall slope (linear trend) for all reaches 1

combined, the J are six parameters for reach-specific deviations from t the $ are six parameters for 0r 0, 1r

reach-specific deviations from $ and , is random error. For these data, it is assumed that the , are 1, rt rt,

independently and normally distributed with mean zero and diagonal covariance matrix having elements

F , where F is variance from model-based sources. That is, the observations of in equation 2 2

(3) are assumed to be serially independent but are weighted by the reciprocals of their variances from

equation (2) to obtain constant model-based variance F . Although data are not normally distributed,

2

the Central Limit Theorem (DeGroot 1975) implies that the are approximately normally distributed;

however, model assumptions only require that the , are approximately normally distributed. Equation (3) rt

is an extension of the analysis of covariance model that accounts for heterogeneity of variance in the

response variable and for the possibility linear trend slopes differ among LTRMP study areas.

Three tests based on Type I sums of squaresfrom equation (3) are relevant (Littell et al. 1991). The F test

for study area r examines the differences due to different intercepts J (adjusted treatment differences) 0r

assuming equal trend slopes. The F test for the main effect t

r

 examines the significance of a single trend

regression of on t

r

 that prevails over the six study areas. Last, the F test for the interaction between

study area and time, denoted by the term $1rt

r

 in equation (3) examines the significance of differences in

trend coefficients $ among study areas. If this last F test is not statistically significant, then one concludes 1r

that among-reach differences in trend slopes could not be detected.

Results

 More than 2,400 Ponar collections were made from the six study areas in summers 1992, 1993, 1994, and

1995. Frequency distributions varied among years; in 1992 low densities (#20 organisms per sample) were

common, and higher densities (>20) occurred in about 4% of the samples (Figure 3). However, after the

experimental design was changed in 1993, the number of organisms per sample were more evenly distributed

between low and high densities. 
(DS)

DS DS

DS

6

Percent composition of target organisms varied among years within study areas. Pool 8 consistently had

higher percentages of mayflies than any of the other four target organisms, whereas Pool 13 had high

percentages of fingernail clams in 1993, 1994, and 1995 when compared with other target organisms.

Pools 4, 8, and 13 had similar temporal patterns for percent composition, but the magnitude of the

percentages varied widely (Figure 4).

Measured depths at sampling sites ranged from 0.20 to 8.3 m with a mean of 1.8 m. More than 93% of

the sample sites were unvegetated. Visual classification of sediments indicated that sample sites in Pools 4,

8, 13, 26, and La Grange Pool were dominated by silt clay, which constituted 46.6% of the sample sites. The

Open River had a predominance of sand at sampling sites. All aquatic areas except main channel borders and

side channels (sand) were dominated by silt clay.

Quality Assurance

More than 60% of the samples brought back to the laboratory for quality assurance had zero mayflies, and

nearly 60% of the samples had zero fingernail clams. Measurement of the laboratory specimens indicated

that 92% of the mayflies and 80% of the fingernail clams were less than or equal to 4 mm in length; mean

lengths were 25.3 mm in field-picked mayflies and 6.5 mm in fingernail clams.

Select Macroinvertebrates

No statistically significant linear trend existed in the overall mean densities of mayflies (P = 0.89),

fingernail clams (P = 0.79), and midges (P = 0.52) across years or the interation between study areas and

years (P = 0.11, P = 0.53, P = 0.13, respectively). However, the overall test for differences in intercepts

among study areas was statistically significant (P < 0.05) for all three organisms (Table 3). That is,

differences in estimated mean densities of mayflies, fingernail clams, and midges that occurred among study

areas were significant. Corbicula fluminea and zebra mussels were not included in the trend

analyses because of low numbers found during sampling (Table 4). 

Ephemeroptera (Mayflies)

Pool 13 contained the highest estimated mean densities of mayflies in 1992, 1993, and 1995

followed by Pool 4 (Table 5; Figure 5). In 1994, Pool 4 had slightly higher of mayflies. The lowest 

of mayflies were from Pool 26, the Open River Reach, and La Grange Pool. No estimated mean densities of

mayflies were calculated for Pool 26 in 1995; field crews were not able to sample certain sites because of

high water. Pool 4 had the largest range in (143.7 m ) compared with other study areas. -2

Although mean densities of mayflies varied over the years among aquatic areas, the IMP aquatic areas,

including the naturally impounded Lake Pepin in Pool 4, and BWC areas supported the highest mean number

of mayflies in Pools 4, 8, 13, and 26 (Table 6). Side channel areas had the highest mayfly densities in the

La Grange Pool study area in 1992–95. Overall, MCB areas supported the lowest densities of mayflies.

The silt clay substrate supported the highest mean numbers of mayflies in all study areas (Table 7). The

large-particle substrates (i.e., sand and gravel rock) had the lowest numbers of mayflies. 
DS DS

DS

DS

DS

7

Sphaeriidae (Fingernail Clams)

Pool 13 contained the highest of fingernail clams in all years (Table 5; Figure 6). In 1993, the of

fingernail clams in Pool 13 was 35 times that found in other study areas for the same year (Table 5). This

wide variability is largely because of the high numbers of fingernail clams found in the impounded area of

Pool 13 in 1993 (Table 6). More than 75% of the samples from Pools 8, 26, and the Open River had zero

fingernail clams.

Within Pool 8, the BWC aquatic area supported the most fingernail clams, whereas Pools 4, 13, and 26

of the IMP aquatic areas, including the naturally impounded Lake Pepin, supported the highest number of

fingernail clams (Table 6). Side channel areas had the highest fingernail clam densities in the Open River.

Densities were less than 14.5 m in 1992 and dropped to less than 1.0 m in 1994 and 1995. Side channel

-2 -2

areas also supported the highest number of fingernail clams in the La Grange Pool, although MCB areas had

close to the same densities in 1994. In 1993–95, the IMP area of Pool 13 supported 35, 7.2, and

4.6 (respectively) times the number of fingernail clams when compared with the next most productive area.

The silt clay substrate supported the highest number of fingernail clams except in Pool 26 where silt clay

with sand had the highest mean densities (Table 7). The large-particle substrates (sand and gravel rock)

supported the lowest densities of fingernail clams.

Chironomidae (Midges)

The monitoring of midge densities began in 1993. Although no significant linear trends were detected,

Pools 4, 8, and 13 experienced year-to-year declinesin midge densities. Pools 4 and 13 contained the highest 

of midges (Table 5; Figure 7). The lowest of midges were from Pool 26 and the Open River. The

maximum estimated mean densities found in these study areas were less than 15 m . Pool 13 had the largest

-2

range in (469.6 m ) compared with other study areas. -2

Midge densities varied widely among aquatic areas over years and study areas. For example, in Pool 8

high midge densities were found in the IMP area in 1993; in 1994, however, the highest midge densities were

found in SC areas (Table 6).

