J. Great Lakes Res. 14(2):148-156Internat. Assoc. Great Lakes Res., 1988

ORGANIC CONTAMINANTS IN ADULT AQUATIC INSECTSOF THE ST. CLAIR AND DETROIT RIVERS, ONTARIO, CANADA

Jan J. H. Ciborowski and Lynda D. CorkumDepartment of Biological Sciences

University of WindsorWindsor, Ontario N9B 3P4

ABSTRACT. Night-flying Trichoptera and Ephemeroptera were attracted using long-wave ultra­violet light and collected from 8 Canadian sites adjacent to the St. Clair and Detroit rivers. Gaschromatographic analysis of the extracts from 40 samples of the insects revealed significant concen­trations ofpentachiorobenzene (QCB), hexachlorobenzene (HCB), octachlorostyrene (OCS), and 16polychlorinated biphenyl (PCB) congeners in almost all animals collected. Principal componentanalysis accounted for 84% of variation in contaminant concentration among samples. The principalcomponents (PCs) correlated highly with concentrations of9 hexa-, hepta-, and octachlorobiphenyls(PC-I,' 46% ofoverall variation), 4 tetra- andpentachlorobiphenyls (PC-II; 17% of variation), QCB,HCB, and OCS (PC-III,' 8%), and 2 trichlorobiphenyls (PCs IVand V; each 6% ofvariation). ValuesofPC-I were significantly greater among Detroit River than among St. Clair River samples. ValuesofPC-II were highest for samples from upstream stations on the two rivers. Values of PC-III werehigher for St. Clair River samples than for Detroit River samples. These trends are consistent withpatterns observed in other biota and sediment previously collected from equivalent sites. Contami­nant levels also varied among taxa collected from the same site, possibly because ofdifferent larvalfeeding habits or microdistribution, or adult flight ability. Collection of adults has potential as aninexpensive alternative to aquatic sampling methods in surveys of biota for organic contamination.ADDITIONAL INDEX WORDS: Toxic substances, chlorinated hydrocarbons, Ephemeroptera,Trichoptera.

INTRODUCTION

Recent research has increasingly stressed theimportance of benthic invertebrates as agents ofcontaminant transfer between sediments andhigher trophic levels in freshwater aquatic systems.Larsson (1984) showed that larval Chironomidaecould accumulate significant levels of PCBs fromcontaminated sediments. Oliver (1984) reportedsimilar capabilities for oligochaete worms. Thetendency of bivalve molluscs to selectively accumu­late toxic organic compounds has stimulatedresearch to assess their potential utility as biomoni­tors (Pugsley et al. 1985, Kauss and Hamdy 1985).

Investigation of invertebrate contamination inaquatic habitats has been hindered by the difficul­ties of obtaining samples efficiently, especially inlarge rivers. Aquatic annelids and larval insects areabundant in both lentic and lotic habitats, but sep­arating organisms from the sediments with whichthey are collected requires expertise and intensive

148

effort. Although molluscs can be retrieved andanalysed individually, they may occur sporadicallyand in low densities. Diver-assisted collection alle­viates some sampling problems, but poor visibility,strong currents, and hazards associated with com­mercial shipping traffic render certain habitatsinaccessible.

Ephemeroptera (mayflies) and Trichoptera(caddisflies) pass most of their lives as aquatic lar­vae, during which time feeding and benthic move­ments bring them into intimate contact with sus­pended and deposited sediments. The wingedadults are largely nocturnally active, at which timethey disperse, mate, and the females oviposit.Many species are attracted to lights, sometimes inenormous numbers. This is a common summerphenomenon at locations along the St. Clair andDetroit rivers. These rivers have been designatedAreas of Concern (International Joint Commis­sion 1985) because of extensive organic contami-

ORGANIC CONTAMINANTS IN AQUATIC INSECTS 149

TABLE1. Location of1986 sample stations and sunset weather conditions. (DR = Detroit River, SCR = St. ClairRiver, DC = overcast).

Latitude Longitude Temp. WindStn. River Designation (North) (West) Date (0C) Sky (km h-1)

1 DR Amherstburg 42°06'01" 83°06'47" 5 July 24 high OC W 2-52 DR R. Canard 42°11'48" 83°06'13" 6 July 28 hazy calm3 DR Windsor A 42°18'23" 83°04'27" 7 July 24 high OC calm4 DR Windsor B 42°20'27" 82°56'56" 9 July 22 clear calm5 SCR Port Lambton 42°38'38" 82°30'14" 14 July 21 clear calm6 SCR Sombra 42°45'04" 82°27'54" 16 July 22 hazy E 2-57 SCR Corunna 42°53'26" 82°27'15" 15 July 24 high OC S 2-58 SCR Sarnia 42°58'26" 82°24'32" 10 July 17 high OC NW 2-5

nant accumulation resulting from release of indus­trial effluents.

