Population status and reproductive potential of the pillar coral, Dendrogyra cylindrus, along the Florida Reef Tract

Guy Harvey Oceanographic Center Facility

The pillar coral, Dendrogyra cylindrus, has been commonly described as widely distributed, but rare throughout the Caribbean. In Florida specifically, there have been few observations of pillar coral and until recently the current population status was relatively unknown, although geologic records indicate that historical abundance may have been higher. Along with various environmental and anthropogenic impacts, reproductive limitation may also be contributing to species decline and limiting recovery. Dendrogyra cylindrus is a gonochoric, broadcast spawner; synchronously releasing gametes from single-sex colonies into the water column. This characteristic reproductive mode combined with the already rare occurrence of adult colonies may be making it difficult for fertilization to occur; however, the sexual reproductive capacity of this regional population has not yet been studied. Due to its recent designation as Threatened under the US Endangered Species Act, efforts to better understand population status and reproductive behavior is needed to promote species conservation and recovery. In our study, submissions of pillar coral locations from the scientific and lay community were compiled, and 573 D. cylindrus colonies along the entire Florida Reef Tract (FRT) have been identified. For each colony demographic and condition data were recorded in a comprehensive database including size (length, width, and height), colony type (morphology), percent mortality, presence and severity of disease and bleaching. To investigate reproductive capacity, tissue samples were collected from 94 colonies within 15 sites distributed along the FRT and were prepared via histological techniques. The sex of each colony, gamete sizes, and number of gametes per unit area (cm2) were recorded and analyzed to determine reproductive potential of individual colonies and also the sex ratio. This discussion will provide a general overview of results found in this study while presenting primary concerns for the rapid and comprehensive development of conservation and management strategies for this FRT pillar coral population.