Int. Revue ges. Hydrobiol. I 78 I 1993 I 4 I 481-491

VAN D. CHRIST MAN^ and J. REESE VOSHELL, jr?

Department of Entomology Virginia Polytechnic Institute and State University

Blacksburg, Virginia 24061, USA Correspondence: Department of Biology, Ricks College, Rexburg, ID 83460, USA * Department of Entomology, Virginia Polytechnic Institute and State University, Blacksburg, Vir-

ginia, USA 24061

Changes in the Benthic Macroinvertebrate Community in Two Years of Colonization of New Experimental Ponds

key words: lentic, macroinvertebrate, community, development, succession

Abstract

The objective of this study was to determine if the benthic macroinvertebrate community structure in a set of experimental ponds changed significantly during the second year oftheir existence. This is an important factor in pesticide registration testing using this type of facility. One year has been esta- blished as sufficient time to develop a complete community but this has never been tested. Compari- sonofthecommunityat theendofyear 1 tothecommunityat theendofyear2showednosignificant differences for community summary measures (total density, taxa richness, diversity, Bray-Curtis similarity index); however, some individual taxa densities were signifcantly lower at the end of year 2. Physicochemieal parameters measured indicated that the ponds were oligotrophic. Submer- ged macraphytes colonized and became established in most ofthe ponds during year 2. With the exception of a few noninsect taxa, the experimental pond communities appeared similar to mature communities in shallow lentic environments. Additionally, the seasonal changes observed in the pond communities followed expected patterns.

1. Introduction

Experimental ponds have been used for a long time to study fisheries management (SWINGLE 1947,1950), ecological principles (HALL eta/. 1970), and effects ofvarious pertur- bations (see review in BUIKEMA d: VOSHELL 1992). ODUM (1984) explained the importance of ecological studies in mesocosms, which he defined as ". . . bounded and partially enclo- sed outdoor experimental setups . . . falling between laboratory microcosms and the large, complex, real world macrocosms" (p. 558). Experimental ponds are a type of mesocosm (BUIKEMA VOSHELL 1992), and the U.S. Environmental Protection Agency has begun to require simulated field studies in pond mesocosms as part of registration requirements for some pesticides (TOUART 1988, TOUART & SLIMAK 1989). Benthic macroinvertebrates are some of the organisms most often studied in experimental ponds (BUIKEMA & VOSHELL 1992). When new lentic environments are constructed, benthic macroinvertebrate com- munities undergo changes for a number of years (PATERSON & FERNANDO 1970, STREET & TITMUS 1979, DANELL & SJOBERG 1982, BARNES 1983, VOSHELL dt SIMMONS 1984). Several studies have described the initial colonization of replicate experimental ponds (HOWICK et al. 1992, FERRINGTON et a/. 1992, LAYTON & VOSHELL 1991); however, there have been no extended studies of changes in the benthic macroinvertebrate community, even though such information is important for interpreting the results of any experiment conducted in replicate ponds.

482 V. D. CHRISTMAN and J. R. VOSHELL

The purpose of this study was to describe and explain the changes in benthic macroin- vertebrates that occurred during the first 2 yr in a set ofreplicate experimental ponds. The ponds were not managed except to maintain constant water level and received no experi- mental treatments. There were no fish in the ponds during the study.

2. Methods and Materials

This study was conducted the Virginia Polytechnic Institute and State University experimental pond facility, which is located at the Southern Piedmont Agricultural Experiment Station near Blackstone (longitude 77°57’30’W latitude 3705’30”N). The facilitiy consists of 12 0.04 ha experimen- tal ponds, each measuring 20.1 X 20.1 m at the water surface and holding about 520 m3 of water at a maximum depth of2.l m. The experimental ponds were first filled with water in January 1988. Addi- tional details about the facility can be found in LAYTON (1989), CHRISTMAN (19911, and ~ Y T O N B VOSHELL (1991).

LAYTON & VOSHELL (1991) had already determined the numbers y d kinds of benthic macroinverte- brates that occurred in all ponds during the first year after filling (January 1988 to February 1989). In this study, we chose six ponds randomly and sampled the benthic macroinvertebrates in them from March 1989 to April 1990. We used the same sampling methods (artificial substrates) and analyzed samples taken at the same interval (4wk) as LAYTON & VOSHELL (1991).

