Abstract Summary
The long-spined sea urchin (Diadema antillarum) was once an abundant reef grazing herbivore throughout the Caribbean. Benthic surveys in the Florida Keys during the 1960-70s revealed average densities of five to ten individuals per square meter. During the early 1980s, 98-99% of Diadema antillarum populations disappeared due to an unknown disease outbreak that appeared to originate at the Panama Canal. Sudden and considerable population reduction from this event resulted in lack of reef herbivory, and contributed to ongoing ecological shifts from coral dominated systems to macroalgae-dominated systems throughout the Caribbean. Diadema antillarum populations have remained very low throughout this region since the substantial reduction in the early 1980s. Currently, depressed populations of this ecologically important herbivore necessitate exploring Diadema antillarum restoration as part of an overall reef restoration initiative. Investigations into Diadema antillarum aquaculture have been occurring for over fifteen years. The purpose of this study is to refine methodology for reliable ex situ reproduction and larval rearing of Diadema antillarum in closed recirculating aquaculture systems (RAS). The intention of this work is to improve the viability of large scale aquaculture for experimental population enhancement. Adult broodstock from the Florida Keys are being conditioned for spawning. A novel RAS incorporating vessel design elements developed by Martin Moe has been constructed. Replicated experiments in 40-L recirculating vessels will be used to investigate larval development in Diadema antillarum. Initial culture parameters tested will include cell density and species composition of microalgae diets. Microalgae species used will include Rhodomonas lens, Isochrysis galbana (T-Iso), and Chaetoceros gracilis. To assess larval development, morphometric features will be examined including larval appendage length and symmetry, body condition, and presence or absence of rudiments. Larval survival and feeding condition will also be assessed. Data collected will be presented. Future studies will test strategies for larval settlement.
