379/V'

PRODUCTION AND ENERGY METABOLISM IN THREE BENTHIC

INSECT POPULATIONS IN A SMALL NORTH CENTRAL

TEXAS POND

THESIS

Presented to the Graduate Council of the

North Texas State University in Partial

Fulfillment of the Requirements

For the Degree of

MASTER OF SCIENCE

by

Daniel J. Benson, B.S.

Denton, Texas

May, 1978

Benson, Daniel J., Production and Energy Metabolism in

Three Benthic Insect Populations in a Small North Central

Texas Pond. Master of Science (Biology), May, 1978, 70 pp.,

20 tables, bibliography, 87 titles.

Annual energy budgets of dominant benthic macro-inver-

tebrates were examined during November 1973 to October 1974

from the benthos of a small pond ecosystem in north-central

Texas. Estimates of annual secondary production (Hynes and

Coleman 1968) were Procladius s. (Diptera, Chironimidae),

-2 -1 -2 -1.2.4 g m y (13 kcal m y ); Tendipes decorus (Diptera,

-2 -1-2-Chironomidae), 6.0 g m y (40 kcal m y ); Brachycercus

-2- -2 -1s (Ephemeroptera, Caenidae), 1.9 g m y 1 (11 kcal m y-).

Energy metabolism was measured in the laboratory at

six seasonally encountered temperatures (5, 10, 15, 20, 25,

and 30 C) on an acclimatization basis, and then extrapolated

to the field. Estimates of annual energy metabolism are

-2 -lProcladius sp., 5.0 kcal m y ; Tend decorus, 17.2

-2y-1 -2Y-1kcal m y ; Brachycercus sp. 40.0 kcal m y.

TABLE OF CONTENTS

LIST OF TABLES...............

LIST OF ILLUSTRATIONS.. .......

Page

iv

... vi

Chapter

I. INTRODUCTION . . . . ..

II. METHODS AND MATERIALS

1

.......... . ........ 4

The Study SitePopulation DynamicsProductionEnergy MetabolismEnergy Flow

III. RESULTS.......................... . . 15

Physical MeasurementsSeasonal Variation in Population

and BiomassProductionEnergy MetabolismEnergy Flow

IV. DISCUSSION....*.... . ............. 52

The Study SitePopulation DynamicsProductionEnergy MetabolismEnergy Flow

BIBLIOGRAPHY. . . . .*. .0.... . . . . .4....-...-....63

iii

LIST OF TABLES

Table Page

I. Benthic Organisms Present in NTSU Golf CoursePond during June, 1973, to October, 1974. . .

II. Density and Biomass Estimates of ChironomidPopulations from the Benthos of theNTSU Pond from July, 1973, to October,1974. . . . . . . . . . .... .-.-.......

III. Density and Biomass Estimates of Two Speciesof Insect and One Species of Annelidfrom the NTSU Pond from July, 1973, toNovember, 1974 . . . . . . . ............

IV. Population Estimates for each Instar of each

Species of Chironomidae from November,1973, to October, 1974......0.0.. .....

V. Biomass Estimates for each Instar of eachSpecies of Chironomiade from November,1973, to October, 1974....................

VI. Population Estimates for each 0.5 mm SizeClass of Brachycercus sp. from November,1973, to October, 1974. ....... &.......

VII. Biomass for Each 0.5 mm Size Class ofBrachycercus sp. from November, 1973, toOctober, 1974 . .......................

VIII. Annual Secondary Production by Procladius sp.from November, 1973, to October, 1974 . .

IX. Annual Secondary Production by Tendipes decorusduring November, 1973, to October, 1974 .

X. Annual Secondary Production by Brachycercussp. from November, 1973, to October,1974. . . . . . . . . . . . . . . -. . . . .o

XI. Comparison of Metabolic Rates among Three Ben-thic Insects at Six Seasonal AcclimationTemperatures... . . . . .. .o.o... -..

iv

Page

XII. ANOVA for Acclimatization Metabolic Rates AmongThree Species of Benthic Insects at Six

Seasonal Temperatures. ....... ......-.-

XIII. Relation of Log Metabolic Rate to Log Dry

Weight in Three Species of Benthic Insects

at Six Seasonal Acclimatization Tempera-tures (AT) . -. . .-- - -0- --0 - --0 -

XIV. ANCOVA for Effect of Log Dry Weight on Log

Weight Specific Metabolic Rates of Three

Benthic Insects at Six Seasonal Acclimati-

zation Temperatures.....0...................

XV. Tukey's Multiple Range Tests of Weight-AdjustedMetabolic Rates for Three Species of Ben-

thic Insects at Six Seasonal Acclimatiza-

tion Temperatures.1..................-.....

XVI. Q1's for Weight-adjusted Metabolic Rates forThree Species of Benthic Insects at Six

Seasonal Acclimatization Temperatures. .

XVII. Annual Energy Flow in Two Species of Midge

Larvae and One Species of Mayfly Nymph

from the Benthos of a Small Pond Ecosys-

tem in North-central Texas ...........

XVIII. Comparisons of Secondary Production in Selec-

ted Populations of Benthic Inverte-brates .................... 0.........

XIX. Comparison of Annual Population Energeticsof Selected Aquatic Insects.............

XX. Comparison of Annual Benthic Community Ener-getics .i.............................

V

LIST OF ILLUSTRATIONS

Figure Page

1. Map of the North Texas State University GolfCourse Pond Showing the Location ofSampling Stations........................

2.a. Temperature Changes in the NTSU Golf CoursePond During June, 1973, to November, 1974.

2.b. Area and Volume Changes in the NTSU GolfCourse Pond During June, 1973, to October,1974.......................................

3. Population Densities and Biomass Estimates forFour Species of Insect and One Species ofAnnelid Found in the NTSU Golf course PondDuring July, 1973, to October, 1974. . . .

4. Population Density and Biomass for the TotalBenthic Community of the NTSU Golf CoursePond During July, 1973, to October, 1974 . ..

5. Acute, weight-adjusted acclimatization R-TCurves of Three Species of Insect Foundin the NTSU Golf Course Pond............a.

vi

INTRODUCTION

Since Lindeman (1942) introduced the concept of tro-

phic dynamics, ecologists have been interested in testing

hypotheses concerning trophic energy relationships and sta-

bility of ecosystems (e.g. Margalef 1963, Odum 1968). Re-

cently, with the introduction of systems theory to ecology

and the widespread availability of the appropriate computer

technology, integrated, holistic studies of ecosystems ne-

cessary to test hypotheses concerning structure and beha-

vior of ecosystems have become possible (e.g. Teal 1962,

Odum 1962, Vollenweider 1969, Schindler and Comita 1972,

Comita 1972, Brylinski 1973). However, considering the in-

creasing importance of surface waters, relatively few holis-

tic studies of aquatic ecosystems are available (e.g. Odum

1957, Welch 1967, Tilly 1968, Patten et al.1975, 1976).

