At night, oxygen is depleted at the
sediment surface. Methylmercury is produced and it moves out of sediments
by diffusion and with zooplankton, which seek protection in sediments during
the day.
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During the day, plankton produce oxygen
at the sediment surface and prevent methylmercury from moving out of sediments.
Plankton, which move up from the sediment surface, may bring methylmercury
to upper waters.
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