Researchers from the University of Michigan and the University of Hawaii have defined the source of increasing levels of mercury in Pacific fish and have defined the chemical process that creates the mercury in the Aug. 25, 2013, issue of the journal Nature Geoscience.
The researchers examined the levels of methylmercury in nine species of Pacific fish that inhabit varying depths of water. They found that deeper living fish have higher levels of methylmercury than fish that live in shallower regions of the ocean.
Mercury is carried in the atmosphere from industrial plants in China and India to the Pacific. The mercury gets into the ocean through rain. The mercury sinks to the bottom of the ocean where bacteria act on it to produce methylmercury. The mercury that is deposited in the ocean is often consumed by smaller animals that die and sink to the ocean floor where the same bacterial process occurs.
Despite international agreements to limit the levels of mercury released into the atmosphere no concrete plan for the reduction of mercury emission exists.
The researchers predict a steady increase in the levels of mercury in Pacific fish that may eventually eliminate the fishing industry in the Pacific due to the deadly effects of mercury on the human fish consumer.