Conceptual illustration of ocean mercury bioaccumulation. Human industrial activity has significantly increased the levels of mercury in the atmosphere. The mercury eventually finds its way into lakes, rivers and the ocean, where it is eaten up by fish and other marine life. Once this mercury gets into the marine food chain, it 'bioaccumulates' in the larger predators. Humans that ingest high levels of mercury could suffer damage to brain function, the nervous system and the kidneys.