What are gross signs of salinity stress?
Clams have the ability to close their valves, or shells, in response to adverse salinity conditions, effectively preventing exposure to the surrounding seawater. Clams can keep their valves closed for several days. During this time they respire anaerobically (without oxygen). Clams subject to salinity stress may exhibit: gaping (a longer-term response), retracted mantle edges (especially in response to abnormally high salinities), or swollen, protruding mantle edges (especially in response to low salinities). Gross signs of adverse environmental conditions in juvenile or adult hard clams may go unnoticed because they are infaunal, living buried in the sediment. However, stressed clams may rise to the surface of the sediment or fail to bury. In laboratory studies, we found that clams held at 25, 35, and 40 ppt actively buried. However, clams did not bury in salinities of 5, 10 or 50 ppt. At 15 and 45 ppt, fewer than 25% of clams had buried after 24 hours. These signs are not necessarily
