Responses of Immature Blackflies (Diptera:simuliidae) to Experimental Pulses of Acidity PDF
Preview Responses of Immature Blackflies (Diptera:simuliidae) to Experimental Pulses of Acidity
11 rS RESPONSES OF IMMATURE BLACKFLIES (DIPTERA: SIMULNDAE) TO EXPERIMENTAL PULSES OF ACIDITY OCTOBER 1991 Environment Environnement Ontario ISBN 0-7729-8949-4 RESPONSES OF IMMATURE BLACKFLIES (DIPTERA: SIMULIIDAE) TO EXPERIMENTAL PULSES OF ACIDITY Report prepared by: CM. Chmielewski TrentUniversity, Peterborough, Ontario R.J. Hall Environmental Sciences and Standards Water Resources Branch Ontario Ministry ofthe Environment OCTOBER 1991 o PRINTEDON RECYCLEDPAPER IMPRIMESUR DUP4PIERRECYCLE Cette publication technique n'est disponible qu'en anglais. Copyright: Queen's Printer for Ontario, 1991 This publication may be reproduced for non-commercial purposes with appropriate attribution. PIBS 1718 ABSTRACT Aninvestigationtodeterminetheresponsesofimmatureblackfliestoexperimentalpulsesofaciditysimulating snowmelt episodes was conducted. Five species ofmatureblackflylarvaeweresubjected to three or four day experimental pH depressions to ca. 4.0 or 3.5 in stream channels. Differences among species in response to aciditywereobserved. AllspeciesexceptSimitlium vinatum andpossiblyS. venustiim wereable totolerate pH depressions to ca. 4.0 while only Cnephia dacotensis and possibly S. decorum were able to tolerate pH depressionstoca.3.5. Thesurvivalofthelarvae(onlylateinstarsweretested)wassignificantlyaffectedbythe acidity while pupal survivalgenerallywas not. The rate ofpupation, however, was decreased in the acidified channelsresultingindecreasedemergencetherealso. Moreabnormallyformedpupaedevelopedintheacidified channels, suggestingthatpupationfollowingsnowmelt ensuressurvivalofthese species. INTRODUCTION Thereleaseofsulphurandnitrogenoxidesintotheatmospherebytheburningoffossilfuelshasbeendesignated themajorcauseforincreasedhydrogenioncontentofprecipitationinrecentyears(Gallowayetal. 1976,Likens etal. 1979). Furthermore, this increased acidityofatmosphericdeposition, bothwet and dry, hasbeen linked tothecorrespondingacidificationoffreshwatersystemsinFinland(Haaplaetal. 1975),Norway(Gjessingetal. 1976, Wright et al 1976, Henriksen and Wright 1977), Sweden (Aimer et al. 1974, Oden 1976, Hultberg and Wenblad 1980),northeasternUnitedStates(CogbillandLikens1974,Hendreyetal. 1980),andeasternCanada (Beamish 1976, Conroy et al. 1976, Jefferies et al. 1979). The most pronounced pH depressions in stream ecosystems occur as a result ofhydrogen ion pulses duringrain storms and especiallyduringsnowmelt. With the onset ofsnowmelt run-off, stream pH levels have dropped from circumneutral to as lowas3.9 in Ontario (Harvey1980). Thesereductionscanoccurwithinhoursandmayalterbenthiccommunitieslongbeforechronic acidification hasbeen detected (Servos and Mackie 1986). TheeffectsofloweredstreampHonmoststreambiotaarewelldocumented,includingsuchgroupsasmayflies, stoneflies,caddisfhesandchironomids(e.g..Bell1971,SutcliffeandCarrick 1973,Halletal. 1980,Raddum and Fjellheim 1984,MacKayandKersey1985, HallandIde 1987),butourknowledgeoftheeffectsofepisodicpH depressionsonblackflies(Diptera:Simuliidae)isdecidedlyscarce. Somestudieshaveindicatedthatblackflies maybe more tolerant ofincreased aciditythanmanyoftheirstream co-habitants (Simpsonetal. 1985,Sharpe etal. 1987,Halletal. 1980,Bernardetal. 1989,Hopkinsetal. 1988). Inparticular,Chmielewski(1989)reported anincrease inblackflyemergencewith increased acidityover a50-year time span. Furthermore, MacKayand Kersey(1985) reported abundant blackflies in acid streams in the Dorset, Ontario area, and Halletal. (1988) showed that P. fuscum/mixtwn complex was not affected when exposed to short-term pulses of acidity in experimentaltransplantsnear Dorset. However,onlyafewstudieshaveidentifiedblackfliestospecies (Stoner etal. 1984,Simpsonetal. 1985,Halletal. 