Mercury in a Marine Pelagic Food Chain1

Phytoplankton, zooplankton, and anchovies collected in Monterey Bay, California, over 10‐month period were analyzed for total mercury. In general, mercury levels were low and no evidence of food chain amplification was observed. Temporal variations of Hg concentrations in phytoplankton were greater than those for zooplankton; however, no seasonal trends were observed for either group. Plankton samples were also collected on a transect between the Hawaiian Islands and Monterey. Mercury levels were approximately equal in inshore and offshore zooplankton. The highest average mercury concentration was found in phytoplankton‐net samples from the open ocean that contained radiolarians and other small zooplankton forms as well as diatoms.