Identifying the ecological drivers of total mercury concentrations in Brook Charr (Salvelinus fontinalis) populations across Western Newfoundland, Canada

Abstract

The transformation of mercury to the toxic methylmercury in anoxic lake sediment, along with its bioaccumulation and biomagnification in lacustrine food webs, makes it a potent environmental toxin with implications for both ecosystem and human health. Multiple ecological factors operating at different scales contribute to the movement of mercury into freshwater systems and its subsequent methylation and concentration in aquatic organisms. This thesis aims to identify ecological factors driving the bioaccumulation and biomagnification of mercury in lacustrine populations of brook charr (Salevelinus fontinalis) from western Newfoundland, Canada. The total mercury (THg) concentrations were measured in brook charr from 34 headwater lakes. The study examined several variables, including individual morphology, stable isotope compositions, and lake productivity, alongside topographical and land cover data derived from geographical information systems. A structural equation model (SEM) was developed to discern the direct and indirect effects of fish growth and size, chlorophyll-a concentration, catchment topography and land cover on mercury accumulation in brook charr. The analysis revealed a strong influence of catchment-scale factors on mercury bioaccumulation in brook charr. These findings highlight the need for employing optimal catchment management practices alongside continuous monitoring of water quality and ecosystem health in remote freshwater sources.