1988),andnonehaveindicatedtoxicityresponsesatthespecificlevel. Therefore, aquestion ofinterest is howdoblackflyimmaturesrespond to short-term pulses ofaciditysimilar to those encountered duringsnowmelt? Based onpast surveys, the hypothesis to be tested in this researchis thatmanyblackflyspecieswillbeabletowithstandshort-term decreasesinpH. VaryingtolerancestolowpH, explained in part bydifferent life historystrategies, are expected at thespecies level. METHODS The ability of different blackfly species to survive snowmelt acid pulses was tested by subjecting larvae to simulated snowmelt pH depressions. The artificial stream channels built by Serves and Mackie (1986) and located adjacent to the outflow ofPlastic Lake, Haliburton County, Ontario (45° 11' lat., 78° 50' long.) were modifiedand used for the acidification experiments (Fig. 1). To avoid using simuliid immatures with an acquired resistance to acidity, lar\'ae were collected from Costello Creek,Algonquin Park, Ontario, a location that hasnot experiencedextreme springpH depressions (between 1984-86themaximumspringpHdepressionwas5.9, HallandIde1987)andhaswaterquality,includingannual pH range, similar toPlasticLake Outfiow (Findeis and ColmanTaylor 1988). A small concrete dam was constructed across Plastic Lake outflowwith a 10-cm A.B.S. plastic overflow pipe leadingtoreservoir #1 (Rl, approximately201) 5 m downstream and thento thewooden plasticized channel system 5 m farther downstream. Here, the pipe divided, filling two larger reservoirs (R2 and R3) of approximately7001each. Allthreereservoirshadoverflows. Reservoir3wasacidifiedbymixing1Nsulphuric acidwithstream waterviaaperistalticpump. This reservoirhad amixingcupandbafflesto ensurecomplete mixingoftheacid. Reservoir2 contained areferencesupplyofstream water. One 7.3-cm manifold from the control and one from the acid reservoir suppUed three flow-through channels (each 3.1 m x28 cm x45 cm). Waterdepthwasapproximately5cm. Meandischargesforthethreeexperimentalrunswereapproximately120 mL/s, 160 mL/s, and390mL/s, respectively. Acidified andcontrol channelswere chosenrandomlyandwere different for each experiment. Chambers were designed to contain larvae in the stream channels while allowing water to flow unimpeded throughthecharmels(Fig. 1). Tworectangularholeswerecutfromoppositesidesof500-mLcylindrical,plastic containers and replaced with Nitcx netting (430-pm mesh for the first experiment and250-A/m for the second and third). Tocatchemergingadults, a6-mm funnelwasinverted andgluedtoalidwithacircularhole ofthe samesize. Thesmallendofthefiinnelprotrudedthroughaholecutinthebottom ofa500-mLNalgenebottle andwasalsoglued. Theemergencechamberwascompletelysealedsothatemergingadultswould flythrough the funnel and dropinto the Nalgenebottle containing70% alcohol. Rocks,sticksandtraihngvegetationwithattachedlarvaeweretakenfromall areasofCostelloCreektocollect the most diverse selection of species as possible and reduce the amount of manipulation. They were then transferredtoaeratedcoolersfilledwithstreamwater. Larvaewerecarefullytransferredtoemergencechambers (50per chamber) with forcepssuspendedwithadrop ofwater between its armsand then placed intowooden streamsidechannelswithin3-4hours. Larvaegreaterthanca. 0.7cmlongwereselectedbecausesmallerlarvae couldescapethroughthemeshofthechambers. Larvaewerenot identifiedat this point tominimize handling effects. Species distribution amongthe chamberswasnot knownbut assumed tobe random. Threerunsoftwo experimentseachwere conducted(Table 1). Startingdateswere chosenon orbefore peak emergence forthegreatest number ofspecies, basedon elevenyears ofemergence datafrom Costello Creek (Davies1950,Hayton1979). Runs 1,2and3werestartedon29April, 19May,and 12June, 1987,respectively. Thefirstrunconsistedof4daysatpH4.0andonedayatpH3.5,thesecondconsistedof3daysat pH4.0and onedayat pH3.5 andthe thirdconsisted of3 days at pH 4.0 and one dayat pH 3.5. Atthebeginningofeachexperiment three emergencechamberswererandomlyplacedineach ofsixchannels (6 channels x 3 chambers/channel x 50 larvae/chamber = 900 larvae). Larvae were allowed to acclimate overnightinthechannels. Deadlarvaewereremovedthefollowingmorninganddiscarded. The pHwasthen decreasedto4.0or3.5intreatment channelswithintwohoursand maintainedatthatleveluntiltheend ofthe experiment. Thechamberswerecheckeddailyanddeadblackflieswereremoved,countedandpreservedin95% ethanol. Attheendofeachexperimenttheremainingemergence chamberswereremovedfrom thechannels, and thehveand deadblackfliespreserved.
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