The objectives of our study were to determine ifadult insects that have emerged from aquatic habi­tats might be useful as a biomonitoring tool and acost effective alternative to sampling organismsdirectly within the aquatic environment. Wewished to evaluate whether enough adults,attracted with longwave ultraviolet light, could becollected to permit analysis for organic contami­nants, and whether samples from sites on the S1.Clair and Detroit rivers harbored significant con­taminant levels.

METHODS

Sample Collection

Adults of aquatic insects were captured at eightCanadian sites approximately 8 km apart along theDetroit and S1. Clair rivers between 4 and 16 July1986 (Table 1). Stations were selected within 30 mof the east riverbank that provided a clear view ofthe river. Sampling was conducted on warm, rela­tively calm evenings from near sunset (2130 hEDT) until approximately 2300 h EDT (Table 1).

A white cotton sheet, which served as a lightreflector and as a substrate for insects, was placedover an automobile hood. Adults were attractedusing a 12V115W DC fluorescent long-wave ultra­violet (UV) lamp (length, 45 cm) placed on thesheet and powered from the automobile battery.Mode of collection varied with taxa. Adult Tri­choptera were captured using hexane-rinsed500-mL amber glass jars. Jar lids had a hole cutinto their center to accommodate the narrow endof a 12.S-cm dia. funnel. Insects were guided ontothe inner surface of the funnel and tapped into the

jar. Several g of dry ice within the jar both anaes­thetized and cooled trapped insects. Hexagenia(Ephemeroptera) adults that alighted on the sheetwere grasped by the wings and placed in amber jarscontaining dry ice. Upon completion of sampling,the sheet was quickly folded to retain insects thathad not been individually captured and trans­ported to the laboratory in a cooler containing dryice. All organisms were stored overnight in afreezer at -20°C prior to processing.

Sample Processing

The small size of the insects necessitated poolingorganisms prior to analysis. The number of ani­mals comprising a sample depended upon bothindividual size and quantities collected. In the lab­oratory, animals were sorted into precleaned glasscontainers using hexane-rinsed forceps. Althoughmany taxa were attracted to the UV light and inci­dentally captured, only four were sufficientlywidespread and abundant to be used for contami­nant analysis. We retained mayflies (Hexageniaand Caenis) and caddisflies (Macronema and "oth­ers"). "Other" caddisflies consisted of animals ofsize and coloration predominant at a particularsite; unusual specimens were not included. Tri­choptera were sorted without the aid of magnifica­tion by summer assistants having minimal entomo­logical training.

Preliminary weighing of individuals of eachtaxon at each site was conducted to estimate num­bers adequate for a sample. We attempted todivide animals evenly to produce at least two repli­cates, each of a total fresh weight between 2 and6 g. A subsample of organisms was taken fromeach replicate for further taxonomic analysis(including up to 100 "other" caddisflies per site, as

150 CIBOROWSKI and CORKUM

available) and biomass determination. Samples forcontaminant analysis were stored at -20°C for upto 6 weeks prior to extraction. Animals used forbiomass determination were weighed singly(Macronema, Hexagenia) or in groups of 6 (otherTrichoptera) or 25 (Caenis) to the nearest 0.1 mgon a Sartorius model 2462 balance immediatelyafter sorting, and again after drying at 60°C for24 h. Sample biomasses were estimated by multi­plying the number of animals in a sample by themean dry weight of animals in the correspondingbiomass subsample.

Extraction and Contaminant Analysis

Analysis for contaminants was performed by theGreat Lakes Institute analytical laboratory, Uni­versity of Windsor, following methods outlined byPugsley et af. (1985). Samples were placed in120 mL of acetonitrile with 40 mL water andhomogenized for 1-1.5 min with a polytronblender. The fluid was filtered under vacuumthrough a sintered glass funnel and placed in aseparatory funnel. The homogenization/filtrationprocedure was repeated once using 50 mL of freshacetonitrile, and twice more with 20-mL lots ofacetonitrile. One mL of concentrated sulphuricacid was added to hydrolyze lipids. The filtrate wasthen extracted by shaking for 2 min with a 150 mLportion and then two 75 mL portions of petroleumether. The petroleum ether extract was washed with200 mL of water and then dried by passagethrough a column containing 15 g of anhydroussodium sulphate. Samples were cleaned up by pas­sage through 20 mm x 40 cm glass columns con­taining 1-2 cm of anhydrous sodium sulphate over20 g of Florisil, eluted with 200 mL of petroleumether, and then concentrated to 5 mL with aKuderna-Danish evaporator.