An artificial substrate sample was taken from each pond on each sampling date to obtain a quanti- tative sample of benthic macroinvertebrates. The samplers were 10.8 cm tall X 12.2 cm diameter, round plastic buckets with 3.8 cm holes drilled in the top and sides. A 1.5 cm layer of topsoil from the site was placed in the bottom of each sampler, and seven 5 cm diameter surface enhancers (tri-pack units, Jaeger Products Inc., Houston, Texas) were placed above the soil. Each sampler simulated appmximately0.01 m20fpond bottom. We placed enough samplers for theentire year in March 1989 and allowed them to colonize for 30 d before retrieving the first ones. The samplers retrieved in March 1989 had been placed previously by LAYTON & VOSHELL (1991). We randomly selected the arti- ficial substrate samplers to be collected on each date. To avoid loss of organisms during retrieval, we placed an inverted plastic funnel over the sampler before it was removed from the bottom, and we placed a lOOpm mesh net under the sampler as soon as it was visible underwater. A complete descrip- tion of the artificial substrate samplers and how they were retrieved can be found in LAYTON (1989), CHRISTMAN (1991). and LAYTON & VOSHELL (1991). The entire sampler and the contents of the net were placed in a labeled plastic bucket filled with 5% formalin for preservation of specimens.

In the laboratory, the artificial substrate samples were washed over a 355 urn mesh soil sieve until water flowing through the sieve was almost clear. The material retained on the sieve was preserved in 70% ethyl alcohol. Benthic macroinvertebrates were sorted later from the detritus and sand with a stereomicroscope at 4-1OX magnification, then identified to the lowest possible taxonomic level. TO determine if significant changes in the benthic macroinvertebrate community occured in the second year, the following measures were compared at the end of year 1 (10 February 1989) and the end of year 2 (5 March 1990) using 2-sample t-tests: total density, taxa richness, percent of density compri- sed by major functional feeding groups (after MERRITT and CUMMINS l W ) , and density of common individual taxa (those with annual mean density 2 1 organism/sampler). The Shannon diverity index was compared using the Hutchinson t-test as described by ZARR (1984). In addition, the Bray- Curtis similarity index was also used to compare the entire community following the design and __. .-

analysis of H R ~ B Y (1987). Water temperature at 1 m was recorded in one pond every 2 hr throughout both years with a Temp-

mentor@ (Ryan Instruments, Redmond, Wash.). We measured several physicochemical parameters (Secchi depth, temperature, dissolved oxygen, pH, hardness, conductivity, alkalinity, nitrate, nitrite) in all ponds at the end of the study on 5 April 1990, using standard methods (American Public Health Association et al. 1985). The same parameters had been measured from 5 February 1988 to 10 Febru- ary 1989 by JENKINS (1990). We made qualitative observations on the types of macrophytes and their abundance in each pond. Similar observations on macrophytes in the ponds had been made during the first year by ROSENZWEIG (1990).

3. Results

Benthic macroinvertebrates showed cyclic trends in total density throughout the study. High densities in autumn were followed by low densities in late spring (Fig. 1). Mean total

Benthic Macroinvertebrates in Experimental Ponds 483

density of benthic macroinvertebrates during year 1 peaked during autumn at about 600 organisms/sampler. Following the peak, densities dropped to about 400 organisms/samp- ler. During year 2, this drop continued until late spring, to a low of about 100 organisms/ sampler. Densities remained relatively stable for several months, and then increased to a maximum of about 800 organisms/sampler in autumn. Densities declined from this peak to about 300 organisms/sampler by the end of year 2 (Fig. 1). These fluctuations in total density were mostly caused by emergence and recruitment of Chironomidae. Taxa rich- ness and diversity increased progressively during the first 8 mo of year 1, then stabilized at about 9 and 1.6, respectively. Taxa richness and diversity did not exhibit extreme fluctua- tions in year 2 as were observed for density (Fig. 1).

Community structure was dominated during both years by members of Diptera (87 % year 1,90 Vo year 2; Fig. 2). Three other orders of insects (Ephemeroptera, Odonata, Tri- choptera) accounted for almost all of the remainder of the benthic macroinvertebrate com- munity in both years. Ephemeroptera declined in relative abundance in year 2, whereas

Figure 1. Measures of benthic macroinvertebrate community structure on each sampling date during first 2 yr after experimental ponds were constructed (25 February 1988 to 5 March 1990).

