Comparing mercury, arsenic, and selenium in several fish species from two Nova Scotia lakes

Abstract

The environmental increase of mercury and arsenic - two contaminants with no biological functions - due to anthropogenic activities is a complex and growing issue. Both mercury and arsenic, in particular methylmercury and inorganic arsenic, can bioaccumulate in the food web. Exposure to elevated concentrations of either can result in serious potential human and wildlife health impacts. This can be further complicated by either the presence or absence of selenium,which is an essential micronutrient . Se can result in health impacts for both humans and wildlife in excess or in deficiency. Selenium is of importance due to its antagonistic relationship with mercury, but in Nova Scotia, water, sediment and soil Se concentrations are typically quite low. For this study, mercury, arsenic and selenium concentrations were analyzed in fish tissue between Shortts Lake (Colchester County), which had low groundwater and sediment arsenic levels,and Morris Lake (Halifax County), which had high groundwater and sediment arsenic levels. The four fish species of interest were: Alosa pseudoharengus (gaspereau or alewife), Micropterus dolomieu (smallmouth bass), Esox niger (chain pickerel), and Morone americana (white perch). Mercury and arsenic concentrations in many individuals of all four species from both lakes exceeded the World Health Organization’s (WHO) daily tolerable intake limit of 0.0177mg/kg, and 0.233mg/kg respectively. The trend between total mercury concentration of fish tissue and the length of fish resulted in a positive correlation in both lakes. Shortts Lake fish tended also had higher total mercury concentrations than those from Morris Lake. Total arsenic concentration did not significantly vary amid fish of the same species between lakes, but gaspereau (alewife) was found to have significantly higher total arsenic concentrations in both lakes compared to the other three fish species. Selenium concentrations did not significantly differ between same species of different lakes, nor between lakes.