Contaminant extracts were analyzed by injectionof 1-p.L samples into a Hewlett-Packard model5790A gas chromatograph (GC) equipped with a25 m x 0.25 mm fused silica column (J & W Scien­tific) and an electron capture detector. Splitlessinjection mode was used at an injector temperatureof 250°C. The column was temperature pro­grammed for 0.5 min at 50°C, heated to 250°C at2°C min-1 and held for 20 min at 250°C. Detectortemperature was 300°C. Helium carrier gas wasdelivered at a rate of 1.5 mL min-I. Detector make­up gas consisted of 5070 methane-95% argon at35 mL min-I. Peak areas of contaminants and stan­dards were measured with a Hewlett-Packard

model 3390A integrator. A blank analysis was con­ducted with each analytic series (2-5 randomlyselected samples).

Contaminants were quantified against a stan­dard mixture consisting of octachlorostyrene(OCS), pentachlorobenzene (QCB), and hexa­chlorobenzene (HCB), each at 5.0 p.g kg-I, andAroclors 1242, 1254, and 1260, each at 20 p.g kg-I.Identification and quantification of 16 PCB conge­neric constituents (see Table 3) was based on peakpatterns, relative retention times, and relative com­position of Aroclors as presented by Tuinstra andTraag (1983). Because relative composition of con­geners in Aroclors can vary from lot to lot, concen­trations of PCBs presented are tentative and mustbe regarded as relative rather than absolute; how­ever, the data are admissible for comparative pur­poses among samples. Analysis of blind samplesfor total PCBs produces results within 5% of truevalues (1986 International Joint CommissionQuality Assurance Program).

Equipment failures necessitated refrigeratingsome extracted samples for up to 18 d prior to GCanalysis. This introduced substantial variation toreplicates (stored samples had higher apparentconcentrations of contaminants due to solventevaporation). To evaluate this, relative concentra­tion of each sample (Y/Y, where Y is the mean ofall replicates of one taxon at one station) wasregressed against storage time for each of the con­taminants examined. Significant relationships (p< 0.01) between relative concentration and stor­age time were found for 11 of 19 compounds (max­imum R2 = 0.39, overall median R2 = 0.22).Accordingly, values of each contaminant were sta­tistically adjusted to a standard storage timeaccording to the derived regression equations(Sokal and Rohlf 1969, pp. 444-445). This proce­dure reduces the variance among replicates takenas a group, without affecting the mean value ofthese replicates.

Insufficient material was available to permitassessment of recovery efficiency or insect lipidcontent. Recovery efficiencies for our system usingbivalve tissues average 70-85% for HCB, OCS,QCB, and total PCBs (Pugsley et af. 1985; unpub­lished data). Calculations were not corrected forprocedural losses.

Statistical Analyses

Concentrations of many of the compounds werehighly correlated with one another among repli-

ORGANIC CONTAMINANTS IN AQUATIC INSECTS 151

cates, taxa, and sites. Consequently, principalcomponent analysis (PCA; Dixon and Brown1979) was used to reduce the data set prior to fur­ther statistical analysis. Concentrations wereLn(Y + 1) transformed prior to analysis. Followingthe PCA analysis, we determined the degree ofassociation between the original 19 variables (com­pounds) and the derived principal componentsusing Spearman's rank correlation coefficient(Sokal and Rohlf 1969). Analyses of variance(ANOVA, unbalanced hierarchical design; SASInstitute Inc. 1985) were then used to test for dif­ferences in values of the principal componentsamong rivers and sites for each taxon, and alsopairs of taxa occurring at common sites. Signifi­cant differences detected among principal compo­nents scores imply equivalent differences in theconcentrations of the contaminants associatedwith each component.

RESULTS

A total of 40 samples was analyzed for PCBs andthree other organochlorine compounds, of whichone sample was strongly deviant from replicates andwas discarded. Adults of Trichoptera were the onlyorganisms collected at all stations. The caddisflyMacronema zebratum Hagen (Hydropsychidae),whose larvae are filter-feeders, comprised the entireTrichoptera collection at Amherstburg. Samples ofTrichoptera from other stations were also domi­nated by genera of hydropsychid net-spinning cad­disflies; primarily Cheumatopsyche spp (Table 2).Leptoceridae were the only other caddisflies com­monly collected. They dominated samples at PortLambton. Mayflies, Caenis (primarily C. latipennisBanks) and Hexagenia (mostly H. limbata (Ser­ville», were each collected at four stations. Overallabundance of flying adults was much reduced at thethree upstream sites of the St. Clair River. This wasreflected in the reduced number of replicates ana­lyzed from these areas.

