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Savannah River Ecology
Laboratory
SEASONAL DYNAMICS OF BENTHIC MACROINVERTEBRATES OF
POND B, SAVANNAH RIVER PLANT
AIKEN, SOUTH CAROLINA
APRIL D. WHICKER'
Savannah River Ecology Laboratory
A Publication of the Savannah River National Environmental Research Park
1988
, Present Address: Natural Resource Ecology laboratory
Colorado State University
Ft. Collins, Colorado 80523
TABLE OFCONTENTS
Introduction 1
Study Site 3
Materials and Methods 3
Resu Its 8
Discussion .. . . . . . . . . . . . .. . . .. . . • . .. . . .. . .. . . .. .. . .. . . . . . . . . . . . . . . . . .. 23
SeasonalChanges in Population Densities. . . . . . . . . . . . . . . . . . . . . . . . . . 24
Population Variations with Water Depth 26
Biomassand Diversity 29
Limitations ofthe Data 31
Summary ..... . .. . . .. .. . . ... . .. .. .. . . ... ... . . . . . ... . ... . . .. .. .. .... . • 32
Acknowledgments 33
Literature Cited 35
INTRODUCTION
Invertebrate communities in freshwater lakes and ponds form a complex array
of trophic relationships, life cycles, species compositions, physiological and morpho
logical adaptations, and habitat utilizations. The benthic invert ebrat es are
undeniably of primary importance in supporting populations of many fish and other
aquatic vertebrates. In a small pond in Indiana, for example, Gerking (1962) showed
that fish were able to consume more benthic invertebrates in one month than were
actually present in the standing crop . Thus, invertebrate production rates must
have been very high, even with heavy predation.
In spite of the importance of these essential faunal components, detailed
studies on communities of benthic invertebrates (those invertebrates associated
with unconsolidated substrate) in standing water are few, perhaps because of
difficulties in species identifications (Brigham et al. 1982, Resh and Unzicker 1975)
and in quantifying abundances (Resh 1979, Cumm ins 1962). However, the
environmental or ecological "health " of a lake is frequently assessed by sampling
invertebrate, especially insect, populations to determine changes in species (or taxa)
composition, as evidence of possible responses to pollution or other perturbations
and stresses (Washington 1984, Resh and Unzicker 1975). The rate of recovery of a
body of water after being impacted is also measured by changes in invertebrate
communities.
The Savannah River Plant (SRP) is a nuclear materials production facility in
South Carolina operated by the U.S. Department of Energy. The site has a number
of reservoirs which are used to store and cool water discharged from nuclear
reactors before the water enters streams, swamps, and/or river systems. These
reservoirs can be impacted by elevated water temperatures, radionuclides, and
chemicals. In the case of one such reservoir, commonly known as Pond B, the input
of radionuclide contamination and thermally elevated effluents ceased in 1964 and
1
since that time, this reservoir has been allowed to recover. It is not known how long
is necessary to achieve a dynamic biotic equilibrium after such stress, but Pond B
currently supports at least 19 species of rooted aquatic macrophytes (Parker et al.
1973).14 species of fish (Bennett and McFarlane 1983).2 species of turtles (Parker et
al. 1973), assorted waterfowl, and alligators. Invertebrate populations have not
been quantitatively studied in this reservoir, since prior aquatic invertebrate
research at the SRP has been focused on other bodies of water which still receive
thermal input: Par Pond, Pond C. and the stream systems.
This study was designed to evaluate the spatial and seasonal distributions.
compositions. and abundances of benthic macroinvertebrates in Pond B after 20
years of postthermal recovery. There are both basic and applied uses for the data
gathered during the study. The examination of species composition and abun
dances as a function of season and water depth adds to the base of general
knowledge on the benthic invertebrates of lentic systems. The current species
composition also provides an indication of a portion of the postthermal community
succession. An estimate of the biomass of the benthic community permits a calcula
tion of the radionuclide inventory in th is ecosystem compartment, if average
concentrations are concurrently determined . Suchdata may then be used to predict
food chain transfers to higher consumers and potential export from the ecosystem .
Specific hypotheses tested were : (1) densities of certain benthic invertebrate
communities vary with season, (2)densities of benthic invertebrates vary with water
depth, and (3) the effect of season on invertebrate density depends on water depth
(i .e. there is an interaction between depth and season). Other community
parameters considered were species composition, diversity, and relative biomass by
taxa.
2
STUDY SITE
Pond B isan 87-ha impoundment that was used asa cooling pond from 1961 to
1964 for a nuclear materials production reactor. Since 1964, it has received only
natural subsurface drainage, precipitation, an undetermined amount of subsurface
ground water, and minimal human disturbance. It may be a reasonable model of
other SRP cooling reservoirs twenty years after thermal discharges cease.
The following description of the limnological properties of Pond B is from
Evans et al. (1983). The mean and maximum depths of Pond Bare 4.4 and 12.2 m,
respectively. The impoundment has annual cyclesof thermal stratification, w ith the
summer thermocline occurring at a depth of 6-7 m. The hypolimnion becomes
depleted in oxygen from mid-April until mid-November. The water has a mean pH
of 6.2 and very low concentrations of dissolved nutrients. Large amounts of
dissolved organic matter and high total iron concentration give the system a
" b lackw at er" appearance. Bottom sediments vary from sand and clay
(predominately kaolinite) to organic detritus. At water depths less than 5 rn, there
is a rich assortment of aquatic plants. The more abundant plants include
Nymphoides cordata, Brasenia schreberi, Nymphae odorata, Cabomba caroliniana,
and Utricu/aria itoridene (F. W. Whicker and R. R. Sharitz, pers. comm .). Primary
aquatic vertebrates include fish (largemouth bass, Micropterus salmoides and
yellow bullhead, /eta/urus nata/is), turtles (Pseudemys scripta). the American
alligator (Alligator mississippiensis) (Parker et al. 1973). and numerous species of
waterfowl, the majority of which are winter migrants.
MATERIALS AND METHODS
Pond B was sampled for benthic macroinvertebrates during winter
(February 7-10), spring (May 1-2), and summer (July 3D-August 7) of 1984. A random
sampling, stratified by depth, is considered an efficient and satisfactory mean s of
3
assessing benthic populations (Cummins 1962, Gerking 1962, Cuff and Coleman
1979), and therefore was used to sample Pond B. A map of the shoreline was
marked with numbered points 10 m apart, from which 20 locations were randomly
chosen for sampling (Fig. 1). Four depth zones (strata) were chosen for sampling at
each location (0.5-1.5 m, 2.0-3.0 rn, 3.5-5.5 m, and> 6.0 m). Water levels fluctuated
within the year, so to insure that the sampled substrate would always be under
water, depths less than 0.5 m were not included. A 0.5 m difference between the
boundaries of contours minimized the chance of overlap during sampling. These
sampling intervals roughly corresponded to changes in vegetation distributions
(0.5-3.0 m, littoral; 3.5-5.5 rn, sublittoral ; and > 6.0 m, profundal). Other
comparable studies have used similar depth zones (Ferraris and Wilhm 1977,
Gerking 1962). Additionally, proportional areas in each contour could be
determined from topographic maps made at the time the impoundment was
created .