Ponds and small lakes comprise a significant part of

the surface waters in the southwestern United States and

the demand for these multi-purpose impoundments is rapidly

increasing. Although it is intuitively obvious that a large

percentage of the surface waters in the United States is

found in small natural and man-made ponds, realization of

their ecological significance is relatively recent (e.g.

Gollop 1954, Smith et al-1964, Lietch 1966, Stuart and

Kantral 1971, Millar 1976, Driver and Pedan 1977). Holistic

1

2

studies on trophic dynamics and energy flow are important

to our understanding and management of these resources.

Therefore, holistic studies of ponds are appropriate and

timely. Accordingly, a systems analysis and modeling pro-

ject of trophic dynamics of a small pond on the golf course

at North Texas State University, Denton, Texas, was begun

in June of 1973. The pond was well suited for this type

of study as it supports a diverse biological community

which is similar to those found in larger impoundments in

North Central Texas. The small size of the pond permitted

more accurate sampling than would be possible in a large

impoundment.

The experimental-components approach, as first pro-

posed formally by Hollings (1966), was utilized in the com-

puter modeling project of the NTSU pond ecosystem. The

major object of my study was to describe the trophic dyna-

mics and energy flow through the macro-benthic community

of the pond. Other compartments of the ecosystem are pre-

sented in four other theses (Jones 1975, Kelly 1975, Smith

1976, Childress in prep.) and several publications and ma-

nuscripts (Jones et al-1977a, Jones et al.1977b, Kelly et

al-1977, Smith et al.1977).

Benthic insects with their high densities and turnover

rates are important agents of energy flow in aquatic eco-

systems as contributors to the diets of many fish. Conse-

quently, there is an increasing emphasis on studies of ben-

thic energetics (e.g. Jonasson, 1972, Welch 1976).

3

In addition, energy budgets of several benthic invertebrates

from a wide variety of aquatic ecosystems are rapidly ap-

pearing in the literature (e.g. Fischer 1966, McDiffett

1970, Lawton 1971, Kimerle and Anderson 1972, Charles et al.

1975, Heiman and Knight 1975). Brown and Fitzpatrick's

(1977) study of a carnivorous lotic insect (Corydalus cor-

nutus, Megaloptera, Corydalidae) is the most complete study

of life-history and population energetics of a benthic in-

vertebrate in the Southwest that I am aware of.

The specific objectives of this study were to taxo-

nomically characterize benthic macroinvertebrates; deter-

mine variations in the population densities and biomasses

of the principal taxa; estimate annual secondary production

of the principal taxa; determine effects of seasonally en-

countered temperatures on energy metabolism of the princi-

pal taxa; and estimate annual energy flow through the ben-

thic community to higher trophic levels.

METHODS AND MATERIALS

The Study Site

The pond (Fig. 1), located in Denton Texas (330 12' N.,

970 10' W.), was built in 1947 as a stock tank and is now

used to irrigate the NTSU golf course and as a water hazard.

Filling is accomplished by runoff from a 10 ha watershed

and a well drilled into the Trinity sandstone. Problems

with the pumping mechanism allowed drastic fluctuations in

water level in the summer and fall months in 1973. By late

fall the pump was working properly and drawdowns were less

severe through 1974, but still represented a principal phy-

sical stress on the pond's biota.

The pond is roughly elliptical,with its major axis

roughly north-south. There is an island in the northern

section and a rip-rapped earthen dam on the southern, deep-

est end. Both the dam on the southern side of the pond and

the shallow channel on the northern side of the island are

rimmed by small stands of black willows (Salix nigra) and

post oaks (Quercus stellata). The eastern side of the pond

is bordered by a dirt road which runs parallel to the pond

a few meters from its edge and which contributed signifi-

cant amounts of dust to the pond. The western side of the

pond is bordered by fairway.

4

5

Ambient air and water temperatures were continuously

monitored with a recording thermograph located in a box on

top of the outlet pipe at the deepest part of the pond.

The water-temperature probe was secured 1 m from the bot-

tom of the pond. Mean temperatures were taken from the

thermograph weekly and plotted for the year. Mean annual

temperature for the pond was 20 C. Mean volume was 15,000

m3 and the mean area was 0.94 ha. The maximal depth of

the pond when full was 3.5 m, the mean depth 1.5 m.

Three distinct substrate types were present in the

pond. The northern 40% of the pond consisted of light-

colored clay and sand. The southern and deeper 40% of the

pond was dark silt and fine organic matter. The perimeter

of littoral zone of the pond (about 3 m from the shoreline)

made up the remaining 20% of the pond. This area contained

leaves from surrounding trees, grass and shrub cuttings

from the golf course, and some algae and attached vegeta-

tion. Most of the algal mats were destroyed early in the

study by seining for fish and by hand-raking by the golf

course groundskeepers, who believed that this vegetation was

responsible for clogging the outlet pipe used for withdraw-

ing water for irrigation.

Population Dynamics

Quantitative samples were taken approximately monthly

from July 1973 to October 1974 at 12 sampling stations which

were selected to reflect the heterogeneity of the bottom

6

(Fig. 1). Thus, four samples were taken from the northern

sand-and-clay substrate, six were taken from the dark-silt

substrate found south of the transect, and two were taken

from the leaf detritus of the littoral zone. The sampling

regime was thus "self-weighted" (Wadley 1952, cited by

Southwood 1966); that is, the number of repetitions taken

in each substrate type is proportional to their relative

size. Station 10 was not sampled between August and

November 1973, or in January, July and August 1974 because

of low water. Samples were taken with a standard-size

Ekman dredge, which gives consistent and reproducible re-

sults (Milbrink 1973) following techniques described by

Southwood (1966). Live organisms were hand-picked in the

laboratory with the aid of a 2X-macroscope. Organisms were

grouped according to family and preserved in 70% ethanol.

A large number of benthic species were present in the

pond throughout the study period (Table 1, Results). How-

ever, species which comprised less than 1% of the samples

taken during July through October 1973 were omitted from

the study. Energy flow studies (production, P and respira-

tion R) were measured from 20 November 1973 to 28 October

1974, for the three species with the highest densities and

biomasses during the first four months of sampling. These

were the mayfly, Brachycercus sp., and chironomids, Procla-

dius sp. and Tendipes decorus. Identification of the chi-

ronomid genera was accomplished by Dr. Bill Stark on adults

7

Fig. 1. Map of the North Texas State University Golfcourse pond showing the location of sampling stations.

