Potential climate signals from the deep-sea gorgonian coral Primnoa resedaeformis

Abstract

The deep-sea gorgonian coral Primnoa resedaeformis has an arborescent skeleton composed of both calcite and a horn-like structural protein called gorgonin. We have investigated potential climate records in corals from Alaska, the eastern seaboard of Canada and the United States, and a Southern Ocean (Pacific sector) seamount. Temperatures at these sites range from 4 to ∼10 °C. δ18O values of the calcite show strong evidence for isotopic disequilibrium. Extraction of δ18O paleotemperatures is therefore not straightforward. Sr/Ca data, analyzed by Secondary Ion Mass Spectrometry (SIMS), suggest that temperature might be a control on calcite Sr/Ca in Primnoa resedaeformis, but that growth-related kinetic effects could also be important. Based on previous 14C, δ13C and δ15N measurements, it has been suggested that particulate organic matter (POM) from the surface is an important carbon source to the polyps and the gorgonin fraction of the Primnoa skeleton. δ15N and δ13C of polyps and gorgonin show similar regional differences to δ15N and δ13C of surface POM. Polyps and contemporaneous gorgonin correlate strongly for both δ13C and δ15N. The influence of nutrient isotopic composition and climate and productivity variations on the isotopic composition of surface POM may therefore be recorded in gorgonin layers. These corals have very long lifespans (several centuries). The potential exists, therefore, to obtain extended records of surface productivity, deep ocean temperature and chemistry of value to climatologists and fisheries managers.