102 Paleontology (Posters) III - Diversity and Paleoecology

Monday, 1 November 2010
8:00 AM - 6:00 PM
Hall D

PREDICTIONS FOR DISSOLUTION OF ANTARCTIC BIVALVES UNDER OCEAN ACIDIFICATION SCENARIOS

Paper number: 102-30
Program: Technical Sessions
Time: 8:00 AM – 6:00 PM

Authors

Abstract

Recent studies suggest that the Southern Ocean could become entirely undersaturated with respect to aragonite by 2030 or by 2050. This holds major ecological implications for calcifying organisms. Current work has focused mainly upon planktonic pteropods, while a dearth of studies pertain to benthic communities. Examining documented mineralogy, microstructure, and bathymetry (continental shelf, inner slope, outer slope, abyssal plain) data for 30 bivalve families south of the Antarctic Convergence reveals that only 5 build shells using composite calcite/aragonite microstructures; 25 rely on presumably less stable aragonitic configurations. Furthermore, 58% of the families contain genera already living in undersaturated polar conditions. We expect that survivability at the Family level under the 2050 scenario would be determined by shell structure/composition and to a lesser extent, bathymetric distribution. Surviving families will be those which have resistant microstructures (inner or outer shell layers of calcite) and a wide bathymetric distribution.

Based on shell compositions of Antarctic bivalves alone, an estimated loss of up to 86% at the species could occur under 2050 predictions. Of the aragonitic families, 14 possess weaker shell microstructures (prismatic, crossed-lamellar) and will be immediately affected by undersaturated conditions; the remaining 9 have more resistant microstructures (fine-grained homogenous, nacreous) and may persist longer. A case study conducted in Explorers Cove, Antarctica, revealed pitting and minor dissolution in living specimens of Laternula elliptica (Laternulidae: homogenous outer layer, nacreous to prismatic inner layers) while living specimens of Adamussium colbecki (Propeamussidae: composite calcite/aragonite layers) do not exhibit shell dissolution. Aragonite is reported to be 35% more soluble than calcite and the findings at Explorers Cove follow this trend. More research on the factors controlling resistance to dissolution is needed to accurately determine the ability of Antarctic bivalves to cope with the predicted onset of acidified ocean conditions.