Interpreting environmental signals from the coralline sponge Astrosclera willeyana

Abstract

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 (~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.

Calibration of sclerosponge oxygen isotope records to temperature using high-resolution δ18O data

“…Assuming that density differences between the surface of the sclerosponge and the basal skeleton in C. nicholsoni are similar to those in Pacific Ocean species Astrosclera willeyana (Fallon et al, 2005) and representative of calyx infilling, approximately one third of the material in each sample from this project is comprised of older skeletal material. Averaging of a recorded signal would therefore be similar in magnitude to the Sr/Ca results presented by Haase-Schramm et al (2005).…”

“…Recently, significant efforts have focused on high-resolution, in situ, calibration of geochemical parameters in sclerosponge skeletons to ambient environmental parameters (Lazareth et al, 2000;Swart et al, 2002;Haase-Schramm et al, 2003;Rosenheim et al, 2004;Fallon et al, 2005;Haase-Schramm et al, 2005;Rosenheim et al, 2005a). Absent from the sclerosponge literature is a highresolution calibration of oxygen isotope values to temperature and oxygen isotope composition of water in which calcification occurred.…”

“…Paleoclimate interest in sclerosponges has spawned several high-resolution calibration studies, but these have been limited to proxies measureable by high-resolution techniques such as laser ablation ICP-MS (Rosenheim et al, 2004;Fallon et al, 2005). Laser micro-sampling techniques are not currently viable for analysis of sclerosponge oxygen isotopes in CaCO 3 because of the high accuracy and precision necessary to calibrate over a 2-5°C seasonal temperature range (Sharp, 1992;Sharp and Cerling, 1996).…”

Constraining initial 230Th activity in incrementally deposited, biogenic aragonite from the Bahamas

“…If reproducible despite the large statistical uncertainties, these data suggest that the success of a regional calibration of Sr/ Ca to temperature in this species (Rosenheim et al, 2004) was unaffected by different average skeletal extension rates of individual sclerosponges. Assuming Caribbean sclerosponge C. nicholsoni has uniform density as do Pacific genera (Fallon et al, 2005), calcification rate is proportional to skeletal extension rates. Thus, the trend of increasing Sr/Ca with decreasing temperature at depth was not amplified by slower calcification rates of deeper sclerosponges, indicating an insignificant or no effect of calcification rate on Sr/Ca to temperature calibration (Rosenheim et al, 2004).…”

A new plate-like hypercalcified chaetetid demosponge (Loiscupula bachendensi gen. nov. sp. nov) from the Cantabrian Zone (Moscovian, Pennsylvanian, NW Spain)

“…Extant forms are commonly found in cryptic habitats such as submarine caves of the reef core, and at depth on fore-reef slopes and walls in both the Caribbean and Indo-Pacific regions (Hartman and Goreau, 1975) in depths ranging from 10 to 185 m (Fallon et al, 2005). In contrast, Palaeozoic chaetetids are common open-shelf organisms, often associated with sunlight and relatively shallow-water carbonates.…”