GOLF COURSEPOND

N

30 o9D90TRANSrT

BRIDGE

to 20 A.O 0 _ o DRAIN

SCALE IN METERS A& INLETaL

9

from an emergence induced in the laboratory. Construction of

length-frequency and head capsule width-frequency histograms

indicated that the species were multivoltine with consider-

able overlap between generations. They could not be sepa-

rated into cohorts.

Production

Annual secondary production (P) of Brachycercus sp.,

Procladius sp. and Tendipes decorus) was calculated accor-

ding to Hynes and Coleman (1968) as modified by Hamilton

(1969) and used by Waters and Crawford (1973).

Body lengths of preserved nymphs of Brachycercus s.

were measured (N = 3627) from the top of the pronotum to

the tip of the abdomen, excluding the cerci. These were

separated into 0.5 mm size classes and counted. Head cap-

sulate widths (HCW) of Procladius sp. and T. decorus (N =

2129) were measured to the nearest 0.05 mm using a dissect-

ing microscope with an ocular micrometer. Four instars

were clearly present in the chironomids. McCauley (1974)

stated that chironomids should have four instars in tempe-

rate climates. All nymphs of Brachycercus sp. and larvae

of Procladius sp. and T. decorus of a given size class or

instar (pupae of the chironomid species were considered a

fifth instar and each instar will be referred to as a size

class hereafter) were dried for 24 h in a vacuum oven at

60 C and cooled in a vacuum dessicator for 2 h. Group

weights were measured on an electronic balance (+ 0.1 mg)

10

and individual weights were calculated as total weight/N.

To correct for weight lost during preservation in alcohol,

dry weights obtained from preserved specimens were in-

creased by 25 percent (Jonasson 1972).

Energy Metabolism

Energy metabolism (R) of Brachycercus s Procladius

sp. and T. decorus and their patterns of metabolic compen-

sation or acclimatization (Prosser 1973) to six seasonally

encountered temperatures, 5, 10, 15, 20, 25 and 30 C, were

examined by indirect calorimetry with a Gilson respirometer.

Six collections of Brachycercus sp. nymphs and Procladius

sp. and T. decorus larvae were taken during 23 October 1974

to 13 October 1975 for respirometry after the pond's tem-

perature had been close to (+ 3 C) 5, 10, 15, 20, 25, or 30

C for 5 days. These temperatures were considered to be

acclimatization temperatures (AT). Specimens, collected at

dusk, were transferred to the laboratory, separated accor-

ding to species, and maintained overnight in aerated and

filtered (0.04 p) pond water at the specimens' AT. An auto-

claved sand substrate was provided for the chironomids to

burrow in and a thin nylon mesh was provided for the may-

flies to cling to.

Mayflies and the chironomids were placed according to

size in Warburg respirometry vessels (N = 10 equal-sized

insects per vessel) at dawn of the following day. The

vessels contained 5 ml of filtered (0.04 p) pond water at

11

the AT and the appropriate substrate. Carbon dioxide was

absorbed with 10% KOH. Experimental temperatures (ET) were

held within + 0.1 C of the AT. Respiration measurements,

begun after a 1-h equilibration period, were taken between

600 and 1800 h CST under light conditions. Oxygen consump-

tion rates were measured directly as al0 2 h~ for the ten

insects in each reaction vessel. After measurements were

completed, the insects were vacuum-dried at 60 C for 24 h

and cooled in a desiccator before dry weights (+ 0.1 mg)

were determined. Metabolic rates were calculated as Pl 02

h~ per individual and pl 02 mg~ dry weight h~ for each

species at each of the six AT's. Because the insects were

relatively inactive and measured at their acclimatization

temperatures, the rates (adjusted to STP) represented rest-

ing acclimatization rates (RAR).

Measuring the insects' RAR required collecting speci-

mens at different times during the year when the pond had

been at the appropriate temperature for at least 5 days.

Thus, weights of experimental AT groups differed consider-

ably (i.e. the insects were in different instars or nymphal

stages). Densities varied and affected the sample sizes

greatly. Thus, when specimens were pooled to produce a

metabolically-significant mass, the number of different ves-

sels (N) was often low, contributing to high variances in

the data. Additional variance occurred because at some AT's

only early or late instars were available, resulting in a

12

very low or very high dry weight, respectively; at some

AT's all instars were present, which produced large vari-

ations in weights. At all times, ten specimens of nearly

equal size were intentionally grouped in each respirometry

vessel to measure the effect of weight on 02 consumption.

Significant differences in mean weight-specific meta-

bolic rates between species at each AT were tested with a

Fisher's t-test. A one-by-three nalysis of variance (va-

riable = py1 02 mg~- dry wt h1 ) was used to examine vari-

ance in weight-specific metabolic rate among the three spe-

cies at each AT. Regression equations were calculated for

log metabolic rate (R) vs log mg dry weight (W) at each AT.

A two-way analysis of covarince (covariate = logl 0

mg dry wt; criterion = log1 0 pl 0 mg - dry wt h) was

used to determine the effect of weight on variance in

weight-specific metabolic rates, and to adjust weight-

specific rates to a common weight. Significant differences

in mean weight-specific metabolic rates within species among

the six AT's were tested with a Tukey's multiple range test.

Values for Q1 0 's were calculated on weight-adjusted mean

metabolic rates for each species between each AT to detect

patterns of metabolic compensation. Weight-adjusted mean

metabolic rates were converted to calories with the oxyca-

loric coefficient (4.825 X 10-3 c 1l ) suggested by

Brody (1945).

13

Energy Flow

Energy flow was calculated for the two chironomid and

the mayfly populations as

Energy Flow (A) = P + R (I)

Where A = Assimilation, P = Production, and R = meta-

bolic energy loss. Values for P and R, empirically deter-

-2 -l -l -lmined as g m y and p1 02 g h respectively, were con-

verted to kcal m 2 y 1 . Caloric equivalents for conversion

of production data followed values from Cummins and Wuycheck

(1971). Metabolic energy losses were summed from November

1973 to October 1974 according to

12R = Z (r w.) (hi (.004825)**

i=l t i ( 2)

Where

rt= The dry weight, temperature specific, metabolicrate of each species at the mean monthly tempe-rature t. ( il 02 g-1 h-1 ). r's for temperaturesother than the six experimentals were interpolatedwith Q10 data.

w = The mean dry biomass per square meter of the popu-lation of each species in the i'th month i.e.(B. + Bi+ )/2

h. Number hours per month, (r and temperatures as-sumed to remain constant f~r 30 days).

