The biotic and abiotic interactions influencing organochlorine contaminants in temporal trends (1992-2003) of three Yukon lakes: focus on Lake Laberge

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dc.contributor.supervisor Stern, Gary A. (Soil Science, Environmental Studies) en
dc.contributor.author Ryan, Michael J.
dc.date.accessioned 2007-03-29T16:09:36Z
dc.date.available 2007-03-29T16:09:36Z
dc.date.issued 2007-03-29T16:09:36Z
dc.identifier.citation Ryan, M.J., G.A. Stern, M.V. Croft, K. Kidd, M. Diamond and P. Roach (2005). Temporal Trends of Organochlorine Contaminants in Burbot and Lake trout from Three Selected Yukon Lakes. Sci. Tot. Environ. 351-352: 501-522 en
dc.identifier.uri http://hdl.handle.net/1993/227
dc.description.abstract Periodic monitoring of contaminant levels in fish from the Yukon Territory indicated that organochlorine (OC) contaminants had rapidly declined since the early 1990s. This study examined OC concentrations, including chlordane (sigma-CHL), sigma-DDT, hexachlorocyclohexane (sigma-HCH), toxaphene (sigma-CHB), sigma-PCB and chlorinated benzenes (sigma-CBz) in sentinel fish (species of consistent annual observation and collection) from two Yukon lakes (Kusawa, Quiet), and from the aquatic food web of a focus lake (Lake Laberge) across several temporal points between 1993 and 2003. OC analysis and phytoplankton counts from dated sediment cores as well as climate data were also collected. Population, morphological (length, weight, age), biochemical (lipid content, delta-13C, delta-15N) and OC contaminant data for fish and invertebrates (zooplankton, snails, clams) were reviewed to elucidate the primary causes for these OC declines. Although some spatial differences in contaminant levels exist between the Yukon lakes, OC concentrations were declining for lake trout in all three lakes, with declines also noted for burbot from Lake Laberge. Several other fish species as well as zooplankton from Lake Laberge exhibited decreases in contaminant levels except northern pike, which registered consistently higher levels from 1993 to 2001. There was no evidence to support the hypotheses of changes in fish trophic levels or food sources with the exception of burbot, which marginally decreased, and northern pike, which climbed a half trophic level. Through OC flux analysis in dated sediments, the hypothesis that declines in abiotic deposition affected the contaminant levels in the food web was also negated. The closure of the Lake Laberge commercial fishery resulted in faster fish growth and larger fish populations, which are contributing to biomass dilution of OC concentrations, higher OC biomagnification factors for some species and likely changes in predator-prey interactions as resource competition increases. The large ratio of OC decreases in the lower vs. higher trophic levels of Lake Laberge have increased food web magnification factors (FWMF) for all six OC groups. It is also suspected that above-average temperatures and below-average precipitation in the lower Yukon region over the 1990s may have contributed towards an increase in lake primary production resulting in biomass dilution of contaminants in zooplankton for all three study lakes. Concurrently, shifts in the Lake Laberge zooplankton community, from climate fluctuations or increased fish predation, have gone from an abundance of Cyclops scutifer in 1993 to dominance by Diaptomus pribilofensis in 2001, although sample sites were limited. Characteristics specific to each species (e.g. body size, composition and metabolism) likely play a role in the significant OC declines measured in zooplankton. Fluctuations in population dynamics, species characteristics and OC contaminant concentrations in the Lake Laberge ecosystem may continue for several years to come. Sentinel species such as lake trout, burbot, whitefish, cisco and plankton should continue to be monitored in all three Yukon lakes for future temporal correlations with contaminants or climate change. en
dc.format.extent 2422314 bytes
dc.format.mimetype application/pdf
dc.language.iso en_US
dc.rights info:eu-repo/semantics/openAccess
dc.subject ecotoxicology en
dc.subject organochlorines en
dc.subject fish en
dc.subject food web en
dc.subject temporal trend en
dc.subject climate en
dc.subject Yukon Territory en
dc.subject sub-Arctic en
dc.subject plankton en
dc.subject sediment en
dc.title The biotic and abiotic interactions influencing organochlorine contaminants in temporal trends (1992-2003) of three Yukon lakes: focus on Lake Laberge en
dc.type info:eu-repo/semantics/doctoralThesis
dc.type doctoral thesis en_US
dc.degree.discipline Soil Science en
dc.contributor.examiningcommittee Goldsborough, Gordon (Botany) Kidd, Karen (Zoology) Hickie, Brendan (Trent University) Amiro, Brian (Soil Science) en
dc.degree.level Doctor of Philosophy (Ph.D.) en
dc.description.note May 2006 en

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