The small-particle substrates (silt clay, silt clay with sand, and sand with silt clay) supported the highest

mean number of midges in all study areas (Table 7). The large-particle substrates (i.e., sand and gravel rock)

along with hard clay had the lowest number of midges.

Corbicula fluminea (Asiatic Clam) and Dreissena polymerpha (Zebra Mussels)

Because of the low number of C. fluminea and zebra mussels, no statistical analyses were undertaken

(Table 4). Low numbers of C. fluminea were found in all study areas. More than 95% of the samples

contained zero C. fluminea and zebra mussels. No study areas had samples with more than 115 m-2

C. fluminea (6 individuals). A TDL aquatic area sample site in Pool 4 contained the highest density of zebra

mussels (1,500 m ; 78 individuals). Densities of zebra mussels are most likely under-represented because

-2

of the sampling method.
8

Discussion

The most widespread annual collections of macroinvertebrates in the UMRS are now being made under

the LTRMP. The Program’s stratified random design is intended to estimate unbiased mean densities of

select macroinvertebrates within aquatic area strata of each study area.

To sample such a large geographic area with large sample sizes, field-picking the macroinvertebrates was

considered the quickest and most economical process. Evaluation of quality control samples showed that

field-picking was adequate for monitoring mayflies and midges and adult fingernail clams greater than 4.0

mm in shell length (Gale 1969; Dukerschein et al. 1996). 

Are the target organism densities observed during the 4 years of LTRMP monitoring low or high in

relation to long-term means? Although LTRMP data yield adequate mean estimates for the trend analysis

reaches, few similar comprehensive inventories were made in the past, and therefore direct comparisons to

pre-LTRMP monitoring are difficult. Four years of monitoring indicate that a great deal of temporal and

spatial variability exist in mayflies, fingernail clams, and midges populations.

We did not detect statistically significant linear trends across the 4 years within study areas for

macroinvertebrates greater than 1.18 mm. Midge densities showed a decline, although not statistically

significant, in each study area. Compared with work done by Hornbach et al. (1993) midge densities reported

in this study seem low. Hornbach found midge densities greater than 4,000 m in a backwater lake in Pool

-2

2. Few studies have examined the abundance and distribution of midges on the UMRS. Midges can constitute

a large portion of the benthic community (Eckblad 1986). 

Differences between study areas were detectable, especially in the high densities of fingernail clams found

in Pool 13. Two possible explanations for Pool 13 having the highest densities of fingernail clams are that

(1) Pool 13 is at the lower end of a pollution gradient that extends downstream from Minneapolis–St. Paul

(Wilson et al. 1995), or that (2) the substrates of the lower, very broad impounded area—3,555 ha—of

Pool 13 are especially suitable for fingernail clams. Clearly, other factors are involved, since Pool 8, which

is also downstream from Minneapolis–St. Paul and is more than 3,500 ha, has relatively low densities of

fingernail clams (<25 m ). An explanation of this phenomenon becomes more complicated when one

-2

considers that mean densities of fingernail clams at specific sites in Lake Onalaska in Pool 7 and areas in

Pool 9 have reached more than 1,000 m in the fall of the year (Eric Nelson, U.S. Fish and Wildlife Service,

-2

personal communication) while mean densities in Pool 8 fall sampling were below 15 m . Gale (1969)

-2

reported fingernail clam population densities for Pool 19 at more than 5,000 m . Sphaeriidae populations -2

in several backwater lakes in Pool 9 varied from 631.8 m in 1976 to 11.3 m in 1989 and then increased -2 -2

to 78.0 m in 1990 (Eckblad and Lehtinen 1991). -2

The densities of mayflies collected in LTRMP sampling are well within the ranges reported by past

studies. Mayfly densities were highly variable, with concentrations as high as 340 m in certain habitats -2

(Fremling and Johnson 1990). Fremling (1989) detected the rebound of Hexagenia in Pool 2 and Lake Pepin

in Pool 4 during the 1980s and a subsequent population decline in 1988. Carlander et al. (1967) showed how

dynamic Hexagenia populations can be in Pool 19 from year to year with estimated whole pool populations

of 3.6 billion in 1959 to 23.6 billion in 1962. Carlander found Hexagenia density ranges in June sampling

of zero to 1,292 m along his transects. -2

Some local studiessuggest that mayfly and fingernail clam densities have been declining (Eckblad 1991;

Wilson et al. 1995). The results from the stratified random sampling of the LTRMP suggest that relatively

low densities throughout the river could be the rule rather than the exception. This apparent conflict of
9

findings is likely due in part to differing purposes and spatial scopes of the studies. Local studies are often

designed to quantify change—often already under way—in a localized area known for its value as a source

for macroinvertebrates and considered at risk because of some destructive event or activity. The stratified

random design of the LTRMP macroinvertebrate component ensures that results from every stratum are

unbiased, enabling the monitoring of trends over whole strata and study areas (Gutreuter 1993).

Declines in macroinvertebrate densities indicated in the localized studies are a cause for concern. The

value of the river macroinvertebrate community as a source of food for fish and waterfowl cannot be

overstated. For example, Mills et al. (1966) reported a decline in the number of fingernail clams that

coincided with a similar decline in the number of diving ducks utilizing the Illinois River. Long-term

monitoring is intended to provide a better understanding of the conditions needed to support viable

macroinvertebrate populations at levels adequate for sustaining native fish and migrating waterfowl. 

Acknowledgments

The Long Term Resource Monitoring Program is a cooperative effort by the Biological Resources

Division of the U.S. Geological Survey, the U.S. Army Corps of Engineers, the Minnesota Department of

Natural Resources, the Illinois Department of Conservation, the Illinois Natural History Survey, the Iowa

Department of Natural Resources, the Missouri Department of Conservation, and the Wisconsin Department

of Natural Resources. Monitoring is conducted by the participating State resource management and research

agencies. Thanks go to these agencies and field station staff, especially K. Douglas Blodgett, Robert Burdis,

Troy Clemment, Lesly Conaway, Steve DeLain, J. Terry Dukerschein, Russ Gent, Robert Hrabik, Matt

O'Hara, Walter Popp, Dirk Soergel, Michael Stueck, Chuck Theiling, and John Tucker. Special appreciation

goes to Pam Thiel, U.S. Fish and Wildlife Service, for the initiation of the macroinvertebrate monitoring

program in 1992 and Steve Gutreuter, U.S. Geological Survey, for statistical assistance.

References

Anderson, K. B. 1977. Musculium transversum in the Illinois River and an acute potassium bioassay method

for the species. M.S. Thesis, Western Illinois University, Macomb. 79 pp.

Brewer, S. K. 1992. Community structure of benthic macroinvertebrates in Navigation Pool No. 8, Upper

Mississippi River: Comparisons between 1975 and 1990. M.S. Thesis, University of Wisconsin–La

Crosse. 47 pp.

Carlander, K. D., C. A. Carlson, V. Gooch, and T. L. Wenke. 1967. Populations of Hexagenia naiads in

Pool 19, Mississippi River, 1959–1963. Ecology 48:873–878.

