Mercury levels in humpback whales, and other Southern Ocean marine megafauna

Highlights: • International agreements under the Minamata Convention necessitate globally coordinated biomonitoring of Hg. • Mercury was reported for the first time in humpback whales, with a view to spatial and temporal biomonitoring. • Further analyses were performed on seven other Southern Ocean species for trophic comparison. • The study highlighted the need for toxicokinetic studies for routine humpback whale Hg biomonitoring via remote biopsy. Mercury is a known potent neurotoxin. The biogeochemical cycle of mercury in the remote Antarctic region is still poorly understood, with Polar climate change contributing added complexity. Longitudinal biomonitoring of mercury accumulation in Antarctic marine megafauna can contribute top-down insight into the bio-physical drivers of wildlife exposure. The bioaccumulative nature of organic mercury renders high trophic predators at the greatest risk of elevated exposure. Humpback whales represent secondary consumers of the Antarctic sea-ice ecosystem and an ideal biomonitoring species for persistent and bioaccumulative compounds due to their extended life-spans. This study provides the first results of mercury accumulation in humpback whales, and places findings within the context of mercury accumulation in both prey, as well as six other species of Antarctic marine megafauna. Combined, these findings contribute new baseline information regarding mercury exposure to Antarctic wildlife, and highlights methodological prerequisites for routine mercury biomonitoring in wildlife via non-lethally biopsied superficial tissues.