1

NOAA Technical Memorandum GLERL-122

ABUNDANCE, BIOMASS, AND SPECIES COMPOSITION OF BENTHIC 

MACROINVERTEBRATE POPULATIONS IN SAGINAW BAY, LAKE HURON, 1987-96

Thomas ˇ. Nalepa1, David L. ˇanslow1, Margaret B. Lansing1, Gregory A. Lang1, Mark ˇord2, 

Gerald Gostenik2, and David J. Hartson2

1

NOAA, Great Lakes Environmental Research Laboratory, Ann Arbor, MI 48105

2

Cooperative Institute for Limnology and Ecosystems Research, GLERL/Univ. of Michigan, Ann Arbor, MI

Great Lakes Environmental Research Laboratory

Ann Arbor, Michigan 

May 2002

UNITED STATES

DEPARTMENT OF COMMERCE

Donald Evans

Secretary

NATIONAL OCEANIC AND

ATMOSPHERIC ADMINISTRATION

Conrad C. Lautenbacher, Jr.

Administrator
2 

NOTICE

Mention of a commercial company or product does not constitute an endorsement 

by the NOAA. Use of information from this publication concerning proprietary 

products or the tests of such products for publicity or advertising purposes is not 

authorized. This is GLERL Contribution No. 1241.

This publication is available as a PDˇ file and can be downloaded from GLERL’s 

web site: www.glerl.noaa.gov. Hard copies can be requested from GLERL, 

Information Services, 2205 Commonwealth Blvd., Ann Arbor, MI 48105.

pubs.glerl@noaa.gov.
3

Table of Contents

1. INTRODUCTION .............................................................................................................................................5

2. DESCRIPTION Oˇ STUDY SITE......................................................................................................................5

3. METHODS ..........................................................................................................................................................7

 3.1 Sampling Dates, Station Locations, and ˇield Procedures..........................................................................7

 3.2 Laboratory Procedures ................................................................................................................................7

 3.3 Biomass Determination ...............................................................................................................................8

4. RESULTS ............................................................................................................................................................8

 4.1 Data Presentation.........................................................................................................................................8

 4.2 Sampler Comparisons..................................................................................................................................9

5. HISTORIC TRENDS IN TOTAL DENSITY...................................................................................................11

6. REˇERENCES ..................................................................................................................................................13

Appendix A. The abundance (number per grab) of all taxa collected between 1987 and 1996 

 with the Ponar grab. Variables in the appendix include year, season (spring=1, summer=2, fall=3), 

 station, replicate number, and taxa..................................................................................................................32

Figures

 

ˇigure 1. Location of sampling sites in Saginaw Bay, 1987-96. Dashed line separates the inner bay 

 from the outer bay. Depth contours are given in meters. • = sampled in 1987 and 1988; 

 O• = sampled in 1987-96; X = sampled in 1991-96 for Dreissena using SCUBA divers........................6

ˇigure 2. Mean total density (no./m2 x 103) of benthic macroinvertebrates in Saginaw Bay, 1987-88 ..............10

ˇigure 3. Mean (± SE) total density of benthic macroinvertebrates in inner Saginaw Bay from

 various surveys. The standard error represents between station variation. Densities in

 1987-96 are from this study..................................................................................................................12

Tables

Table 1. Location, water depth, and dominant substrate type at each of the sites sampled in Saginaw Bay, 

 Lake Huron. Samples for Dreissena in 1991-96 were taken by divers using SCUBA ..........................16 

Table 2. Stations sampled during each sampling period, 1987-96 .......................................................................17 

Table 3. List of taxa collected in Saginaw Bay, 1987-96. The 4-letter code identifies each taxa in 

 Appendix 1. Also given is the length-weight relationship used to determine AˇDW biomass 

 for each taxa. The number in parenthesis refers to the equation used to determine the AˇDW 

 of that particular taxa. Length-weight relationships for Dreissena polymorpha are given in Table 4 ...18 

Table 4. Relationship between shell-length (SL) and ash free dry weight (AˇDW) for Dreissena 

 polymorpha in late summer/fall, 1991-96. The relationship was described by the linear 

 regression equation; LnAˇDW = a + bLnSL, where AˇDW is given in mg and SL is given in mm....22 
4 

Table 5. Mean (X + SE) annual density (no. per m2) of major macroinvertebrate groups at the 

 stations sampled over the entire 1987-96 period. The standard error (SE) was derived from 

 the mean density in the spring, summer, and fall (n=3) of each year. The group “Others” 

 includes Isopoda, Ephemeroptera, Hirudinea, Tricoptera, and Gastropoda...........................................23 

Table 6. Mean (X + SE) annual biomass (g AˇDW per m2) of major macroinvertebrate groups 

 (excluding Dreissena) at the stations sampled over the entire 1987-96 period. The standard 

 error (SE) was derived from the mean density in the spring, summer, and fall (n=3) of 

 each year. The group “Others” includes Isopoda, Ephemeroptera, Hirudinea, Tricoptera, 

 and Gastropoda .......................................................................................................................................26

Table 7. Mean (X + SE) annual density (no. per m2) of Dreissena polymorpha at sites in inner 

 and outer Saginaw Bay in 1991-96. Samples were collected in the fall of each year by 

 divers using SCUBA ..............................................................................................................................28

Table 8. Mean biomass (g AˇDW m-2) of Dreissena polymorpha at stations in inner and outer Saginaw 

 Bay in 1991-96. Samples were collected in the fall of each year by divers using SCUBA..................28

Table 9. Type of grab sampler and mesh size used in previous macroinvertebrate surveys 

 conducted in inner Saginaw Bay ............................................................................................................29

Table 10. Densities (X + SE) of the major benthic macroinvertebrate groups collected with the 

 Ponar and Peterson grabs in Saginaw Bay in 1987/88. The source of variation (SE) was 

 the mean density on each sampling date over the two-year period. The two samplers were 

 compared using a paired t-test after ln+1 transformation. Each sampling date was considered 

 an individual replicate. A conversion value (Ponar/Peterson) was determined only when 

 the difference between samplers was significant (P < 0.05).................................................................29

Table 11. Mean density (no./m2 + SE) of major benthic macroinvertebrate groups in 1987/88. 

 Stations in the inner bay were grouped by substrate (I, II, III), and stations in the outer bay 

 were grouped by depth (IV, V, VI). Differences between the groups for the inner and outer 

 bay were tested using ANOVA (ln +1 transformed). ns = not significantly different ........................30

Table 12. Density of major macroinvertebrate groups in previous surveys conducted in inner 

 Saginaw Bay. The value given in parenthesis is the density corrected to Ponar equivalents. 

 Correction factors are given in the text.................................................................................................31
5

Abundance, Biomass, and Species Composition of Benthic Macroinvertebrate

Populations in Saginaw Bay, Lake Huron, 1987-96.

T.ˇ. Nalepa, D.L. ˇanslow, M.B. Lansing, G.A. Lang, M. ˇord, 

G. Gostenik, and D.J. Hartson

1.0 INTRODUCTION

This technical report gives the basic results of benthic macroinvertebrate surveys conducted in Saginaw 

Bay between 1987 and 1996. Yearly surveys were conducted over this time period to assess trends in 

macroinvertebrate density, biomass, and species composition. When the surveys were initiated in 1987-88, the 

main objective was to assess the response of the benthic community to phosphorus abatement programs that were 

implemented in the mid-1970s. Improvements in water quality were reported after these programs (Bierman et 

al. 1984), and a two-year sampling program in 1987-88 was designed to determine if similar improvements were 

evident in the macroinvertebrate community. When the zebra mussel (Dreissena polymorpha) became established 

in the Great Lakes in 1988 (Hebert et al. 1989), sampling was resumed in 1990 and continued through 1996 

with the objective of assessing impacts of Dreissena. Dreissena colonized the bay in 1991 (Nalepa et al. 1995). 

Thus, the data collected during the time of this study can be divided into two distinct periods: post-phosphorus 

abatement/pre-Dreissena (1987-90) and post-Dreissena (1991-96). 

Data are presented in this report with little attempt at interpretation; detailed analysis and discussions of 

relevance will be provided in other publications. Rather, the purpose of this report is to provide the raw data and 

basic details of the sampling program, including station locations and characteristics, sampling methods, and 

laboratory procedures. In addition, results of a comparative study of two samplers, the Peterson and Ponar grabs, 

is presented. The former grab was used in benthic surveys conducted in the bay in the 1950s and 1960s, while the 

latter grab has been used since the early 1970s. The relative efficiency of these two grabs was examined to more 

accurately depict density trends from the 1950s to the present. 

2.0 DESCRIPTION OF STUDY SITE

Saginaw Bay is a shallow, well-mixed extension of the western shoreline of Lake Huron (ˇigure 1). The bay is 

21-42 km wide, about 82 km long, and has a drainage basin of about 21,000 km2. Total area of the bay is 2.77 

x 109 m2, and total water volume is 24.54 x 109 m3. The bay can be functionally divided into an inner and outer 

region by a line extending along its narrowest width (21 km) from Sand Point to Point Lookout (ˇigure 1). A 

broad shoal and several islands (Charity Islands) along this line provide a natural demarcation between the two 

regions. The outer bay can be differentiated from Lake Huron by a line from Pte. aux Barques to Au Sable point. 

Differences in physical and chemical features of the inner and outer bay regions are distinct (Beeton et al. 1967; 

Smith et al. 1977). The inner bay has a mean depth of 5.1 m, is nutrient-rich, and is heavily influenced by input 

from the Saginaw River, which accounts for over 70% of the total tributary flow into the bay. The outer bay has a 

mean depth of 13.7 m and is more influenced by the colder, nutrient-poor waters of Lake Huron. 

Circulation within the inner and outer bay is generally weak; currents average about 7 cm s-1 in the inner bay 

and about 11 cm s-1 in the outer bay (Danek and Saylor 1977). Exchange and flushing of water in the inner bay 

occurs when winds blow along the long axis of the bay (southwest/northeast). Dominant winds in the summer 

are from the southwest. Little exchange occurs when winds are perpendicular to the long axis (west/east). Most 

water exhange/flushing between the inner and outer bay occurs on the northern side of the bay within a deep 

channel between Point Lookout and Charity Island. Although some water may exit the inner bay along the 

southern shoreline, it is of minor significance because of the shallowness of the region (Danek and Saylor 1977). 
6 

N

10 Km

Charity

Island

5

5

5

10

10

20

30

40

50.0 5

10

4

4o00' 4

4o10' 4

3o50' 4

3o40' 84o00' 83o40' 83o20'

Sand Point

Point

Au Gres

Point

Lookout

Saginaw

River

6

2

58

68

4

108

14

15

168

7

5

18

22

16

25

26

278

30 31

13

35

11

10

19

20

23

24

45

50

53

55

57

27

x

x

x

x

x

x

x

x

28

43

Figure 1. Location of sampling sites in Saginaw Bay, 1987-96. Dashed line separates the inner bay from 

the outer bay. Depth contours are given in meters. • = sampled in 1987 and 1988 only; O• = sampled in 

1987-96; X = sampled in 1991-96 for Dreissena using SCUBA divers. 
7

ˇurthermore, preliminary results of Lagrangian current measurements in the outer bay during the summers of 

1992 and 1993 suggest that the flushing of inner bay waters into Lake Huron is episodic in nature (M. McCormick 

unpublished data).