Carlson, C. A. 1968. Summer bottom fauna of the Mississippi River, above Dam 19, Keokuk, Iowa. Ecology

49:162–169.

Cochran, W. G. 1977. Sampling techniques. 3rd edition. John Wiley & Sons, New York.

Colbert, B. K., J. E. Scott, J. H. Johnson, and R. C. Solomon. 1975. Environmental inventory and assessment

of Navigation Pools 24, 25, and 26, Upper Mississippi and Lower Illinois Rivers: An aquatic analysis.

Technical Report Y-75-2, U.S. Army Corps of Engineers, Waterways Experiment Station, Vicksburg,

Mississippi. 137 pp. + Appendixes
10

DeGroot, M. H. 1975. Probability and statistics. Addison-Wesley, Reading, Massachusetts. 607 pp.

Dukerschein, J. T., R. Gent, and J. Sauer. 1996. Recovery of macroinvertebrates by screening in the field:

A comparison between coarse (1.18 mm)- and fine (0.66 mm)-mesh sieves. Journal of Freshwater Ecology

11:61–65.

Eckblad, J. W. 1986. The ecology of Pools 11–13 of the Upper Mississippi River: A community profile.

U.S. Fish and Wildlife Service Biological Report 85. 90 pp.

Eckblad, J. W. 1991. LTRMP Observational Bulletin No. 1. Status of macroinvertebrate populations of the

Upper Mississippi River. Report by Luther College, Decorah, Iowa, for the U.S. Fish and Wildlife

Service, Environmental Management Technical Center, Onalaska, Wisconsin, April 1991. EMTC 91-03.

8 pp. (NTIS # PB91-197863)

Eckblad, J. W., and S. F. Lehtinen. 1991. Decline in fingernail clam populations (Family Sphaeriidae) from

backwater lakes of the Upper Mississippi River. Journal of Freshwater Ecology 6:353–361.

Elstad, C. A. 1977. Macrobenthic survey of Navigation Pool No. 8 of the Upper Mississippi River, with

special reference to ecological relationships. M.S. Thesis, University of Wisconsin–La Crosse. 231 pp.

Emge, W. P., R. C. Solomon, J. H. Johnson, C. R. Bingham, B. K. Colbert, and R. W. Hall. 1974. Physical,

biological, and chemical inventory of twenty-three side channels and four river border areas, middle

Mississippi River. Technical Report Y-74-5, U.S. Army Corps of Engineers, Waterways Experiment

Station, Vicksburg, Mississippi. 163 pp. + Appendixes

Fremling, C. R. 1964. Mayfly distribution indicates water quality on the Upper Mississippi River. Science

146:1164–1166.

Fremling, C. R. 1973. Factors influencing the distribution of burrowing mayflies along the Mississippi River.

Pages 12–15 in W. L. Peters and J. G. Peters, editors. Proceedings of the First International Conference

on Ephemeroptera. E. J. Brill Publishers, Leiden, Netherlands.

Fremling, C. R. 1989. Hexagenia mayflies: Biological monitors of water quality in the Upper Mississippi

River. Journal Minnesota Academy of Science 55:139–143.

Fremling, C. R., and D. K. Johnson. 1990. Recurrence of Hexagenia mayflies demonstratesimproved water

quality in Pool 2 and Lake Pepin, Upper Mississippi River. Pages 243–248 in Mayflies and stoneflies:

Proceedings of the Fifth International Ephemeroptera Conference and the Ninth International Plecoptera

Conference. J. C. Campbell, editor. Kluwer Academic Publishers, Belgium. 

Gale, W. F. 1969. Bottom fauna of Pool 19, Mississippi River with emphasis on the life history of the

fingernail clam, Sphaerium transversum. Ph.D. Dissertation, Iowa State University, Ames. 234 pp.

Gutreuter, S. 1993. A statistical review of sampling of fishes in the Long Term Resource Monitoring

Program. National Biological Survey, Environmental Management Technical Center, Onalaska,

Wisconsin, December 1993. EMTC 93-T004. 15 pp. (NTIS # PB94-150828)

Hoopes, D. T. 1960. Utilization of mayflies and caddisflies by some Mississippi River fishes. Transactions

of the American Fisheries Society 89:32–34.
11

Hornbach, D. J., T. Deneka, M. Hu, B. S. Payne, and A. C. Miller. 1993. Temporal and spatial variability

in midge assemblages from a backwater lake in Pool 2, Mississippi River. Hydrobiologia 252:133–141.

Hubert, W. A., G. E. Darnell, and D. E. Dalk. 1983. Evaluation of wintering benthic macroinvertebrates of

Pool 13 of the Upper Mississippi River. U.S. Army Corps of Engineers, Rock Island District, Rock Island,

Illinois. Letter Order NCR-LO-83-C12. 30 pp.

Jackson, G. A., C. E. Korschgen, P. A. Thiel, J. M. Besser, D. W. Steffeck, and M. H. Bockenhauer. 1981.

A long-term resource monitoring plan for the Upper Mississippi River System. Volume 1. Contract Report

14-16-009-81-903 for the Upper Mississippi River Basin Commission, Bloomington, Minnesota. 966 pp.

+ Appendixes

Jude, D. J. 1968. Bottom fauna utilization and distribution of ten species of fish in Pool 19, Mississippi River.

M.S. Thesis, Iowa State University, Ames. 238 pp.

Littell, R. C., R. J. Freund, and P. C. Spector. 1991. SAS System for linear models. 3rd edition. SAS

®

Institute Inc., Cary, North Carolina. 329 pp. 

Lowenberg, C. 1993. 1989 Systemic land cover/land use data in EPPL7 format. National Biological

Survey, Environmental Management Technical Center, Onalaska, Wisconsin, December 1993.

EMTC 93-P008. 6 pp. + 2 diskettes

Lubinski, K. S. 1993. A conceptual model of the Upper Mississippi River ecosystem. U.S. Fish and Wildlife

Service, Environmental Management Technical Center, Onalaska, Wisconsin. EMTC 93-T001. 23 pp.

Mills, H. B., W. C. Starrett, and F. C. Bellrose. 1966. Man's effect on the fish and wildlife of the Illinois

River. Illinois Natural History Survey, Biological Notes 57. 24 pp.

Myslinski, E., and W. Ginsburg. 1977. Macroinvertebrates as indicators of pollution. American Water Works

Association Journal 69:538–544.

Norris, R. H., and A. Georges. 1992. Analysis and interpretation of benthic macroinvertebrate surveys. Pages

234–286 in Freshwater biomonitoring and benthic macroinvertebrates. D. M. Rosenberg and V. H. Resh,

editors. Chapman and Hall, New York. 