** = Oxycaloric coefficient for poikilotherms; Brody(1945).

Consumption rates for the chironomids were calculated

by assigning a 0.4 assimilation efficiency (A/C) (Welch 1968).

14

To my knowledge, there are no consumption data in the lite-

rature for caenid mayflies. Consumption was estimated for

Brachycercus sp. by using the consumption rate of fresh

jvater detritivores (3.0 g food g body wtWi day ) in Patten

et al (1975). Caloric equivalent of aquatic leaf detritus

(4249.6 cal g~ 1 ) was taken from Cummins and Wuycheck (1971).

Energy consumed but not put into production or consumed

in respiration was assumed lost as feces and urine (FU =

C -A).

RESULTS

Physical Measurements

Figure 2 presents physical data taken over the study

period. Water temperatures (Fig. 2a) ranged from 32 C in

mid-August to 4 C in early January, when the pond was par-

tially covered with ice for several days. Fluctuations in

water level (Fig. 2b) were drastic at times because of

drawdowns to water the greens, and subsequent refilling by

rain and well water. Volume was maximal in mid-June 1973

(18,900 m3) and early November 1973 (18,800 m3). Three

major drops in volume occurred during the study. The first

(to 13,000 m3) lasted from mid-July until late August 1973,

the second (to 10,900 m3) was in early January 1974, and

the third in March (to 11,500 m3). During these drawdowns

a large percentage of the animal and vegetable matter was

eliminated from the littoral zone.

During the 16 months of sampling (July 1973 to October

1974), the classes Insecta, Gastropoda and Annelida domi-

nated the benthic macroinvertebrates. Insects, especially

dipterans and ephemeropterans, were the most important in

terms of biomass and numbers throughout the study. Table I

lists the organisms which were identified.

The chironomids comprised 38% of the numbers and 26%

of the biomass of the benthic community. Procladius is a

15

16

Fig. 2a. Temperature changes in the NTSU golf coursepond during June, 1973, to November, 1974.

Fig. 2b. Area and volume changes in the NTSU golfcourse pond during June, 1973, to October, 1974.

40

30

w9 20

w-.

w

10

- 0e

" 0

* 0 :0 .0

* 0

.

*e 00.0

J J A SO ND J F M A M J J A S ON

1973 1974

20.0AREA

VOLUME15.0 L

10.0.

J JASON D L F MA MJ J A SO

1973 b, 1974

17

0

10.0

M3m

4

5.0

18

predacious genus which feeds mainly on other tendiped lar-

vae (Wirth and Stone 1956). Tendipes (Kiefferulus) decorus

(Johannsen) is a primary consumer (Wirth and Stone 1956)

commonly found in shallow, oxygen-deficient ponds and, may

produce several generations per year (Johanssen 1905). The

other dipteran studied was a phantom midge, Chaoborus sp.

(Chaoboridae), which accounted for 10% of the population

and 1% of the biomass of the macrobenthos. Chaoborus s.

is also a predator, chiefly on zooplankton (Wirth and Stone

1956). The most abundant inhabitant of the benthos during

the study was Brachycercus sp., which accounted for 50% of

the population and 59% of the biomass of the macrobenthos.

Brachycercus nymphs are tiny (less than 5mm) and are usual-

ly found in lotic habitats (Day 1957).

Dragonfly larvae, Somatachlora sp. (Odonata, Zygoptera,

Lebellulidae) were encountered in less than 1% of the sam-

ples, but turned out to be important in the energy flow of

the benthos, as certain species of fish fed on them very se-

lectively (Jones 1975; Childress, in preparation). The

annelid, Haplotaxis gordioides, comprised 14% of the popu-

lation and 12% of the biomass.

The biting midge Palpoya sp., the burrowing mayfly,

Hexagenia sp., and the small white freshwater snail, Physa

virgata, were encountered rarely and they were not important

in the diet of any of the fish examined by Jones (1975).

Therefore, they were not considered in this study.

19

TABLE 1. Benthic organisms present in NTSU golf coursepond during June 1973 to October 1974.

Class Order Family Genus Species

Insecta:Diptera;

Chironomidae,Tendipes decorusProcladius sD

Chaoboridae,Chaoborus s.

Ceratapog nidae,Palpoya

Odonata;Libellulidae,

Somatochlora sp.Ephemeroptera;

Caenidae,Brachycercus s-p.

Ephemeridae,Hexagenia sp.

Gastropoda:Bassommatophora;

Physidae,:Physa virgata

Anne lida:Oligochaeta;

Haplotaxidae,Ha.potaxis gordioides

20

Dragonfly larvae, although selected for by certain fish

(Jones 1975), had such low population densities that viable

density estimates could not be made.

The littoral zone (stations lA and 4A, Fig. 1) ap-

peared to be the preferred habitat for all species. Chiro-

nomids, mayflies and oligocheates were always found in these

two sampling stations, but were absent on more than 30% of the

sampling dates from the ten other stations combined. Chao-

borus sp. also preferred the littoral zone, occuring in 42%

of the time in samples from stations lA and 4A, and an ave-

rage of 15% in the other ten stations combined.