A numbered stake was placed at each designated location and all sampling
was done on a transect extending toward deeper water, perpend icular to the
shoreline at the stake. Although all 20 locations were used each season, the exact
position of the sampling station, therefore depth within each zone , var ied . This
further randomized sampling within a zone and made it possible to position the
boat at any depth falling within an appropriate contour interval. Although
potentially 80 stations (20 locations, 4 depth zones) could be used, some locations
were in bays, the maximum depths of which did not exceed the shallow zones.
Therefore, only 52 stations were routinely sampled (Fig. 1).
Samples were taken with a Ponar grab, measuring 1S x 15 em. Sampled
substrates varied between sand, sand-clay, and silt. A Ponar grab tends to be an
efficient sampler in most bottom substrates, excluding mud (Downing 1984,
Flannagan 1970, Howmiller 1971). In w inter, two drops of the grab were made at
4
.00
100..0 00
00 0..
0
O'N
POND B. SAVANNAH RIVER PLANT
SOUTH CAROLINA
Figure 1. Sampling locations on Pond B, Savannah River Plant, South Carolina .Tics indicate 20 randomly selected stations, and solid circles representapproximate sampling locations with in depth zones. The first circle is inthe 0.5-1.5 m depth zone (l ittoral), the second is in the 2.0-3.0 m zone(l ittoral), the third is in the 3.5-5.5 m zone (subl ittoral), and the fou rth is> 6.0 m (profundal) .
5
each station; but because the variability between locations within a zone was
greater than the variability between drops, only one drop was made in subsequent
seasons. When the number of samples that can be processed is restricted, use of a
single sample per location is generally considered adequate for estimating density,
especially of abundant organisms (Cuff and Coleman 1979, Deevey 1941). Density
of macroinvertebrates was expressed as numbers per square meter of benthos
sampled.
Vegetation and benthic material brought up in the Ponar were immediately
washed through a No. 30 (590 micron) U.S. Standard Sieve. The U.S. Environmental
Protection Agency (EPA) has defined macroinvertebrates as those organisms which
are reta ined by this size sieve (Weber 1973). Washed material was placed into a
polyethylene bag and covered with 80% ethanol. 8ags were stored for later
sorting, which was completed within two months. In the laboratory, benthic
material was again washed and the remaining material was sorted by hand for
organisms. Invertebrates were stored in vials w ith ethanol for counting and ident i
fication . Taxonomic keys used for identification were primarily those of Brigham et
al. (1982), Pennak (1978), Usinger (1956), and Wood (1982). Identifications were
made to "reasonable" taxa, considering the availability and completeness of keys,
ages of instars, and sample preparation that would be necessary to further refine
the classifications .
Estimates of mean dry mass per individual were made for most taxa for each
season. All invertebrates were oven-dried 24 h at 60°C before weighing. Weights
were obtained using an analytical balance and recorded to the nearest 0.1 mg.
Depending on size of the animal and availability of specimens, members of a taxa
were either weighed individually or composited . A composited sample could
represent two to several hundred individuals for which a mean mass per ind ividual
was calculated . Frequently, several composited samples could be obtained per ta xa;
6
for these, a weighted mean mass was calculated from the proportional number of
animals in each composited sample. Both shells and soft parts were included in snail
weights. Masses of some uncommon taxa, represented by a very few small
individuals (such asOrthrotrichia), could not be estimated.
From the above information on invertebrate density and mass and the area of
the lake in each depth zone, biomass could be estimated for each depth zone, as
well as for the entire lake. In making these estimates, the 0.5 m increments that
were not included in the sampling were accounted for in biomass estimates of the
lake.
Diversity was calculated using the Shannon-Wiener formula:
H' = -E(Pi)(1 n Pi)
where Pi indicates the proportion of total samples belonging to the ith taxa (Krebs
1978). Although the Shannon-Wiener index may not be considered by some to be
the best measure of diversity for aquatic systems (Washington 1984), it is widely
used and generally understood, and the EPA recommends using a modified
Shannon-Wiener to estimate mean diversity in aquatic stud ies (Weber 1973). In this
paper, the index is being used only to investigate patterns of diversity within one
system.
Two-way analyses of variance (SPSS: MANOVA, Hull and Nie 1981) were used
to test for differences in mean abundances by depth and season for total
invertebrates and for the most common taxa (Chaoborus, Ceratopogonidae,
Chironimidae, and Amphipoda) . The following were investigated : main effects of
depth and season, interactions of depth with season, simple effects of density
changes within a season by depth zone, and changes w ith in a depth zone across
each season. The data required natural logarithmic transformations to reduce the
nonhomogeneity of variances before analyses were conducted . Statistical
significance is reported using p < 0.05.
7
RESULTS
Forty taxonomic groups of macroinvertebrates representing 10,400 indiv iduals
were identified during the three seasons of sampling in Pond B (Table 1).
The abundances of benthic macroinvertebrates var ied both among depth
contours and seasons (Tables 2, 3, and 4). In general, the densities of individuals
in a taxon declined with increasing water depth w ithin a season, asdid the number
of taxa found. A summary of density estimates by major taxa (Table 5) shows clearly
the changes w ith season and depth. In winter, although 33 taxa were identified at
0.5-1.5 m, only the annelids, amphipods, and dipteran larvae were found at the
deepest contour (Tables 2, 5). By spring, amphipods were no longer found in the
deep water (Tables 3, 5), and by summer, only dipterans occurred in the deep water
zone (Tables 4, 5).
The primary exception to declining densities w ith depth was among the
dipterans. In each season, densities of Chaoborus (phantom midges) increased
significantly by factors of 15-80 with increasing depth (Table 6). An overall increase
in total invertebrate numbers with increasing water depth (Fig. 2, Table 5) was
primarily due to sign ificant increases in Chaoborus in all seasons. However,
Chaoborus did not show significant changes in densities in the shallowest and
deepest water zones across seasons (Table 6). Densities of Ceratopogonidae (biting
midges) did not change significantly with water depth in any season (Table 6), but
did show significant seasonal decreases. Bysummer, this group was nearly absent at
all depths (Table 4). Although chironomids (nonbiting midges) did not change
significantly with depth in w inter (Table 6), they showed a fourfold increase in
density with depth by spring. Chironomids also exhibited significantly declining
densities from winter through summer.
8
Table 1. Summary of taxonomic classifications of macroinvertebrates identifiedduring the benthic sampling of Pond B during 1984.