Owens, T., and J. J. Ruhser. 1996. Long Term Resource Monitoring Program standard operating procedures:

Aquatic areas database production. National Biological Service, Environmental Management Technical

Center, Onalaska, Wisconsin, March 1996. LTRMP 95-P008-6. 4 pp. + Appendix (NTIS # PB96-172267)

Paloumpis, A. A., and W. C. Starrett. 1960. An ecological study of benthic organisms in three Illinois River

flood plain lakes. American Midland Naturalist 64:406–435.

Ranthum, R. G. 1969. Distribution and food habits of several species of fish in Pool 19, Mississippi River.

M.S. Thesis, Iowa State University, Ames. 207 pp.

Reice, S. R., and M. Wohlenberg. 1992. Monitoring freshwater benthic macroinvertebrates and benthic

processes: Measures for assessment of ecosystem health. Pages 287–305 in Freshwater biomonitoring

and benthic macroinvertebrates, D. M. Rosenberg and V. H. Resh, editors. Chapman and Hall, New York.
12

Rosenberg, D. M., and V. H. Resh. 1993. Freshwater biomonitoring and benthic macroinvertebrates.

Chapman and Hall, New York. 

Sauer, J. 1996. Annual status report: 1992 macroinvertebrate sampling. National Biological Service,

Environmental Management Technical Center, Onalaska, Wisconsin, February 1996. LTRMP 96-P001.

18 pp. + Appendix A (NTIS # PB96-158860)

Sauer, J. S. 1997a. Annual status report, 1993: Macroinvertebrate sampling. U.S. Geological Survey,

Environmental Management Technical Center, Onalaska, Wisconsin, February 1997. LTRMP 97-P001.

17 pp. (NTIS #PB97-153662)

Sauer, J. 1997b. Annual status report, 1994: Macroinvertebrate sampling. U.S. Geological Survey,

Environmental Management Technical Center, Onalaska, Wisconsin, February 1997. LTRMP 97-P002.

19 pp. (NTIS #PB97-153670)

Sauer, J. 1997c. Annual status report, 1995: Macroinvertebrate sampling. U.S. Geological Survey,

Environmental Management Technical Center, Onalaska, Wisconsin, April 1997. LTRMP 97-P003.

18 pp. (NTIS #PB97-159719)

Sauer, J. 1997d. Annual status report, 1996: Macroinvertebrate sampling. U.S. Geological Survey,

Environmental Management Technical Center, Onalaska, Wisconsin, April 1997. LTRMP

97-P004. 18 pp.

Steingraber, M. T., and J. G. Wiener. 1995. Bioassessment of contaminant transport and distribution in

aquatic ecosystems by chemical analysis of burrowing mayflies (Hexagenia). Regulated Rivers: Research

& Management 11:201–209.

Thiel, P. A., and J. S. Sauer. 1995. Long Term Resource Monitoring Program procedures: Macroinvertebrate

monitoring. National Biological Service, Environmental Management Technical Center, Onalaska,

Wisconsin, August 1995. LTRMP 95-P002-2. 9 pp. + Appendixes A–G

Thompson, D. 1973. Feeding ecology of diving ducks on Keokuk Pool, Mississippi River. Journal of

Wildlife Management 37:367–381.

Tucker, J. K. 1995a. Windrow formation of two snails (Families Viviparidae and Pleuroceridae) colonized

by the exotic zebra mussel, Dreissena polymorpha. Journal of Freshwater Ecology 9:85–86.

Tucker, J. K. 1995b. Colonization of unionid bivalves by the zebra mussel, Dreissena polymorpha, in

Pool 26 of the Mississippi River. Journal of Freshwater Ecology 9:129–134.

U.S. Fish and Wildlife Service. 1993. Operating Plan for the Upper Mississippi River System Long Term

Resource Monitoring Program. Environmental Management Technical Center, Onalaska, Wisconsin,

Revised September 1993. EMTC 91-P002R. 179 pp. (NTIS #PB94-160199)

Wilcox, D. B. 1993. An aquatic habitat classification system for the Upper Mississippi River System.

U.S. Fish and Wildlife Service, Environmental Management Technical Center, Onalaska, Wisconsin, May

1993. EMTC 93-T003. 9 pp. + Appendix A (NTIS # PB93-208981)
13

Wilson, D. M., T. J. Naimo, J. G. Weiner, R. V. Anderson, M. B. Sandheinrich, and R. E. Sparks. 1995.

Declining populations of the fingernail clam Musculium transversum in the Upper Mississippi River.

Hydrobiologia 304:209–220. 

Table 1. Macroinvertebrate random sample sites by study area and aquatic area—parentheses indicate numbers of

historical (fixed) sites.

Study area and floodplain Contiguous channel

year shallow backwater Impounded Side channel border

Contiguous Main

a

Pool 4

1992 22 (3) 25 24 (1) 25 25

1993 S 57 (3) 44 (1) 10 10

1994 S 57 (3) 44 (1) 10 10

1995 S 57 (3) 44 (1) 10 10

b

Pool 8

1992 24 (1) 23 (2) 14 (11) 23 (2) 25

1993 S 34 49 (11) 19 (2) 10

1994 S 34 49 (11) 19 (2) 10

1995 S 34 49 (11) 19 (2) 10

Pool 13

1992 25 23 (2) 24 (1) 20 (4) 25

1993 S 43 (2) 46 (1) 14 (4) 15

1994 S 43 (2) 46 (1) 14 (4) 15

1995 S 43 (2) 46 (1) 14 (4) 15

Pool 26

1992 S 30 31 29 (3) 27 (4)

1993 S 40 27 34 (3) 17 (4)

1994 S 40 27 34 (3) 17 (4)

1995 S 40 27 34 (3) 17 (4)

Open River

1992 S S S 32 (16) 46 (2)

1993 S S S 64 (16) 43 (2)

1994 S S S 64 (16) 43 (2)

1995 S S S 64 (16) 43 (2)

La Grange Pool

1992 S 23 (18) S 35 (7) 41 (1)

1993 S 22 (18) S 35 (7) 40 (1)

1994 S 22 (18) S 35 (7) 40 (1)

1995 S 22 (18) S 35 (7) 40 (1)

CFS was reclassified into other aquatic areas in 1993. a

Impounded for Pool 4 is defined as Lake Pepin. b
14
15

Table 2. Sampling dates for macroinvertebrate sampling.

Sampling period

Study area and year Starting date Ending date

Pool 4

1992 June 13 June 30

1993 May 3 May 14

1994 May 2 May 10

1995 May 9 May 11

Pool 8

1992 June 15 June 26

1993 May 24 June 10

1994 May 23 June 6

1995 May 22 June 2

Pool 13

1992 June 2 June 23

1993 April 12 June 1

1994 May 10 June 1

1995 May 11 May 19

Pool 26

1992 June 2 June 26

1993 April 12 June 10

1994 May 10 May 31

1995 May 11 May 19

Open River

1992 June 1 June 12

1993a

1994 April 4 April 12

1995 April 3 April 17

La Grange Pool

1992 June 8 June 24

1993 April 28 May 12

1994 May 2 May 12

1995 May 1 May 10

Not sampled because of flooding. a

Table 3. Results of analysis of covariance on weighted pool/reachwide means with year, study area, and

their interactions as independent variables. Those independent variables shown with an * significantly (P < 0.05)

influenced the dependent variables. 

