"Global and Regional Variation of Mercury Sources to Oceanic Fish"
Marine apex predators accumulate high levels of mercury (Hg) as neurotoxic methylmercury (MeHg). Across ocean basins, however, variation in Hg bioaccumulation in oceanic fish is not well understood. To examine global patterns of Hg pollution and bioavailability in the world's oceans, we determined mercury accumulation rates (MARs) of bluefin tuna populations from four ocean basins. MARs for bluefin tuna populations are highest in the Mediterranean Sea and decrease as North Pacific Ocean > Indian Ocean > North Atlantic Ocean, which corresponds to current levels of Hg pollution and natural sources of Hg to the world's oceans. In addition, MARs increase in proportion to the concentrations of MeHg in seawater, phytoplankton and zooplankton from each region, linking MeHg accumulation in bluefin tuna to MeHg bioavailability at the base of each basin's food web. In the North Pacific Ocean, mercury stable isotope ratios in Pacific bluefin tuna indicate shifts in the source of MeHg as fish age. Mercury stable isotopes also show that MeHg in oceanic food webs in the western North Pacific Ocean has a different source or undergoes different transformations before entering the oceanic food web than in the central and eastern North Pacific. Connecting MeHg accumulated in marine predators from the western North Pacific and other ocean basins to specific anthropogenic sources remains challenging and will require higher resolution observations of Hg concentrations and stable isotopes in coastal and oceanic air, water and biota.

Zoom Recording ID: 98935302803 UUID: yptllkZxSp+v38GTmRwzmg== Meeting Time: 2023-04-07 03:25:08pmGMT