PHYLUM PLATYHELMINTHES
Class Turbellaria
PHYLUM ANNELIDA
Class Oligochaeta
Class Hirudinea
PHYLUM MOLLUSCA
Class GastropodaFamily Planorbidae
Helisoma ancepsHelisoma trivolvisMenetus
Family PhysidaePhyse/la heterostropha
PHYLUM ARTHROPODA
Class Amphipoda
Class Hydracarina
Class InsectaOrder Diptera
Family CeratopogonidaeFamily Chaoboridae
ChaoborusFamily ChironomidaeFamily Tabanidae
ChrysopsOrder Coleoptera
Family CurculionidaeFamily Oytiscidae
CelinaHydroporus-HygotusI/ybius
Family HydrophilidaeBerosus
Family ChrysomelidaeDonacia
Family HaliplidaeHaliplus
9
Table 1. Continued
Order TrichopteraFamily Polycentropodidae
PolycentropusFamily Leptoceridae
OecetisFamily Hydroptilidae
OxyethiraOrthrichia
Family PhryganeinaeAgrypnia
Order LepidopteraFamily Pyralidae
EoparargyractisParapoynx
Order EphemeropteraFamily Leptophlebiidae
ParaleptophlebiaFamily Caenidae
CaenisOrder Odonata
Suborder ZygopteraFamily Lestidae
LestesFamily Coenagrionidae
ArgiaEnallagmaIschnura
Suborder An isopteraFamily Corduliidae
EpicorduliaTetragoneuria
Family LibellulidaeCelithemisErythemisPerithemisPachidiplaxLadona
10
Table 2. Winter densi~je~ (number of. individualslm2 of substrate) of majortaxa of benthic Invertebrates 10 Pond B. Numbers in parentheses areone standard error of the mean.
DEPTH (m) 0.5-1.5 2.0-3.0 3.5-5.5 >6.0NUMBER OF STAnONS (N) 20 16 9 7
Turbellaria 8 (4) 0 0 0Oligochaeta 77 (42) 6 (3) 7 (5) 6 (6)Hirudinea 23 (13) 4(3) 0 0Helisoma anceps 33 (13) 76 (31) 15 (5) 0Helisoma trivolvis 4 (4) 0 0 0Menetus 1 (1) 1(1) 0 0Physella heterostropha 30(11) 25 (14) 2 (2) 0Amphipoda 600(111) 114 (22) 37 (11) 3 (3)Hydracarina 1(1) 13 (6) 15 (10) 0Ceratopogonidae 217(78) 104 (26) 106 (37) 114 (55)Chaoborus 141(128) 635 (276) 600(163) 2203 (776)Chironomidae 2210 (226) 1808 (304) 1654 (290) 2168 (432)Chrysops 37 (9) 1(1) 0 0Curculionidae 12 (9) 0 0 0Celina 31(20) 0 0 0Hydroporus-Hygotus 0 4 (2) 0 0lIybius 2 (2) 0 0 0Berosus 12 (6) 0 0 0
Donada 9 (5) 0 0 0
Haliplus 0 1 (1) 0 0
Polycentropus 221(58) 50 (20) 2 (2) 0
Oecetis 66 (18) 32 (12) 12 (10) 0
Oxyethira 3 (2) 0 0 0
Orthrichia 0 0 0 0
Agrypnia 1 (1) 0 0 0
Eoparargyractis 8 (4) 22 (10) 2 (2) 0
Parapoynx 2 (2) 0 0 0
Paraleptophlebia 14 (5) 0 0 0
Caenis 7 (4) 1 (1) 0 0
Lestes 1 (1) 6 (3) 0 0
Argia 1 (1) 0 0 0
Enallagma 33 (12) 25 (8) 0 0
Ischnura 0 0 0 0
Epicordulia 0 0 2 (2) 0
Tetragoneuria 1 (1) 3 (2) 0 0
Celithemis 80 (12) 15 (5) 15 (6) 0
Erythemis 1 (1) 0 0 0
Perithemis 0 0 0 0
Pachidiplax 32 (9) 1 (1) 0 0
Ladona 0 0 0 0
11
Table 3. Spring densities (number of individualslm2 of substrate) of majortaxa of benthic invertebrates in Pond B. Numbers in parentheses areone standard error of the mean.
DEPTH em) 0.5 -1.5 2.0-3 .0 3.5-5.5 >G.ONUMBER OFSTATIONS IN) 20 16 8 7
Turbellaria 0 0 0 0Oligochaeta 33 (24) 14 (5) G(G) 19 (B)Hirudinea 9 (7) 3 (3) 0 0Helisoma anceps 13 (7) 22 (10) 11 (7) 0Helisoma trivolvis 2 (2) 0 0 0Menetus 0 0 0 0Physel/a heterostropha 7 (4) 19 (8) 0 0Amphipoda 87 (28) 94 (31) 78 (37) 0Hydracarina 0 0 0 0Ceratopogonidae 42 (13) 39 (19) 22 (17) 25 (19)Chaoborus 29 (20) 194 (99) 289 (78) 1048 (321)Chironomidae 480{11G) 331 (GO) 822 (35G) 19G8 (5GO)Chrysops 9 (5) 3 (3) 0 0Curculionidae 7 (4) 3 (3) 0 0Celina 1G (7) 0 0 0Hydroporus-Hygotus 0 0 0 0I/ybius 0 0 0 0Berosus 2 (2) 0 0 0Donacia 7 (4) 3 (3) 0 0Haliplus 0 0 0 0Polycentropus 100 (35) 56 (21) 0 0Oecetis 11 (5) 8 (6) 11 (7) 0Oxyethira 9 (G) 0 0 0Orthrichia 2 (2) 0 0 0Agrypnia 0 0 0 0Eoparargyractis 2 (2) 0 0 0Parapoynx 0 0 0 0Paraleptophlebia 0 0 0 0Caenis 4 (3) 3 (3) 0 0Lestes 2 (2) 0 0 0Argia 0 0 0 0Enal/agma 7 (4) 3 (3) G(G) 0Ischnura 0 3 (3) 0 0Epicordulia 0 0 0 0Tetragoneuria 0 0 0 0Celithemis 33 (14) 39 (12) G(G) 0Erythemis 0 0 0 0Perithemis 0 0 0 0Pachidiplax 2 (2) 0 0 0Ladona 0 0 0 0
12
Table 4. Summer densities (number of individualslm2 of substrate) of majortaxa of benthic invertebrates in Pond B. Numbers in parentheses areone standard error of the mean.
