HYPOSALINITY STRESS TOLERANCES OF THE CORALS MONTASTRAEA CAVERNOSA AND PORITES ASTREOIDES IN SOUTHEAST FLORIDA AND IMPLICATIONS FOR COASTAL FRESHWATER MANAGEMENT

Coastal development shifts natural hydrology through water redirection, increased impervious surfaces, and increased connectivity to the coastal ocean through inlets. In Southeast Florida, watershed alterations can cause flash-freshening in nearshore coastal habitats, threatening coral reef ecosystems. This study assessed the hyposalinity tolerance threshold of two prominent scleractinian corals in Southeast Florida. In a series of experiments, we determined that Montastraea cavernosa corals have an LC50 of 19 PSU but can survive for at least 21 days at an intermediately stressful salinity of 25 PSU. Porites astreoides corals demonstrated an LC50 of 19 PSU, but experienced mortality when exposed to 25 PSU for 17–18 days. Prior to mortality, corals displayed decreased polyp activity, altered coloration, and decreased tissue integrity. These data suggest that lower-volume, longer-duration releases of freshwater from reservoirs may preserve coral health in Southeast Florida.