Dependent variables

Independent 

variable Ephemeroptera Sphaeriidae Chironomidae

Year P = 0.89 P = 0.79 P = 0.52

Study area *P = 0.0001 *P = 0.0095 *P = 0.0341

Year*study area P = 0.11 P = 0.53 P = 0.13
16

Table 4. Estimated mean number of Corbicula fluminea and zebra mussels per square meter by year and study area,

weighted by areas of strata. Numbers in parentheses are ±1 standard error. N = sample number.

Study area and year Corbicula fluminea Zebra mussels

 (N) (m ) (m )

-2 -2

Pool 4

1992 (122) 0.3 (±0.03) S 

1993 (121) 0 (±0.0) S 

1994 (126) 0.1 (±0.1) S 

1995 (120) 0 (±0.0) 27.2 (±27.2)

Pool 8

1992 (109) 0 (±0.0) S 

1993 (109) 0 (±0.0) S 

1994 (110) 0 (±0.0) S 

1995 (109) 0 (±0.0) 0.2 (±0.2)

Pool 13

1992 (118) 0 (±0.0) S 

1993 (119) 0.2 (±0.2) S 

1994 (125) 0 (±0.0) S 

1995 (118) 0 (±0.0) 10.1 (±6.8)

Pool 26

1992 (117) 2 (±1.1) S 

1993 (66) 0 (±0.0) S 

1994 (124) 0.7 (±0.7) S 

1995 (69) S S

a a 

Open Riverb

1992 (92) 1 (±0.6) S 

1994 (84) 2 (±1.2) S 

1995 (112) 2 (±1.1) 2.4 (±2.0)

La Grange Pool

1992 (102) 0.4 (±0.4) S 

1993 (98) 0 (±0.0) S 

1994 (126) 10 (±2.9) S 

1995 (98) 1 (±0.7) 9.0 (±9.0)

No estimated mean densities were calculated for Pool 26 in 1995; field crews were not able to sample certain sites because of high a

water.

No macroinvertebrate monitoring was done in the Open River in 1993 because of high water. b
17

Table 5. Reachwide estimated mean number of Ephemeroptera, Sphaeriidae, and Chironomidae per square meter by

year and study area, weighted by areas of strata. Numbers in parentheses are ±1 standard error. N = sample number.

Study area and year Ephemeroptera Sphaeriidae Chironomidae

 (N) (m ) (m ) (m )

-2 -2 -2

Pool 4

1992 (122) 59 (±18.2) 47 (±18.5) S

1993 (121) 128 (±36.2) 74 (±10.8) 317 (±39.0)

1994 (126) 203 (±50.0) 88 (±12.2) 184 (±32.5)

1995 (120) 178 (±35.9) 61 (±13.3) 81 (±13.9)

Pool 8

1992 (109) 51 (±24.6) 15 (±11.4) S

1993 (109) 118 (±40.9) 22 (±11.0) 50 (±9.4)

1994 (110) 86 (±27.6) 11 (±5.0) 27 (±15.8)

1995 (109) 55 (±14.2) 6 (±3.0) 11 (±3.9)

Pool 13

1992 (118) 120 (±30.5) 84 (±27.6) S

1993 (119) 155 (±39.3) 2,596 (±494.3) 509 (±94.8)

1994 (125) 194 (±35.8) 594 (±156.5) 75 (±34.1)

1995 (118) 182 (±51.7) 276 (±81.9) 40 (±9.4)

Pool 26

1992 (117) 21 (±9.5) 15 (±9.4) S

1993 (66) 7 (±1.9) 1 (±0.5) 10 (±2.1)

1994 (124) 21 (±6.3) 5 (±2.9) 14 (±7.7)

1995 (69) S S S

a

Open River

1992 (92) 22 (±12.0) 5 (±3.4) S

1993 S S S

b

1994 (84) 19 (±8.6) 1 (±0.5) 8 (±3.6)

1995 (112) 12 (±5.5) 0 (±0.0) 14 (±5.0)

La Grange Pool

1992 (102) 13 (±6.3) 4 (±2.4) S

1993 (98) 11 (±4.8) 17 (±9.5) 52 (±14.3)

1994 (126) 27 (±8.5) 51 (±12.5) 57 (±9.9)

1995 (98) 6 (±3.5) 15 (±8.2) 32 (±12.1)

No estimated reach wide densities since sampling was not completed because of flooding. a

Not sampled because of flooding. b
18

Table 6. Mean number of organisms per square meter by study area and aquatic area with all years combined. Numbers in parentheses below target organisms are

±1 standard error. N = sample number. BWC = contiguous backwaters, MCB = main chanel borders, IMP = impounded areas, SC = side channels, and TDL = tributary

delta lake.

Study and year Ephemeroptera Sphaeriidae Chironomidae Corbicula sp. Zebra mussels

area (N) (m ) (m ) (m ) (m ) (m )

Aquatic area

-2 -2 -2 -2 -2

Pool 4 BWC

1992 (25) 116.2 (±35.9) 25.4 (±8.7) S 0.0 (±0.0) S

1993 (57) 74.2 (±18.4) 12.8 (±2.9) 202.8 (±32.2) 0.0 (±0.0) S 

1994 (60) 103.8 (±20.7) 22.8 (±5.8) 233.0 (±61.2) 0.3 (±0.3) S 

1995 (56) 55.6 (±12.6) 8.2 (±2.6) 116.1 (±16.5) 0.0 (±0.0) 0.7 (±0.7)

a b 

MCB

1992 (25) 31.5 (±27.6) 15.4 (±9.2) S 0.8 (±0.8) S 

1993 (10) 1.9 (±1.9) 1.9 (±1.9) 40.4 (±34.2) 0.0 (±0.0) S 

1994 (10) 25.0 (±25.0) 0.0 (±0.0) 23.1 (±21.0) 0.0 (±0.0) S 

1995 (11) 57.7 (±57.7) 7.0 (±3.9) 10.5 (±6.0) 0.0 (±0.0) 17.5 (±17.5)

SC

1992 (24) 29.6 (±10.7) 7.2 (±3.4) S 0.0 (±0.0) S 

1993 (10) 28.8 (±20.5) 1.9 (±1.9) 86.5 (±50.3) 0.0 (±0.0) S 

1994 (10) 103.8 (±101.7) 1.9 (±1.9) 134.6 (±80.2) 0.0 (±0.0) S 

1995 (10) 21.2 (±12.3) 11.5 (±9.6) 11.5 (±5.1) 0.0 (±0.0) 0.0 (±0.0)