All taxa at all sites contained detectable levels ofboth PCBs and other organochlorine compounds(Table 3). Five principal components accountedfor 84070 of the variation in contaminant concen­trations among samples. The first principal com­ponent (PC-I) accounted for 46% of overall varia­tion and was highly positively correlated withconcentrations of nine PCB congeners (primarilyhexa-, hepta-, and octachlorobiphenyls) and nega­tively correlated with HCB concentration (Table4). PC-II explained an additional 17070 of variation

TABLE 2. Relative taxonomic composition (percent)of "other" Trichoptera used in contaminant analysis.Figures in bold face are family totals. All specimenscollected at station 1 were Macronema zebratum(Hydropsychidae).

STATION

Taxon 1 2 3 4 5 6 7 8

Hydropsychidae 100 70 84 94 36 65 98 98Cheumatopsyche spp 64 76 94 27 52 82 94Hydropsyche spp 6 7 9 13 16 4Potamyia sp. 1

Lepidostomatidae 0 0 0 0 13 0 0Lepidostoma sp. - - 13 - -

Leptoceridae 30 16 6 59 22 2 1Ceraclea spp - 21 16 4 16 13 - 1Mystacides spp 4Oecetus spp 8 - 30 9 2 -Triaenodes sp. 1 - - 9 -Unidentified 1 1 -

Molannidae 0 0 0 0 0 0 1Molanna sp. 1

Polycentropodidae 0 0 0 5 0 0 0Neureclipsis sp. I -Polycentropus sp. - - - 4 -

Total No. examined NA 100 100 103 70 23 99 100

and was associated with five tetra- and penta­chlorobiphenyls. Three contaminants, QCB,HCB, and OCS, were positively correlated withvalues of PC-III, which accounted for 8% of over­all variation. PC-IV and PC-V were each highlycorrelated with a different trichlorobiphenyl andeach removed an additional 6% of variation.

Spatial trends in contaminant concentrationswere evident for all taxa, and these patterns arereflected in site-to-site variation in mean principalcomponent scores (Fig. 1).

Detroit River samples of Trichoptera (stations1-4, Table 3) had high concentrations of highlychlorinated PCBs (PCBs associated with PC-I) andrelatively low non-PCB organochlorine concentra­tions. Maximum concentrations of each of the PCBcongeners (except PCB 18) were recorded in Tri­choptera from the two Windsor stations (stations 3and 4, Table 3). Mean values of PC-I for DetroitRiver Trichoptera were significantly greater thanvalues for the St. Clair River (Fig. lA; p < 0.01).

In contrast, Trichoptera collected from the St.Clair River (stations 5-8, Table 3) had significantlyhigher QCB, OCS, and especially HCB concentra­tions than their Detroit River counterparts. Thiswas reflected in significant differences in meanscores of PC-III (Fig. lC; P < 0.01).

Significant variation was also evident among tri­chopteran samples collected from upstream versus

10-0CItN

TABLE 3. Mean (and S.E.) concentration of organic contaminants (p.g kg-I dry weight) in aquatic insect taxa among stations.CONTAMINANT

No. -1 Dry PCB PCB PCB PCB PCB PCB PCB PCB PCB PCB PCB PCB PCB PCB PCB PCBStn. Taxon sample WI. (g) N QCB HCB OCS 18 28 52 66 87 95 97 101 118 138 141 153 170 180 187 194

1 Macronema 150 1.9328 5 3.99 32.94 42.98 0.06 1.98 3.75 20.4 2.84 7.77 1.86 19.02 13.80 25.71 2.97 29.25 6.30 22.80 12.33 3.78(1.497) (2.811) (3.601) (0.057) (0.435) (0.471) (2.472) (0.399) (1.581) (0.204) (5.853) (3.066) (2.991) (1.401) (3.732) (3.366) (3.360) (1.242) (1.152)

Macronema 108 1.1718 l' <0.49 10.75 21.18 <0.09 1.50 1.92 12.81 2.28 <3.84 1.56 10.44 15.78 27.33 2.25 35.52 22.62 34.02 17.49 8.55NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA

Trichoptera 500 0.8958 3 1.28 19.51 36.21 0.63 2.01 9.60 19.17 6.30 23.88 4.05 25.74 30.48 45.06 9.96 48.84 11.40 37.41 20.13 4.11(Other) (0.648) (1.844) (4.647) (0.543) (0.660) (2.772) (4.503) (1.767) (6.600) (0.873) (6.882) (7.833) (12.138) (3.564) (12.882) (6.108) (12.144) (5.493) (1.212)

Caenis 1850 1.2536 2 2.24 25.54 10.47 0.57 1.83 8.58 15.30 5.10 13.56 4.29 14.37 13.65 19.62 1.35 20.64 1.35 9.27 5.52 0.84(0.310) (4.776) (0.185) (0.750) (0.510) (2.466) (2.124) (1.017) (1.587) (0.933) (4.554) (4.257) (3.543) (1.347) (4.758) (0.078) (3.084) (1.362) (0.846) n