DEPTH (m) 0.5-1.5 2.0-3.0 3.5-5.5 >6.0NUMBER OFSTATIONS (N) 20 16 8 6
Turbellaria 0 0 0 0Oligochaeta 0 17 (9) 0 0Hirudinea 4 (3) 0 0 0Helisoma anceps 7 (4) 19 (10) 0 0Helisoma trivolvis 2 (2) 3 (3) 0 0Menetus 0 0 0 0Physella heterostropha 7 (7) 8 (6) 0 0Amphipoda 82 (26) 58 (26) 0 0Hydracarina 0 0 0 0Ceratopogonidae 2 (2) 0 11 (7) 0Chaoborus 27 (8) 186 (44) 1055 (293) 2103 (867)Chironomidae 233 (88) 81 (21) 56 (25) 259 (35)Chrysops 7 (4) 3 (3) 0 0Curculionidae 29 (10) 0 0 0Celina 49 (23) 0 0 0Hydroporus-Hygotus 0 0 0 0lIybius 0 0 0 0Berosus 0 0 0 0Donacia 4 (3) 0 0 0Haliplus 0 0 0 0Polycentropus 16(11} 0 0 0Oecetis 2 (2) 0 0 0Oxyethira 2 (2) 3 (3) 0 0Orthrich ia 0 0 0 0Agrypnia 0 0 0 0Eoparargyractis 0 0 0 0Parapoynx 4 (3) 0 0 0Paraleptophlebia 0 0 0 0Caenis 0 3 (3) 0 0Lestes 0 3 (3) 0 0Argia 0 0 0 0Enallagma 13 (7) 22 (8) 0 0Ischnura 0 0 0 0Epicordulia 0 0 0 0Tetragoneuria 0 0 0 0Celithemis 9 (5) 8 (8) 0 0Erythemis 2 (2) 0 0 0Perithemis 2 (2) 0 0 0Pachidiplax 0 3 (3) 0 0Ladona 2 (2) 0 0 0
13
Table 5. Summary of densities (number of individualslm2) of the major groups ofbenthic invertebrates in Pond B. Numbers in parentheses are onestandard error of the mean.
DEPTH em}
TAXON SEASON 0.5-1.5 2.0-3.0 3.5-5.5 >6.0
Annelida Winter 100 (43) 10 (3) 7 (5) 6 (6)Spring 42 (25) 17 (6) 6 (6) 19 (13)Summer 4 (1) 17 (9) 0 0
Gastropoda Winter 69 (21) 103 (44) 17 (5) 0Spring 22 (8) 41 (14) 22 (17) 0Summer 16 (9) 31 (13) 0 0
Amphipoda Winter 600 (111) 114 (22) 37 (11) 3 (3)Spring 87 (28) 94 (31) 78 (37) 0Summer 82 (26) 58 (26) 0 0
Diptera Winter 2605 (269) 2548 (435) 2385 (315) 4485 (632)Spring 560 (127) 564 (103) 1117 (343) 3041 (580)Summer 269 (88) 270 (54) 1122(313) 2362 (861)
Coleoptera Winter 66 (25) 10 (6) 0 0Spring 32 (12) 6 (4) 0 0Summer 82 (24) 0 0 0
Trichoptera Winter 282 (66) 82 (24) 15 (12) 0Spring 122 (37) 64 (21) 11 (11) 0Summer 20 (11) 3 (3) 0 0
Lepidoptera Winter 10 22 2 (2) 0Spring 2 0 0 0Summer 4 0 0 0
Ephemeroptera Winter 7 1 (1) 0 0Spring 4 3 (3) 0 0Summer 0 3 (3) 0 0
Odonata Winter 151 (20) 51 (12) 17 (7) 0Spring 44 (14) 45 (12) 12(11) 0Summer 28 (12) 39 (17) 0 0
14
Table 6. Results of two-way analyses of variance for changes in densities(number/m2) of total invertebrates and several major taxa from Pond B.Main effects of depth zone and season, interactions, and simple effects ofdifferent zones within one season and of one zone across seasons areconsidered. Significance levels are indicated for p < 0.05 as ", p < 0.01 as**, and not significant (p > 0.05) asns.
TAXA OF BENTHIC INVERTEBRATES
SOURCE OF Total Amphi- CeratfJ- Chaoborus ChironomidaeVARIATION poda pogomdae
Main effects:
Depth zone ** ** ns ** **Season ** ** ** ** **
Interaction:
Zone by season ** ** ns ns *
Simple effects:
Change in number byzone within season :
Winter ns ** ns ** nsSpring ** ns ns ** **
Summer ** * ns ** **
Change in number byseason within
a zone:
Zone 0.5-1.5 m ** ** ** ns **Zone 2.0-3.0 m ** * ** ** **Zone 3.5-5.5 m ** ns ** ** **Zone> 6.0 m ** ns **ns ns
15
SUMMER
± I SE
SPRING
2 3 4
WINTER
o
N~ 5000
!13~
~4oo0IIIUl~
0:Ul
~ 3000o0:
~:E
2000II.a
>- jlJIIIIIII 11!::~ 1000
DEPTH ZONE
Figure 2. Changes in density of all benthic macroinvertebrates in Pond B during1984. Depth zones are 1: 0.5-1.5 m, 2: 2.0-3.0 m, 3: 3.5-5.5 m, and4: > 6.0 m.
16
Densities of total invertebrates showed significant differences due to the
combined effects of season and water depth (Table 6). When the data were
analyzed for simple effects, the densities were not significantly different among
zones in winter and the densities in the deepest zone did not change significantly
with season. However, densities decreased in the other zones w ith season and
differences in densities occurred among zones in spring and summer.
Among the insects, the dipterans were most abundant in all seasons, followed
by: (1) the Trichoptera (caddisflies), represented by Polycentropus and Oecetis, (2)
the Odonata (damsel- and dragonfl ies), primarily Enallagma and Celithemis,
respectively, and (3) the Coleoptera (beetles), primarily Celina. The decrease in
abundance with depth was obvious within these groups (Tables 2-5). From winter
to summer, trichopterans and odonates showed major declines in population
numbers; however, beetles appeared to maintain more stable population numbers
across seasons. Other major invertebrate groups (Annelida, Gastropoda, and
Amphipoda) followed patterns of population change similar to those of insects
other than dipterans. Snailswere the only molluscs found . Britton and Fuller (1979)
recorded Anodonta asthe only clam occurring in Pond B.
Not only did densities of individuals in a taxa usually decl ine by season and
with depth, but the number of taxa represented in the sampling declined (Table 7).
Because the winter collection had two samples taken at each station (104 samples),
the number of taxa in each set of 52 samples is shown separately. Combin ing
sample sets increased the taxa represented by 0-3 taxa per depth because the
doubled sample effort only slightly increased the probability of encountering very
rare species.
Diversity declined with depth in all seasons, but spring and summ er diversities
exceeded that of winter in the shallower zones (Fig. 3). The greatest changes in
diversity with depth occurred in summer, when only dipterans were found in the
17
Table 7. Numbers of taxa of benthic macroinvertebrates identified in each depthzone in Pond B. Two numbers in winter indicate numbers of taxa fromeach of two drops of the dredge.
DEPTH (m)SEASON 0.5-1.5 2.0-3.0 3.5-5.5 >6.0
Winter 33,26 17,20 11, 13 4,5
Spring 24 17 9 4
Summer 21 14 3 2
deepest zones. Therefore, although both numbers of individuals and taxa were
higher in winter, by spring and summer there was a more even distribution of
ind ividuals among those taxa, especially in the shallower zones.