TDL

1992 (24) 48.1 (±14.6) 58.4 (±23.5) S 0.0 (±0.0) S 

1993 (44) 149.9 (±42.0) 94.4 (±13.3) 364.1 (±38.4) 0.0 (±0.0) S 

1994 (46) 235.4 (±52.4) 111.2 (±14.7) 178.5 (±21.6) 0.0 (±0.0) S 

1995 (43) 218.2 (±40.3) 77.4 (±16.0) 79.2 (±13.9) 0.0 (±0.0) 34.9 (±34.9)

Pool 8 BWC

1992 (23) 42.6 (±19.3) 6.7 (±3.7) S 0.0 (±0.0) S 

1993 (29) 149.2 (±65.2) 41.1 (±31.1) 39.8 (±10.5) 0.0 (±0.0) S 

1994 (32) 105.2 (±30.0) 14.4 (±8.0) 38.5 (±11.0) 0.0 (±0.0) S 

1995 (31) 62.0 (±19.5) 9.9 (±6.3) 12.2 (±3.6) 0.0 (±0.0) 0.0 (±0.0)
Table 6. Continued

Study and year Ephemeroptera Sphaeriidae Chironomidae Corbicula sp. Zebra mussels

area (N) (m ) (m ) (m ) (m ) (m )

Aquatic area

-2 -2 -2 -2 -2

19

IMP

1992 (14) 46.7 (±26.3) 17.9 (±15.0) S 0.0 (±0.0) S 

1993 (52) 123.5 (±25.4) 20.7 (±3.9) 66.2 (±7.6) 0.0 (±0.0) S 

1994 (49) 110.7 (±34.6) 12.2 (±4.4) 12.2 (±6.6) 0.0 (±0.0) S 

1995 (49) 82.4 (±16.3) 7.5 (±2.2) 13.3 (±3.5) 0.0 (±0.0) 0.0 (±0.0)

MCB

1992 (25) 14.6 (±6.3) 0.8 (±0.8) S 0.0 (±0.0) S 

1993 (10) 0.0 (±0.0) 3.8 (±2.6) 9.6 (±7.7) 0.0 (±0.0) S 

1994 (10) 1.9 (±1.9) 0.0 (±0.0) 3.8 (±2.6) 0.0 (±0.0) S 

1995 (10) 1.9 (±1.9) 3.8 (±3.8) 0.0 (±0.0) 0.0 (±0.0) 0.0 (±0.0)

SC

1992 (23) 10.9 (±6.3) 0.8 (±0.8) S 0.0 (±0.0) S 

1993 (18) 111.1 (±61.4) 7.5 (±3.5) 41.7 (±12.8) 0.0 (±0.0) S 

1994 (19) 61.7 (±36.1) 10.1 (±4.5) 56.7 (±49.6) 0.0 (±0.0) S 

1995 (19) 8.1 (±7.1) 0.0 (±0.0) 9.1 (±7.1) 0.0 (±0.0) 1.0 (±1.0)

Pool 13 BWC

1992 (23) 36.0 (±14.1) 109.5 (±50.1) S 0.0 (±0.0) S 

1993 (41) 93.8 (±24.7) 118.2 (±36.2) 264.1 (±59.2) 0.0 (±0.0) S 

1994 (48) 392.2 (±60.2) 176.3 (±39.3) 143.8 (±43.3) 0.0 (±0.0) S 

1995 (44) 153.8 (±32.4) 117.1 (±29.2) 93.1 (±18.0) 0.0 (±0.0) 1.3 (±1.0)

IMP

1992 (24) 199.5 (±45.2) 81.7 (±16.1) S 0.0 (±0.0) S 

1993 (45) 221.4 (±43.5) 6047.9 (±1104.7) 939.3 (±132.3) 0.4 (±0.4) S 

1994 (47) 137.9 (±33.3) 1270.5 (±337.9) 43.4 (±33.0) 0.0 (±0.0) S 

1995 (48) 238.4 (±52.8) 536.6 (±154.6) 18.0 (±6.9) 0.0 (±0.0) 16.0 (±9.2)

MCB

1992 (25) 34.6 (±15.2) 10.0 (±5.0) S 0.0 (±0.0) S 

1993 (15) 64.1 (±47.8) 175.6 (±128.9) 189.7 (±135.1) 0.0 (±0.0) S 

1994 (15) 1.3 (±1.3) 2.6 (±1.7) 50.0 (±39.8) 0.0 (±0.0) S 

1995 (15) 110.3 (±87.7) 59.0 (±37.3) 2.6 (±1.7) 0.0 (±0.0) 17.9 (±15.3)
Table 6. Continued

Study and year Ephemeroptera Sphaeriidae Chironomidae Corbicula sp. Zebra mussels

area (N) (m ) (m ) (m ) (m ) (m )

Aquatic area

-2 -2 -2 -2 -2

20

SC

1992 (21) 54.0 (±25.1) 80.6 (±43.3) S 0.0 (±0.0) S 

1993 (18) 191.2 (±56.0) 157.1 (±48.6) 32.1 (±15.6) 0.0 (±0.0) S 

1994 (15) 23.1 (±11.1) 43.6 (±20.8) 7.7 (±3.7) 0.0 (±0.0) S 

1995 (11) 134.6 (±62.3) 47.2 (±24.5) 1.7 (±1.7) 0.0 (±0.0) 5.2 (±5.2)

Pool 26 BWC

1992 (30) 0.6 (±0.6) 3.2 (±2.1) S 0.0 (±0.0) S 

1993 (32) 37.9 (±10.4) 7.8 (±3.0) 81.1 (±16.6) 0.0 (±0.0) S 

1994 (40) 151.9 (±32.0) 13.5 (±6.8) 88.0 (±25.6) 0.5 (±0.5) S 

1995 (41) 5.2 (±2.4) 0.9 (±0.7) 46.0 (±17.6) 0.0 (±0.0) 0.0 (±0.0)

IMP

1992 (31) 47.8 (±23.2) 94.9 (±39.1) S 7.4 (±4.2) S 

1993 (27) 121.1 (±36.8) 22.1 (±9.4) 136.0 (±26.4) 0.0 (±0.0) S 

1994 (27) 118.2 (±36.4) 40.6 (±23.3) 45.6 (±14.7) 0.0 (±0.0) S 

1995 (27) 21.4 (±11.2) 0.7 (±0.7) 31.3 (±15.0) 0.0 (±0.0) 3.6 (±2.9)

MCB

1992 (27) 21.4 (±9.4) 17.1 (±12.0) S 2.1 (±1.6) S 

1993 (3) 0.0 (±0.0) 0.0 (±0.0) 0.0 (±0.0) 0.0 (±0.0) S 

1994 (19) 5.1 (±2.9) 4.0 (±2.8) 9.1 (±8.1) 1.0 (±1.0) S 

1995 S S S S S 

c

SC

1992 (29) 21.2 (±9.8) 1.3 (±0.9) S 0.0 (±0.0) S 

1993 (4) 0.0 (±0.0) 0.0 (±0.0) 0.0 (±0.0) 0.0 (±0.0) S 

1994 (38) 9.1 (±3.7) 0.0 (±0.0) 1.5 (±0.9) 0.0 (±0.0) S 

1995 (1) 0.0 0.0 (±0.0) 0.0 0.0 (±0.0) 0.0 (±0.0)

