Poigner, Harald

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Geophysical Research AbstractsVol. 14, EGU2012-6576, 2012EGU General Assembly 2012© Author(s) 2012Element ratios between digestive gland and gill tissues of the Antarcticbivalve Laternula elliptica as a proxy for element uptake from differentenvironmental sourcesH. Poigner (1), D. Monien (2), P. Monien (2), M. Kriews (1), H.-J. Brumsack (2), D. Wilhelms-Dick (3), and D.Abele (1)(1) Alfred Wegener Institute for Polar and Marine Research, Bremerhaven, Germany (harald.poigner@awi.de), (2) Institutefor Chemistry and Biology of the Marine Environment, University of Oldenburg, Oldenburg, Germany, (3) Department ofGeosciences, University of Bremen, Bremen, GermanyTrace metals in bivalve carbonate shells are frequently used as environmental or paleoclimate proxies. Carbonatemineralogy and animals’ physiology affect the incorporation of elements from different environmental sources intobivalve shells. Generally, metals from particulate matter are assimilated via the digestive tract; whereas dissolvedmetals are absorbed via gills. Therefore, measurements of element concentrations deposited in the shell matrix donot necessarily allow inference with respect to the assimilation pathways. In this study, we used element ratiosbetween digestive gland (DG) and gills (cDG/cGill) of the Circum-Antarctic clam Laternula elliptica to identifypredominating assimilation pathways and potential sources of bio-available metals. This normalization betweentissues of each individual eliminates the effects of individual age and physiological condition (e.g. accumulationover lifetime, metabolic activity) on metal assimilation. These effects also minimize the reproducibility, when ab-solute element concentrations are compared between individuals from different locations. Therefore, an additionalnormalization is required. We favored “ellipsoid shell volume” over shell length or soft tissue weight as more con-servative approximation for intra- and intersite comparisons. Metal concentrations in DG, gills, and hemolymphof the bivalve L. elliptica, collected at Potter Cove (King George Island, Antarctic Peninsula), were analyzed bymeans of inductively coupled plasma - optical emission spectroscopy and mass spectrometry after total acid di-gestion. The element ratios (cDG/cGill) indicate a predominant assimilation of Al, Ca, Fe, K, Mn, and Mg fromthe dissolved phase. These high Al and Fe concentrations in gill tissues and hemolymph are in contrast to the lowsolubility of Al and Fe in seawater. But high dissolved Fe concentrations in pore waters (up to 1400 µg L-1 dueto suboxic sediment conditions) and glacial melt waters enriched in dissolved Al (of approx. 54 µg L-1 due toweathering processes) with respect to seawater concentrations (5.4-13.5 µg L-1) are likely bio-available sources atPotter Cove. In contrast, Cd, Cu, and Sr are mainly assimilated via the digestion of particulates. Since most stud-ies on metal incorporation into bivalve shells have provided mathematical correlations to environmental data, thisproxy-based approach provides a more causal relationship between sources and assimilation pathways. It improvesthe interpretation of element variations (if independent from shell mineralogy) in bivalve shells, especially, wherea full characterization of the biogeochemical environment of the bivalves is lacking.

Element ratios between digestive gland and gill tissues of the Antarctic bivalve Laternula elliptica as a proxy for element uptake from different environmental sources

Element ratios between digestive gland and gill tissues of the Antarctic bivalve Laternula elliptica as a proxy for element uptake from different environmental sources

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