Bottom substrates within the bay range from mostly cobble/rock to silt. The inner bay has a shallow sand bar that 

extends along the eastern side of the bay from the Saginaw River to Charity Island. Another sand bar extends 

along the western shoreline to Point Au Gres. Both sand bars have irregular areas of cobble with patches of 

gravel, pebbles, and varying amounts of overlying silt. The bars extend into the shorelines as extensive flats grade 

into marshes. Water depth between the two sand bars gradually increases to a maximum of 14 m. The proportion 

of fine-grained material gradually increases along this depth gradient as a function of sediment deposition 

(Robbins 1981). At depths greater than 6 m, the substrate consists of fine-grained material (silt and clay) and 

sediment deposition ranges from 0.04 to 0.70 g/cm2/yr (Robbins 1981). Based on areal estimates of substrate type 

given by Wood (1964) and Robbins (1981), we estimate that 70% of the bottom in the inner bay consists of sand, 

gravel, and cobble, and 30% consists of silt/mud.

In the outer bay, the east shore is rocky, as is the area around the Charity Islands. The western shore has extensive 

sandy areas, with rock and clay found near Point Lookout. Most of the offshore region of the outer bay has a 

bottom consisting of silty sand.

 

3.0 METHODS

3.1 Sampling Dates, Station Locations, and ˇield Procedures 

Samples for benthic macroinvertebrates were collected at 30 sites in 1987 and 1988, and at 10 sites in 1990-96 

(ˇigure 1). The exact location (longitude, latitude), water depth, and prevalent substrate type at each of the sites 

are given in Table 1. Samples were collected three times a year (spring, summer, and fall) except in 1996 when 

samples were collected only in summer and fall (Table 2). Because of poor weather conditions or mechanical 

failures, not all sites were sampled on each sampling date. One site (Station 28) was not sampled after summer 

1987. Each site sampled corresponded to a site that was sampled in an previous investigations within the bay. 

Decisions on which sites to re-sample were based on type of sampler used, detail of benthic data provided, and 

overall spatial coverage of the bay. In 1987 and 1988, triplicate samples were collected at each site with both 

a Ponar and a Peterson grab, but only the Ponar was used thereafter. Sampling area of the Ponar was 0.047 m2, 

while that of the Peterson was 0.069 m2. After collection, each replicate sample was washed from the grab into 

a large tub, and then into an elutriation device (Nalepa et al. 1985). The device was fitted with a sleeve made of 

0.5-mm mesh nitex. All collected material was washed through the sleeve and into a collection jar. The retained 

material was then preserved in 5% buffered formalin containing rose bengal stain.

Beginning in fall 1991 and continuing each fall through 1996, we took additional samples specifically for 

Dreissena at eight sites using SCUBA divers. These sites were mostly in areas with cobble (Stations 5, 6, 15, 19, 

27) that could not be effectively sampled with a grab sampler. Three of the eight sites were also sampled with 

the Ponar grab (Stations 13, 14, 16) (ˇigure 1). At each site, divers randomly placed a 0.25 or 0.5 m2 frame on 

the bottom and hand-collected all hard material within the frame area. After all material had been removed, the 

surface area within the frame was re-sampled using a diver-operated suction device fitted with a nitex net with 

0.5-mm openings (Winnell and Jude 1987). This procedure ensured that all loose mussels were included in the 

sample. Triplicate samples were randomly collected at each site, with divers moving 2-3 m between replicates. 

3.2 Laboratory Procedures

Material collected in the grab samplers and retained by the 0.5-mm sleeve was placed into a white enamel pan and 

organisms were picked, counted, and sorted into major groups (amphipods, oligochaetes, sphaeriids, chironomids, 

Dreissena, and others) with the aid of a 1.5x lighted magnifier lamp. When the number of organisms in a sample 
8 

was extremely large, the sample was proportionately split and only a portion picked and sorted. All organisms 

in the Ponar samples were identified to the lowest practical taxonomic level. Turbellarians and nematodes 

were observed in the samples but, since methods were not quantitative for these groups, their numbers were 

not recorded. ˇor oligochaetes, between 75-100 individuals in a replicate (proportionately split with a ˇolsom 

plankton splitter when numbers were high) were cleared in lactophenol before identification. Oligochaetes were 

mounted on microscope slides (in glycerine) and their images were then projected onto a sheet of paper using a 

microscope drawing tube and traced. Individuals were identified, and taxonomic designations placed alongside 

the respective traced image. Only individuals with a prostomium were identified and tabulated; fragments 

(without prostomium) traced but not counted. ˇor chironomids, head capsules were teased off the body, cleared 

in lactophenol, and mounted on microscope slides with mentum side up. The corresponding body was mounted 

alongside the head capsule and the image traced as for oligochaetes. Up to 100 chironomids were identified in a 

given sample. If the number of individuals exceeded 100 in a given sample, the sample was proportionately split 

with a folsom plankton splitter such that at least 50 individuals were identified. 

3.3 Biomass Determination

ˇor most taxa (Amphipoda, Isopoda, Oligochaeta, Chironomidae), biomass (ash free dry weight) was derived 

from length-weight relationships taken from the literature (Table 3). If a length-weight relationship for a 

given taxa was not available, it was assigned the relationship of a closely-related form. When length-weight 

relationships were available for only dry weight, ash-free dry weight (AˇDW) was assumed to be 90 % of 

dry weight (Johnson and Brinkhurst 1971). A length weight relationship was determined directly on two taxa, 

Chironmus semireductus -gr. and Dreissena polymorpha. ˇreshly collected individuals were placed into preweighted, aluminum planchets, dried at 60oC for 48 h, and weighed to the nearest 0.1 mg. AˇDW was obtained 

by re-weighing the specimens after ashing at 550oC for 1 h. Lengths were measured directly or determined from 

traced images using a digitizer (Quigley and Lang 1991). Weights of C. semireductus-gr. were determined on at 

least 25 individuals collected on various dates in 1988 and in 1996. Weights of Dreissena were measured on at 

least 23 individuals collected in late summer/fall of each year, 1991-96. Individuals for length-weight conversions 

were collected at Station 5 (inner bay) every year, and at Station 19 (outer bay) in 1995 and 1996 (Table 4). 

Biomass was determined by measuring lengths of individuals in a given sample and then converting to weight. 

When samples were split for the identification of oligochaetes and chironomids, lengths of all identified 

individuals were converted to weight and then proportionately multiplied to get total biomass. Length-weight 

conversions are based on the finding that preservation does not alter length (Erman and Erman 1975). ˇor 

Dreissena, lengths were measured on up to 500 animals in each sample using a computer scanner and adapted 

software. If more individuals were present in the sample, the sample was proportionately split. Biomass of 

other benthic groups (Sphaeriidae, Gastropoda, Tricoptera, Ephemeroptera, Hirudinea, and Diptera other than 

Chironomidae) were determined directly from preserved specimens within a given sample; that is, all individuals 

were placed in pre-weighed planchets and weights determined as described above. While sphaeriidae do not lose 

weight upon preservation (Johnson and Brinkhurst 1971), other taxa do, and therefore biomass of these other 

taxa may be underestimated. These taxa, however, generally constituted only a small portion of total biomass at a 

given site.

4.0 RESULTS

4.1 Data Presentation

The abundance (number per grab) of all taxa collected between 1987 and 1996 with the Ponar grab is provided 

in Appendix 1. Variables in the appendix include year, season (spring=1, summer=2, fall=3), station, replicate 

number, and taxa. In the appendix, individual taxa were assigned a 4-letter code as shown in Table 3. Mean 

annual density and biomass for the major benthic groups at sites sampled every year (Stations 4, 7, 10, 11, 13, 
9

14, 16, 20, 23, 24) are given in Tables 5 and 6. Mean annual density and biomass of Dreissena from the divercollected samples are given in Tables 7 and 8. 

Spatial distribution patterns of total macroinvertebrate density in 1987/88 are given in ˇigure 2. Data collected 

in these two years were used to depict distribution patterns because of the large number of sites sampled (30 

compared to 10 in other years). To further summarize spatial patterns, sites in the inner bay were grouped into 

three habitat categories based on water depth and substrate type: (1) sand/gravel, 3.0-4.8 m; (2) silty sand, 4.0-

9.0 m; and (3) silt, 6.7-11.8 m (Table 9). The only site that did not fit into one of these categories was Station 

31. Water depth at this site was only 3.2 m, and the substrate differed from all other sites, consisting of coarse 

plant debris/silt. This site was located in the center of a shallow, confined embayment (Wildfowl Bay) and was 

not representative of the bay in general. In comparing these three habitat categories, total density in the inner bay 

was clearly related to increased water depth and the amount of fine grained material (Table 9). In the outer bay, 

substrates consisted of silty sand at all sites, and depths ranged from 10 to 30 m (Table 1). Since substrates were 

generally similar, the nine outer bay sites were grouped into three categories based on water depth: 10-13 m, 16-

22 m, and 28-30 m. These depth categories are consistent with prior characterization of depth-macroinvertebrate 

associations in other regions of the Great Lakes for similar depths and substrate types (Cook and Johnson 1974, 

Mozley and Howmiller 1977). In contrast to the inner bay, total density decreased with increased water depth 

(Table 9).