Seasonal Variation in Population Size and Biomass

Population density (N = Nm ) and biomass (B = mg dry

wt m-2) estimates are given in Tables 2 and 3 and Figures

3 and 4. Procladius sp. (see Fig. 2a and b) had an increas-

ing density (308 m-2 to 903 m-2) and biomass (28 mg m-2to

166 mg m-2) from 22 November to 20 December 1973. By 20

January 1974, the population had decreased to 184 m-2 with

a concomitant drop in biomass to 23 mg m-2. By the 22 Fe-

bruary sampling date, Procladius sp. had increased to 2254

m -2 with a biomass of 202 mg m-2 Numerous pupae (popula-

tion estimate of pupae 21 m-2 and biomass estimate of 19 mg

--2m 2 ) were found in the February 1974 samples indicating

that peak emergence occurred in February-March. The density

declined drastically by 18 March 1974 to 281 m-2 with a

corresponding drop in biomass to 17 mg m-2. There was a

21

general decline in density for Procladius sp. throughout

the rest of the spring and summer of 1974 to a low of 22

m-2 by the last sampling date, 22 October. Biomass also

declined slowly over this time period, with notable increases

on 19 April 1974 (to 24 mg m-2) and 27 July 1974 ( to 30

mg m-2

Tendipes decorus (see Figure 2c and d) was the dominant

chironomid and the second most abundant species present in

the pond during the study period. On 22 November 1973,

T. decorus was at a population level of 239 m-2, slightly

less than that of Procladius sp. on the same date (308 m-)2

The biomass estimate for T. decorus on that date was 111 mg

m -2. T. decorus exhibited a gain in both number and bio-

mass in December, (population was 706 m-2) with a biomass

of 224 mg m-2 on 20 December 1973), and by January 1974, it

had doubled (1693 m-2), but with a biomass decrease (167

mg m-2). Emergence in November 1973 was indicated by the

presence of a few pupae. By 22 February 1974, T. decorus

had declined to 410 m-2 but exhibited an increased biomass

of 247 mg m-2. By 18 March 1974, T. decorus had repeated

the pattern of doubling its density while decreasing in bio-

mass. By 18 March 1974, the population had increased to 841

m-2 and 150 mg m-2. Pupae were present in March and again

on 19 April 1974, indicating emergence occurred during these

months. Although there were more pupae in April than in

22

March, (25 m-2 in March and 33 mg m-2 in April), the pupae

in April were smaller than those in March, (31 mg m in

March and 12 mg m-2 in April 1974). The total population

of T. decorus decreased in April to 426 m- with a decrease

in biomass to 57 mg m.-2 The samples gathered on May 30,

1974, showed a decrease in both number and biomass (285 m-2

and 32 mg m-2). In the following month, density again de-

creased (to 216 m-2), whereas biomass increased to 43 mg

m- 2, ( on 29 June 1974). On 27 July the population for T.

decorus was 194 m-2, another decrease, while the biomass

was 68 mg m-2, a one-third increase. By 24 August 1974 the

density had risen to 410 m-2 while the biomass remained

about the same at 66 mg m .-2 On 28 September 1974 a few

pupae were present,indicating emergence; and both density

and biomass estimates doubled to 746 m and 120 mg m-2. On

28 October 1974, twice as many pupae were found as the pre-

vious month, but they weighed only about half as much (5 m-2

and 7 mg m-2 on 28 September, and 13 m-2 and 4 mg m-2 on 28

October 1974. The population of T. decorus behaved similar-

ly, with density almost doubled (1202 m-2) and biomass re-

duced by almost two-thirds (46 mg m-2) during the same pe-

riod.

Generally, both species showed high densities and bio-

masses during the winter and low values during the summer,

(see Fig. 3 e and f). The drop in biomass during January,

1974, coincided with the severe drawdown.

23

Brachycercus sp. (see Fig. 3g and h) exhibited large,

asynchronous variations in its population and biomass

through the study period. On 30 July 1973, the population

-2 -2was 545 individual.s/m with a biomass of 57 mg m-. By

26 August 1973, the population had dropped to 205 N m

with a biomass of 7 mg m-2, the lowest during the 16-month

study period. Population continued to decrease and on 25

September 1973, it reached 193 m-2, but with a higher bio-

mass of 25 mg m-2. By 16 October 1973, the population had

increased to 2007 m-2 with a biomass of 132 mg m-2 . By 22

November 1973, the population had decreased to 901 m-2

-2but the biomass had more than quadrupled to 590 mg m .

The following month population had doubled and biomass had

almost tripled from the previous month, 2080 m-2 and 1448

mg m-2 respectively on 20 December 1973. Although the po-

pulation increased to 2507 m-2 in January 1974 the biomass

decreased to 195 mg m.-2 By 22 February 1974 the density

was halved to 1230 m-2, while biomass remained nearly the

same at 128 mg m-2. By 18 March 1974 the population densi-

ty (2953 m-2) of Brachycercus sp. had recovered to the De-

-2cember 1974 level, as did the biomass (1151 mg m ). Those

levels were maintained through 19 April 1974 with a popu-

lation level of 2284 m-2 and a biomass estimate of 1339 mg

m -2. By 30 May 1974 there was a drastic decrease in both

numbers and biomass (440 m-2 and 45 mg m-2 ). There was an

increase again in both by 29 June 1974 (to 1061 m-2 and 215

mg m-2), followed by a gradual decrease through July until

o Q0 0 O O O OC rOCr OMO0mmwI H L C ) N CN r e co w atl N q lrH()IH (N r o H

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HH(

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4

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26

Fig. 3. Population densities (upper figures) andbiomass (lower figures) estimates for four species of insectand one species of annelid found in the NTSU golf coursepond during July, 1973, to October, 1974. [a-b. Procladiussp. b-c. Tendipedes decorus. c-d. all chironomids, (i.e.the sum of a-d). e-f Brachycercus sp. g-h. Procladius sp.1-3. Haplotaxis gordioides. k-l Total benthic community,(i.e. the sum of a-j3 .

__LLLL L Th~ h

z-V N) AIISN30

L~LL..~LJ~i4LLIc

2

4

a

2

0

0

I fit LL.L..I00 0 8o 0 00

IN

UPE OW

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2

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t

0

CliP.-

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10

( z.VIN AIISN30

71~

(Z-&W N) '4SN30

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j0

(-W N) AjJSN30

00

C\j

0

4

L~ L~ J L~iV)

I a I I

cu

0

00

2

29

Fig. 4. Population density (a) and biomass (b) for the totalbentt.ic community of the NTSU golf course pond during July, 1973 toOctober, 1974.

2500

2000

1500

1000

500

J A S0 ND J F M A M J J A S0973

1974b.

5000

4000

z 30 0 0

z2000

1000

A 0 N D J F M A M J J A S 01973

1974

30

31

24 August 1974, when there were only 24 m- 2 of these may-

flies with a biomass of 1 mg m- 2 . The population gradually

increased through 28 October 1974 to a level of 368 m-2

while the biomass stayed essentially the same. Pre-emergent

nymphs (nymphs with dark wing pads) were present throughout

the year and generally followed patterns exhibited by the

younger nymphs.

The phantom midge, Chaoborus sp. (Fig. 3i and j) showed

significant levels of population and biomass only in the

late summers of the study. On 30 July 1973 there were ap-

proximately 72 m-2 of Chaoborus sp. with a weight of 15 mg-2 -m . On 26 August 1973 there were only 20 m-2 but the bio-

mass was 10 mg m-2, more than the previous month. Chaoborus

sp. was at low densities until the following year/,when the

population jumped from 0 to 133 m-2, with a biomass of 33

-2mg m2, (28 September 1974). By 29 October 1974 the popu-

lation and biomass of Chaoborus sp. was halved to 76 m-2

and 13 mg m-2

The oligochaete H. gordioides (see Fig. 3k and 1) was

present throughout the study period in fairly high densities,

averaging 14% of the population and 12% of the biomass.

H. gordioides generally maintained synchronous fluctuations

in these estimates. High densities and biomass were obser-

ved on 31 May 1974 (1128 m-2 and 263 mg m-3) and on 28 Sep-

-2tember 1974 (1518 m- and 111 mg m-).