Trichoptera 550 1.1568 3 1.50 15.65 35.79 0.87 2.67 12.75 23.64 8.79 29.22 5.07 38.22 46.32 62.25 19.59 76.56 24.24 70.02 36.27 12.12 ..(Other) (0.274) (2.376) (3.992) (0.471) (1.581) (3.888) (3.717) (1.377) (1.575) (0.831) (4.935) (10.095) (11.694) (4.146) (15.462) (7.143) (15.549) (6.798) (1.632) =0

Caenis 2000 0.7200 2 1.16 21.88 17.54 0.72 6.18 8.16 32.82 10.08 32.70 6.63 28.89 23.91 42.33 9.78 37.59 6.87 19.26 17.67 2.13 :=(1.162) (1.705) (0.126) (0.708) (0.279) (8.151) (1.377) (0.384) (1.611) (0.330) (0.627) (0.174) (2.193) (1.086) (0.027) (6.858) (0.228) (3.900) (0.219)

~4 Trichoptera 600 1.1111 4 2.65 20.77 40.94 0.84 2.01 11.88 22.44 10.38 24.84 6.39 30.48 35.04 62.64 11.01 59.34 14.28 55.14 24.45 4.95(Other) (0.382) (1.588) (9.069) (0.195) (0.726) (1.797) (3.027) (1.608) (0.480) (1.077) (4.188) (17.619) (6.933) (1.950) (16.050) (5.736) (11.271) (5.352) (1.347)

00Hexagenia 110 1.2578 3 9.48 119.25 17.33 0.09 0.27 4.92 10.23 2.94 11.49 3.21 8.34 9.09 16.65 3.03 18.45 3.09 10.53 5.34 2.16 ~

(0.750) (7.746) (1.469) (0.092) (0.261) (0.738) (1.554) (0.504) (0.927) (0.432) (2.313) (2.034) (0.600) (1.065) (2.835) (1.590) (2.361) (0.756) (1.140) ..Trichoptera 375 0.9222 2 2.84 48.48 147.19 0.36 0.63 6.95 8.10 4.68 4.17 2.34 18.18 11.91 20.88 1.68 18.39 4.17 12.51 4.74 <0.30 ~

(Other) (1.134) (8.140) (39.937) ~0.351) (0.630) (3.498) (0.945) (1.230) (1.266) (1.095) (14.580) (3.480) (4.578) (0.078) (4.962) (4.179) (4.080) (0.027) NA ==-Caenis 3750 1.2747 3 16.Q7 222.68 253.32 0.30 0.06 2.55 19.29 5.76 27.30 4.68 17.28 15.03 20.13 1.14 16.98 0.12 6.27 3.72 0.36 n(1.077) (24.677) (17.454) (0.366) (0.042) (2.541) (2.709) (2.886) (14.061) (0.351) (1.656) (2.010) (1.584) (0.288) (1.644) (0.108) (1.242) (0.804) (0.219)0Hexagenia 120 2.0274 2 1.50 31.35 6.10 0.18 0.36 4.14 9.21 1.92 8.49 1.41 5.40 4.35 6.00 0.57 8.01 3.63 4.35 1.68 0.93

~(0.211) (7.229) (1.514) (0.009) (0.001) (1.836) (1.569) (0.024) (3.357) (0.027) (0.273) (0.336) (0.495) (0.084) (0.723) (1.701) (0.900) (0.420) (0.051)

6 Trichoptera 175 0.4783 1 3.73 45.28 261.19 2.73 <0.15 7.56 14.64 6.69 8.28 3.57 17.79 7.05 27.06 2.34 18.60 <0.33 36.60 4.44 5.85(Other) NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA

~Caenis 1000 1.0650 1 6.23 84.95 97.98 0.15 0.06 8.19 13.05 4.32 23.88 2.97 11.61 9.30 11.31 0.60 9.93 <0.15 2.94 2.16 0.63NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA

Hexagenia 82 1.3962 I 3.70 133.30 36.22 0.48 0.90 3.30 10.65 3.48 8.46 2.58 15.33 10.05 16.20 1.68 19.17 7.23 9.51 3.96 <0.21NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA

Trichoptera 500 1.2450 2 2.06 40.42 181.07 0.69 0.72 3.69 14.64 5.46 13.20 3.18 14.25 9.36 25.98 2.61 18.27 3.48 13.05 5.31 <0.24(Other) (0.105) (0.004) (31.434) (0.267) (0.306) (0.348) (4.092) (0.777) (6.255) (0.387) (1.659) (1.338) (3.300) (1.113) (2.052) (3.474) (1.221) (1.794) NA

