Our objective was to study the effects of experimental flooding of a small wetland lake on the methyl mercury (MeHg) concentrations in aquatic insects and to compare MeHg concentrations in insects with those in water and fish from the same system. Insects were collected from the shorelines of the experimental reservoir before and after flooding, an undisturbed wetland lake, and an oligotrophic lake, all in the Experimental Lakes Area in northwestern Ontario. Samples were identified to the lowest possible taxon and categorized into functional feeding groups (FFGs; predators or collector/shredders). The insects were analyzed for MeHg and total Hg using clean techniques. Contamination was not a problem because levels of MeHg in insects were much higher than background concentrations. Odonata, Corixidae, Gerridae, Gyrinidae, and Phryganeidae/Polycentropodidae exhibited increases in MeHg concentrations in response to flooding. When data were grouped into FFGs, increases were observed in predators. There were insufficient numbers of collector/shredders collected to make a definitive conclusion on MeHg increases. Predators exhibited an approximately threefold increase in MeHg concentrations after flooding compared with a 20-fold increase in water concentrations and a four- to five-fold increase in fish concentrations. Trends in MeHg concentrations in aquatic insects from reservoirs and natural lakes in Finland and northern Québec were similar to ours. Evidence of an increase in MeHg concentrations in the lower food web helps explain increases in MeHg concentrations in fish from reservoirs because food is the major pathway of MeHg uptake in fish tissue.
Eighty‐four species of Chironomidae were collected, using emergence traps, from three poor fens located in the Experimental Lakes Area (ELA) of northwestern Ontario. Of these, 37 were considered to be true peatland fauna. The majority (23) of the peatland species are new North American or Canadian records and, of these, 10 are previously undescribed. Numbers m−2 yr−1 emerging from the fens were similar to neighbouring lakes but biomass (mg) m−2 yr−1 emerging was much less, indicating the small average size of the fen chironomids. Emergence began in early May and was virtually completed by late July‐early August in all three years of the study. Most of the emergence occurred early in the season. Eight species accounted for ≥90% of the emergence. Five of these, Gymnometriocnemus (R.) acigus Saeth., Doithrix villosa Saeth. and Subl., Pseudorthocladius (s.s.) destitutus Saeth. and Subl., P. (s.s.) curtistylus (Goetgh.), and Paramerina nr. smithae (Subl.) had univoltine life cycles and relatively stichronous emergences. Pseudosmittia forcipata (Goetgh.) was bivoltine, and Limnophyes minimus (Meig.) and Smittia nr. nudipennis Geotgh. had protracted emergence periods that made voltinism difficult to determine. Characteristic features of the chironomid fauna of peatlands at ELA are discussed. The general applicability of these features to peatlands, and needs for further research in these neglected but extensive Canadian habitats are considered.
RosrNsEnc, D. M., aNo A. P. Wrrns. 1976. Cornmunity and species responses of Chironomidae (Diptera) to contamination offresh waters by crude oil and petroleum products, rvith special reference to the Trail River, Northwest Territolies. J. Fish. Res. Board Can. 33: 1955-1963.On oiled and unoiled arlificial substrates in the Trail River, Norlhwest Territories, communities of Chironomidae were different durinlg open-water periods but were similar over the winter. Greater numbers ofspecies and individuals ofOrthocladiinae occurred on the oiled than on the unoiled artificial substrates. The reverse wils true for Tanypodinae and Chironominae. Ten species ofChironomidae showed a positive response to the presence ofoil,9 species showed a negative response, and 10 species were apparently unaffected. Based on the results ofthis study and a litelature review, I I species of Chilonomidae showing either positive or negative responses to contamination by oil or petroleum products r,vere evaluated fbr their potential to indicate oil contamination of freshwater ecosystems. Three criteria were used: taxonomic soundness, wide zoogeographic distribution, and numbers in the community. We predict that Nilotunyptrs fimbriatns (Walk.), Cricotopus bit:inctus (Mei61.), and C. varipes Coq., individually or as an assemblage, would fulfill this role. RosrNBpnc, D. M.. eNo A. P. WrrNs. 1976. Cornmunity and species responses of Chilonomidae (Diptera) to contamination of flesh wa.ters by crude oil and petroleum products, with special reference to the Trail River, Northwest Territories. J. Fish. Res. Board Can. 33: 1955-1963.Sur des substrats artificiels avec oLr sans gr6trole de la rivibre Trail, Territoires du NordOuest, les communaut6s de Chironomidae diffbrent quand I'eau est libre de glace, mais sont semblables en hiver. Les Orthocladiinae sont plus nombreux tant en espdces qu'en individus dans les substrats artificiels avec p6trole que sans p6trole. On observe le contraire pour les Tanypodinae et les Chironominae. Dix espbces de Chironomidae manifestent une r6ponse positive i la presence de petrole, 9 espdces une r6ponse negative et l0 espbces semblent inaffectdes. En nous basant sur les r6sultats de cette dtude et sur une revue de la litt6rature, nous avons 6valud le potentiel, comme indicateur de contamination d'6cosystdmes d'eau douce par le p6trole. de I I espbces de Chironomidae montrant des r6ponses soit positives soit negatives i la contamination par le pdtrole ou parles produits p6troliers. Nous avons utilis6 trois critbres: solidit6 taxonomique, r6partition geographique ritendue, et nombres dans la communaut6. Nous sommes d'avis que Nilotunyptts Jimbr-irrlrrs (Walk.), Cricoloprts bi(in(tus (Meig.) et C. varipe-s (Coq.), individuellement ou en groupe, pourraientjouer ce rdle.
A simple method for subsampling unsorted benthic macroinvertebrates by weight is described for different types of samples obtained from lentic and lotic environments. It is especially useful for samples containing large amounts of filamentous algae that preclude the use of conventional subsampling methods. The method provided random dispersions of individuals in the original samples. Overall variability of the subsamples was low for artificial substrate and catastrophic drift samples. Variability was higher for regular drift samples, which had the lowest numbers of individuals of the three sample types. The method produced considerable savings in time spent sorting. Subsampling approaches for community level studies are discussed.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.