4.2 Sampler Comparisons 

A number of benthic surveys have been conducted in Saginaw Bay beginning in the mid-1950s, and of interest 

were trends in populations from that time period to the 1987-96 time period of this study. When assessing 

long term trends based on data derived from different studies, an important consideration is the comparability 

of sampling techniques employed. A list of previous benthic surveys conducted in Saginaw Bay along with 

the type of sampler and mesh size used is given in Table 10. While all surveys used comparable mesh sizes to 

separate organisms from the sediment, different samplers were used to collect the organisms. Surveys in the 

1950s and 1960s used either the Petersen or Ekman grabs, while surveys in the early 1970s and thereafter used 

the Ponar. Previous studies have shown that the Peterson and Ekman have different efficiencies relative to the 

Ponar. The Peterson grab is less efficient at collecting organisms than other samplers, including the Ponar (Sly 

1969, ˇlannagan 1970). The main reason for this inefficiency is that the jaws of the Peterson have solid tops that 

impede the free flow of water during descent. This creates a preceding shock wave that blows away organisms 

at the sediment surface just before impact. In addition, the Peterson lacks side plates which allows sediments to 

be squeezed out the sides as the jaws close. The Ekman has an open top and, because it does not create a shock 

wave, takes a representative sample in soft substrates (mud/silt); however, it is not as efficient on hard substrates 

because of its relatively light weight (ˇlannagan 1970, Howmiller 1971). ˇurther, the Ekman has a closing 

mechanism that is triggered by a messenger deployed from the surface. ˇor various reasons, this limits its use in 

deeper waters and under rough weather conditions. With a recognized need for a sampler that can be used in the 

Great Lakes in a variety of substrates and conditions, the Ponar grab was developed in the late 1960s and became 

the sampler of choice by the early 1970s (Powers and Robertson 1967). Modifications of the Ponar included 

screens on top of the jaws to permit water flow during descent, and side plates to retain sediments during jaw 

closure. Yet, despite the former modification, the Ponar probably still generates somewhat of a shock wave since 

it collects fewer organisms compared to the Ekman or diver-collected cores in soft sediments (Howmiller 1971, 

Nalepa et al. 1988).

We compared the relative efficiency of the Peterson and Ponar by taking samples with both grabs at select 

sites in the inner bay in 1987 and 1988. The intent was to generate a correction factor so densities reported in 

earlier surveys that used the Peterson might be corrected to Ponar equivalents. Mean densities of the major 

macroinvertebrate groups derived from both samplers are given in Table 11. The efficiency of the Peterson 

relative to the Ponar varied depending upon the substrate. At sites with a soft substrate (silt), the Peterson 

collected significantly fewer oligocheates and chironomids than the Ponar (P > 0.05, paired t-test, ln +1 

transformed). On average, oligochaete densities were 2.88 times greater in the Ponar, while chironomid densities 
10 

Figure 2. Mean total density (no./m2 x 103) of benthic macroinvertebrates in Saginaw Bay, 1987-88. 

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11

were 3.76 times greater. Sphaeriid densities were 15 times greater in the Ponar, but the difference was not 

significant because of low and variable density estimates. At sites with sand substrate, the two samplers gave 

comparable densities for all groups (Table 11). The lower efficiency of the Peterson in silt, but not sand, is 

consistent with the “shock-wave” effect. The greater shock wave generated by the Peterson is more likely to 

displace fine-grain, flocculent sediments (along with associated organisms) than coarser, heavier sediments. We 

did not compare the relative efficiencies of the Ekman and Ponar, but others have shown that the comparability of 

the two samplers is also substrate dependent. ˇor instance, a study in Green Bay, Lake Michigan, showed that the 

Ekman collected 1.8 times more oligochaetes and 1.3 times more chironomids than the Ponar in silt, but that the 

two samplers gave comparable densities in sand (Howmiller 1971). 

5.0 HISTORIC TRENDS IN TOTAL DENSITY

We focused on examining macroinvertebrate trends in the inner bay because most earlier surveys were conducted 

in this portion of the bay. Also, because the inner bay is a semi-confined system, macroinvertebrate populations in 

the inner bay should closely reflect long-term shifts in nutrient loads and system productivity. To examine trends, 

sites sampled in earlier studies were placed into two regions based on sampling depth and substrate type. Sites 

in the deep-water/silt region had a water depth of > 6 m and a soft bottom (silt/mud), while sites in the shallowwater/sand region had a water depth of < 5 m and a hard bottom (sand/gravel). These two site groupings were 

representative of the depositional and non-depositional regions of the inner bay, respectively, and benthic communities at sites with these habitat characteristics were distinctly different (Table 9). Sites for comparative analysis 

were chosen based on their general location and proximity to sites sampled in 1987-96. If collections were made 

with a Peterson grab, densities of oligochaetes and chironomids at sites in the deep-water/silt region were multiplied by 2.88 and 3.76, respectively, and if collections were made with an Ekman grab, densities were divided by 

1.8 and 1.3 (see conversion factors above). Mean densities of these earlier surveys were thus converted to Ponar 

equivalents. No correction factors were applied to densities at sites in the shallow-water/sand region. Densities 

and converted densities of the major groups from earlier surveys are given in Table 12. Sites sampled in 1987-96 

that were considered representative of the deep-water/silt region were Stations 4, 7, 10, and sites considered representative of the shallow-water/sand region were Stations 13, 14, and 16. These inner bay sites were sampled over 

the entire 1987-96 period.

Between the mid-1950s and the early-1970s, trends in total density were similar in the deep-water/silt region and 

shallow-water/sand region. In both regions, total density generally increased from the mid-1950s to reach a peak 

in the mid-1960s, and then decreased in the early-1970s (ˇigure 3). Yet, while general trends in total densities 

were similar, temporal differences in total densities were far more pronounced in the deep-water/silt region. Densities in this region increased from < 2,500 m-2 in the 1950s to 43,000 m-2 in the mid-1960s, and then declined to 

15,000 m-2 in the early 1970s. In contrast, total densities in the shallow-water/sand region only ranged from 2,500 

to 5,200 m-2 over the entire time period.

Increases in total density between the 1950s and 1960s were likely a result of increasing nutrient loads and high 

system productivity (Vollenweider et al. 1974). Standing stocks of macroinvertebrate populations are directly 

related to pelagic productivity in lake systems (Rasmussen and Kalff 1987, Saether 1980). Nutrient abatement 

programs were implemented in the mid-1970s, and total phosphorus in the inner bay declined up to 14%, and 

chlorophyll declined up to 61% by 1980 (Bierman et al. 1984). Given these declines in pelagic productivity, it 

may be expected that total macroinvertebrate density would decrease. Total density indeed declined in the shallow-water/sand region, but not in the deep-water/silt region. Mean total density in 1987-90, which may be considered the post-phosphorus abatement/pre-Dreissena period, was 871 m-2 in the shallow-water/sand region and 

20,359 m-2 in the deep-water/silt region (ˇigure 3). Thus, total mean density in the former region was lower than 

found just before abatement efforts in the early 1970s as might be expected, but mean density in the latter region 

was actually higher. Reasons for the atypical response of the benthic community in the deep-water/silt region are 

not clear, but likely related to elevated river loadings in the mid-1980s. Most organic input into the bay enters via 
12 

Figure 3. Mean (±SE) total density of benthic macroinvertebrates in inner Saginaw Bay from 

various surveys. The standard error represents between-station variation. Densities in 1987-96 

are from this study.

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the Saginaw River, and high river discharge rates were observed in both 1985 and 1986 (Limno-Tech 1995). In 

particular, 1986 was marked by a 100-year flood event that displaced 8-200 cm of surface sediment material from 

river margins into the bay (Ludwig et al. 1993). High densities observed in 1987-90 may have been a response to 

these elevated inputs. Organic material from these discharge events would most likely settle into the deep-water/

silt region (depositional zone) and serve as food for the benthos. Declines in total density between 1988 and 1991 

would indicate that populations were returning to levels more at equilibrium with the carrying capacity of the bay 

prior to these discharge events (ˇigure 3).

After Dreissena became established in the bay in 1991 and peaked in 1992 (Table 7), total densities (excluding Dreissena) varied by bay region. Mean annual density in the shallow-water/sand region tended to increase 

between 1993 and 1996 (ˇigure 3), but total density in 1996 was still lower than densities found in the pre-abatement period. Mean annual density in the deep-water/silt region declined just after Dreissena peaked in 1992, but 

by 1996 had increased to near levels found in1991 just prior to the peak, but still below densities found in the 

pre-abatement period. 

6.0 REFERENCES

Alexander, H.C. 1963. Bottom ˇauna Survey, Saginaw Bay, June 15-16, 1962. Internal Report, Dow Chemical 

Company, Midland, MI, 3 p.

Batchelder, T.L. 1973. Saginaw Bay Ecological Survey, 1971. Internal Report, Dow Chemical Company, Midland, MI, 56 p. 

Beeton, A.M., S.H. Smith, and ˇ.H. Hooper. 1967. Physical Limnology of Saginaw Bay, Lake Huron. Great 

Lakes ˇishery Commission Technical Report 12.

Bierman, V.J., D.M. Dolan, and R. Kasprzyk. 1984. Retrospective analysis of the response of Saginaw Bay, Lake 

Huron, to reductions in phosphorus loadings. Environ. Sci. Technol. 18:23-31. 

Cook, D.G., and M.G. Johnson. 1974. Benthic macroinvertebrates of the St. Lawrence Great Lakes. J. Fish. Res. 

Bd. Can. 31:763-782.

Danek, L.J., and J.H. Saylor. 1977. Measurements of the summer currents in Saginaw Bay, Michigan. J. Great 

Lakes Res. 3:65-71.

Erman, D.C., and N.A. Erman. 1975. Macroinvertebrate composition and production on some Sierra Nevada 

minerotrophic peatlands. Ecology 56:591-603.

ˇlannagan, J.ˇ. 1970. Efficiencies of various grabs and cores in sampling freshwater benthos. J. Fish. Res. Board 

Can. 27:1691-1700.

Hebert, P. D. N., B.W. Muncaster, G.L. Mackie. 1989. Ecological and genetic studies on Dreissena polymorpha

(Pallas): a new mollusk in the Great Lakes. Can. J. Fish. Aquat. Sci. 46:1587-1591.

Howmiller, R.P. 1971. A comparison of the effectiveness of Ekman and Ponar grabs. Trans. Amer. Fish. Soc. 

100:560-564. 

Johnson, M. G., and R.O. Brinkhurst. 1971. Production of benthic invertebrates of Bay of Quinte and Lake Ontario. J. Fis. Res. Board Can. 28:1699-1714.

Limno-Tech. 1995. A preliminary ecosystem modeling study of zebra mussels (Dreissena polymorpha) in Sagi-
14 

naw Bay, Lake Huron. Report for Great Lakes Program, State University of New York at Buffalo, Ann Arbor, 

MI, 120 p. 

Ludwig, J.P., H.J. Auman, H. Kurita, M.E. Ludwig, L.M. Campbell, J.P. Giesy, D.E. Tillit, P. Jones, N. Yamashita, S. Tanabe, and R. Tatsukawa. 1993. Caspian turn reproduction in the Saginaw Bay ecosystem following a 

100-year flood event. J. Great Lakes Res. 19:96-108.

Mozley, S. C., and R.P. Howmiller. 1977. Environmental status of the Lake Michigan region: zoobenthos of 

Lake Michigan. Argonne National Lab. Rep. No. ANL/Es-40. Vol. 6. U. S. Energy Research and Development 

Administration. 