All values are means of six ponds (k standard deviation).

484 v. D. CHRISTMAN and J. R. VOSHELL

Odonata and Trichoptera increased in relative abundance. The community was comprised predominantly of two functioatil feeding groups in both years: collector-gatherers and pre- dators (Fig. 2). Collector-gatherers were the highest proportion of the community in both years, but their proportion decreased somewhat in year 2. The relative abundance of predators increased in year 2, and a third functional feeding group (piercer-herbivores) achieved a measurable ievei of abundance (Fig. 2).

Orders

Year 1 Year 2

Diptera (87.

(4.7%) )

Functional Feeding Groups

Year 1 Year 2

Figure 2. Summary O f StNCtUre and function of benthic macroinvertebrate community in experi- mental ponds during each of first 2 yr after construction. Values are percents of total numbers col- lected in all six ponds during the entire year. Year 1,25 February 1988 to 25 February 1989; Year 2,

25 March 1989 to 5 April 1990.

Of the 48 taxa collected during the 2 yr study, 34 were collected in year 1 and 45 were col- lected in year 2 (Table 1). In the second year, 3 taxa previously present did not reappear and 14 taxa appeared for the first time. Almost two-thirds of all taxa (31 of 48) occurred in both years. Of the taxa lost in year 2, none were considered to be common (annual mean 2 1 organism/sampler). Only Oqerhira was a common taxon among those gained in year 2. The most abundant taxa in both years were Chironominae/Orthocladiinae and Tanypo- dinae from the family Chironomidae (Table 1). It was not feasible to identifiy the chirono- mid larvae beyond the subfamiliy level.

Statistical Analysis. Results of the statistical comparison of the community occuring at the end of year 1 to the community occuring at the end of year 2 are shown in Tables 2 and 3. Statistical tests were not conducted for annual means because the samples of benthic macroinyertebrate populations on successive dates were not independent. The question addressed in these statistical tests was: “Did an additional year of natural development in the pond ecosystem result in a benthic macroinvertebrate community that was signifi- cantly different from the one that existed at the end of the first year?”

Benthic Macroinvertebrates in Experimental Ponds 485

Total density, taxa richness, diversity, and percent of each functional feeding group were not significantly different between the end of year 1 and the end of year 2 (Table 2). Density of the two most abundant taxa, Chironominae/Orthocladiinae and Tanypodinae, also were not significantly different between the ends of the two years. The only statisti- cally significant differences were for three individual taxa (Callibaetis, Cuenis, Coenagrio- nidae), all of which were lower at the end of year 2. Althought a t-test was not appropriate because Oxyethira was not present in year 1, the density attained during year 2 (2.4 orga- nisms/sampler) was a significant change.

Table 1. Density of individual taxa occurring in experimental ponds during each of first 2 yr after construction. Means and ranges are expressed as number of organisrns/artificial substrate sampler for the entire year. Year 1,25 February 1988 to 25 February 1989; Year2, 25 March 1989 to 5 April 1990; *, mean<0.1 organisrn/artificial substrate sampler; +, taxa present but unable to be quantified because early instars could not be distinguished con-

sistently.

Year 1 Year 2 Year 1 Year 2 Taxa Mean Range Mean Range Taxa Mean Range Mean Range

Nematoda Annelida Oligochaeta Crustacea Amphipoda Talitridae

Hyalella Arachnida Acari Insecta Ephemeroptera Baetidae

Callibaetis Leptophlebiidae

Leptophlebia Caenidae

Caenis Ephemeridae

Hexagenia Odonata Aeshnidae

Anax Gomphidae

Gomphus Macromiidae

Macromia Corduliidae

Tetrago neuria Libellulidae

Celithemis Elyihemis Erythrodiplax Ladona Libellula

8

0.7

0.1

8

15.8

0.1

12.6

0.8

0.7

0.1

+ 1.3 +

+ +

(0-8.3)

(0-0.7)

(0-73.5)

(0-0.2)

(0-38.2)

(0-2.7)

(0-2.7)

(0-0.3)

(0-4.3)

