Coralline sponges (sclerosponges) have been proposed as a new source for paleo subsurface temperature reconstructions by utilizing methods developed for reef-building corals. However unlike corals, coralline sponges do not have density variations making age determination difficult. In this study we examined multiple elemental rations (B, Mg, Sr, Ba, U) in the coralline sponge Astrosclera willeyana. We also measured skeletal density profiles along the outer ''living'' edge of the sponges and this data indicates significant thickening of skeletal material over intervals of 2-3 mm or 2-3 years. This suggests that any skeletal recovered environmental record from Astrosclera willeyana is an integration of signals over a 2-3 year period. Sponge Sr/Ca seemed to hold the most promise as a recorder of water temperature and we compared Sr/Ca from 2 sponges in the Great Barrier Reef and one from Truk in Micronesia to their respective sea surface temperature record. The correlations were not that strong ({approx} r=-0.5) but they were significant. It appears that the signal smoothing due to thickening or perhaps even some biologic control on Sr skeletal partitioning limits the use of Sr/Ca as an indicator of water temperature in Astrosclera willeyana