Nalepa, T.ˇ., and M.A. Quigley. 1980. The macro-and meiobnethos of southeastern Lake Michigan near the 

mouth of the Grand River, 1976-77. NOAA Data Rep. ERL GLERL-17. Great Lakes Environmental Research 

Laboratory, Ann Arbor, MI. 

Nalepa, T.ˇ., M.A. Quigley, K.M. Childs, J.M. Gauvin, T.S. Heatlie, M.P. Parker, and L. Vanover. 1985. Macrobenthos of southern Lake Michigan, 1980-81. NOAA Data Rep. ERL-GLERL-28. Great Lakes Environmental 

Research Laboratory, Ann Arbor, MI. 

Nalepa, T.ˇ., M.A. Quigley, and R.W. Ziegler. 1988. Sampling efficiency of the Ponar grab in two different benthic environments. J. Great Lakes Res. 14:89-93. 

Nalepa, T.ˇ., J.A. Wojcik, D.L. ˇanslow, and G.A. Lang. 1995. Initial colonization of the zebra mussel (Dreissena polymorpha) in Saginaw Bay, Lake Huron: population recruitment, density, and size structure. J. Great 

Lakes Res. 21:417-434.

Powers, C.ˇ., and A. Robertson. 1967. Design and evaluation of an all-purpose benthios sampler. In: Studies on 

the environment and eutrophication of Lake Michigan, eds. J.C. Ayers and D.C. Chandler, pp. 126-133. Great 

Lakes Res. Div. Spec. Rep. 30, University of Michigan, Ann Arbor, MI.

Quigley, M.A., and G.A. Lang. 1989. Measurement of amphipod body length using a digitizer. Hydrobiologia 

171:255-258.

Rasmussen, J.B., and J. Kalff. 1987. Empirical models for zoobenthic biomass in lakes. Can. J. Fish. Aquat. Sci. 

44: 990-1001.

Robbins, J.A. 1981. Sediments of Saginaw Bay, Lake Huron: Elemental composition and accumulation rates. A 

ˇinal Report to the Environmental Protection Agency, Duluth, MN, 107 p.

Saether, O.A. 1980. The influence of eutrophication on deep lake benthic invertebrate communities. Prog. Water 

Technol. 12:161-180.

Shannon, E. S., H.C. Alexander, C.M. ˇetterolf, and M.E. Newton. 1967. Saginaw Bay Biological Survey, JulyAugust, 1965. Internal Report, Dow Chemical Company, Midland, MI, 13 p. 

Sly, P.G. 1969. Bottom sediment sampling. Proc. 12th Conf. Great Lakes Res., Int. Assoc. Great Lakes Res. pp. 

855-870.

Smith, V.E., K.W. Lee, J.C. ˇilkins, K.W. Hartwell, K.R. Rygwelski, J.M. Townsend. 1977. Survey of chemical 

factors in Saginaw Bay (Lake Huron). EPA 600/3-77-125. U. S. Environmental Protection Agency, Duluth, MN.
15

Surber, E.W. 1954. Results of a biological survey of Saginaw Bay, July 16, 17, 1954. Report to the Michigan 

Water Resources Commission, Lansing, MI.

Surber, E.W. 1955. Results of a biological survey of Saginaw Bay, July 25, 26, 1955. Report to the Michigan 

Water Resources Commission, Lansing, MI.

Vollenweider, R.A., M. Munwar, and P. Stadelmann. 1974. A comparative review of phytoplankton and primary 

production in the Laurentian Great Lakes. J. Fish Res. Board Can. 31:739-762.

Winnell, M.W., and D.J. Jude. 1987. Benthic community structure and composition among rocky habitats in the 

Great Lakes and Keuka Lake, New York. J. Great Lakes Res. 13:3-17. 

Wood, L. E. 1964. Bottom sediments of Saginaw Bay, Michigan. J. Sediment. Petrol. 34:173-184. 
16 

Table 1. Location, water depth, and dominant substrate type at each of the sites sampled in

Saginaw Bay, Lake Huron. Samples for Dreissena in 1991-96 were taken by divers using 

SCUBA. 

Station Latitude Longitude Water Depth (m) Substrate

Sampled, 1987-88

2 43 39.63 83 39.17 4.2 Medium to coarse sand, some silt

18 43 51.49 83 49.20 4.5 Coarse sand, some silt

22 43 49.30 83 30.80 4.5 Silty sand

25 43 52.00 83 35.40 7.6 Silty sand

26 43 51.18 83 36.08 11.8 Silt

28 43 56.90 83 43.80 5.5 Medium to coarse sand 

30 43 53.17 83 27.17 4.0 Silty sand

31 43 53.14 83 22.48 3.2 Silt, organic plant debris

35 43 58.43 83 30.08 6.4 Medium to coarse sand

43 44 04.40 83 21.00 11.8 Coarse sand, pebbles

45 44 10.10 83 26.20 17.9 Silty sand

50 44 07.90 83 12.10 30.3 Sandy silt

53 44 06.00 83 14.40 22.2 Silty sand

55 44 10.90 83 21.10 22.4 Silty sand

57 44 14.30 83 26.16 10.1 Silty sand

58 43 42.30 83 46.20 5.8 Silty sand

68 43 43.40 83 48.90 5.8 Silty sand

108 43 43.20 83 35.60 4.8 Medium to coarse sand, some silt

168 43 47.70 83 44.50 7.8 Silt

278 43 55.30 83 41.60 9.1 Silt

Sampled, 1987-96

4 43 44.65 83 52.07 6.7 Silt

7 43 50.28 83 47.57 7.0 Silt 

10 43 56.50 83 37.43 11.0 Silt

11 44 01.23 83 34.42 9.0 Silty sand

13 43 57.57 83 29.32 3.0 Sand, pebbles/gravel

14 43 44.30 83 38.45 3.6 Sand, pebbles/gravel

16 43 50.82 83 33.75 3.0 Sand, pebbles/gravel

20 44 07.57 83 30.00 16.0 Silty sand

23 44 13.25 83 15.75 28.0 Sand, some silt

24 44 00.08 83 17.00 12.5 Silty sand

Sampled for Dreissena, 

1991-96

5 43 53.72 83 51.63 3.0 Cobble, pebbles/gravel, sand patches

6 43 58.08 83 49.25 4.0 Sand, gravel, some cobble

13 43 57.57 83 29.32 3.0 See above

14 43 44.30 83 38.45 3.6 See above

15 43 45.67 83 31.58 5.0 See above

19 44 03.17 83 26.52 4.0 Cobble, bedrock, sand patches

27 44 02.33 83 06.66 5.5 Cobble, bedrock
17

Table 2. Stations sampled during each sampling period in 1987-96.

Sampling Date

Station

4 7 10 11 13 14 16 20 23 24 2 18 22 25 26 28 30 31 35 43 45 50 53 55 57 58 68 108 168 278

1987

 Apr 29-30, May 14-16 x x x x x x x x x x x x x x x x x x x x x x x x x

 Jul 4-10 x x x x x x x x x x x x x x x x x x x x x x x x x x x x

 Oct 17-19, 27-29, Nov 11 x x x x x x x x x x x x x x x x x x x x x x x x x x x x

1988

 May 4-5, 12 x x x x x x x x x x x x x x x x x x x x x x x

 Jul 5-8 x x x x x x x x x x x x x x x x x x x x x x x x x x x x x

 Oct 21, Nov 2-4 x x x x x x x x x x x x x x x x x x x x x x x

1990

 May 30 x x x x x x x x x x

 Jul 17,19 x x x x x x x x x x

 Sep 5 x x x x x x x x x x

1991

 Jun 17-18 x x x x x x x x x x

 Jul 23-25 x x x x x x x x x x

 Sep 9-11 x x x x x x x x x x

1992

 May 27-30, Jun 3 x x x x x x x x x x

 Jul 20-21 x x x x x x x x x x

 Sep 9, 14 x x x x x x x x x x

1993

 May 17-18 x x x x x x x x x x

 Jul 11 x x x x x x x

 Sep 8 x x x x x x x x x x

1994

 Jun 6, 9-10 x x x x x x x x x x

 Jul 11-13 x x x x x x x x x x

 Sep 8-9 x x x x x x x x x x

1995

 May 17-19 x x x x x x x x x x

 Jul 12 x x x x x x x x x x

 Sep 12 x x x x x x x x x x

1996

 Jul 22,31 x x x x x x x x x x

 Oct 4-5 x x x x x x x x x x
18 

Table 3. List of taxa collected in Saginaw Bay, 1987-96. The 4-letter code identifies each taxa in 

Appendix 1. Also given is the length-weight relationship used to determine AFDW biomass. The 

number in parenthesis refers to the equation used to determine the AFDW of that particular taxa. 

Length-weight relationships for Dreissena polymorpha are given in Table 4.

Taxa Code Weight Determination Reference

Amphipoda

 Pontoporeiidae

 Diporeia spp DIPO LnAˇDW = -4.856+2.501LnL Johnson and Brinkhurst (1971)

 Gammaridae

 Gammarus sp. GAMM LnAˇDW = -4.264+2.444LnL Johnson and Brinkhurst (1971)

 Hyalellidae

 Hyallela sp. HYAL LnAˇDW = -4.264+2.444LnL

Isopoda

 Ascellidae

 Caecidotea racovitzai CRAC LnAˇDW = -4.366+2.489LnL Johnson and Brinkhurst (1971)

Polychaeta

 Manyunkia speciosa MSPE

Hirudinea

 Glossiphoniidae

 Helobdella stagnalis HSTA

 Piscicolidae

 Piscicola sp. PISC

Oligochaeta 0.25 mg DW per cm body length Nalepa and Quigley (1980)

