Mercury (Hg) and organochlorine pesticides (OCP) in mesopelagic and demersal fish of the Labrador Sea and Canadian Arctic

Abstract

Warming polar waters are leading to the decline of sea-ice and the expansion of subarctic species towards higher latitudes. Northward fish movement is shifting the fate of environmental pollutants in Arctic trophic webs. Here I measure contaminant concentrations for total mercury (THg), methylmercury (MeHg), and a range of legacy organochlorine pesticides (OCPs) in mesopelagic and demersal fish in the Labrador Sea and the Canadian Arctic collected between 2016 and 2021. Muscle tissue samples were collected from three pelagic fish species (Arctic cod [Boreogadus saida], capelin [Mallotus villosus], glacier lanternfish [Benthosema glaciale]) and three demersal fish (abyssal grenadier [Coryphaenoides armatus], blue hake [Antimora rostrata], and Greenland halibut [Reinhardtius hippoglossoides]). The objectives were to determine (1) how contaminant concentrations in pelagic and demersal fish vary spatially across the Canadian Arctic and subarctic regions; and (2) how ecology (measured from stable isotope ratios of δ15N and δ13C) and habitat (pelagic and demersal) influence contaminant concentrations in these fish species. Hg concentrations were best explained by species, trophic level, area, and habitat, while OCP concentrations were explained by species, trophic level, and habitat. These findings can be used to predict future contaminant concentrations in Arctic trophic food webs given climate-driven ecological changes.