Base de données de recherche des TNO

Régions: South Slave Region

étiquettes: contaminants, biology, food web, fish

Objectif(s): The goal of this research is to conduct sediments coring and food web studies to better understand the factors affecting long-term contaminant trends in predatory fish in Great Slave Lake.

Description du projet: This licence is being issued for the scientific research application no. 991. The goal of this research is to conduct sediments coring and food web studies to better understand the factors affecting long-term contaminant trends in predatory fish in Great Slave Lake. For several years the researchers have been conducting studies to find out if contaminant levels are changing in lake trout and burbot in Great Slave Lake. They have been seeing some changes with mercury levels increasing and HCH levels declining in fish. However, there have been other changes in the fish, especially lake trout which appear to contain less fat and to be feeding closer to shore than in the 1990s. Because contaminant levels in lake trout and burbot can be affected by changes in their biology and in the lake in which they live, the researchers want to do more studies to find out what is affecting contaminant trends. Specifically, they need to find out if contaminant inputs to the lake have been changing and to learn more about contaminants in the Great Slave Lake food web. The researchers will collect sediment cores at three locations on Great Slave Lake (West Basin, offshore Slave River, and East Arm). A 8.6-cm internal diameter gravity corer will be used. Up to 4 cores will be collected per location. Sediment cores will be sectioned at 0.5 cm intervals down to ca. 10 cm, at 1 cm intervals down to 20 cm, and at 2 cm intervals thereafter. Sediment core slices will be freeze-dried and percent water calculated. Cores will be dated using 210Pb and most likely 137Cs techniques. Approximately 15 core slices from each location will be analyzed for organic carbon and nitrogen and phosphorus (to assess changing productivity). Other analyses, including legacy OCs, mercury and other metals, grain size (to assess a changing hydrological environment), and algal remains (to assess changing lake productivity) will be postponed until 2009/2010. Food web sampling will be conducted during summer 2009, and will include collections of mysids, amphipods, plankton, benthic invertebrates, and forage fish and, ideally, will continue in 2010 to provide a 2-year data base for more effective 1994-1995 comparisons. Most food web samples will be collected using plankton (plankton, mysids, amphipods) or seine (forage fish) nets towed behind a boat. Benthic invertebrate samples will be collected using a dipnet (nearshore) or PONAR grab (offshore). Some benthic invertebrate and plankton samples will be collected quantitatively (and preserved) so that species abundance/composition can be determined. All other samples will be freeze-dried, and subsamples analysed for stable isotopes, mercury, and possibly organochlorines and other emerging contaminants of concern. Communities and agencies will be kept informed of the results through telephone, email, and other communications. Community visits may also take place, depending on interest and schedules. The fieldwork for this study will be conducted near Lustel’ke, Fort Resolution and Hay River from March 6 to September 30, 2009.