Impacts of Forest Management on the Distribution of Mercury in Slimy Sculpin (Cottus cognatus)
Forests play an integral role in Canada’s natural resource economy and also provide key ecological services to nearby aquatic environments, such as flood control and water quality regulation. Disturbances like forestry can threaten stream integrity by altering a forest’s ability to provide such services. In areas like the Black Brook (BB) District of New Brunswick, one of the most intensively managed sites in Canada, increased mercury levels in stream waters and biota have been observed. However, distributions of mercury contamination in downstream areas remain largely unknown. Thus, this project evaluated the impacts of forestry upon the spatial distribution of total mercury (THg) in the fish species slimy sculpin (Cottus cognatus), as well as discerned sex-dependent variations. Slimy sculpin was an ideal species to use for studying mercury contamination, as individuals exhibit high site fidelity and are a sensitive indicator of mercury as a benthic species. THg concentrations (μg/kg wet weight (ww)) were measured in fish sampled in 2017 from five upstream to downstream sites located within the BB District. Six to ten fish of each sex and of similar length were sampled from each site. THg was measured from homogenized tissue using the DMA-80 Direct Mercury Analyzer. A significant positive interaction between THg μg/kg ww and fish length (mm) was found in females, F(1, 37) = 14.59, p < 0.001, but not males, providing evidence for sex-dependent variations. Overall, this project provided insights into necessary future steps that must be taken to address spatial and sex-dependent variations in mercury contamination.