Sclerosponges are a unique group of tropical organisms that secrete aragonite skeletons across a habitat range from the near surface to 200 m. Because sclersosponges can live for >1000 years, and their aragonite geochemistry is in isotopic equilibrium with seawater, the skeletons contain an invaluable archive of continuous near surface environmental conditions during the Holocene. When oxygen isotope and trace element data are collected from a suite of specimens, it is possible to reconstruct water column temperature and salinity as a function of depth and time. Funds from this SGER will be used to locate and collect sclerosponges from a 200 m depth transect along Desecheo Island, Puerto Rico, using mixed-gas/rebreather diving technology (to 100 m) and an ROV (100-200 m depth). The Caribbean Coral Reef Institutes will provide the ROV to this project at no cost to NSF. Collected sclerosponges will be dated using U/Th and analyzed for their skeletal geochemistry to calibration and validate the geochemical proxies for paleothermometry.