Trichoptera 325 1.2144 2 21.37 187.27 415.40 0.54 0.66 16.05 20.43 9.81 33.27 6.12 28.80 18.42 16.95 1.35 14.79 <0.12 4.89 2.49 0.54(Other) (3.072) (27.591) (100.029) (0.726) (0.660) (10.698) (4.965) (4.959) (23.688) (2.175) (13.380) (8.514) (0.174) (1.338) (0.603) NA (1.221) (2.496) (0.318)

Hexagenia 67 0.8546 2 2.62 18.63 <0.41 <0.15- <0.09 8.46 8.76 6.24 15.03 6.33 23.49 14.94 21.03 4.89 37.53 5.85 15.78 6.24 5.49(2.617) (2.049) NA NA NA (0.619) (2.218) (0.795) (7.425) (1.920) (1.920) (0.741) (1.692) (0.987) (2.238) (4.347) (0.579) (1.080) (0.180)

• 1 replicate discarded.

ORGANIC CONTAMINANTS IN AQUATIC INSECTS

TABLE 4. Correlation between concentration 0/ organic contaminants and principal components.

Principal Component

153

Compound Designation1

2,2',3,4,4',5,5'-Heptachlorobiphenyl PCB 1802,2',4,4',5,5'-Hexachlorobiphenyl PCB 1532,2',3,4',5,5',6'-Heptachlorobiphenyl PCB 1872,2',3,4,4',5'-Hexachlorobiphenyl PCB 1382,2',3,3',4,4',5,5'-Octachlorobiphenyl PCB 1942,2',3,4,5,5'-Hexachlorobiphenyl PCB 1412,3',4,4',5-Pentachlorobiphenyl PCB 1182,2',4,5,5'-Pentachlorobiphenyl PCB 1012,2',3,3',4,4',5-Heptachlorobiphenyl PCB 1702,3',4,4'-Tetrachlorobiphenyl PCB 662,2' ,3' ,4,5-Pentachlorobiphenyl PCB 972,2',3,5',6-Pentachlorobiphenyl PCB 952,2',5,5'-Tetrachlorobiphenyl PCB 522,2',3,4,5'-Pentachlorobiphenyl PCB 87Pentachlorobenzene QCBHexachlorobenzene HCBOctachlorostyrene OCS2,4,4'-Trichlorobiphenyl PCB 282,2',5-Trichlorobiphenyl PCB 18

PC-I

0.889**0.879**0.842**0.824**0.824**0.805**0.756**0.644**0.532**0.498*0.2620.1630.1550.376

-0.227-0.458*0.0260.2470.107

PC-II PC-III PC-IV

0.151 -0.191 0.1830.328 -0.171 0.2330.195 -0.214 0.3640.318 -0.063 0.3190.226 -0.200 -0.0610.400 -0.128 0.0430.457* 0.084 0.1470.523** 0.086 0.0820.124 -0.380 0.0730.430* 0.242 0.454*0.866** 0.048 0.0610.825** 0.073 0.1980.783** -0.114 -0.2110.739** 0.053 0.1200.091 0.819** -0.135

-0.239 0.787** -0.217-0.108 0.759** -0.0170.018 -0.281 0.900**0.269 0.159 0.045

PC-V

0.2160.0240.0040.225

-0.1330.0260.0930.2970.2730.1110.144

-0.1240.0610.448*

-0.206-0.0190.3290.0840.847**

IPCB numbering follows Ballschmiter and Zell 1980. *p<O.Ol **p<O.ool

downstream sites within each river. Samples fromupstream stations had higher concentrations of 4-,5-, and 6-chlorine PCBs (those associated with PC­II) than occurred in downstream samples (PCBs 52to 153, Table 3). However, whereas the contrastsfor samples from the Detroit River occurredbetween the two upstream stations (3 and 4) andthe two downstream sites (1 and 2), St. Clair Riverstation differences were between the single Sarniasite (8) and the three downstream stations (5, 6,and 7, Table 3). Analysis of variance indicated sig­nificant within-river differences among PC-IIscores, with which these PCB congeners werehighly correlated (Fig. IB; P < 0.05). Values ofPC-II did not differ between rivers (p > 0.05).

There were no discernable trends in concentra­tion of the two trichlorobiphenyls found in Tri­choptera (p > 0.05; Figs. ID and IE).

Ephemeroptera tended to have low concentra­tions of PCBs associated with PC-I relative to Tri­choptera from comparable sites (stations 4, 5, 7,and 8, Table 3; Fig. IA). Hexagenia samples fromSarnia (station 8) had higher concentrations ofPCBs associated with PC-II (Fig. IB) and lowernon-PCB organochlorine concentrations (Fig. IC)than did Hexagenia samples from stationsupstream and downstream of Lake St. Clair (sta-

tions 4, 5, and 6). Overall, Trichoptera had signifi­cantly higher levels of QCB, HCB, and OCS thandid Hexagenia (expressed as mean PC-III values,Fig. IC; p < 0.05).