8 Pantala + Perithemis +

0.8 (0-6.5) Sympetrum + Coenagrionidae 4.0 (0-16.8)

Argia Anomalagrion Enallagma + Ishnura +

* Hemiptera Corixidae Notonectidae *

Buenoa + 4.6 (0.3-11.7) Noronecta

Trichoptera Polycentropodidae 8

11.7

0.2

0.4

8

*

* 9.0 + + i-

+ +

Cernotina (3.1-33.5) Hydroptilidae

Hydroptila (0-1.0) Orthotrichia

Oxyethira Leptoceridae

Phryganeidae Agtypnia

Coleoptera Haliplidae

Peltodytes Gyrinidae

(0.8-25.5) Dineutus Dytiscidae

Agabus Bidessonotus Hydroporus Laccophilus

(0-1.0) Oecetis

*

*

0.7 (0-2.7)

0.1 (0-1.0) 0.4 (0-2.5) + +

+

+ + + 5.0 (0.5-12.3)

+ 4.8 (0.5-12.0)

*

+ * 0.1 (0-1.3) * 0.1 (0-1.3)

0.1 (0-0.8)

8

2.4 (0-10.5)

0.2 (0-0.5)

0.3 (0-1.3)

*

0.1 (0-0.5) 0.2 (0-0.7) + + + +

486 V. D. CHRISTMAN and J. R. VOSHELL

Year 1 Year 2 Year 1 Year 2

Taxa Mean Range Mean Range Taxa Mean Range Mean Range

Hydrophilidae 0.4 (0-1.2) 0.2 (0-1.2) Chironomidae Berasus + 0.2 (0-1.2) Chiro/Ortho 10.4 (048.0) 197.6 (72.3-352.3) Trapisternis Tanypodinae 53.1 (0-144.2) 112.4 (17.8-389.5) *

Diptera Tabanidae 0.6 (0-2.2) Tipulidae * Gastropoda Chaoboridae * 8 Lirnnophila Ceratopogonidae 6.1 (0-12.7) 14.1 (0.3-48.8) Ancylidae 8

Table 2. Comparison of community structure at end of year 1 (10 Feb. 1989) and end of year 2 (5 Mar. 1990). M e w are for six ponds. All density values are numbers of organisms/ artificial substrate sampler.

Parameter 10 Feb. 1989

Mean S. D. 5 Mar. 1990

Mean S. D.

Total Density Taxa Richness Diversity *

(Shannon) Percent

Collectors Percent

Predators Callibaetis

Density Caenis

Density Coenagrionidae

Density Libellulidae

Density Ceratopogonidae

Density Tanypodinae

Density Chironominae

Density

403.2a 8Sa

1 .6a

71.3a

28.7a

20.7'

11.2a

16.8*

3.7=

6.1a

84Sa

253.8=

145.1 1.6

0.4

12.3

12.2

15.8

4.7

16.2

6.2

3.8

63.2

84.3

1 .5a

61.0a

38AP

3.0b

4.7b

3.0b

9.7a

9.3a

105.7O

172.0a

56.3 1.9

0.2

9.0

8.8

2.4

3.9

3.0

8.6

11.4

32.1

48.8

Means across rows followed by different letters are significantly different; 2-sample T-test (n= 6); P<O.OS.; *Calculated using the Hutchinson 7"test (ZARR 1984).

The Bray-Curtis similarity index was probably the most informative measure for com- paring the communities between years because it analyzes the presence and relative abun- dance of all taxa simultaneously. This index can range from 0 (least similar) to 1 (most simi- lar).The mean values reported in Table 3 indicate a high degree of similarity, both within and between years. More importantly, an analysis of variance conducted according to HRUBY (1987) indicated that there were no significant differences (P50.05) in similarity.

Environmental Characteristics. Results of physicochemical measurements are pre- sented in Table 4 and Figure 3. These values indicate that water quality in the ponds was not detrimental to aquatic life (USEPA 1976); however, nutrient and chlorophyll a concentra- tions were indicative of oligotrophic conditions. Water temperature was very warm but typical for ponds at this latitude and elevation. Annual temperature patterns were almost identical during both years (Fig. 3). It was not possible to make statistical comparison be-

Tab

le 3

. Br

ay-C

urtis

Sim

ilari

ty I

ndex

val

ues

for

com

pari

son

of b

enth

ic m

acro

inve

rteb

rate

com

mun

ity o

ccur

ing

at e

nd o

f ye

ar 1

(10

Feb.

