Toxic compounds are produced by phytoplankton or their associated bacteria. Among the
thousands of species of microscopic algae at the base of the marine food chain are a few dozen
which produce potent toxins. One major category of public health impact from Harmful Algal Blooms occurs when toxic phytoplankton are filtered from the water by shellfish such as clams, mussels, oysters, scallops, etc., which then
accumulate the algal toxins to levels that are potentially lethal to humans or other consumers (Shumway, 1990)