Open River MCB

1992 (46) 18.4 (±10.8) 3.8 (±3.0) S 0.8 (±0.6) S 

1993 S S S S S 

1994 (35) 20.9 (±9.4) 0.5 (±0.5) 8.2 (±3.9) 1.6 (±1.2) S 

1995 (42) 11.9 (±5.8) 0.0 (±0.0) 10.1 (±4.1) 1.8 (±1.1) 2.7 (±2.3)

d
Table 6. Continued

Study and year Ephemeroptera Sphaeriidae Chironomidae Corbicula sp. Zebra mussels

area (N) (m ) (m ) (m ) (m ) (m )

Aquatic area

-2 -2 -2 -2 -2

21

SC

1992 (46) 47.7 (±20.3) 14.2 (±6.9) S 1.7 (±1.0) S 

1993 S S S S S 

1994 (49) 7.1 (±2.8) 0.4 (±0.4) 3.9 (±1.6) 2.4 (±1.1) S 

1995 (70) 10.4 (±3.5) 0.0 (±0.0) 41.5 (±12.1) 1.6 (±0.9) 0.0 (±0.0)

La Grange BWC

Pool 1992 (23) 20.9 (±9.9) 4.2 (±3.0) S 0.8 (±0.8) S 

1993 (25) 16.9 (±7.0) 13.8 (±8.0) 91.5 (±22.4) 0.0 (±0.0) S 

1994 (42) 44.0 (±13.0) 39.4 (±13.4) 54.0 (±9.6) 0.5 (±0.5) S 

1995 (24) 1.6 (±1.1) 6.4 (±3.0) 54.5 (±24.1) 0.0 (±0.0) 0.0 (±0.0)

MCB

1992 (41) 8.0 (±4.1) 2.8 (±1.7) S 0.0 (±0.0) S 

1993 (38) 5.6 (±3.2) 17.2 (±9.1) 27.3 (±9.6) 0.0 (±0.0) S 

1994 (42) 11.4 (±4.9) 57.2 (±12.0) 57.7 (±9.9) 16.5 (±4.6) S 

1995 (39) 7.9 (±5.2) 19.7 (±11.5) 14.8 (±3.8) 2.5 (±1.3) 15.8 (±15.8)

SC

1992 (38) 8.6 (±3.0) 10.6 (±6.3) S 1.0 (±0.7) S 

1993 (35) 22.0 (±7.1) 48.9 (±27.8) 26.4 (±5.2) 0.0 (±0.0) S 

1994 (42) 67.3 (±14.7) 61.8 (±11.4) 74.6 (±13.7) 11.7 (±3.0) S 

1995 (35) 12.6 (±3.9) 33.0 (±11.7) 50.0 (±14.0) 0.5 (±0.5) 1.6 (±1.6)

Chironomidae not sampled in 1992. a

Zebra mussels not sampled in 1992–1994. b

Pool 26, MCB not sampled in 1995 because of flooding. c

Open River not sampled in 1993 because of flooding. d
22

Table 7. Mean number of organisms per square meter by study area and substrate type. Numbers in parentheses below

target organisms are ±1 standard error. N = sample number. 

Study Predominant Ephemeroptera Sphaeriidae Chironomidae

area substrate (N) (m ) (m ) (m )

-2 -2 -2

Pool 4 Hard clay (6) 16.0 (±16.0) 6.4 (±4.1) 72.1 (±6.0) 

Silt clay (226) 170.9 (±17.0) 57.5 (± 5.8 ) 164.9 (±21.4)

Silt clay w/sand (93) 109.6 (±18.5) 48.8 (± 7.4 ) 265.0 (±27.4)

Sand w/silt clay (36) 23.0 (±8.6) 7.5 (±2.7) 273.5 (±65.5)

Sand (113) 1.9 (±0.6) 6.0 (±2.0) 63.9 (±15.8)

Gravel rock (13) 1.5 (±1.5) 0.0 (±0.0) 23.7 (±14.5)

Pool 8 Hard clay (18) 84.4 (±83.3) 17.1 (±6.2) 22.4 (±10.0)

Silt clay (142) 159.3 (±18.7) 17.5 (±3.4) 35.8 (±5.6)

Silt clay w/sand (104) 66.4 (±13.2) 14.8 (±8.8) 49.0 (±14.3)

Sand w/silt clay (72) 15.0 (±5.2) 10.7 (±2.2) 23.3 (±5.1)

Sand (100) 2.7 (±1.1) 1.0 (±0.4) 5.7 (±2.0)

Gravel rock (1) 134.6 (±0.0) 0.0 19.2

Pool 13 Hard clay (6) 22.4 (±12.6) 2,717.9 (±2,660.4) 22.4 (±18.9)

Silt clay (253) 248.1 (±19.6) 1,089.2 (±217.3) 260.0 (±38.9)

Silt clay w/sand (104) 118.0 (±20.9) 836.5 (±274.7) 236.7 (±64.0)

Sand w/silt clay (50) 5.8 (±1.9) 245.0 (±92.2) 110.8 (±48.6)

Sand (63) 2.1 (±1.4) 29.3 (±17.1) 0.8 (±0.6)

Gravel rock (4) 0.0 (±0.0) 9.6 (±9.6) 0.0

Pool 26 Hard clay (32) 37.3 ( ±21.8) 2.4 (1.7) 29.8 (±13.0)

Silt clay (213) 64.1 (±9.4) 23.8 (±6.8) 77.6 (±9.8)

Silt clay w/sand (33) 61.8 ±23.9) 28.0 (±12.2) 30.8 (±25.4)

Sand w/silt clay (9) 6.4 (±4.5) 4.3 (±4.3) 6.4 (±4.5)

Sand (82) 7.0 (±3.1) 0.5 (±0.3) 0.0 (±0.0)

Gravel rock (7) 22.0 (±19.0) 0.0 (±0.0) 6.4 (±6.4)

Open River Hard clay (20) 11.5 (±3.2) 0.0 (±0.0) 7.5 (±3.9)

Silt clay (76) 60.0 (±14.3) 9.1 (±4.2) 56.9 (±16.7)

Silt clay w/sand (28) 7.6 (±4.0) 4.8 (±4.8) 41.4 (±12.5)

Sand w/silt clay (14) 5.5 (±4.2) 0.0 (±0.0) 0.0 (±0.0)

Sand (115) 1.8 (±1.4) 0.3 (±0.2) 3.6 (±1.4)

Gravel rock (35) 1.6 (±0.9) 0.0 (±0.0) 2.7 (±2.1)

La Grange Pool Hard clay (28) 2.1 (±1.1) 27.5 (±6.5) 48.1 (±18.1)

