Cellular reactions to sedimentation and temperature stress in the Caribbean coral Montastraea cavernosa

We present evidence of cellular responses to increased sedimentation and temperature in Montastraea cavernosa collected off Broward County, Florida. We sampled corals from six different sites approximately, 500-1000 m off shore, 10-15m depth. Six samples were collected from four sites adjacent to areas of underwater marine dredging (project sites), while the remaining two samples were obtained far away from the influence of the marine dredging (control sites). SSTs around collection time ranged 0.6-0.9 degrees C over the 40-year monthly mean. All specimens collected at project sites exhibited histopathological evidence of mild to moderate sedimentation stress including changes in size and number of mucocytes in epidermis and gastrodermis, attenuation of the epidermal and gastrodermal tissues, presence of cellular debris, and changes in number of zooxanthellae. These findings corroborate results of laboratory-based, sand-application experiments. In addition to the above-noted changes, one specimen exhibited multiple lesions consisting of unusual gastrodermal detachment with infiltration of amoebocytes into the adjacent mesoglea. Tissues surrounding detachment injuries exhibited marked to severe cellular changes. Accumulations of amoebocytes at lesion sites are seldom observed in wild corals. This response may be part of an organized reaction to injury and infection, as has been documented in sea anemones and gorgonians; however, further research is needed on the nature and role(s) of the scleractinian amoebocytes.