Levels of exposure which were not lethal were sometimes found to increase susceptibility to disease or to cause behavioral abnormalities affecting spawning. Some compounds did not harm the oysters themselves, but killed their food organisms. Copper and lead were found to cause thinning of shells over time and changes in respiration. At high concentrations, certain petroleum compounds caused starvation, because the oysters closed their shells and stopped feeding. One study found exposure to pesticides in combination to have more severe effects than exposure to single pesticides.
Oysters are vulnerable to a wide variety of point and non-point source pollutants.
Diatoms have glass-like walls and a wide variety of lovely, symmetrical shapes. Because wetlands trap sediments and pollutants and slow Flood waters, tilling them also worsens the effects of all the problems listed above. Written by Sigrun Gadwa. Funding provided by the Community Foundation of Greater New Haven and the Long Island License Plate Fund. Information provided by the Aquaculture Division of the State of Connecticut Department of Agriculture, by Tallmadge Brothers, Inc., and by the New Haven Historical Society.