Samples of Caenis varied among sites primarilywith reference to QCB, HCB, and OCS concentra­tions (Table 3). Samples from the St. Clair River(stations 5 and 6) had much higher concentrationsof these chemicals than did collections from theDetroit River (stations 2 and 3, Table 3). St. ClairRiver Caenis in general also had greater concentra­tions of the three non-PCB compounds than dideither Trichoptera or Hexagenia occurring atequivalent sites (p < 0.05; Fig. IC). Caenis sam­ples from the upper Detroit River (station 3) dif­fered from remaining Caenis samples (stations 2,5, and 6) in having greater levels of highly chlorin­ated PCBs (associated with PC-I, Fig. IA) andlower concentrations of HCB (Table 3).

DISCUSSION

To be potentially useful for biomonitoring, natu­rally occurring organisms should meet several cri­teria. Taxa should be widespread and accessibleacross a range of environmental conditions. Sam­ples must provide data sufficiently precise that site-

to-site variation can be discerned with reasonableconfidence; and the derived measurements mustaccurately reflect contaminant patterns of thebiota at large. Our study shows that adult aquatic

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insects may be easily collected using UV lightattraction in numbers adequate for contaminantanalysis. Variability in contaminant concentrationswas sufficiently low that we could detect signifi­cant differences in contaminants among taxa andwithin single taxa among sites. Note, however, thatour "replicates" at sites represent single, large sam­ples that were partitioned in the laboratory.Accordingly, they reflect variation in our subsam­pling and processing methods rather than on-siteenvironmental variability. Nevertheless, each col­lection represents an integrated sample of individ­uals from a potentially extensive surrounding area.Spatial patterns of contamination indicated by oursamples appear to correspond with results of otherstudies of organic contaminants in biota and sedi­ments of the St. Clair and Detroit rivers.

Trichoptera were present at all eight sites of boththe Detroit and St. Clair rivers; Caenis were col­lected at two sites on each river; and three of fourHexagenia sites were located on the St. Clair River.Concentrations of highly chlorinated PCBs (hexa-,hepta-, and octachlorobiphenyls) were signifi­cantly greater in Trichoptera emerging fromDetroit River sites than in samples from St. ClairRiver sites. Levels of non-PCB organochlorinecompounds (QCB, HCB, and OCS) were higher inTrichoptera collected from the St. Clair River thanfrom the Detroit River. Additionally, upstream/downstream variation in contaminant concentra­tions was evident in both rivers; greatest concen­trations of less highly chlorinated PCBs (tri-, tetra-,and pentachlorobiphenyls) were found in samplesfrom upstream sites. Similar spatial trends wereevident among sites for the mayfly, Caenis. Yetconcentrations of both PCBs and certain otherorganochlorides in Caenis differed from levels inthe caddisflies. Concentrations of HCB were typi­cally higher in the mayfly taxa than in caddisflies,with the exception of the Sarnia samples, where thetrend was reversed.

Our detection of elevated OCS concentrations atSt. Clair River sites and high PCB levels atupstream Detroit River sites is consistent withassessments of local contamination by earlier work­ers (e.g., Thornley and Hamdy 1984, Kauss andHamdy 1985, Pugsley et af. 1985, Struger et af.1985).

Several studies (Frank et af. 1977, Thornley andHamdy 1984, Kauss and Hamdy 1985, Oliver andBournbonniere 1985, Smith et af. 1985) cite theDetroit River's western (USA) shore as the majorsource of PCBs deposited in the western basin of

A

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FIG. 1. Means (± 1 S.E.) of principal componentscores for insect samples collected at various sites on theDetroit and St. Clair rivers. Station numbers corres­pond to those listed in Table 1. Solid lines and circles,all Trichoptera; dashed lines and open circles, Caenis;open squares, Hexagenia. A: PC-I, correlated with con­centrations of PCBs 101, 118, 138, 141, 153, 170, 180,182, and 194; B: PC-II, correlated with PCBs 52, 66,87, 95, 97, and 101; C: PC-III, correlated with QCB,HCB, and OCS; D: PC-IV, correlated with PCB 28 andPCB 66; E: PC- V, correlated with PCB 18 and PCB 87.

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ORGANIC CONTAMINANTS IN AQUATIC INSECTS 155

Lake Erie. Thornley and Hamdy (1984) reportedsediment total PCB concentrations in excess ofOntario guidelines (50 p.g/kg) for dredging at over59010 of Detroit River sites that they sampled.Among the Canadian samples they examined,greatest total PCB concentrations occurred withinan area that includes our two upstream sites on theDetroit River. Kauss and Hamdy (1985) examinedshort-term contaminant uptake by caged fresh­water mussels suspended within the water columnat shoreline sites on the St. Clair and Detroit riv­ers. They reported detectable total PCB levels insamples primarily from Canadian sites betweenWindsor and Amherstburg.

