Mercury evolution in freshwater fish from reservoirs in Newfoundland, Canada

French, Kenneth J. (1997) Mercury evolution in freshwater fish from reservoirs in Newfoundland, Canada. Masters thesis, Memorial University of Newfoundland.

[English] PDF (Migrated (PDF/A Conversion) from original format: (application/pdf)) - Accepted Version Available under License - The author retains copyright ownership and moral rights in this thesis. Neither the thesis nor substantial extracts from it may be printed or otherwise reproduced without the author's permission. Download (19MB) [English] PDF - Accepted Version Available under License - The author retains copyright ownership and moral rights in this thesis. Neither the thesis nor substantial extracts from it may be printed or otherwise reproduced without the author's permission. (Original Version)

Abstract

Return times of 7-12 years have been recently hypothesized for salmonids collected from recently (post-1980) created reservoirs in NF. These return times have been primarily based on reservoir age though factors such as the flooded riparian zone and acidity have all been postulated to affect return times. It was the goal of this study to improve upon predictions of return times for Newfoundland by expanding the current database of mercury in fish and by incorporating several of these factors. -- An investigation into sediment mercury levels in 34 non-impounded headwater lakes across NF indicated that acidity had no effect on the amount of mercury accumulated at the lake bottom. Watershed area to lake area ratio (WA:LA) was found to be significant in explaining the variation observed in sediment mercury levels. This suggested that large watershed can deposit significant amounts of mercury sorbed to organic material to small lakes that then act as sinks for this metal. This relationship was further supported by the positive correlation between lake colour and WA:LA. -- The slope of the relationship between mercury concentration and fork length for salmonids was found to change significantly over time. Reservoir age and conductivity were found to be significant in predicting the slope of the relationship between fish mercury levels and fork length for ouananiche (Salmo salar) and brook trout (Salvelinus fontinalis). Only the per cent Area Flooded was significant in predicting the slope for arctic charr (Salvelinus alpinus). Slope variability between the three control ponds and between pre-impoundment and post-impoundment mercury data precluded determination of return times for either species. -- An investigation into mercury time series data for a number of impounded and non-impounded sites indicated that high slopes may be characteristic of non-impounded sites and of old reservoirs. Results suggested that impoundment lowers the slope during the first 4 to 5 years following inundation by increasing mercury levels in smaller fish more so than in larger fish. Slopes appeared to return to pre-impoundment levels approximately 5 to 6 years after inundation. Weighted regression indicated that mercury increase in a selected size interval following impoundment was 8 to 73 times faster than the decline after mercury levels peaked.

Actions (login required)

View Item