The sum of the biomass and density estimates of each

of the species (Fig. 4a and b), shows the general pattern

32

of high numbers and biomass in the colder winter months

when water levels were high and fish predation was lower

(Jones 1975). The large drop in biomass (to 412 mg m- 2 )

during January was not correlated with a similar drop in

population. On the contrary, the largest population level

occurred January 1974 (4708 m- 2 ).

Production

Table 4 and 5 show the distribution of population den-

sities and biomasses for the two chironomids according to

instar. There were large numbers of first instar larvae

which weigh very little. This trend is gradually reversed

until the largest chironomids are found within the fourth

instar. Apparently there is quite a bit of energy expendi-

ture during pupal transformation in T. decorus prior to em-

ergence, as pupae averaged 50% less in weight than fourth

instar larvae.

Tables 6 and 7 present estimates of population and

biomass apportioned between size classes of 0.5 mm in the

mayfly Brachycercus sp. Size class 1 was not encountered

(all nymphs exceeded 0.5 mm). Size classes 2 and 3 were

represented by much smaller numbers than expected, probably

due to the difficulty of separating them and loss through

the sieve bucket. Graphing size classes against frequency

yielded a bell-shaped curve, skewed to the right.

Annual secondary production by the two chironomids and

the mayfly are presented in Tables 8, 9 and 10 (constructed

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HO

r-L O

> o.

(NI U)

0U) r-

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Cd

4-)4J1

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U)

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z

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r-I E

a)

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oNcoceomo qz Co N Ln N

0 m r m O LOOCn0 (L)N 00o o r-i r-i m N Ln qv Ln* 0 0 0 . 0 . . .

C* C S 5 So 0m m

OH r-3 LC) Nr-A 2m *-ql o to 0

0 00 0 00 00 00 H0r-0Lr-C0r- qql r- r- k.0 l - 0 c q 0r-i W-14LO n () r N Nr-q (Y)

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r- CN (Y)4LT k0C-0 m D

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40

after Waters and Crawford 1973). Annual production was

approximately 2.4 g m-2 for Procladius sp. and 6.0 g m-2

for T. decorus for a total of 8.4 g m-2. The production

estimate for the caenid mayflies was approximately 1.9 g

-2 -lm y . The total production for the three species was

-2 -l10.3 g9m y

Energy Metabolism

Effects of seasonally encountered temperatures (AT)

on respiration rates (R) and patterns of metabolic compen-

sation to them in Brachycercus sp., Procladius sp. and T.

decorus are shown in Figure 5 and Tables 10-15. Mean meta-

bolic rates are statistically compared (Fisher's t test

between species at each AT in Table 11. The effect of spe-

cies on variance of log-transformed weight specific rates

was significant (p<0.05; ANOVA) at all but the 10 and 15 C

AT (Table 12). Differences in mean rates among species

were reduced at 10, 15 and 20 C. Regression equations for

the relation of log dry weight (mg) with log respiration

rate ( 1 02 h~ ) are presented in Table 13. Regression co-

efficients at 10, 25, and 30 C for Brachycercus sp. and at

5, 10 and 20 C for T. decorus were significantly different

(p<0.05; Student's t test). Effects of variation in weight

within species on variation in weight-specific metabolic

rate was highly significant (p<0.01; ANCOVA; Table 14).

Weight-adjusted weight-specific metabolic rates at each AT

41

TABLE 11. Comparison* of metabolic rates** among threebenthic insects at six seasonal acclimatizationtemperatures.

Acclimatization/DeterminationTemperature

C(Date) zcIadius sp. T. decorus Brachycercussp.

2.0+2.8 3.1+2.4 2.3+1.4

(16; 2.1) (21;0.9) (26;3. 0)***

5 0.3+1.0. 1.4+1.5 1.6+1.4(1-4-74) (3;5.4) (3;1.8) (4;1.1)

10 1.7+1. 3 2.3+1.1 1.9+1.4

(3-1-74) (3;2.8) (3;1.7) (6;3.6)

15 1.3+1.3 1.6+5.5 2.5+1.6

(11-15-74) (2;2.2) (3;0.6) (3;1.2)

20 3.5+1.4 2.5+1.2 2.0+1.2(10-13-75) (4;2.1) (4;1.9) (4;2.5)

25 7.7+1.1 6.5+1.6 3.0+1.1(5-21-74) (2;0.3) (3;0.3) (5;5.2)

30 4.2+1.0 6.6+1.2 3.4+1.0(8-11-74) (2;1.7) (5;0.5) (4;6.2)

*means not underscoreddifferent (p Z-0.05, Fishers

by a common line are significantlyt-test).

**Rates not adjusted for weight difference among speciesor temperature groups (ul 02 mg- h-1 ).

***(N;wt) where N is the number of reaction vessels con-taining 10 insects of nearly equal sizes and wt is the meanmg dry wt of the 10 insects in each vessel.

42

TABLE 12. ANOVA for acclimatization metabolic rates amonthree species of benthic insects at six seasonalacclimatization temperatures.

Source Sum Degreesof of of Variance F PVariance__- Squares Freedom

5 CAmong

SpeciesWithinTotal

10 CAmong

SpeciesWithinTotal

15 CAmongSpecies

WithinTotal

20 CAmong

SpeciesWithinTotal

25 CAmong

SpeciesWithinTotal

35 CAmong

SpeciesWithinTotal

0.8646

0.13541.0001

0.0281

0.04280.0709

0.1165

1.13751.2540

0.1230

0.10840.2314

0.3485

0.09810.4467

0.1913

0.03830.2297

2

79

2

9

11

2

5

7

2

9

11

2

7

9

2

810

0.4323 22.3432* 0.0009

0.0193

0.0141 2.9602 0. 1028

0.0048

0.0583 0.2560

0. 2275

0.0615 5.1039* 0.0330

0. 0120

0.1743 12.4286*

0.0140

0.0957 19.9605*

0.0048

0. 0050

0.0008

*Significant (P < 0.05).

0.7837

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47

Fig. 5. Acute, weight-adjusted acclimatization R-Tcurves of three species of insect found in the NTSU golfcourse pond.

w

w

10 5

CC)

-x

2w

w

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49

are given in Table 15 and illustrated in Figure 5. Dif-

ferences between adjusted rates within species at different

temperatures were tested using Tukey's multiple range test

(Table 15). Interpolated values for the two chironomids

at 15 C are presented in parentheses and were used for Q

calculations (Table 16). Differences between 5 and 10 C

were especially great for Brachycercus sp. and Procladius

sp. At the time of the 15 C experiment, both chironomids

were emerging and only small numbers of each instar were

available. Consequently, large variations in size and

metabolic rates, and small N's produced large variances

in the data at 15 C. Therefore, values were interpolated

for Procladius sp. and T. decorus at 15 C.

