title: Iron assimilation by the clam Laternula elliptica: Do stable isotopes (δ⁵⁶Fe) help to decipher the sources?
abstract: Iron stable isotope signatures (δ(56)Fe) in hemolymph (bivalve blood) of the Antarctic bivalve Laternula elliptica were analyzed by Multiple Collector-Inductively Coupled Plasma-Mass Spectrometry (MC-ICP-MS) to test whether the isotopic fingerprint can be tracked back to the predominant sources of the assimilated Fe. An earlier investigation of Fe concentrations in L. elliptica hemolymph suggested that an assimilation of reactive and bioavailable Fe (oxyhydr)oxide particles (i.e. ferrihydrite), precipitated from pore water Fe around the benthic boundary, is responsible for the high Fe concentration in L. elliptica (Poigner et al., 2013 b). At two stations in Potter Cove (King George Island, Antarctica) bivalve hemolymph showed mean δ(56)Fe values of -1.19 ± 0.34‰ and -1.04 ± 0.39 ‰, respectively, which is between 0.5‰ and 0.85‰ lighter than the pool of easily reducible Fe (oxyhydr)oxides of the surface sediments (-0.3‰ to -0.6‰). This is in agreement with the enrichment of lighter Fe isotopes at higher trophic levels, resulting from the preferential assimilation of light isotopes from nutrition. Nevertheless, δ(56)Fe hemolymph values from both stations showed a high variability, ranging between -0.21‰ (value close to unaltered/primary Fe(oxyhydr)oxide minerals) and -1.91‰ (typical for pore water Fe or diagenetic Fe precipitates), which we interpret as a "mixed" δ(56)Fe signature caused by Fe assimilation from different sources with varying Fe contents and δ(56)Fe values. Furthermore, mass dependent Fe fractionation related to physiological processes within the bivalve cannot be ruled out. This is the first study addressing the potential of Fe isotopes for tracing back food sources of bivalves.
authors.affiliation: Alfred Wegener Institute Helmholtz Centre for Polar and Marine Research, 27570 Bremerhaven, Germany. Electronic address: Harald.Poigner@awi.de.
authors.forename: Harald
authors.initials: H
authors.lastname: Poigner
authors.affiliation: Alfred Wegener Institute Helmholtz Centre for Polar and Marine Research, 27570 Bremerhaven, Germany.
authors.forename: Dorothee
authors.initials: D
authors.lastname: Wilhelms-Dick
authors.affiliation: Alfred Wegener Institute Helmholtz Centre for Polar and Marine Research, 27570 Bremerhaven, Germany. Electronic address: Doris.Abele@awi.de.
authors.forename: Doris
authors.initials: D
authors.lastname: Abele
authors.affiliation: University of Cologne, Institute for Geology and Mineralogy, 50674 Cologne, Germany.
authors.forename: Michael
authors.initials: M
authors.lastname: Staubwasser
authors.affiliation: Alfred Wegener Institute Helmholtz Centre for Polar and Marine Research, 27570 Bremerhaven, Germany; University of Cologne, Institute for Geology and Mineralogy, 50674 Cologne, Germany.
authors.forename: Susann
authors.initials: S
authors.lastname: Henkel
mesh_terms: D000818:Animals; D000864:Antarctic Regions; D049872:Bivalvia / Q000378:metabolism*; D005591:Chemical Fractionation; D005290:Ferric Compounds; D007501:Iron / Q000378:metabolism*; D007503:Iron Isotopes; D007554:Isotopes / Q000032:analysis; D014867:Water / Q000032:analysis
chemical_list: D005290:Ferric Compounds; D007503:Iron Isotopes; D007554:Isotopes; D014867:Water; C092844:ferric oxyhydroxide; D007501:Iron
keywords: Antarctica; Bivalve; Hemolymph; Iron; Stable isotopes