 Enchytraeidae ENCH

 Lumbriculidae 

 Stylodrilus heringianus SHER

 Tubificidae

 Aulodrilus americanus AMME

 Aulodrilus limnobius ALIM

 Aulodrilus pigueti APIG

 Aulodrilus pluriseta APLU

 Branchiura sowerbyi BSOW

 Ilyodrilus templetoni ITEM

 Isochaetides freyi IˇRE

 Limnodrilus cervix LCER

 Limnodrilus claparedianus LCLA

 Limnodrilus hoffmeisteri LHOˇ

 Limnodrilus hoffmeisteri variant LHOV

 Limnodrilus maumeensis LMAU

 Limnodrilus profundicola LPRO

 Linmodrilus spiralis LSPI

 Limnodrilus udekemianus LUDE

 Potamothrix bavaricus PBAV

 Potamothrix bedoti PBED

 Potamothrix moldaviensis PMOL

 Potamothrix vejdovskyi PVEJ

 Quistadrilus multisetosus QMUL

 Rhyacodrilus coccineus RCOC

 Rhyacodrilus sodalis RSOD

 Spirosperma ferox SˇER

 Spirosperma nikolskyi SNIK

 Tasserkidrilus americanus TAME

 Tasserkidrilus superiorensis TSUP

 Tubifex ignotus TIGN
19

Table 3. Continued

Taxa Code Weight Determination Reference

 Tubifex tubifex TTUB

 Varichaetadrilus angustipenis VANG

 Immatures

 without hair setae IMWO

 with hair setae IMWH

 Naididae

 Amphicaeta leydigi ALEY

 Arcteonais lomondi ALOM

 Chaetogaster sp. CHAE

 Dero digitata DDIG

 Nais sp. NAIS

 Nais alpina NALP

 Nais barbata NBAR

 Nais bretscheri NBRE

 Nais communis NCOM

 Nais elinguis NELI

 Nais pardalis NPAR

 Nais pseudobtusa NPSE

 Nais simplex NSIM

 Nais variabilis NVAR

 Opistonais serpentina OSER

 Piguetiella michiganensis PMIC

 Pristina longiseta PLON

 Slavina appendiculata SAPP

 Specaria josinae SJOS

 Stylaria fossularis SˇOS

 Stylaria lacustris SLAC

 Uncinais uncinata UUNI

 Vejdovskyella intermedia VINT

Diptera

 Ceratopogonidae

 Bezzia sp. BEZZ

 Chironominii

 Chironomus sp. CHIR 1

 Chironomus anthracinus CANT LnDW = 0.0359 + 2.844 LnL (1) Nalepa and Quigley (1980)

 Chironomus halophilus gr. CHAL (1)

 Chironomus plumosus gr. CPLU (1)

 Chironomus semireductus- gr. CSEM LnDW = -4.441 + 2.262 LnL (2) This study

 Chironomus semireductus- gr.A CSEA (2)

 Chironomus semireductus- gr.B CSEB (2)

 Chironomus semireductus- gr.C CSEC (2)

 Cladopelma sp. CLAD (1)

 Cryptochironomus sp. CRYP (1)

 Cryptochironomus cf.digitatus CDIG (1)

 Cryptochironomus eminentia CEMI (1)

 Cryptochirnomus fluviatilis CˇLU (1)

 Cryptochironomus cf. fulvus CˇUL (1)

 Cryptochironomus cf. rolli CROL (1)

 Demicryptochironomus sp. DEMI (1)

 Dicrotendipes sp. DICR (1)

 Dicroneomodestus sp. DNEO (1)

 Endochironomus sp. ENDO (1)

 Endochironomus subtendens ESUB (1)
20 

Table 3. Continued

Taxa Code Weight Determination Reference

 Glyptotendipes sp. GLYP (1)

 Harnischia sp. HARN (1)

 Lenziella sp. LENZ (1)

 Microtendipes pedellus-gr MPED (1)

 Parachironomus arcuatus-gr. PARC LnDW = 0.0800 + 2.2817 LnL (3) Nalepa and Quigley (1980)

 Paracladopelma camptolabis PCAM (4)

 Paracladopelma cf. nais PNAI (4)

 Paracladopelma udine PUDI LnDW = 0.9879 + 2.4456 LnL (4) Nalepa and Quigley (1980)

 Paracladopelma winnelli PWIN (4)

 Paralauterborniella sp. PLAU (5)

 Paratendipes sp. PTEN (1)

 Polypedilum sp. POLY (5)

 Polypedilum fallax PˇAL LnDW = 1.0890 + 2.3190 LnL (5) Nalepa and Quigley (1980)

 Polypedilum cf halterale PHAL (5)

 Polypedilum cf. laetum PLAE (5)

 Polypedilum nereis PNER (5)

 Polypedilum cf. scalaenum PSCA (5)

 Polypedilum simulans PSIM (5)

 Polypedilum tuberculum PTUB (5)

 Pseudochironomus sp. PSEU (1)

 Pseudochironomus nr. fulviventris PˇUL (1)

 Stempellinella sp. STEM (1)

 Stichochironomus sp. STIC (1)

 Tanytarsini

 Cladotanytarsus sp. CTAN LnDW = 0.1557 + 3.1419 LnL (6) Nalepa and Quigley (1980)

 Cladotanytarsus mancus gr. CMAN (6)

 Cladotanytarsus vanderwulpi gr. CVAN (6)

 Micropsectra sp. MICR (6)

 Paratanytarsus sp. PARA (6)

 Rheotanytarsus sp. RHEO (6)

 Tanytarsus sp. TANY (6)

 Othocladiinae

 Heterotrissocladius changi HCHA LnDW = 0.8129 + 2.1946 LnL (7) Nalepa and Quigley (1980)

 Heterotrissocladius oliveri HOLI (7)

 Hydrobaenus pilipes HPIL (7)

 Nanocladius sp. NANO (7)

 Orthocladius sp. ORTH (7)

 Paracladius cf.conversus PCON (7)

 Parakiefferiella sp. PKIE (7)

 Psectrocladius sp. PSEC Ln DW = 0.5524 +2.7083 LnL (8) Nalepa and Quigley (1980)

 Psectrocladius psilopterus gr. PPSI (8)

 Pseudosmittia sp. PSMI (7)

 Thienemannimyia sp. THIE (7)

 Tanypodinae TAYP

 Ablabesmyia sp. ABAL (9)

 Ablabesmyia monilis AMON (9)

 Hayesomyia senata HAYE (9)

 Procladius sp. PROC LnDW = -5.413 + 2.275 LnL (9) Nalepa and Quigley (1980)

 Tanypus neopunctipennis TNEO (9)

 Diamesinae

 Cricotopus sp. CRIC (10)

 Cricotopus festivellus CˇES (10)

 Cricotopus ornatus CORN (10)
21

Table 3. Continued

Taxa Code Weight Determination Reference

 Cricotopus slyvestris-gr. CSLY (10)

 Monodiamesia depictinata MDEP (10)

 Monodiamesia tuberculata MTUB LnDW = 0.7460 + 2.661 LnL (10) Nalepa and Quigley (1980)

 Potthasia cf. longimanus PLOG (10)

Pelecypoda

 Sphaeriidae

 Pisidium sp. PISI

 Dreisseniidae 

 Dreissena polymorpha DPOL

Gastropoda

 Hydrobiidae

 Amnicola limosa ALMO

 Probythinella lacustris PLAC

 Bithyniidae

 Bithynia tentaculata BTEN

 Physidae

 Physa sp. PHYS

 Pleuroceridae

 Pleurocera acuta PACU

 Valvatidae

 Valvata sincera VSIN

 Valvata tricarinata VTRI

Ephemeroptera

 Baetidae

 Caenis sp. CAEN

 Ephemeridae

 Hexagenia sp. HEXA

Tricoptera

 Leptoceridae

 Oecetis sp. OECE
22 

Table 4. Relationship between shell length (SL) and ash free dry weight 

(AFDW) for Dreissena polymorpha in late summer/fall, 1991-96. 

The relationship was described by the linear regression equation: 

LnAFDW = a + bLnSL, where AFDW is given mg and SL is given in mm. 

Station Date n a b r

2

5 16 Nov 91 25 -6.986 3.375 0.96

5 10 Sep 92 24 -5.613 2.681 0.94

5 9 Sep 93 23 -6.383 2.752 0.95

5 17 Oct 94 25 -3.293 1.737 0.84

5 18 Sep 95 25 -3.382 1.713 0.82

5 29 Aug 96 26 -2.456 1.521 0.74

19 25 Sep 95 25 -3.648 2.136 0.60

19 29 Aug 96 24 -2.615 1.809 0.69
23

Table 5. Mean (X + SE) annual density (no. per m2) of major macroinvertebrate groups at the stations sampled 

over the entire 1987-96 period. The standard error (SE) was derived from the mean density in the spring, summer, and fall (n=3) of each year. The group “Others” includes Isopoda, Ephemeroptera, Hirudinea, Tricoptera, and 

Gastropoda. 