Brachycercus sp. appeared to compensate from 10 to 20

(Q10 = 0.8) and from 25 to 30 C, (Q1 0 = 1.5) but not for

temperature changes from 5 to 10 (Q1 0 = 4.0) and from 20

to 25 C (Q1 0 = 4.2). Procladius sp. appeared to compensate

only between 25 and 30 C (Q10 = 0.6). T. decorus exhibited

a Q10 greater than 2.0 only between 5 and 10 C (Q10 = 2.7)

and appeared insensitive to temperature changes at all

other experimental temperatures.

Annual Energy Flow

Estimated annual energy flow (A = P + R) through the

three benthic insect populations is shown in Table 15.

Brachycercus sp. processed the most energy (C= 263 kcal m-2

y~1 ), although the estimated assimilation efficiency for

50

Brachycercus sp. was only 19% (A = 51 kcalrn2 y ). The

ratios of energy to total benthic production (P) and the

total energy of total benthic respiration (R), to assimila-

ted energy (A) were 51% and 49% respectively (P= 64 kcal

-2 -l -2 -l -2 -lm y , R + 62 kcal m y , A= 126 kcal m y ). Brachy-

cercus sp. used 78% of its A for respiration (R = 40 kcal

-2 -1m y ) and apportioned only 22 % into production of bio-

mass (P= 11 kcal m2yl). Procladius sp. and T. decorus

transformed much more energy of assimilation (A = 18 kcal

-2 -1 -2 -1m y , and 57 kcal m y , respectively, into production

-2 -l -2 -lof biomass (P = 13 kcal m y and 40 kcal m y ) than to

- 2 -1 -) -respiration (R =5 kcal m y and 17 kcal m'yl). The

ratio of P to R for the three populations is about 50%.

51

TABLE 17. Annual energy flow* in two species of midgelarvae and one species of mayfly nyph from thebenthos of a small pond ecosystem in north-centralTexas.

rl u enies Brachycerdus Total

C** 45 (10.7)

FU** 27 (6.5)

A 18 (4.2)

R 5 (1.0)

P 13 (3.2)

142 (33.4)

85 (19.9)

57 (13.5)

17.2 (3.9)

40 (9.6)

263 (62.8)

212 (50.7)

51 (11.9)

40 (9.4)

11 (2.5)

450 (107.1)

324 (77.1)

126 (30.0)

62 (14.7)

64 (15.3)

*IBP Notation.

Values are in kcal m-2 -1, kj m-2 -1

**Calculated from literature values: All other dataare empirical or are summed from empirical data (seeMethods and Materials for formulae).

52

DISCUSSION

Generally, a very low number of species was found on

any given sampling date. Recently, Driver (1977) concluded

that chironomid species diversity is directly related tothe stage of development of the plant community, which inturn is greatly affected by changes in water level. Thenumber of species present in the benthos in the NTSU pond

appears to have resulted from the effects of water fluctu-

ations and the mechanical and chemical removal of the algae

mat early in the study.

Trees contributed an unknown amount of energy into thebenthos. The littoral zone consisted primarily of leaf

detritus, among which were found more mayflies and chirono-

mids than in the other substrate types combined. The rela-tionship between temperature and fish predation and the

consequent effect on the benthic invertebrates will be dis-

cussed in the following section.

Population Dynamics

The benthic invertebrates exhibited several drastic

fluctuations in population densities and biomass in responseto several environmental factors. Drawdowns always reducedbiomass and numbers by effectively eliminating the littoralzone (Fig. 2b, Fig. 4). Fish predation on the benthos was

53

significant only when water temperature exceeded 15 C

(Jones 1975). This accounts for the inverse relationship

between the benthic population and temperature (Fig. 2a,

Fig. 4).

Environmental stresses affected population dynamics to

the extent that life histories of macroinvertebrate popula-

tions was obscured. However, generalized life histories

and probable trophic positions are available from the lite-

rature. The presence of only two species of chironomids

probably resulted from the drastic fluctuations in water

level (Driver 1977). T. decorus, a common chironomid in

warm, shallow, oxygen-deficient ponds, is a secondary pro-

ducer which feeds on algae and detritus. It often exhibits

a multivoltine life cycle in warm waters (Wirth and Stone,

in Usinger 1969). Procladius spp. are encountered in lakes

and ponds where prey items are abundant. It therefore fills

the trophic position of a secondary consumer. Pupae of

Procladius were encountered only from February 1973 through

March 1974 (Table 4), indicating the possibility of a uni-

voltine life cycle with a 4-month winter emergence. How-

ever, absence of pupae in the samples may be an artifact

of the lower population densities in warmer months. Annual

turnover ratios (TR) of both species are very high (Table

16), and a high TR is gemerally thought to be typical of

species which exhibit more than one generation per year

(Waters 1969, McClure and Stuart 1976).

54

Brachycercus sp. appears to be multivoltine with con-

siderable brood overlap. Clifford et al (1973) summarized

ephemeropteran life cycles on a latitudinal basis and sta-

ted that mayflies in the South should display that pattern.

However, Brachycercus sp. exhibited a low TR (Table 16)

which is characteristic of univoltine or bivoltine species

(e.g. Jonasson 1972, Kimerle and Anderson 1976). Brachy-

cercus sp. may be a detritivore. The largest numbers (more

than 60%) of this tiny mayfly were encountered in the leaf

detritus and other allocthanous material in the littoral

zone. Biomass and population densities (Fig. 3, g and h)

were severely disturbed by water fluctuations (Fig. 2a).

The effect of fish predation was the same as that observed

in the chironomids.

Production

Production estimates are notably higher than litera-

ture values (Table 16). Turnover ratios for T. decorus and

Procladius sp. are much higher than the reported range for

aquatic insects (2.5-5, Waters 1969), while the turnover

ratio for Brachycercus sp. is lower. Production rates are

direct reflections of complex interactions of environmental

factors and may vary considerably from year to year. There-

fore, until more long term averages are available (e.g.

Jonasson 1972) comparisons between species, localities,

habitats, etc., may not be very meaningful.

55

TABLE 18. Comparisons of secondary production in selectedpopulations of benthic invertebrates.

