Otolith Chemistry of Common Sculpins (Myoxocephalus scorpius) in a Mining Polluted Greenlandic Fiord (Black Angel Lead-Zinc Mine, West Greenland)

Abstract

Sculpins are widely used as key species for monitoring heavy metal pollution near arctic mine sites. Typically, metal concentrations in liver and muscle tissue have been used as a proxy for metal exposure but such analyses lack temporal information of uptake and accumulation. Otoliths (ear bones) are considered metabolically stable and can potentially contain a complete record of the fish’s metal exposure history. To investigate the otolith chemistry of sculpins and the potential of these as records of metal exposure, common sculpins (Myoxocephalus scorpius) were collected at five sites near a former Pb–Zn mine in West Greenland. Otoliths were analyzed by laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) for 12 elements of which Mg, Mn, Sr, Ba, and Pb were detected. The highest Pb concentrations were found within the otoliths from the most Pb-polluted sites near the mine (up to 0.6 ppm), and decreasing concentrations were observed in a gradient away from the mine. Notably, Pb and Sr variations were closely correlated and showed an annual oscillatory pattern with peaks consistently found in the winter zones. It is not clear to what the extent high winter-time accumulation of Pb in the otoliths is due to high winter-time exposure of Pb through diet or water and/or to physiological processes such as growth in the sculpins. The study indicates that LA-ICP-MS analyses of sculpin otoliths have the potential to become a valuable method for assessing time-resolved metal loading near mine sites but also that more studies are required to investigate the links between metal sources, pathways, and processes affecting otolith metal deposition.