198

9) to

that

occ

urin

g at

end

of y

ear

2 (5

Mar

. 199

0).

m

CI

Yea

r 1

Yea

r 2

Yea

r 1 v

s Y

ear2

1

r. 3

n 2

1 0.86 0.77

0.80 0.84

0.59

1 0.89

0.78

0.82

0.75

0.81

I 0.71 0.68

0.80

0.87 0.71

0.66

2 Y

1

Pond

s Po

nds

Pond

s +

-'I

2

4 6

9 I1

i

-1

2

4 6

9 I1

4-

I2

4

6 9

I1

2 4

.-

0.77

0.79

0.88 0.56

2 0.70

0.90

0.72

0.78

2 0.79 0.78

0.85

0.90 0.79

0.69

2 s 0.88 0.68 0.71

4 0.66

0.71

0.73

4 0.53 0.47

0.64

0.70

0.48 0.58

$ i.5 6

0.74 0.70

6 0.73

0.82

6

0.79 0.80

0.84

0.83 0.78 0.66

5' 9

0.55

9 0.8 1

9 0.68 0.64

0.62

0.71

0.68

0.49

11

11

11

0.74 0.68 0.71

0.76

0.71

0.55

Mea

n *

0.74

0.71

0.70

S. D

. 0.1 1

0.07

0.11

* Ana

lysis

of v

aria

nce c

ondu

cted

acc

ordi

ng to

HRUBY

(1987) in

dica

ted

that

ther

wer

e no

signi

fican

t diff

eren

ces (

p

ces.

0.

05) b

etw

een

any o

f the

mat

ri-

m

X

U g. (D 2 c

488 V. D. CHRISTMAN and J. R. VOSHELL

Table 4. Ranges for environmental characteristics measured in experimental ponds

Parameter year 1 10 Feb. 1989 5 Apr. 1990

Dissolved oxygen, Temperature, OC 3.9- 30.0 11.6- 12.8 11.8 - 14.0

11.6- 12.8 9.8 - 11.8 PH 6.6- 8.6 7.5- 7.7 7.1 - 8.5

mg/liter 5.8- 12.8

Alkalinity,

Hardness, mg CaCO3/liter 26.0- 60.8 34.2- 49.8 20.0 - 37.1

mg CaCOJ/liter 20.0- 85.0 50.0- 70.0 50.0 - 70.0 Conductivity,

pmhos 25OC NO2, mglliter N03, mg/liter Secchi, m Chlorophyll a,

mg/liter

Figure 3.

132.6-252.5 148.7-1 85.1 68.0 -125.0 O.O-. 0.03 0.0 - 0.0 0.0- 1.68

0.0- 1.76 0.0- 0.03 0.09- 0.28 0.3- 2.2 1.1- 1.4 0.6 - 2.1

0.0- 21.2 2.1- 12.3 0.0 - 4.7

40

30

20

10

0 J : : : : : : : : : l : : : : ; : : : : : : ; : I I

M A M J J A S O N D J F M A M J J A S O N D J F Temperature of Pond 5 at 1 m from 1 March 1988 to 28 February 1990.

Yearl: 1 March 1988 to 28 Februarv 1989 Annual mean temperatur = 17.6'C, Accumulated-degree-days = 6414;

Year 2: 1 March 1989 to 28 February 1990 Annual mean temperature = 17.S°C, Accumulated degree-days = 6400

tween years for the physicochemical parameters listed in Table 4 because measurements were not made on similar dates. Ranges among ponds for the one date on which measure- ments were made in year 2 (5 April 1990) generally overlapped with ranges of the same parameters among ponds in year 1.

Emergent macrophytes were well established at the edges of the ponds throughout most of year 1, including: Carex, Cyperus, Eleocharis, Hypericum, Junms, Ludwigia, and Qpha (R?SENZWEIG 1990). A submerged macrophyte, Potamogeton, was first observed in one pond about midway through year 2 (June 1989). By the end of year 2 , Potamogeton was present in five of the ponds that were included in this study and covered approximately 5 to 95 Yo of the bottom of those ponds.