The mean estimate of mass per individual animal for each taxa (Table 8) was
multiplied by the appropriate density estimates (Tables 2, 3 and 4) and the results
summed across taxa by season and depth to obta in estimates of biomass per unit
area (Fig. 4). In winter and summer, biomass declined by over 40 % from the
shallowest to the deepest water. Within a zone, biomass decl ined approximately
75% from winter through summer. Biomass estimates in the shallow zones were
similar in spring and summer; however, biomass increased in the deepest zone in
spring. Although total density increased somewhat in the deeper water (Fig. 2), the
animals causing th is increase were very small (Chaoborus and chironomids; Table 8)
and thus did not greatly increase biomass in deep water (Fig . 4).
Although some groups of animals were relatively abundant (e.g. trichopterans
and amphipods; Table 5), their contribution to the biomass at any particular time
was very small (Fig. 5). Two groups of animals, snails and odonates, had small
18
2.0
1.8.... 1.8...c
~ ~4..c..!i 1.2
Ic0c 1.0ca.c:I/)
.8-)-
t: .6I/)a::w
A>is
.2
0234
WINTER234
SPRING
DEPTH ZONE
234SUMMER
Figure 3. Changes in macroinvertebrate d iversity among seasons (1984) andwater depths in Pond B. Depth zones are 1: 0.5-1.5 rn, 2 : 2.0-3.0 m,3: 3.5-5.5 m, and 4: > 6.0 m.
19
Table 8. Estimates of dry mass (mg/individual) by taxa of benthicinvertebrates from Pond B. "T" Indicates traceamounts, but not enough mass or individuals to obtainestimates of weight.
TAXONOMICCLASSIFICATION
TurbellariaOfigochaetaHirudineaHelisoma ancepsHelisoma trivolvisMenetusPhysella heterostrophaAmphipodaHydracarinaCeratopogonidaeChaoborusChironomidaeChrysopsCurculionidaeCelinaHydroporus-HygotuslIybiusBerosusDonaciaHaliplusPolycentropusOecetisOxyeth iraOrthrichiaAgrypniaEoparargyractisParapoynxParaleptophlebiaCaenisLestesArgiaEnal/agmaIschnuraEpicorduliaTetragoneuriaCelithemisErythemisPerithemisPachidiplaxLadona
WINTER0.270.611.658.03
31.601.552.060.090.200.220.070.234.670.210.100.33
17.45.67
7.76T
0.160.26
To
12.350.370.700.780.091.203.051.19o
11.107.771.59
19.801.50.93o
20
SPRINGo
0.691.386.022.00o
2.680.09o
0.170.120.301.630.230.17ooT
0.50o
0.190.11
TToTooT
3.60o
1.083.10oo
3.00oo
1.70o
SUMMERo
0.35T
5.2519.50
o1.780.07oT
0.080.10
35 .330.480.19ooo
0.10oTTTTooToT
0 .40o
0.58ooo
0.23T
0.601.401.80
2.0
1.8
1.6
~
N 1.4E<,0 1.2>..."0 1.0-(J)(J) .8<l:~0 .6Ul
.4
.2
02 3 4
WINTER234
SPRING
DEPTH ZONE
2 3 4
SUMMER
Figure 4. Estimate of biomass of ben thic macroinvertebrates per unit area inPond B. Depth zones are 1: 0.5-1.5 rn, 2: 2.0-3.0 m, 3: 3.5-5.5 rn, and4 : > 6.0m.
21
WINTER
Cl'llronomldo•
e e.c1.0-10
SUMMER
'1.0
Otl'llf Dipt.,o
O.S.Ul
2.0->.0 5,S·D.II
DEPTH ZONE 1m)
100
.0
eo
<0
20
0'''0
Ctlironom ldll.
..!lIOO...
~OOIii
110.,.,..,.~40..0...z'" 20u
'"'t0
0.5-1.15
SPRING
DEPTH ZONE (m) OEPTH ZONE (m)
Figure 5. Changes in relative composit ions of macroinvertebrate biomass duringdifferent seasonsand at different depths in Pond B.
22
populations, but comprised 30-60% of the biomass (per unit area) in all but the
deepest zone . The snails showed proportionally high biomass becauseboth the soft
body tissue and the external shell were used to estimate mass. Odonates, especially
dragonfly larvae, while perhaps not as heavy as beetle or larger caddisfly larvae
(Table 8), were much more abundant. At the deeper stat ions, Chaoborus and
chironomids dominated in both numbers and biomass. The 40-60% of biomass
shown as "other dipterans" in summer (Fig. 5) was due exclusively to the presence
of several large deerfly (Chrysops) larvae. Although Chrysops had been present in
greater numbers in winter and spring (Tables 2 and 3), its mass increased by a factor
of7 in summer.
Biomass estimates per unit area were combined by area of the lake within
individual depth contours. These values were then weighted by the proportion of
the lake comprised by that contour and summed to estimate total biomass for the
entire lake (Table 9). For the lake as a whole, the littoral zone had the greatest
biomass, followed by the profundal zone. The sublittoral usually showed declines in
density and biomass of most major invertebrate groups that were common in
shallow water (Table 5), but did not show the increases in density and biomass of
dipterans that characterized the greatest depths. Biomass declined from winter
through summer over the entire lake .
DISCUSSION
Deta iled studies on communit ies of benthic macroinvertebrates are
uncommon in lentic ecosystems, but compared to the few studies conducted in
various locations of the United States, Pond B is fairly typical in terms of animal
density, biomass,spatial distributions, and representative taxa .
23
Table 9. Biomassestimates of benthic macroinvertebrates from Pond B. Theareas between zones were included in the biomass estimates.
DEPTH AREA INVERTEBRATE BIOMASS(DRY KG)ZONE (m) (ha) WINTER SPRING SUMMER
Littoral 0-2.0 26 458 120 104
Littoral 2.0-3.5 15 192 72 50
Sublittoral 3.5-6.0 19 116 74 17
Profundal > 6.0 27 184 197 46
TOTAL 87 950 463 217
Seasonal Changes in Population Densities
Documentation of complete seasonal cycles of benthic macroinvertebrate
populations is rare. Of the few comprehensive studies done on the composition and
abundance of invertebrates, most have been carried out on a single lake and only
during spring and summer (Mittelbach 1981, Gerk ing 1962, Ferraris and W ilhm
1977), although the most extensive study (Deevey 1941) was conducted on 36 lakes
over a period of three years. However, even in that study, only one lake (Linsley
Pond) was sampled monthly for 14 months, and sampling was only done in the
sublittoral and profundal zones. Deevey states that, "In all lak es which have been
carefully studied, maximum populations have been observed in the winter, ...
minimum in the spring or early summer." Invertebrates of Linsley Pond generally
followed th is pattern. Mittelbach (1981) and Ferraris and Wilhm (1977) found both
declining numbers and biomass from spring through August. In an Ok lahoma
reservoir with similar depths and Iimnological characteristics of Pond B, Ferraris and
24
Wilhm (1977) estimated population ranges of 144-16,639 organismslm2 in March
and 114-4686 organisms/m2 in July and August. Over a two-year period in a shallow
pond in Minnesota, Dineen (1953) found densities of benthic invertebrates to be
300-500 organismslm2 in spring to 800-4200 organismslm2 in fall and winter. In
South Carolina at Par Pond on the Savannah River Plant, Thorp and Bergey (1981)
found seasonal population densities of 14,000 organismslm2 in December, 6000
organismslm2 in April, and increasing to 12,000 organisms/m2 again in August.