Macroinvertebrate Group

Station/Year Oligochaeta Chironomidae Sphaeriidae Amphipoda Dreissena Others

Station 4

1987 26,058 + 6,939 2,559 + 1,554 100 + 100 0 + 0 0 + 0 0 + 0

1988 20,744 + 1,431 1,287 + 588 105 + 56 0 + 0 0 + 0 0 + 0

1990 20,337 + 2,891 1,825 + 735 52 + 27 0 + 0 0 + 0 0 + 0

1991 8,175 + 1,987 1,216 + 352 33 + 13 0 + 0 21 + 12 0 + 0

1992 7,597 + 2,019 1,573 + 699 12 + 12 0 + 0 0 + 0 0 + 0

1993 2,249 + 581 1,233 + 299 137 + 30 10 + 6 21 + 12 0 + 0

1994 1,791 + 566 666 + 31 31 + 17 26 + 13 0 + 0 0 + 0

1995 4,570 + 1,433 2,511 + 1,531 5 + 2 14 + 14 0 + 0 0 + 0

1996 7,633 + 1,577 4,537 + 3,088 36 + 14 7 + 7 0 + 0 4 + 4

Station 7

1987 12,048 + 6,907 1,430 + 844 150 + 150 0 + 0 0 + 0 0 + 0

1988 18,552 + 1,446 1,299 + 312 240 + 80 2 + 2 0 + 0 0 + 0

1990 15,297 + 1,777 1,285 + 521 33 + 17 0 + 0 0 + 0 0 + 0

1991 8,666 + 452 1,595 + 485 152 + 114 0 + 0 0 + 0 0 + 0

1992 6,940 + 1,726 1,097 + 516 112 + 52 0 + 0 26 + 19 2 + 2

1993 976 + 203 605 + 243 348 + 87 12 + 12 86 + 12 0 + 0

1994 588 + 183 471 + 101 233 + 157 12 + 6 114 + 62 0 + 0

1995 1,479 + 645 3,234 + 2,420 12 + 2 14 + 14 0 + 0 14 + 14

1996 1,817 + 46 1,135 + 36 182 + 46 7 + 7 21 + 21 0 + 0

Station 10

1987 20,056 + 3,515 1845 + 1,106 52 + 33 0 + 0 0 + 0 0 + 0

1988 24,290 + 2,270 1321 + 572 73 + 31 0 + 0 0 + 0 0 + 0

1990 11,400 + 418 757 + 353 33 + 5 2 + 2 0 + 0 0 + 0

1991 6,947 + 1,149 1,228 + 643 98 + 52 14 + 11 21 + 12 0 + 0

1992 6,631 + 1,950 900 + 228 109 + 57 0 + 0 0 + 0 0 + 0

1993 1,940 + 1,192 614 + 357 519 + 194 5 + 5 0 + 0 0 + 0

1994 1,247 + 466 671 + 104 212 + 101 7 + 7 14 + 14 0 + 0

1995 1,016 + 262 873 + 338 102 + 48 12 + 12 7 + 7 0 + 0

1996 4,405 + 1,656 543 + 179 4 + 4 0 + 0 0 + 0

Station 11

1987 10,757 + 5,567 1,654 + 777 490 + 71 5 + 2 0 + 0 0 + 0

1988 7,104 + 164 664 + 79 0 + 0 0 + 0 0 + 0

1990 2,535 + 1,218 3,810 + 1,261 450 + 57 14 + 0 0 + 0 5 + 2

1991 1,457 + 345 1,483 + 666 455 + 258 10 + 6 0 + 0 10 2

1992 3,023 + 1,530 4,489 + 3,164 395 + 120 17 13 114 + 63 0 + 0

1993 1,616 + 360 904 + 368 835 + 281 76 + 53 2,884 + 2,788 36 + 18

1994 2,232 + 222 1,269 + 300 74 + 30 57 + 25 50 + 26 12 + 2

1995 4,627 + 3,099 3,232 + 2,134 50 + 31 43 + 39 0 + 0 0 + 0

1996 2,945 + 75 1,935 + 764 225 + 39 54 + 11 36 + 26 14 + 7
24 

Table 5. Continued

Macroinvertebrate Group

Station/Year Oligochaeta Chironomidae Sphaeriidae Amphipoda Dreissena Others

Station 13

1987 1,142 + 883 157 + 116 7 + 4 71 + 22 0 + 0 0 + 0

1988 1,221 93 71 171 0 0

1990 362 + 91 157 + 122 2 + 2 67 + 56 0 + 0 7 + 4

1991 938 + 389 545 + 427 21 + 14 133 + 51 57 + 29 31 + 24

1992 231 + 77 36 + 25 19 + 17 21 + 15 164 + 26 0 + 0

1993 521 + 114 296 + 46 43 + 43 203 + 132 7 + 7 21 + 14

1994 328 + 83 133 + 123 7 + 4 267 + 113 942 + 795 2 + 2

1995 621 + 433 48 + 29 2 + 2 57 + 37 0 + 0 5 + 5

1996 818 + 225 68 + 39 0 + 0 207 + 7 157 + 134 7 + 7

Station 14

1987 518 + 196 226 + 95 5 + 5 29 + 18 0 + 0 0 + 0

1988 555 + 182 44 + 10 38 + 13 67 + 41 0 + 0 49 + 15

1990 476 + 28 150 + 136 38 + 23 19 + 19 0 + 0 71 + 49

1991 659 + 170 74 + 34 95 + 19 52 + 28 21 + 21 38 + 13

1992 371 + 46 131 + 64 21 + 8 55 + 10 92 + 82 7 + 4

1993 436 + 198 95 + 28 5 + 2 655 + 367 1,291 + 266 69 + 13

1994 812 + 293 38 + 28 10 + 10 338 + 155 871 + 697 17 + 17

1995 681 + 82 60 + 56 5 + 5 552 + 338 2,228 + 1,001 5 + 5

1996 789 + 318 707 + 671 0 + 0 857 + 350 10,339 + 7,400 43 + 43

Station 16

1987 844 + 662 37 + 27 61 + 61 116 + 23 0 + 0 0 + 0

1988 275 + 131 10 + 5 12 + 6 14 + 14 0 + 0 29 + 29

1990 488 + 188 79 + 44 10 + 6 33 + 30 0 + 0 17 + 9

1991 872 + 299 552 + 449 17 + 9 36 + 12 36 + 26 19 + 19

1992 345 + 64 55 + 10 0 + 0 36 + 26 0 + 0 2 + 2

1993 616 + 321 512 + 437 0 + 0 624 + 269 2,185 + 1,913 21 + 18

1994 343 + 58 40 + 34 0 + 0 117 + 52 0 + 0 5 + 5

1995 864 + 353 33 + 11 2 + 2 167 + 84 1,178 + 348 0 + 0

1996 1189 + 39 211 + 104 25 + 25 107 + 36 7 + 7 0 + 0

Station 20

1987 2,454 + 1,017 1,568 + 1,009 107 + 77 7 + 4 0 + 0 2 + 2

1988 2,430 + 1,069 1,409 + 445 666 + 296 0 + 0 0 + 0 2 + 2

1990 797 + 275 1,171 + 345 345 + 261 2 + 2 0 + 0 2 + 2

1991 659 +145 778 + 529 109 + 29 0 + 0 0 + 0 0 + 0

1992 1,473 + 175 605 + 321 50 + 27 0 + 0 7 + 7 0 + 0

1993 1,196 + 321 646 + 227 98 + 68 13 + 10 14 + 14 2 + 2

1994 1,366 + 940 486 + 159 98 + 77 12 + 2 0 + 0 0 + 0

1995 4,127 + 963 2,306 + 1,325 100 + 25 12 + 9 0 + 0 0 + 0

1996 2,253 + 425 2,599 + 1,985 61 + 18 7 + 7 0 + 0 0 + 0

Station 23

1987 482 + 175 252 + 156 219 + 135 574 + 401 0 + 0 107 + 50

1988 469 + 178 281 + 97 350 + 31 1,190 + 536 0 + 0 109 + 13

1990 212 + 66 121 + 23 114 + 28 693 + 84 0 + 0 98 + 77

1991 569 + 192 186 + 143 93 + 46 1,154 + 824 0 + 0 7 + 7

1992 202 + 52 45 + 2 50 + 25 240 + 178 0 + 0 5 + 5

1993 246 + 75 134 + 27 66 + 34 590 + 62 0 + 0 4 + 4

1994 431 + 10 233 + 66 102 + 29 371 + 33 0 + 0 0 + 0

1995 793 + 233 707 + 397 167 + 71 50 + 39 0 + 0 0 + 0

1996 957 + 21 607 + 514 336 + 57 82 + 32 0 + 0 4 + 4
25

Table 5. Continued

Macroinvertebrate Group

Station/Year Oligochaeta Chironomidae Sphaeriidae Amphipoda Dreissena Others

Station 24

1987 5,581 + 1,936 840 + 461 12 + 6 0 + 0 0 + 0

1988 2,517 + 1,839 1,535 + 1,271 75 + 39 7 + 7 0 + 0 0 + 0

1990 1,169 + 185 521 + 173 24 + 13 7 + 7 0 + 0 2 + 2

1991 1,792 + 559 593 + 184 57 + 26 4 + 4 0 + 0 0 + 0

1992 1,454 + 849 797 + 384 40 + 25 10 + 6 0 + 0 5 + 5

1993 1,100 + 778 685 + 557 57 + 36 32 + 18 0 + 0 0 + 0

1994 878 + 294 386 + 116 2 + 2 14 + 8 0 + 0 2 + 2

1995 4,370 + 470 3,823 + 3,067 15 + 9 0 + 0 0 + 0 0 + 0

1996 1,489 + 296 725 + 632 0 + 0 43 + 14 0 + 0 0 + 0
26 

Table 6. Mean (X + SE) annual biomass (g AFDW per m2) of major macroinvertebrate groups (excluding 

Dreissena) at the stations sampled over the entire 1987-96 period. The standard error (SE) was derived

from the mean density in the spring, summer, and fall (n=3) of each year. The group “others” includes Isopoda, 

Ephemeroptera, Hirudinea, Tricoptera, and Gastropoda. 