Benthic Macroinvertebrates in Experimental Ponds 489

4. Discussion An additional year of natural development m the experimental ponds brought about

very few changes in the benthic macroinvertebrate community. Total density fluctuated a lot in both years, but the overall magnitude was similar. Taxa richness and diversity reached plateaus within year 1 and changed very little thereafter. The same orders of insects and functional feeding groups were dominant in both years. A high proportion of taxa occurred in both years, and almost all of the taxa gained or lost between years were considered to be rare. A statistical analysis of a measure that integrated presence and rela- tive abundance of all members of the community (Bray-Curtis Similarity Index) showed no significant differences between the community at the end of year 1 and the community at the end ofyear 2. Results from the experimental ponds appear to disagree with other stu- dies that have found significant changes in the benthic macroinvertebrate community for several years after the construction of new lentic environments, especially between the first and second years (BARNES 1983, VOSHELL & SIMMONS 1984, KRZYZANEK et ul. 1986). It is possible, however, that the continued change and further establishment of aquatic macrophytes in the ponds may result in further changes in the macroinvertebrate com- munity (KAMPALA 1972, DANELL & SJOBERG 1982, BARNES 1983).

There are several factors that may explain why the community in the experimental ponds changed so little between years 1 and 2. There were numerous sources of colonizing organisms close to the experimental ponds (LAYTON & VOSHELL 1991), and most of the taxa having the necessary adaptions for life in shallow lentic environments were able to reach the ponds during the first year. Other investigators have speculated that changes in avail- able food and habitat are largely responsible for observed changes in the benthic macro- invertebrate community (MCLACHLAN 1969). Often, new lentic environments, contain large quantities of terrestrial organic matter, which provides a temporary food source for some taxa. In addition, the decomposition of the terrestrial organic matter releases nutrients that cause plankton to be especially abundant during the first year. Usually, aquatic macrophytes, which are essential habitat for some taxa, do not become well esta- blished until 1 or more yr after a new lentic environment is constructed. In the experimen- tal ponds, food and habitat for benthic macroinvertebrates probably were very similar in the first 2 yr. All terrestrial vegetation was removed with bulldozers during construction, and the topsoil used to line the pond bottoms had low concentrations of organic matter and nutrients (LAYTON 1989, JENKINS 1990). Although submerged macrophytes did not appear in the experimental ponds until year 2, emergent macrophytes were well established early enough in year 1 to provide suitable habitat for organisms requiring vege- tative substrate to maintain their positions or to lay their eggs. Lastly, there appeared to be no changes in water quality between years that would bring about biological effects.

5. Summary Ecological succession is a phenomenon that takes place over a much longer time period

than was investigated in this study. Subtle differences in the benthic macroinvertebrate community between the first 2 yr, such as the statistically significant changes in a few com- mon taxa and the gain or loss of some rare taxa, are evidence that succession is taking place in the experimental ponds. Factors such as the continuing increase in abundance of the submerged macrophyte Potumogeton may contribute to further subtle changes in the benthic macroinvertebrate community. However, the major attributes of the structure and function of lhe benthic macroinvertebrate community were established during the first year after construction of the experimental ponds and did not change significantly during the second year. One year may be sufficient to establish a relatively complete community for the purposes of pesticide registration testing in this type of facility.

490 V. D. CHRISTMAN and J. R. VOSHELL

6. Acknowledgement We are grateful for the assistance JAMES L. TRAMEL, JR. and W. B. WILKINSON, 111 for on-site admin- istration and management of the experimental pond facility. Persons who provided valuable techni- cal assistance included: STEPHEN w. HINER, MICHAEL 0. WEST, T. MICHAEL WILLIAMS and LOURDES M. GEORGE. This research was partially supported by the Virginia Agricultural Experiment Station, Hatch Program.

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KRZYZANEK, E., H. KASZA, W. KRZANOWSKI, T. KUFLIKOWSKI, & G. PAJAK, 1986: Succession of com- munities in the Goczalkowice Dam Reservoir in the period 1955-1982.-Arch. Hydrobiol. 106:

LAYTON, R. J., 1989: Macroinvertebrate colonization and production in new experimental ponds. Ph. D. dissertation.-Virginia Polytechnic Institute and State University, Blacksburg.

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