Species Trophic HabitatLevel

Chironomus anthracinus b Lake Esrom, Sweden

Tendipedes decorus b NTSU pond, Texas, USA

Baetis vernus d German river

Ephemerella subvaria d Minn. stream, USA

Deleatidium sp. a New Zealand river

Procladius sp. a NTSU pond, Texas, USA

Brachycercus sp. d NTSU pond, Texas, USA

Chironomus anthracinus b Uchinsk Res. USSR

Baetis bicaudatus d Mt. stream, Utah, USA

Baetis vagans d Valley Creek, Minn. USA

Procladius crassinervis a Loch Leven, Scotland

Procladius choreus a Loch Leven, Scotland

Glyptotendipes barbibes b Lagoon, Ore. USA

Procladius pectinatus a Lake Esrom, Sweden

Hexagenia limbata c Kansas Res. USA

Coroterpes mexicanus d Brazos R., Texas, USA

Psilotanypus rufovittatus a Loch Leven, Scotland

Procladius simplicistilus a Loch Leven, Scotland

*a = carnivorous chironomid, b = herbivorous chirono-mid, c = carnivorous mayfly, d = herbivorous mayfly.

56

TABLE 18 --Continued

Production Turnover Sourcemg m 2 y Ratio

12900 1.2 Jonasson 1972

6031 19.6 This study

5300 Illies 1974

3330 7.2 Waters and Crawford 1973

2820 2.7 Winterborn 1976

2449 19.8 This study

1920 1.6 This study

1800 2.3 Sokolava 1968

1400 Pearson and Kramer 1972

1100 9.7 Waters 1975

1059 2.2 Charles et al. 1975

896 3.3 Charles et al. 1975

532 8.5 Kimerle and Anderson 1971

500 1.9 Jonasson 1972

400"- Horst 1976

300 15.4 McClure and Stuart 1976

263 10.6 Charles et al. 1975

166 2.4 Charles et al. 1975

57

Energy Metabolism

Although some attention has been given to respiration

in chironomids (e.g. Jonasson 1972, McFarland and McClusky

1972, Erman and Helm 1970, Harp and Campbell 1973, Edwards

1975), I am not aware of any studies on Tendipes decorus or

southern species of Procladius. Respiration studies on

ephemeropterans are also rare. Kamler (1971) has reported

on Cleon dipteran from a pond in Poland, and Ulanski and

McDiffett (1972) have reported on Isonychia sp. (Baetidae)

and Stenonema fuscum (Heptigeniidae), with emphasis on di-

urnal variations in metabolic rates. I am not aware of

any respiration studies on mayfly nymphs from the family

Caenidae. Weight adjusted metabolic rates fall within the

ranges reported for these families. However, since caenid

nymphs are much smaller than any other mayfly family, high-

er weight specific rates were expected.

Comparisons of metabolic rates (Table 11 and 12) reveal

that differences in rates, and the effect of species differ-

ences on rates are reduced at 10- 15 and 20 C. In addition,

weight adjusted metabolic rates (Table 15, Fig. 5) and Q10

values calculated on weight adjusted rates, show that the

three species studied appear to exhibit some insensitivity

to temperature changes at the same "mid-range" temperatures

(Fig. 5), which are commonly encountered when numbers arid

58

individual biomass (growth) are increasing. This could be

of selective advantage to insect populations which are

significantly decreased by environmental pressures (i.e.

fish predation) which are closely correlated with increas-

ing temperature.

Reports of metabolic compensation (Precht et al.1955,

Precht 1958, Prosser 1974) in vertebrate and invertebrate

poikilotherms are common in the literature. A partial list

includes: Berg 1953, Korg 1954, Berg 1966, Bishop and

Gordon 1967, Newell and Pye 1970, Dunlap 1969, 1971, Fitz-

patrick et al 1971, 1972, Dame 1972, Fitzpatrick 1972a, b,

1973, Miller and Mann 1973. At present, there are few re-

ports of metabolic compensation in aquatic insects (Pattee

1955, Parhon 1909, Sayle 1928, Lawton 1971, Brown and Fitz-

patrick 1977), and many thermal ecologists (Bullock 1955,

Keister and Buck 1964, Vernberg and Vernberg 1969) have

concluded that the ability to metabolically compensate is

relatively poor in this large class.

Energy Flow

Population and community energetics of several benthic

insects are presented in Tables 18 and 19. Populations

with high assimilation efficiency appear to place more of

energy into metabolism (i.e. Numbers 1-5 average 64% of

A allocated to R). Brachycercus sp. appears to be an excep-

tion to this generalization, as is Procladius pectinatus

(Jonasson 1972). Species which exhibit a low A appear to

59

TABLE 19. Comparison of annual population energetics ofselected aquatic insects.

Species Studied Trophic Type of EcosystemLevel* and Location

Chironomus anthracinus b Oligotrophic Lake,(Chironomidae) Sweden

Glyptotendipes barbipes a Sewage lagoon,(Chironomidae) N.W., USA

"midges" b Florida river,(Chironomidae) S., USA

Tanypodinae Larvae a Large loch,(Chironomidae) Scotland

Chaoborus falvicans Oligotrophic lake,(Diptera, Chaoboridae) Sweden

Tendipedes decorus a Eutrophic pond,(Chironomidae) S.W., USA

Corydalus cornutus e River, S.W., USA(Meggloptera)

Procladius sp. a Eutrophic pond,(Chironomidae) S.W., USA

Brachycercus sp. d Eutrophic pond,(Ephemeroptera) S.W., USA

Procladius pectinatus Oligotrophic lake,(Chironomidae) Sweden

Pyrrhosoma nymphyla e Eutrophic ponds,(Odonata, Zygoptera) England

*a = carnivorous chironomid, b = herbivorous chironomid,c = carnivorous mayfly, d = herbivorous mayfly, e = aquaticcarnivore

60

TABLE 19--Continued

A

kcal

437

437

287

140

65

57

33

18

51

10

1

P

m-2 -lY

75

192

123

57

14

40

16.7

13

11

3

0.6

RSource

362

245

141

82

51

17

16

5

40

7

0.6

Jonasson 1972

Kimerle and Anderson 1972

Odum 1957

Charles et al. 1975

Jonasson 1972

This study

Brown and Fitz patriot 1978

This study

This study

Jonasson 1972

Lawton 1971

61

TABLE 20. Comparison of annual benthic community energetics.

Type of A P REcosystem SourceLocation kcal m- 2 -

Oligotrophic 532 100 432 Jonasson 1972lake, Sweden

Sewage lagoon 437 245 192 Kimerle and AndersonN.W., USA 1972

Georgia Pond 409 326 183 Welch 1967 (Cited byS.E., USA Welch 1976)

Florida River, 574 246 282 Odum 1957S.E., USA

Texas Pond 126 64 62 This studyS.W., USA

Small lake, 9 3 6 Welch 1976CanadianArctic

62

place more available energy into production (P) of bio-

mass.

The energy flow through the benthic insects in the

NTSU pond appears to be low when compared to data for other

benthic systems. Fluctuations in water level, intense fish

predation and the loss of the algal mat probably contributed

significantly to a low annual energy flow.

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