Silt clay (225) 30.9 (±4.3) 35.0 (±6.4) 56.8 (±6.2)

Silt clay w/sand (89) 13.8 (±3.3) 29.2 (±5.9) 50.3 (±7.9)

Sand w/silt clay (24) 5.6 (±5.6) 18.4 (±7.8) 26.4 (±8.0)

Sand (56) 1.7 (±0.9) 6.9 (±4.3) 31.2 (±11.3)

Gravel rock (–) 0.0 (±0.0) 0.0 (±0.0) 0.0 (±0.0)
Pool 4

Pool 8

Pool 13

La Grange Pool

Pool 26

Open River

4%

5%

16% 11%

64%

7%

21% 16%

41%

15%

10%

9%

25%

33% 23%

44%

20%

5% 2%

29%

51%

7%

42%

22%

10% 2%

66%

Main channel border

Side channel

Contiguous backwater

Impounded

Non-sampled aquatic area

Lake Pepin

Illinois river mile 

157.8-80.2

La Grange

River mile

29-85

Open River

River mile 

203-241.5

Pool 26

River mile 

753-797

Pool 4

River mile 

679-703

Pool 8

River mile 

522.7-557

Pool 13

23

Figure 1. Long Term Resource Monitoring Program study areas for macroinvertebrate sampling.

Figure 2. River miles and percentage of aquatic area in each study area.
1992 1993 1994 1995

0%

20%

40%

60%

80%

100%

1992 1993 1994 1995

0%

20%

40%

60%

80%

100%

1992 1993 1994 1995

0%

20%

40%

60%

80%

100%

1992 1993 1994 1995

0%

20%

40%

60%

80%

100%

1992 1993 1994 1995

0%

20%

40%

60%

80%

100%

1992 1993 1994 1995

0%

20%

40%

60%

80%

100%

Pool 4

Pool 8

Pool 13

Pool 26

Open River

La Grange Pool

1

2

Sphaeriidae

Chironomidae

Corbicula fluminea

Dreissena polymorpha

Ephemeroptera

24

Figure 3. Frequency of target organisms in samples, 1992–1995.

Figure 4. Percent composition of target organisms: 1 = Zebra mussel sampling initiated in 1995, 2 = Midge sampling

initiated in 1993.
25

Figure 5. Estimated mean number of Ephemeroptera per square meter by study area, weighted by area of strata. Bars

indicate ±1 standard error.
26

Figure 6. Estimated mean number of Sphaeriidae per square meter by study area, weighted by area of strata. Bars

indicate ±1 standard error.
27

Figure 7. Estimated mean number of Chironomidae per square meter by study area, weighted by area of strata. Bars

indicate ±1 standard error.
A-1

Appendix. Macroinvertebrate Collection Sheet
REPORT DOCUMENTATION PAGE Form Approved

OMB No. 0704-0188

Public reporting burden for this collection of information is estimated to average 1 hour per response, including the time for reviewing instructions, searching existing

data sources, gathering and maintaining the data needed, and completing and reviewing the collection of information. Send comments regarding this burden estimate or

any other aspect of this collection of information, including suggestions for reducing this burden, to Washington Headquarters Services, Directorate for Information

Operations and Reports, 1215 Jefferson Davis Highway, Suite 1204, Arlington, VA 22202-4302, and to the Office of Management and Budget, Paperwork Reduction

Project (0704-0188), Washington, D.C. 20503

1. AGENCY USE ONLY (Leave blank) 2. REPORT DATE 3. REPORT TYPE AND DATES COVERED

April 1998

4. TITLE AND SUBTITLE 5. FUNDING NUMBERS

Temporal analyses of select macroinvertebrates in the Upper Mississippi River System, 1992–1995

6. AUTHOR(S)

Jennifer S. Sauer

7. PERFORMING ORGANIZATION NAME AND ADDRESS 8. PERFORMING ORGANIZATION

U.S. Geological Survey 

Environmental Management Technical Center

575 Lester Avenue

Onalaska, Wisconsin 54650

 REPORT NUMBER

9. SPONSORING/MONITORING AGENCY NAME(S) AND ADDRESS(ES) 10. SPONSORING/MONITORING

U.S. Geological Survey 

Environmental Management Technical Center 98-T001

575 Lester Avenue

Onalaska, Wisconsin 54650

 AGENCY REPORT NUMBER

11. SUPPLEMENTARY NOTES

12a. DISTRIBUTION/AVAILABILITY STATEMENT 12b. DISTRIBUTION CODE

Release unlimited. Available from National Technical Information Service, 5285 Port Royal Road, Springfield, VA 22161 

(1-800-553-6847 or 703-487-4650. Available to registered users from the Defense Technical Information Center, Attn: 

Help Desk, 8725 Kingman Road, Suite 0944, Fort Belvoir, VA 22060-6218 (1-800-225-3842 or 703-767-9050).

13. ABSTRACT (Maximum 200 words)

The annual variability in mayflies (Ephemeroptera), fingernail clams (Sphaeriidae), and midges (Chironomidae) in six study areas of the Upper Mississippi River System

from 1992 to 1995 was examined. Spatial distribution is also discussed for these organisms along with the Asiatic clam (Corbicula fluminea) and the zebra mussel

(Dreissena polymorpha). Sample allocation within each reach was based on a stratified random design where strata were aquatic areas. No significant linear trends

across years were found in estimated reachwide mean number of organisms. However, the overall test for differences in intercepts among study areas was statistically

significant (P < 0.05) for mayflies, fingernail clams, and midges. No statistical difference in trend slopes among reaches were detected. In 1993, the estimated mean density

of fingernail clams in Pool 13 was 35 times that found in other study areas. Overall, impounded aquatic areas and silt clay substrates supported higher numbers of the

select macroinvertebrates. 

14. SUBJECT TERMS 15. NUMBER OF PAGES

Asiatic clam (Corbicula fluminea) benthic aquatic macroinvertebrates, Corbicula, fingernail claims (Sphaeriidae), mayflies 26 pp. + Appendix

(Ephemeroptera), midges (Chironomidae), Mississippi River, zebra mussel (Dreissena polymorpha)

16. PRICE CODE

17. SECURITY CLASSIFICATION 18. SECURITY CLASSIFICATION 19. SECURITY CLASSIFICATION 20. LIMITATION OF ABSTRACT

 OF REPORT OF THIS PAGE OF ABSTRACT

Unclassified Unclassified Unclassified
The Long Term Resource Monitoring Program (LTRMP) for the Upper Mississippi

River System was authorized under the Water Resources Development Act of 1986 as 

an element of the Environmental Management Program. The mission of the LTRMP

is to provide river managers with information for maintaining the Upper Mississippi 

River System as a sustainable large river ecosystem given its multiple-use character.

The LTRMP is a cooperative effort by the U.S. Geological Survey, the U.S. Army Corps

of Engineers, and the States of Illinois, Iowa, Minnesota, Missouri, and Wisconsin.