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| Titel |
Element ratios between digestive gland and gill tissues of the Antarctic bivalve Laternula elliptica as a proxy for element uptake from different environmental sources |
| VerfasserIn |
H. Poigner, D. Monien, P. Monien, M. Kriews, H.-J. Brumsack, D. Wilhelms-Dick, D. Abele |
| Konferenz |
EGU General Assembly 2012
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 14 (2012) |
| Datensatznummer |
250064440
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| Zusammenfassung |
| Trace metals in bivalve carbonate shells are frequently used as environmental or paleoclimate
proxies. Carbonate mineralogy and animals’ physiology affect the incorporation of
elements from different environmental sources into bivalve shells. Generally, metals
from particulate matter are assimilated via the digestive tract; whereas dissolved
metals are absorbed via gills. Therefore, measurements of element concentrations
deposited in the shell matrix do not necessarily allow inference with respect to the
assimilation pathways. In this study, we used element ratios between digestive gland (DG)
and gills (cDG/cGill) of the Circum-Antarctic clam Laternula elliptica to identify
predominating assimilation pathways and potential sources of bio-available metals.
This normalization between tissues of each individual eliminates the effects of
individual age and physiological condition (e.g. accumulation over lifetime, metabolic
activity) on metal assimilation. These effects also minimize the reproducibility,
when absolute element concentrations are compared between individuals from
different locations. Therefore, an additional normalization is required. We favored
“ellipsoid shell volume” over shell length or soft tissue weight as more conservative
approximation for intra- and intersite comparisons. Metal concentrations in DG, gills, and
hemolymph of the bivalve L. elliptica, collected at Potter Cove (King George Island,
Antarctic Peninsula), were analyzed by means of inductively coupled plasma -
optical emission spectroscopy and mass spectrometry after total acid digestion. The
element ratios (cDG/cGill) indicate a predominant assimilation of Al, Ca, Fe, K,
Mn, and Mg from the dissolved phase. These high Al and Fe concentrations in
gill tissues and hemolymph are in contrast to the low solubility of Al and Fe in
seawater. But high dissolved Fe concentrations in pore waters (up to 1400 μg L-1
due to suboxic sediment conditions) and glacial melt waters enriched in dissolved
Al (of approx. 54 μg L-1 due to weathering processes) with respect to seawater
concentrations (5.4-13.5 μg L-1) are likely bio-available sources at Potter Cove. In
contrast, Cd, Cu, and Sr are mainly assimilated via the digestion of particulates. Since
most studies on metal incorporation into bivalve shells have provided mathematical
correlations to environmental data, this proxy-based approach provides a more causal
relationship between sources and assimilation pathways. It improves the interpretation of
element variations (if independent from shell mineralogy) in bivalve shells, especially,
where a full characterization of the biogeochemical environment of the bivalves is
lacking. |
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