Characterization of symbiotic algae, genus Symbiodinium, in corals at St. Lucie reef, Florida

The unique coral reef at St. Lucie Reef (Stuart, FL) persists despite environmental variability from extensive freshwater discharges, summer upwelling, and thermal
instability. By examining the symbiotic zooxanthellae, or Symbiodinium, that reside
in corals, we can gain insight to coral physiology impacted by local stressors. Two
scleractinian corals, Montastraea cavernosa and Pseudodiploria clivosa were sampled
over 1.5 years, including both wet and dry seasons. Zooxanthellae were isolated and
quantitatively characterized using standard measurements and molecular techniques.
Both coral species varied in zooxanthellae biomass, where Pseudodiploria clivosa had
Higher cell densities and chlorophyll concentrations than Montastraea cavernosa. Over
time, these parameters varied, but were not significantly altered by fresh water discharge events. Symbiodinium diversity and abundance were identified by ITS2 region amplification and next-generation sequencing .Novel associations between Symbiodinium and each coral explained the observed physiological differences. The symbioses remained stable throughout and could indicate local adaptation for St. Lucie Reef corals.