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

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 (sigm...

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Bibliographic Details
Main Author: Ryan, Michael J.
Other Authors: Stern, Gary A. (Soil Science, Environmental Studies)
Language:en_US
Published: 2007
Subjects:
Online Access:http://hdl.handle.net/1993/227
id ndltd-MANITOBA-oai-mspace.lib.umanitoba.ca-1993-227
record_format oai_dc
collection NDLTD
language en_US
sources NDLTD
topic ecotoxicology
organochlorines
fish
food web
temporal trend
climate
Yukon Territory
sub-Arctic
plankton
sediment
spellingShingle ecotoxicology
organochlorines
fish
food web
temporal trend
climate
Yukon Territory
sub-Arctic
plankton
sediment
Ryan, Michael J.
The biotic and abiotic interactions influencing organochlorine contaminants in temporal trends (1992-2003) of three Yukon lakes: focus on Lake Laberge
description 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.
author2 Stern, Gary A. (Soil Science, Environmental Studies)
author_facet Stern, Gary A. (Soil Science, Environmental Studies)
Ryan, Michael J.
author Ryan, Michael J.
author_sort Ryan, Michael J.
title The biotic and abiotic interactions influencing organochlorine contaminants in temporal trends (1992-2003) of three Yukon lakes: focus on Lake Laberge
title_short The biotic and abiotic interactions influencing organochlorine contaminants in temporal trends (1992-2003) of three Yukon lakes: focus on Lake Laberge
title_full The biotic and abiotic interactions influencing organochlorine contaminants in temporal trends (1992-2003) of three Yukon lakes: focus on Lake Laberge
title_fullStr The biotic and abiotic interactions influencing organochlorine contaminants in temporal trends (1992-2003) of three Yukon lakes: focus on Lake Laberge
title_full_unstemmed The biotic and abiotic interactions influencing organochlorine contaminants in temporal trends (1992-2003) of three Yukon lakes: focus on Lake Laberge
title_sort biotic and abiotic interactions influencing organochlorine contaminants in temporal trends (1992-2003) of three yukon lakes: focus on lake laberge
publishDate 2007
url http://hdl.handle.net/1993/227
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spelling ndltd-MANITOBA-oai-mspace.lib.umanitoba.ca-1993-2272014-01-31T03:30:01Z The biotic and abiotic interactions influencing organochlorine contaminants in temporal trends (1992-2003) of three Yukon lakes: focus on Lake Laberge Ryan, Michael J. Stern, Gary A. (Soil Science, Environmental Studies) Goldsborough, Gordon (Botany) Kidd, Karen (Zoology) Hickie, Brendan (Trent University) Amiro, Brian (Soil Science) ecotoxicology organochlorines fish food web temporal trend climate Yukon Territory sub-Arctic plankton sediment 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. 2007-03-29T16:09:36Z 2007-03-29T16:09:36Z 2007-03-29T16:09:36Z Electronic Thesis or Dissertation 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 http://hdl.handle.net/1993/227 en_US