Macroinvertebrate Group

Station/Year Oligochaeta Chironomidae Sphaeriidae Amphipoda Other Total

Station 4

1987 2.05 + 0.55 4.85 + 2.62 <0.01 + <0.01 0 + 0 0 + 0 6.90 + 0.314

1988 1.42 + 0.41 2.78 + 1.01 0.01 + <0.01 0 + 0 0 + 0 4.20 + 1.41

1990 1.65 + 0.15 8.73 + 3.47 <0.01 + <0.01 0 + 0 0 + 0 10.38 + 3.53

1991 0.72 + 0.16 4.13 + 2.56 <0.01 + <0.01 0 + 0 0 + 0 4.85 + 2.51

1992 0.61 + 0.11 3.45 + 1.76 0 + 0 <0.01 + <0.01 0 + 0 4.06 + 1.72

1993 0.25 + 0.06 3.31 + 0.58 0.01 + 0.0 <0.01 + <0.01 0 + 0 3.57 + 0.63

1994 0.23 + 0.08 0.80 + 0.47 <0.01 + <0.01 0.01 + 0.01 0 + 0 1.05 + 0.52

1995 0.52 + 0.12 3.73 + 1.43 0 + 0 <0.01 + <0.01 0 + 0 4.26 + 1.33

1996 0.67 + 0.04 3.18 + 1.76 <0.01 + 0.0 0.01 + 0.01 <0.01 + <0.01 3.86 + 1.80

Station 7

1987 1.34 + 0.29 2.23 + 0.28 <0.01 + <0.01 0 + 0 0 + 0 3.57 + 0.51

1988 1.73 + 0.06 3.04 + 0.59 0.01 + <0.01 0 + 0 0 + 0 4.78 + 0.59

1990 1.33 + 0.19 6.55 + 2.50 <0.01 + <0.01 0 + 0 0 + 0 7.89 + 2.68

1991 0.84 + 0.04 4.87 + 2.62 0.01 + <0.01 0 + 0 0 + 0 5.71 + 2.66

1992 0.59 + 0.14 5.56 + 2.45 0.01 + <0.01 0 + 0 0 + 0 6.16 + 2.44

1993 0.11 + 0.04 1.30 + 1.14 0.01 + <0.01 0.01 + 0.01 0 + 0 1.43 + 1.14

1994 0.08 + 0.03 0.42 + 0.28 0.01 + 0.01 0.02 + 0.01 0 + 0 0.53 + 0.30

1995 0.17 + 0.07 5.65 + 1.31 <0.01 + <0.01 0.01 + 0.01 0 + 0 5.83 + 1.38

1996 0.20 + 0.05 1.01 + 0.78 0.01 + <0.01 0.01 + 0.01 0 + 0 1.23 + 0.83

Station 10

1987 1.62 + 0.29 1.83 + 0.12 <0.01 + <0.01 0 + 0 0 + 0 3.45 + 0.22

1988 1.84 + 0.11 2.21 + 0.41 0.01 + <0.01 0 + 0 0 + 0 4.06 + 0.51

1990 1.05 + 0.04 3.25 + 0.27 <0.01 + <0.01 0 + 0 0 + 0 4.30 + 0.24

1991 0.59 + 0.10 5.25 + 3.02 0.01 + <0.01 <0.01 + <0.01 0 + 0 5.85 + 2.95

1992 0.47 + 0.13 4.52 + 1.46 0.01 + <0.01 0 + 0 0 + 0 5.01 + 1.34

1993 0.19 + 0.11 2.84 + 2.45 0.02 + 0.01 <0.01 + <0.01 0 + 0 3.05 + 2.56

1994 0.15 + 0.04 1.18 + 0.57 0.01 + <0.01 <0.01 + <0.01 0 + 0 1.34 + 0.60

1995 0.11 + 0.02 2.30 + 1.62 0.02 + 0.01 0.01 + 0.01 0 + 0 2.43 + 1.60

1996 0.41 + 0.08 5.90 + 2.75 0.02 + <0.01 <0.01 + <0.01 0 + 0 6.33 + 2.84

Station 11

1987 0.62 + 0.29 0.80 + 0.47 <0.01 + <0.01 <0.01 + <0.01 0 + 0 1.46 + 0.52

1988 0.59 + 0.02 1.51 + 0.47 0.09 + 0.02 0 + 0 0 + 0 2.19 + 0.52

1990 0.27 + 0.15 2.59 + 0.86 0.41 + 0.01 <0.01 + <0.01 0.07 + 0.06 2.96 + 0.80

1991 0.14 + 0.03 0.61 + 0.36 0.04 + 0.02 <0.01 + <0.01 0.01 + 0.01 0.80 + 0.40

1992 0.25 + 0.08 1.17 + 0.42 0.03 + 0.02 0.01 + <0.01 0 + 0 1.46 + 0.47

1993 0.15 + 0.01 0.49 + 0.39 0.03 + 0.01 0.04 + 0.03 0.01 + <0.01 0.72 + 0.37

1994 0.24 + 0.02 0.38 + 0.18 0.01 + <0.01 0.02 + 0.01 0.04 + 0.03 0.69 + 0.13

1995 0.34 + 0.22 2.46 + 0.88 0.01 + <0.01 0.02 + 0.01 0 + 0 2.81 + 0.89

1996 0.27 + 0.03 1.03 + 0.25 0.01 + <0.01 0.02 + 0.01 <0.01 + <0.01 1.33 + 0.24

Station 13

1987 0.08 + 0.04 0.01 + 0.01 <0.01 + <0.01 <0.01 + <0.01 0 + 0 0.14 + 0.04

1988 0.08 + 0.08 <0.01 + <0.01 0.01 + 0.01 0.09 + 0.09 0 + 0 0.18 + 0.18

1990 0.03 + <0.01 0.01 + 0.01 0 + 0 0.01 + 0.01 <0.01 + <0.01 0.05 + 0.01

1991 0.06 + 0.02 0.05 + 0.01 <0.01 + <0.01 0.02 + 0.01 <0.01 + <0.01 0.13 + 0.03

1992 0.03 + <0.01 0.01 + 0.01 <0.01 + <0.01 0.15 + 0.01 0 + 0 0.05 + 0.02

1993 0.05 + <0.01 0.02 + <0.01 <0.01 + <0.01 0.08 + 0.02 <0.01 + 0 0.16 + 0.02

1994 0.04 + 0.01 0.01 + 0.01 0 + 0 0.12 + 0.04 0.09 + 0.09 0.26 + 0.09

1995 0.04 + 0.02 0.01 + <0.01 0 + 0 0.02 + <0.01 0.01 + 0.01 0.08 + 0.03

1996 0.06 + 0.02 0.01 + <0.01 0 + 0 0.07 + 0.01 0.03 + 0.03 0.16 + <0.01
27

Table 6. Continued

Macroinvertebrate Group

Station/Year Oligochaeta Chironomidae Sphaeriidae Amphipoda Other Total

Station 14

1987 0.03 + 0.01 0.04 + 0.02 0 + 0 0.01 + 0.01 0 + 0 0.08 + 0.02

1988 0.05 + 0.01 0.01 + <0.01 <0.01 + <0.01 0.02 + 0.01 0.01 + 0.01 0.10 + 0.04

1990 0.04 + <0.01 0.02 + 0.02 <0.01 + <0.01 <0.01 + <0.01 0.01 + 0.01 0.08 + 0.03

1991 0.05 + 0.01 0.03 + 0.02 <0.01 + <0.01 0.02 + 0.01 <0.01 + <0.01 0.11 + 0.01

1992 0.05 + <0.01 0.02 + 0.01 <0.01 + 0.0 0.04 + 0.02 <0.01 + <0.01 0.10 + 0.02

1993 0.05 + 0.02 0.02 + 0.01 0 + 0 0.23 + 0.11 0.01 + <0.01 0.31 + 0.13

1994 0.08 + 0.02 0.01 + 0.01 <0.01 + <0.01 0.23 + 0.14 0.01 + 0.01 0.33 + 0.13

1995 0.06 + <0.01 0.03 + 0.03 0 + 0 0.64 + 0.47 <0.01 + <0.01 0.73 + 0.51

1996 0.06 + 0.03 0.03 + 0.03 0 + 0 0.42 + 0.19 1.84 + 1.84 2.34 + 1.97

Station 16

1987 0.06 + 0.04 0.01 + 0.01 0 + 0 0.08 + 0.04 0 + 0 0.15 + 0.01

1988 0.04 + 0.02 <0.01 + <0.01 <0.01 + 0.0 0.02 + 0.02 0.01 + 0.01 0.06 + 0.03

1990 0.04 + 0.02 0.02 + 0.01 <0.01 + 0.0 0 + 0 <0.01 + <0.01 0.06 + 0.02

1991 0.07 + 0.02 0.10 + 0.08 <0.01 + 0.0 <0.01 + 0.0 <0.01 + <0.01 0.18 + 0.06

1992 0.04 + 0.02 0.01 + <0.01 0 + 0 0.01 + 0.01 0 + 0 0.06 + 0.02

1993 0.06 + 0.02 0.04 + 0.04 0 + 0 0.26 + 0.10 0.02 + 0.01 0.37 + 0.10

1994 0.03 + 0.01 0.01 + <0.01 0 + 0 0.06 + 0.03 <0.01 + <0.01 0.10 + 0.03

1995 0.06 + 0.02 0.01 + <0.01 0 + 0 0.10 + 0.05 0 + 0 0.17 + 0.07

1996 0.09 + 0.02 0.02 + <0.01 0 + 0 0.02 + 0.01 0 + 0 0.13 + 0.01

Station 20

1987 0.24 + 0.09 0.25 + 0.10 0.01 + 0.01 0.01 + <0.01 <0.01 + <0.01 0.51 + 0.12

1988 0.27 + 0.13 0.16 + 0.04 0.04 + 0.01 0 + 0 0 + 0 0.46 + 0.16

1990 0.08 + 0.02 0.44 + 0.11 0.01 + <0.01 <0.01 + <0.01 0 + 0 0.52 + 0.13

1991 0.07 + 0.02 0.54 + 0.36 0.01 + <0.01 0 + 0 0 + 0 0.62 + 0.38

1992 0.15 + 0.03 0.49 + 0.38 0.01 + <0.01 0 + 0 0 + 0 0.64 + 0.39

1993 0.13 + 0.04 0.61 + 0.56 0.01 + <0.01 0.02 + 0.01 <0.01 + <0.01 0.76 + 0.58

1994 0.13 + 0.05 0.14 + 0.07 0.01 + 0.01 <0.01 + <0.01 0 + 0 0.27 + 0.10

1995 0.34 + 0.10 0.68 + 0.55 0.01 + 0.01 <0.01 + <0.01 0 + 0 1.04 + 0.55

1996 0.20 + 0.04 0.73 + 0.58 <0.01 + 0 0.01 + 0.01 0 + 0 0.93 + 0.62

Station 23

1987 0.05 + 0.01 0.04 + 0.02 0.01 + 0.01 0.20 + 0.07 0.06 + 0.02 0.37 + 0.12

1988 0.05 + 0.01 0.05 + 0.01 0.03 + 0.01 0.31 + 0.07 0.08 + 0.01 0.52 + 0.05

1990 0.02 + 0.02 0.02 + 0.01 0.01 + <0.01 0.20 + 0.05 0 + 0 0.25 + 0.05

1991 0.06 + 0.02 0.01 + <0.01 0.01 + <0.01 0.20 + 0.09 <0.01 + <0.01 0.28 + 0.11

1992 0.02 + <0.01 0.01 + <0.01 <0.01 + <0.01 0.05 + 0.03 0 + 0 0.09 + 0.03

1993 0.03 + <0.01 0.02 + <0.01 <0.01 + <0.01 0.14 + 0.06 0 + 0 0.18 + 0.06

1994 0.04 + <0.01 0.03 + 0.01 0.01 + <0.01 0.09 + 0.04 0 + 0 0.17 + 0.05

1995 0.07 + 0.02 0.15 + 0.06 0.01 + <0.01 0.03 + 0.02 <0.01 + <0.01 0.26 + 0.08

1996 0.10 + 0.01 0.03 0.02 0.04 + 0.01 0.02 + <0.01 0 + 0 0.19 + <0.01

Station 24

1987 0.38 + 0.13 0.46 + 0.22 0.01 + <0.01 0.01 + 0.01 0 + 0 0.86 + 0.25

1988 0.19 + 0.13 0.17 + 0.08 0.01 + <0.01 0 + 0 0 + 0 0.37 + 0.21

1990 0.09 + 0.01 0.19 + 0.09 <0.01 + 0.0 <0.01 + <0.01 0 + 0 0.29 + 0.09

1991 0.12 + 0.03 0.42 + 0.33 0.01 + 0.01 <0.01 + <0.01 0 + 0 0.56 + 0.32

1992 0.12 + 0.05 0.19 + 0.11 <0.01 + <0.01 <0.01 + <0.01 <0.01 + <0.01 0.32 + 0.17

1993 0.10 + 0.06 0.17 + 0.15 <0.01 + <0.01 <0.01 + <0.01 0 + 0 0.28 + 0.21

1994 0.07 + 0.02 0.06 + 0 0 + 0 <0.01 + <0.01 0 + 0 0.13 + 0.03

1995 0.35 + 0.02 0.89 + 0.34 <0.01 + <0.01 0 + 0 0 + 0 1.24 + 0.34

1996 0.13 + 0.02 0.15 + 0.13 0 + 0 0.01 + <0.01 0 + 0 0.29 + 0.11
28 

Table 7. Mean (X + SE) annual density (no. per m2) of Dreissena polymorpha at sites in inner and outer Saginaw 

Bay in 1991-96. Samples were collected in the fall of each year by divers using SCUBA. 

