Effects of copper and decreased salinity on survival rate and development of Tridacna gigas larvae

Giant clams (Family: Tridacnidae) are endangered species distributed in the Indo-Pacific region. In this study, survival rate and development of Tridacna gigas larvae were studied for three days in ambient water (32 psu), copper (2.5 microg Cu(2+) L(-1)), reduced salinities (25 and 20 psu) and the combination of copper and 25 psu salinity. No significant differences were found in larval development between treatments. The survival rates decreased considerably with reduced salinities although the combination of copper and reduced salinity gave synergistic effects. As a consequence, this could limit population growth of giant clams in coastal areas and could also explain the absence of larval settlement on reefs close to harbours or river mouths. More research is needed to understand the basic requirements and stress tolerance in giant clam larvae for reef restoration and other management actions to be successful.