Meeting Abstract

P3.31  Friday, Jan. 6  The Mg-Calcite levels of Antarctic echinoderms: implications for ocean acidification and further support for a latitudinal gradient in levels of Mg-Calcite MCCLINTOCK, J.B*; AMSLER, M.O.; ANGUS, R.A.; CHALLENER, R.C.; SCHRAM, J.B.; AMSLER, C.D.; MAH , C.L.; CUCE, J.; BAKER, B.J.; Univ. of Alabama at Birmingham; Univ. of Alabama at Birmingham; Univ. of Alabama at Birmingham; Univ. of Alabama at Birmingham ; Univ. of Alabama at Birmingham; Uni. of Alabama at Birmingham; Museum of Natural History, Smithsonian Inst.; University of South Florida; University of South Florida

The Southern Ocean is considered to be the canary in the coal mine with respect to the first impacts of ocean acidification (OA). As such, calcite and aragonite are expected to become undersaturated within 50 and 100 years. Echinoderms, whose skeletons are comprised of high magnesium carbonate (greater than 4% mol MgCO3), are even more vulnerable to OA than organisms whose skeletons are comprised of aragonite or calcite. Currently there is almost no information on the Mg-Calcite composition of Antarctic echinoderms, a group known to be a major contributor to the global marine carbon cycle. Here we report the Mg-Calcite compositions of 26 species of Antarctic echinoderms representing four classes. As seen in tropical and temperate echinoderms, Mg-calcite levels varied with taxonomic class with sea stars and brittle stars with the highest levels. Both classes are key players in Antarctic benthic communities, and are likely to be the first echinoderms challenged by near-term OA. When combined with published data for echinoderms from primarily temperate and tropical latitudes, our findings support the hypothesis that Mg-Calcite level varies inversely with latitude. The basis of this relationship has been suggested to include temperature, light, salinity, seawater saturation state and/or physiological factors. We propose that predation is also worthy of consideration as crushing predators decline with increasing latitude. As such, high latitude echinoderms may not require as high a ratio of magnesium to calcite to strengthen their skeletal elements.