Macroinvertebrate densities of Pond B declined dramatically by season and
were well within these published ranges with winter densities of 3000 to 4500
organisms/m2, spring densities of 900-3000 organisms/m2 and summer densities of
400-2300 organismslm2. Similar values for Pond B have been recent ly reported by
Kondratieff (1985) . These numbers are considerably lower than estimates of
benthic invertebrates in Par Pond (Thorp and Bergey 1981). That study, however,
was only conducted at depths less than one meter and included much smaller
organisms than are usually included in other such studies.
The decline in numbers by season is commonly attributed to the emergence of
overwintering larvae of aquatic insects (M ittelbach 1981, Deevey 1941) . Many
aquatic insects have a one-year life cycle and overwinter as larvae, and then emerge
as adults in spring and/or summer. Adults then become reproductively active, lay
eggs, and the larvae emerge. The tiny larvae may start appearing in mid- to late
summer and fall, but they may be difficult to find when sampling. As the larvae
grow, larger ones are likely to be sampled. thus fall and winter densities increase.
Another factor in seasonal sampling is the change in water temperature and
chemistry (Jonasson 1978). Most southern lakes achieve a very distinct thermal
stratification during the summer. This results in little mixing between the shallow
warm water and the deeper cooler water. Oxygen depletion usually occurs at the
deeper depths and water at those depths may become hypoxic. Some organisms
25
will not be able to survive such low oxygen levels or chemical changes and thus will
migrate or die (Deevey 1941). After an artificial thermal and chemical
destratification was conducted in summer on an Oklahoma reservoir, densities and
diversities of invertebrates actually increased in the deep water (Ferraris and Wilhm
1977). Pond Bhas been shown to stratify thermally and exhibit oxygen depletion at
deeper depths (Evan et al. 1983).
Gerking (1962) attributed a decline in bottom invertebrates from July to
August to predation by fish . Bluegills in this Ind iana pond were considered to be
highly efficient at cropping invertebrates, and seasonal changes in bluegill
population dynamics and foraging behavior heavily impacted the bottom fauna.
Mittelbach (1981) offered some support for this hypothesis with studies on prey size
and seasonal util ization by blueg ills in a Michigan pond. However, Thorp and
Bergey (1981) did not find appreciable differences in invertebrate populations
between control sites and experimental sites from which fish and turtles were
excluded.
Other factors that could influence benth ic population sampling are changes in
aquatic plant biomass and structure. Increased plant abundance in summer may
decrease the substrate collection efficiency and also prov ide protection for
escaping, mobile invertebrates, thus lowering apparent densities.
Population Variations with Water Depth
In his description of the vertical distribution of organisms along depth
gradients, Deevey (1941) described a "sublittoral minimum" condition in which the
number of organisms was least in the middepth zones (sublittoral) and greatest in
the shallow (littoral) and deeper water (profundal) zones. Deevey suggested that
the sublittoral minimum may be caused in part by predation by fish because (a) the
vegetation in the littoral provided invertebrates with protection from fish and (b)
26
the oxygen depletion and depth of the profundal excluded fish . Therefore, the
heaviest predation occurred in the sublittoral, severely reducing the invertebrates.
Gerking (1962) also found the greatest numbers of animals at the 0-2 m and> 6 m
depths, and fewer animals in the 2-4 m and 4-6 m depths. He felt this was a
"sublittoral minimum" and described it as a zone in which the habitat provided by
the flocculent plants was not as favorable asthat of the littoral or profundal zones,
and thus was not capable of supporting dense populations. Ferraris and Wilhm
(1977) observed that 3-5 m depths were less densely populated than either the
littoral and profunda!. For a Danish lake, Jonasson (1978) reported a decrease in
invertebrate densities in the transition zone between littoral and sublittoral, and
then an increase in densities from the sublittoral to the profunda!.
In Pond B,the minimum number of animals was at a middepth zone, and then
increased again at the deepest stations. In winter, the minimum was at the 3.5-5.5
m depth, and in spring and summer at the 2.0-3.0 m depth . Analyses of variance
indicated that, unlike spring and summer densities, winter densities did not differ
across zones. The greatest densities were clearly in the profundal zone, but it was
not clear whether or not the littoral was more productive than any sublittoral zone
in Pond B. Gerking (1962) similarly failed to find statistically significant differences
in populations by depth (almost identical depths used in Pond B), but he believed
that "the similarity in the quantities of bottom fauna in the littoral and profundal
zones masked the effect of the sublittoral in the analysis of variance" and that real
differences did occur among the four depth zones. This might also be true of the
winter densities in Pond B.
Pond Bshowed depth-faunal relationsh ips typical of similar lakes. However, as
observed by Thorp and Diggins (1982), this is not a simple inverse relationship
between density and depth. There are some differences in behavior among taxa.
27
In general, changes in macroinvertebrate densities in Pond B with depth could
be attributed to the declining numbers of individuals, and the eventual elimination,
of most taxa with depth. New taxa (at least at the resolution level used in this
study) did not appear at depth; rathe r populations there were extensions of
populations occurring in shallower zones. Only a few taxa are adapted to live in the
profundal zone, but those animals that can seem to flourish . At about 6 m,
Chaoborus increased dramatically, thereby increasing total density. Chaoborus was
the only group of organ isms that significantly increased by depth in each season
studied. This increase of Chaoborus, and usually only Chaoborus, in deep water has
been observed in several other locations (Ferraris and Wilhm 1977, Deevey 1941,
Thorp and Diggins 1982).
An earlier study (Thorp and Diggins 1982) conducted on Par Pond, SRP, during
the winter and spring and at similar depths, found very similar trends at their
control sites for the major taxonomic groups. The dominant odonates (Celithemis
and Enallagma) in Par Pond were also those of Pond B and all odonates had greater
densities at depths <2 m. Dens ities of the Ceratopogonidae were evenly
d istributed across depth, aswas also observed in Pond B.
Of the macroinvertebrates, the Chironomidae were usually numerically
dominant at all depths sampled in Pond B and also in lakes at other geographic
locations, such as Oklahoma (Ferraris and Wilhm 1977), New York and Connecticut
(Deevey 1941), and South Carolina (Thorp and Bergey 1981, Thorp and Diggins
1982). The Chironomidae exhibited uniform population densities in winter across
depths, but in spring and summer generally increased with depth. Because of the
different generation times of the chironomids, even population data taken at
monthly intervals could show widely fluctuating patterns of densities with depth
(Deevey 1941); therefore, to accurately describe the chironomid populations of
Pond B, more frequent sampling would be necessarythan was possible in this study.