Kauss and Hamdy (1985) detected QCB, HCB,and OCS in tissues of mussels from sites betweenSarnia and Corunna, Ontario. Pugsley et at. (1985)sampled sediments and naturally occurring musselsfor OCS throughout the Lake Huron-Lake Eriecorridor and found sediments to contain maximalOCS amounts at scattered sites throughout the St.Clair River. Too few mussels were collected fromthis river for them to ascertain contamination pat­terns in biota.

Despite this overall consistency of results, ourultimate interpretation of the significance of con­taminant levels in insects among sites is limited bylack of information regarding larval microhabitatsof the animals collected. For example, we cannotbe certain that all insects collected at a site emergedlocally. Although this is a reasonable assumptionfor Caenis adults, which are weak fliers and livefor only a few hours (Edmunds et at. 1976), cad­disfly adults can survive for extended periods andcan undertake extensive upstream flights (Roos1957). Hexagenia adults are susceptible to long­distance transport by prevailing winds . We believethat variation in contaminant concentrationsamong taxa at single sites partially reflects this dif­ferential flight behavior. For example, the markeddifferences in contaminant levels observed betweenHexagenia and Trichoptera collected at the Sarniasite (station 8, Table 3) could be explained in termsof upstream flight tendencies by caddisflies fromhighly contaminated downstream reaches coinci­dentally with passive aerial transport of Hexageniafrom upwind emergence sites on Lake Huron.

Malicky (cited in Chantaramongkol 1983)described a flight range of up to several hundredmeters for caddisflies attracted to light traps onlarge European rivers. Our collection ofMacronema zebratum at only the Amherstburgand River Canard sites on the Detroit River is con-

sistent with the apparently local distribution of lar­vae of this species (Thornley and Hamdy 1984) andsuggests that Malicky's estimate is generally appli­cable to the Lake Huron/Lake Erie connectingchannel. Dispersal of this magnitude implies thatthe contaminant concentration measured from anadult insect sample is an integrated value repre­senting biota from a substantial area surroundingthe collection site.

Observed variation in contaminant level amongtaxa at a site may additionally reflect differences inmicrodistribution and/or feeding habits of imma­tures. Hydropsychid larvae frequent erosionalhabitats and filter suspended particles from thewater using silken nets. Accordingly, the classes ofcontaminants to which they are exposed duringfeeding might differ substantially from those ofthe mayfly taxa that we collected. Both Caenis andHexagenia inhabit depositional areas. Caenis feedon organic particles that have settled and accumu­lated on the riverbed. Hexagenia ingest similarfood when they leave their burrows to filter at themud/water interface.

Such feeding specializations, especially amongHydropsychidae, could be useful in assessingsources of specific organic contaminants. Somegenera, such as Macronema, tend to consume pri­marily very fine organic particles (Wallace andSherberger 1974, Wallace 1975) whereas others(e.g., Cheumatopsyche) derive most of theirenergy from larger particles and small inverte­brates (Benke and Wallace 1980). Since manyorganic contaminants adsorb to small particles« 64 p'm; Eadie et at. 1982a, 1982b), differences incontaminant concentrations among taxa may pro­vide a measure of relative distribution of contami­nants among the various food categories.

In view of the high contaminant levels that weobserved in samples, the ultimate fate of adultinsects merits consideration. Most adults undoubt­edly die and decompose at their site of mating oroviposition. However, appropriate weather condi­tions coincident with mass adult emergence cantransport large numbers of animals inland. Wehave no information as to the potential importanceof such contaminant transfer to terrestrial habitatsrelative to other loadings, but believe that it war­rants further investigation.

Despite the limitations described above, webelieve that adult aquatic insects have potential asa cost-effective alternative to sampling organismsdirectly in the aquatic environment because largenumbers can be quickly collected and effectively

156 CIBOROWSKI and CORKUM

used to evaluate local contamination. This elimi­nates many difficulties associated with aquaticsampling in that little specialized equipment isneeded and animals are collected independently ofsurrounding sediments.

ACKNOWLEDGMENTS

We wish to thank the Great Lakes Institute (GLI)staff for their assistance in analysing the samples.R. Lazar, B. Muncaster, and S. Noble providedadvice on GC preparatory procedures. G. D. Haf­fner, D. J. Innes, and I. M. Weis reviewed themanuscript. A. V. Provonsha kindly identifiedCaenis specimens. Costs of sample analysis weredefrayed by grants from the Ontario Ministry ofthe Environment and the World Wildlife Fund toGLI. Other aspects of the project were supportedby a grant from the Natural Sciences and Engineer­ing Research Council of Canada to J. J. H.Ciborowski.

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