Mercury lands in marine ooze

Abstract

Photosynthetic algae called diatoms can trap mercury in deep-sea sediments, a new study finds. These diatom-rich oozes may store up to 20% of the toxic metal released into the atmosphere by human activity over the past 150 years (Science 2018, DOI: 10.1126/science.aat2735). As a volatile metal, mercury easily enters the atmosphere from natural sources, such as erupting volcanoes, and human sources, coal burning in particular. Some of that mercury eventually dissolves in the oceans. A team led by Harald Biester, a geochemist at the Technical University of Braunschweig, has now found that diatoms somehow absorb a significant portion of the dissolved mercury, pulling it down to the seafloor when the microorganisms die. The researchers sampled diatom oozes in sediment cores taken from the bottom of the Southern Ocean at three locations around Antarctica. They found some of the highest mercury accumulation rates measured in marine environments. The scientists estimate that