28
Biomass and Diversity
Productivity (mass per area over time) is an important parameter for under
standing trophic relationsh ips and consumer dynamics of a lake (Gerking 1962,
Jonasson 1978). However, because secondary productivity is difficult to measure,
many studies have relied on the more easily measured parameter of standing crop
(biomass, or mass/area) as being indicative of productivity levels. Biomass
comparisons among lakes can thus be made even with single season samples,
although very productive lakes with high turnover rates could exhibit standing
crops similar to those of less productive lakes. Biomass estimates of benthic inverte
brates of Pond B, averaged over the entire area, ranged from 2.5 kg dry wtlha in
summer to 10.3 kg dry wtIha in winter. Since the samples were preserved in alcohol
before drying and weigh ing, there may have been some loss in mass due to the
preservative (Howmiller 1972, Stanford 1973, Down ing 1984). However, most other
studies also share this problem. Gerking (1962) found an average of 11 kg dry wtlha
in July and 6 kg dry wtlha in August for a lake in Indiana. This lake was only 3 ha
and fairly shallow, and would be expected to be more productive on the average
than Pond B. For 36 lakes, Deevey (1941) reported summer values of 11 to 348
kg/ha, wet weight. Assuming water contents of 80-90 %, these values are probably
5-10 times higher than the equivalent dry weight. Mittelbach (1981) summarized
biomass estimates for vegetated littoral zones from several studies as 4-36 kg dry
wtIha and reported his own estimates as rang ing from 15 kg dry wtIha in May to 8
kg dry wtlha in August. The littoral area of Pond B ranged from 4 kg dry wtlha in
summer to 15 kg dry wtIha in winter. In a similar study on Pond B and Par Pond,
Kondratieff (1985) reported seasonal mean bio mass of 5 kg/ha and 34.9 kg/ha,
respectively, averaged over all depths.
29
As with some other lakes (M ittelbach 1981, Ferraris and Wilhm 1977), Pond B
generally showed decreasing biomass with increasing depth (Fig . 4). Even though
invertebrate density was greater in the deepest waters, it was comprised of very
small organisms which did not contribute greatly to the biomass. However, when
the area of the lake in each zone was considered, the profundal contained more
biomass than the sublittoral (Table 9). A different pattern of biomass with depth
has been shown with Jonassen's (1978) work on a Danish lake in which biomass
increased with depth from 0-10 m, then decreased at depths >10 m.
Diversity (Shannon-Wiener Index) is a combined measure of the number of
species or taxa and their relative contributions to the total number of individuals.
Communities comprised of many species but with only one or two species
representing the vast majority of ind ividuals are not very diverse. However, a more
diverse community has many specieswith a good representation of individuals from
many taxa (higher "evenness" ). Since the diversity index is a relative measure,
patterns can be compared across communities, with respect to t ime (season) and
space (depth). Ferraris and Wilhm (1977) found decreasing diversity with depth
over the range of 1-8 m in late summer which they attributed to a decrease in the
number of species and an increase in Chaoborus. Similarly, in Pond B, diversity
declined w ith depth for all seasons (Fig. 3) (also, Kondratieff 1985), because an
increasingly larger proportion of the individuals were from only one or two taxa .
Chaoborus increased w ith depth as did chironomids, except in winter, but most
other taxa d isappeared at depths. However, in the shallow water «3.0 m)
diversity generally increased from winter through summer. Although density
decreased in these contours through time (Fig. 2), the proportion of individuals per
taxa became more balanced (Tables 1,2,3) because the Chironomidae showed such
marked declines from w inter through summer. Hence diversity increased.
30
Related to diversity, but not accounting for abundance in any way, was the
number of taxa represented in an area. This could be a simple and straightforward
measure of change in a system. Pond B clearly showed fewer different kinds of
animals in progressively deeper water and from winter through summer. Similar
trends were found in an Oklahoma reservoir (Ferraris and Wilhm 1977), and in a
Danish lake (Jonasson 1978) in which 300 specieswere identified in the littoral zone,
50 species in the sublittoral, and less than 20 in the profunda!.
Limitations of the Data
This study provides baseline information on the structure and distribution of
benthic invertebrates in Pond B. However, these data were taken at three-month
intervals, and some changes in community structure could have been overlooked.
The estimates of density and biomass are point estimates in time and the decline
between winter and summer may not have been linear; rather, maxima and minima
may have occurred between sampling periods. However, because processing
benthic samples is so labor intensive, increasing the number of sampling periods to
detect such changes would have been prohibitive. If the goal of the study had been
only to identify which animals were present and how their populations changed
through time, all the sampling could have been concentrated in the most
productive shallow waters. More experimental w;ork could also have allowed
production estimates to be made. These estimates would be important for nutrient,
chemical, or radionuclide cycling studies, and for trophic level and food base
considerations, as large year-to-year variations may occur in benthic populations.
There were a number of sources of potential error and variability in the
estimates of the parameters presented in this paper. In addition to the statistical
error that is inherent in all sampling schemes, there was also error (or bias)
associated with the sampling device, animals' avoidance behavior and spatial
31
distributions, the handsorting of the animals, the estimates of dry mass per
individual (single samples, composite samples), the measurement of the surface
area of the lake, the measurement of the contours of the lake, and potential loss of
mass during preservation in alcohol. There was no way to accurately estimate the
magnitude of these errors ; however, most of these sources of error would be
expected to remain relatively constant across sampling depths and dates.
Therefore, comparisons could still be made across sample groups while observing
trends in the data. It was these trends in the data that were most important to this
study. Comparisons to other studies should also be made with some caution ,
because sampling and sorting methods used among investigators, and physical and
limnological properties of the lakes, may vary.
SUMMARY
Pond B, an 87-ha, 20-yr postthermal reactor cooling impoundment on the
Savannah River Plant , South Carolina, was sampled during three seasons (winter,
spring, and summer, 1984) to measure temporal and spatial variations in density,
biomass, and divers ity of benthic macroinvertebrates. The benthos at 52 stations,
representing four depth zones, were sampled using a Ponar grab. Some 100400
ind ividual organisms were hand-sorted and ident ified to forty taxa, and the mean
dry mass pe r ind ividual was est imated.
The densities of invertebrates generally declined from winter through summer
within each depth zone. In each season, the greatest total densities occurred in the
deepest zone due to the large number of Chaoborus. Standing crop of dry biomass
also decreased from winter through summer. Biomass generally declined with
depth in winter and summer, but not in spring. Major contributions to the total
biomass were shared by many taxa at depths less than 3 m, but the biomass in
sublittoral and profundal was dominated by Chironomidae and Chaoborus.
32
Diversities (Shannon-Wiener Index) decreased markedly with depth in all seasons.
Statistical tests examining differences in the measured parameters among seasons,
sampling depth and their interactions are reported.
