Reduced salinity decreases the fertilization success and larval survival of two scleractinian coral species

Successful reproduction by scleractinian corals is essential for the maintenance of populations that form the foundation of coral reef ecosystems. Laboratory experiments were done to determine the effects of reduced salinity on the fertilization success and larval survival of two coral species, Platygyra daedalea and Acropora millepora, from the Great Barrier Reef, Australia. Fertilization rates of P. daedalea and A. millepora were significantly reduced at 25.8 psu and 33.1 psu, respectively, and completed blocked at 18.4 psu for A. millepora. The estimated larval survival times were similar from 36.8 to 25.8 psu (P. daedalea 291-312 h, A. millepora 207-264 h), whereas the 18.4 psu treatment resulted in estimates of 153 h and 24 h for P. daedalea and A. millepora, respectively. These results demonstrate that reduced salinity is detrimental to the reproductive success of these corals, and if salinity is lowered by natural or anthropogenic sources during spawning, this would lead to decreased reproductive success and recruitment on reefs.