Reproductive characters of the elliptical star coral Dichocoenia stokesi (Cnidaria: Scleractinia) were investigated based in histological examination of tissues collected in southeastern Florida between September 1999 and September 2000. The study population was predominantly gonochoric with a small incidence of hermaphroditism. Dichocoenia stokesi exhibits intermediate egg size (312.2 ± 40.4μm; mean ± SD) compared with other scleractinian species, suggesting a moderately lecithotrophic larval stage. Although spawning was not directly observed in this study, two separate spawning events per year are inferred from histological slide analyses; the first in late August or early September, and the second in early October. Sea water temperature was significantly positively correlated with female gonadal development in D. stokesi, whereas insolation was significantly inversely correlated with gonadal development. A recent epizootic of White Plague Type II in south Florida appears to be skewing local D. stokesi populations toward smaller - and potentially less fecund - colony sizes, although colony size and fecundity were not correlated in this study. The mean fecundity of the study population is estimated as 1138.1 eggs cm-2 yr-1.

Coral reefs are one of the most economically important ecosystems on the planet. Despite their great contribution to the world economy, anthropogenic influence via carbon dioxide emissions is leading to unprecedented changes with concerns about subsequent negative impacts on reefs. Surface ocean pH has dropped 0.1 units in the past century; in spite of this rapid shift in oceanic chemistry, it is unclear if individual species or life stages of Caribbean stony corals will be more sensitive to ocean acidification (OA). Examined is the relationship between CO2-induced seawater acidification, net calcification, photosynthesis, and respiration in three model Caribbean coral species: Orbicella faveolata, Montastraea cavernosa, and Dichocoenia stokesi, under near ambient (465 ± 5.52 ppm), and high (1451 ± 6.51 ppm) CO2 conditions. A species specific response was observed for net calcification; D. stokesi and M. cavernosa displayed a significant reduction in CaCO3 secreted under OA conditions, while O. faveolata fragments showed no significant difference. At the cellular level, transmission electron micrographs verified that all species and treatments were actively calcifying. Skeletal crystals nucleated by O. faveolata in the high CO2 treatments were statistically longer relative to controls. These results suggest that the addition of CO2 may shift the overall energy budget, causing a modification of skeletal aragonite crystal structures, rather than inhibiting skeletal crystal formation. Consequential to this energy shift, Orbicella faveolata belongs in the category of Scleractinian corals that exhibit a lower sensitivity to ocean acidification.