These data serve as a measure of the current status of macroinvertebrate
populations in Pond B and as a baseline against which future changes may be
compared as the process of postthermal recovery continues. These data are
probably reasonably representative of other postthermal, softwater reservoirs in
the southeastern region of the United States. The biomass values and trends with
season and depth were, in fact, similar to comparable information from most other
lentic systems reported in the literature. These data from Pond B may also be used
to construct radionuclide inventory estimates for the benthic macroinvertebrate
component of the Pond B ecosystem. Pond B vertebrates such asfish and waterfowl
may depend upon these benthic invertebrates as a food base. Thus, this
information should be useful in the interpretation of ecological and radioecological
studies and in the construction of general energy-flow and radiocontaminant
cycling models for this lake ecosystem.
ACKNOWLEDGMENTS
I would like to thank the people at the Savannah River Ecology Laboratory
who especially encouraged and supported this project: I. Lehr Brisbin, John
Bowling, and John Pinder. Helpful and enthusiastic field and laboratory assistance
were given by Donna Mayer, Yvonne Downs, and Eric Peters. Boris Kondratieff
kindly helped identify the odonate larvae. Jan Hinton typed the final report. A
special and warm thanks go to Barbara Taylor and Ward Whicker. I deeply
appreciate the support that was given to me by James K. Detling during the final
stages of this project.
33
This Pond B project was supported by the Savannah River Ecology Laboratory's
National Environmental Research Park Program, under a contract (DE-AC09
76SROO-819) between the Institute of Ecology of the University of Georgia and the
United States Department of Energy.
34
LITERATURE CITED
Bennett, D. H. and R. W. McFarlane. 1983. The Fishesof the Savannah River Plant:
National Environmental Research Park. Publication (SRO-NERP-12) of the
Savannah River National Environmental Research Park. Aiken, South Carolina.
Brigham, A. R., W. U. Brigham, and A. Gnilka, eds. 1982. Aquatic Insects and
Oligochaetes of North and South Carolina. Midwest Aquatic Enterprises.
Mahomet,lIIinois.
Britton, J. C. and S. L. H. Fuller. 1979. The Freshwater Bivalve Mollusca (Unionidae,
Sphaeriidae, Corbicul idae) of the Savannah River Plant, South Carolina.
Publication (SRO-NERP-3) of the Savannah River National Enviro nment al
Research Park. Aiken, South Carolina.
Cuff, W. and N. Coleman. 1979. Optimal survey design: lessons from a stratified
random sample of macrobenthos. 1.Fish. Res. Board Can. 36:351-361.
Cummins, K. W. 1962. An evaluation of some techniques for the collection and
analysis of benthic samples with special emphasis on lotic waters. Am. MidI.
Nat. 67:477-504.
Deevey, E. S. 1941. Limnological studies in Connecticut VI. The quantity and
composition of the bottom fauna of thirty-six Connecticut and New York
lakes. Ecol. Monogr. 11:413-455.
Dineen, C. F. 1953. An ecolog ical study of a Minnesota pond. Am . MidI. Nat.
50:349-376.
Downing, 1. A. 1984. Sampling the benthos of standing waters. !D.: A Manual on
Methods of the Assessment of Secondary Productivity in Freshwaters, 1. A.
Downing and F. H. Rigler, eds. Blackwell Scientific Publications, Oxford.
Evans, D. W., 1. J. Alberts, and R. A. Clark. 1983. Reversible ion-exchange f ixation of
cesium-137 leading to mobilization from reservoir sediments. Geochim.
Cosmochim. Acta 47 :1041-1049.
35
Ferraris, C and J. Wilhm. 1977. Distribution of benthic macroinvertebrates in an
artificially destratified reservoir. Hydrobiologia 54: 169-176.
Flannagan, J. F. 1970. Efficiencies of various grabs and corers in sampling
freshwater benthos. J.Fish. Res. Board Can. 27: 1691-1700.
Gerking, 5. D. 1962. Production and food utilization in a population of bluegill
sunfish. Ecol. Monogr. 32:31-78.
Howmiller, R. P. 1971. A comparison of the effectiveness of Ekman and Ponar
grabs. Trans. Am. Fish. Soc. 100:560-564.
Howmiller, R. P. 1972. Effects of preservation on weights of some common
macrobenthic invertebrates. Trans. Am. Fish. Soc. 101:743-746.
Hull, C H. and N. H. Nie. 1981. SPSS Update 7-9. McGraw-HilI. New York.
Jonasson, P. M. 1978. Zoobenthos of lakes . Internationale Vereinigung fOr
Theoretische und Angewandte Limnologie 20: 13-37.
Kondratieff, B. C, M. J. Chimney, and W . B. Painter. 1985. Final report on the
macroinvertebrates of Par Pond and Pond B: January 1984-June 1985 ECS-SR
21. Prepared by Environmental & Chemical Sciences, Inc. for E. I. du Pont de
Nemours &Co. Aiken, South Carolina.
Krebs, J. 1978. Ecology, the Experimental Analysis of Distribution and Abundance.
Harper and Row, New York.
Mittelbach, G. G. 1981. Patterns of invertebrate size and abundance in aquatic
habitats. Can. J. Fish. Aquatic Sci. 38:896-904.
Parker, E. D., M. F. Hirshfield, and J. W . Gibbons. 1973. Ecological comparisons of
thermally affected aquatic environments. J.Water Poll. Cont. Fed. 45:726-733.
Pennak, R. W. 1978. Freshwater Invertebrates of the United States, 2nd ed. Wiley
and Sons. New York.
Resh, V. H. 1979. Sampling variability and life history features: basicconsiderations
in the design of aquatic insect studies. J.Fish. Res. Board Can. 36:290-311.
36
Resh, V. H. and J. D. Unzicker. 1975. Water quality monitoring and aquatic
organisms: the importance of species identifications. J. Water Poll. Cont. Fed.
47:9-19.
Stanford, J. A. 1973. A centrifuge method for determining live weights of aquatic
insect larvae, with a note on weight loss in preservative. Ecology 54:449-451.
Thorp, J. H. and E. A. Bergey. 1981. Field experiments on responsesof a freshwater,
benthic macroinvertebrate community to vertebrate predators. Ecology
62:365-375.
Thorp, J. H. and M. R. Diggins. 1982. Factors affecting depth distribution of
dragonflies and other benthic insects in a thermally destabilized reservoir.
Hydrobiologia 87:33-44.
Usinger, R. L. 1956. Aquatic Insects of California . University of California Press.
Berkeley, California.
Washington, H. G. 1984. Diversity, biotic and similarity indices: a review with
special relevance to aquatic ecosystems. Water Res. 18:653-694.
Weber, C. I. (ed.). 1973. Biological field laboratory methods for measuring the
quality of surface waters and effluents. EPA-6701/4-73-001. U.' S.
Environmental Protection Agency. Cincinnati, Ohio.
Wood, D. H. 1982, The Aquatic Snails (Gastropoda) of the Savannah River Plant,
Aiken, South Carolina. Publication (SRO-NERP-10) of the Savannah River
National Environmental Research Park. Aiken, South Carolina.
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