Prevalence, severity, lethality, and recovery of dark spots syndrome among three Floridian reef-building corals

Abstract

Disease affects the growth and survival of reef building corals. Prevalence, severity, lethality, and recovery of dark spots syndrome (DSS) was measured on three common scleractinian corals, Montastraea annularis complex, Siderastrea siderea, and Stephanocoenia michelinii on seven reefs in the Florida Keys. Between 2002 and 2004, DSS was the most common disease, responsible for 71.2% ± 5.7 S.E. of all disease infections in the total coral population. Prevalence ranged from 26.3% ± 17.6 S.E. for M. annularis, 7.5% ± 2.9 for S. siderea to 3.0% ± 0.1 for S. michelinii. DSS severity (expressed as the percent of diseased colony surface area) ranged from 0.55% ± 0.12 S.E. for M. annularis, 4.8% ± 0.63 for S. siderea to 0.83% ± 0.31 for S. michelinii. DSS rarely caused whole colony mortality (0.0% yr − 1 for Montastraea annularis, 0.3% yr − 1 for Siderastrea siderea, and 3.8% yr − 1 for Stephanocoenia michelinii), but was a significant source of partial mortality. During the 2002–2003 survey period, net tissue loss per annum due to DSS was 0.3% yr − 1 for M. annularis, 1.0% yr − 1 for S. siderea, and 8.8% yr − 1 for S. michelinii. Total net tissue loss for these three species, from all sources of mortality, was 0.45%, 1.0%, and 8.8% respectively, demonstrating that DSS was the only source of mortality for S. michelinii and S. siderea during this period, and accounted for two-thirds of all tissue loss from M. annularis colonies. DSS recovery rates were variable, depending on the target species. DSS signs in 86.8% of M. annularis colonies and 73.3% of S. michelinii colonies identified in 2002 and 2003 persisted through the end of the survey (2004). By contrast, among S. siderea only 33.3% of colonies affected in 2002 and 2003 continued to exhibit disease signs by 2004. Annual recovery rates from DSS were also species-dependent: 32.9% of DSS-affected S. siderea colonies recovered annually, but, by contrast, only 6.6% and 10.0% of DSS-affected M. annularis and S. michelinii colonies had done so. DSS appears to be a significant source of both whole and partial mortality for S. michelinii, but not for the other two species during this survey.