Year

Station 1991 1992 1993 1994 1995 1996

 Inner Bay

 5 28,244 + 2,457 75,296 + 29,280 237 + 48 2,959 + 422 1,018 + 348 3,067 + 431

 6 4,453 + 1,387 3,620 + 2,444 3,557 + 1,616 10,724 + 4,862 2,291 + 774 61 + 23

 13 8,956 + 6,720 376 + 60 855 + 449 211 + 79 150 + 71

 14 209 + 115 63,242 + 18,999 7,506 + 3,459 3,900 + 880 2,564 + 425 5,426 + 809

 15 43,117 + 1,050 5,556 + 2,492 7,341 + 2,828 9,725 + 2,336 6,728 + 742 17,600 + 186

 16 27 + 27 46,360 + 7,780 4,831 + 1,768 1,727 + 614 60 + 19 6,981 + 947

Mean 15,210 + 8,718 33,838 + 13,003 3,975 + 1,312 4,982 + 1,716 2,145 + 1,009 5,548 + 2,663

 Outer Bay

 19 2,480 + 1,219 57,640 + 19,985 3,328 + 900 21,669 + 7,773 17,776 + 1,912 19,349 + 2,116

 27 3,408 + 2,772 4,695 + 2,542 5,813 + 2,384 9,925 + 1,590 3,824 + 525 6,981 + 1,670

Mean 2,944 + 464 31,168 + 26,473 4,570 + 1,243 15,797 + 5,872 10,800 + 6,976 13,165 + 6,184

Table 8. Mean biomass (g AFDW m-2) of Dreissena polymorpha at stations in inner and outer Saginaw Bay in

1991-96. Samples were collected by divers in fall of each year.

Year

Station 1991 1992 1993 1994 1995 1996

 Inner Bay

 5 10.48 106.86 0.18 5.65 2.05 5.88 

 6 4.39 8.88 6.72 16.18 6.27 0.23 

 13 24.66 0.74 2.55 0.66 0.26 

 14 0.09 143.98 11.55 8.84 6.05 17.99 

 15 34.14 8.60 3.38 12.95 9.38 33.46 

 16 0.01 78.23 4.39 3.83 0.14 22.53 

Mean 10.02 + 6.30 61.87 + 23.14 4.49 + 1.72 8.33 + 2.19 4.09 + 1.51 13.39 + 5.51

 Outer Bay

 19 0.57 88.20 12.28 56.52 99.27 137.98 

 27 0.73 19.49 15.29 32.55 27.10 57.54 

Mean 0.65 + 0.08 53.85 + 34.36 13.79 + 1.51 44.54 + 11.99 63.19 + 36.09 97.76 + 40.22
29

Table 9. Type of grab sampler and mesh size used in previous macroinvertebrate surveys

conducted in inner Saginaw Bay.

Year Grab Sampler Mesh Size Reference

1954 Peterson, Ekman 0.595 Surber (1954)

1955 Peterson 0.595 Surber (1955)

1956 Peterson 0.595 Schneider (unpublished data)

1962 Ekman 0.595 Alexander (1963)

1965 Peterson 0.595 Shannon et al. (1967)

1971 Ponar 0.595 Batchelder (1973)

1987-96 Ponar 0.50 This study

Table 10. Densities (X + SE) of the major benthic macroinvertebrate groups collected with the Ponar and Peterson grabs in Saginaw Bay in 1987/88. The source of variation (SE) was the mean density on each sampling date 

over the two-year period. The two samplers were compared using a paired t-test after ln+1 transformation. Each 

sampling date was considered an individual replicate. A conversion value (Ponar/Peterson) was determined only 

when the difference between samplers was significant (P < 0.05). 

Station Substrate Ponar Peterson P-Value Ponar/Peterson

 Group:Oligochaeta

4 Silt 30,453 + 3611 11,677 + 1,650 <0.001 2.61

7 Silt 23,472 + 1,954 8,897 + 1,533 0.002 2.64

10 Silt 27,583 + 1,838 8,079 + 1,692 0.002 3.41

13 Sand 1,420 + 684 858 + 257 0.497

14 Sand 880 + 201 835 + 231 0.705

16 Sand 746 + 359 462 + 149 0.592

Group:Chironomidae

4 Silt 2,019 + 3,611 588 + 162 0.001 3.43

7 Silt 1,556 + 545 445 + 68 0.011 3.50

10 Silt 1,633 + 610 375 + 60 0.006 4.35

13 Sand 147 + 84 224 + 157 0.599

14 Sand 153 + 70 208 + 109 0.617

16 Sand 20 + 12 28 + 21 0.882

Group: Sphaeriidae

4 Silt 147 + 90 2 + 1 0.068

7 Silt 185 + 80 11 + 6 0.182

10 Silt 66 + 23 14 + 3 0.309

13 Sand 22 + 17 26 + 9 0.441

14 Sand 25 + 9 19 + 7 0.728

16 Sand 9 + 4 11 + 6 0.988

Group: Amphipoda

4 Silt 0 + 0 0 + 0 -

7 Silt 1 + 0 0 + 0 -

10 Silt 0 + 0 0 + 0 -

13 Sand 76 + 23 71 + 25 0.415

14 Sand 27 + 10 22 + 11 0.153

16 Sand 54 + 24 41 + 13 0.713
3

0

Table 11. Mean density (no./m2 + SE) of major benthic macroinvertebrate groups in 1987/88. Stations in the inner bay were grouped by substrate (I, II, III), and stations in the outer bay were grouped by depth (IV, V, VI). Differences between the groups for the inner and outer bay were tested using ANOVA (ln +1 transformed). ns = not significantly different. 

Group Station

Depth

(m) Substrate Oligochaeta Chironomidae Amphipoda Sphaeriidae Total

Inner BayI 13,14,16,18,28 3.0-4.8 sand/gravel 1,111 + 281 202 + 94 60 + 21 58 + 19 1,441 + 374

II 2,11,22,25,30,35,

58,68,108 4.2-9.0 silty sand 5,870 + 808 2,163 + 801 15 + 7 250 + 49 8,327 + 1,281

III 4,7,10,26,168,278 6.7-11.8 silt 20,954 + 1,909 1,412 + 159 <1 + <1 86 + 19 21,951 + 2,019

P < 0.01 P< 0.01 P < 0.01 P <0.01 P <0.01

Outer BayIV 24,43,57 10-13 silty sand 4,952 + 659 4,559 + 439 117 + 5 385 + 298 10,025 + 84

V 20,45,53,55 16-22 silty sand 3,043 + 300 1,010 + 282 93 + 39 189 + 72 4,337 + 306

VI 23,50 28-30 silty sand 2,304 + 1,094 191 + 44 1,209 + 254 222 + 45 3,982 + 1,159

ns P < 0.01 P < 0.05 ns P < 0.01
31

Table 12. Density of major macroinvertebrate groups in previous surveys conducted in inner 

Saginaw Bay. The value given in parenthesis is the density corrected to Ponar equivalents. 

Correction factors are given in the text. 

Macroinvertebrate Group

Year Station Oligochaeta Chironomidae Sphaeriidae Amphipoda Others Total

Substrate:Silt

 19541 1 5,165 (2,840) 516 (397) 43 0 861 4,141

5 2,152 (1,183) 2,109 (1,623) 22 11 22 2,861

8 5,816 (2,841) 65 (49) 43 22 43 2,998

Mean 2,288 + 553 836 + 787 2,667 + 912

 19552 6 54 (156) 129 (485) 0 86 495 1,222

8 43 (124) 64 (241) 0 0 204 569

9 699 (2,013) 11 (41) 0 0 0 2,054

Mean 764 + 624 256 + 128 1,281 + 430

 19563 7A 916 (2,688) 38 (133) 2,837

60 230 (662) 339 (1,187) 1,901

Mean 1,892 + 1132 660 + 527 2,369 + 468

 19624 2 19,669 (10,818) 0 0 0 0 10,818

 19655 7 8,005 (23,054) 452 (1,700) 22 0 0 24,776

8 10,803 (31,113) 355 (1,335) 22 0 0 32,470

9 26,695 (76,388) 1,388 (5,219) 32 0 0 81,639

10 5,789 (16,672) 398 (1,496) 0 0 0 18,168

11 12,513 (36,037) 1,399 (5,260) 0 0 0 41,279

16 16,215 (46,699) 2,614 (9,898) 11 0 0 56,597

34 8,055 (23,054) 2,486 (9,347) 0 0 0 32,401

35 18,345 (52,834) 1,657 (6,230) 0 0 0 59,064

Mean 38,231 + 6,972 4,692 + 1123 43,302 + 7452

 19716 18 14,956 1,790 0 0 0 16,746

22 12,008 1,338 0 0 0 13,346

23 11,534 749 43 0 0 12,326

28 16,151 1,307 0 22 0 29,806

Mean 13,662 + 1,123 2,499 + 602 14,975 + 1,261

Substrate:Sand

 19541 2 2,313 183 0 0 0 2,496

4 1,560 236 43 0 0 1,839

6 817 193 32 118 1,160

9 2,195 656 75 32 75 3,033

10 4,271 291 0 11 75 4,648

Mean 2,231 + 575 312 + 88 2,635 + 593

 19552 3 4,623 75 108 0 0 4,806

4 8,737 108 32 0 32 8,909

10 312 301 11 176 11 811

11 3,692 570 368 0 43 4,673

14 183 97 334 247 377 1,238

15 1,496 161 463 0 129 2,249

Mean 3,173 + 1332 219 + 78 3,781 + 1,235

 19624 3 4, 648 43 0 0 0 4,691

 19655 28 721 22 0 97 22 862

29 6,681 753 0 43 11 7,488

30 473 355 0 11 22 861

32 3,518 581 0 11 0 4,110

37 3,163 215 0 11 0 7,499

38 8,339 495 0 0 0 8,834

40 6,628 86 0 0 0 6,714

Mean 4,217 + 1,162 358 + 101 5,195 + 1,243

 19716 21 1,689 1,858 0 0 0 3,547

24 1,033 323 0 215 0 1,571

25 4,100 484 0 0 0 4,584

29 1,549 968 43 0 0 2,560

Mean 2,093 + 684 858 + 304 3,066 + 647

1

Surber (1954); 2Surber (1955); 3Schneider (unpublished data); 4Alexander (1963); 5Shannon et al. (1967); 6Batchelder (1973)
32

Appendix 1.

The abundance (number per grab) of all taxa collected 

between 1987 and 1996 with the Ponar grab. Variables in 

the appendix include year, season (spring=1, summer=2, 

fall=3), station, replicate number, and taxa. Individual taxa 

were assigned a 4-letter code as shown in Table 3. 

Data are contained in an MS Excel file at:

ftp://ftp.glerl.noaa.gov/publications/tech_reports/glerl-122.