title: How Do Radionuclides Accumulate in Marine Organisms? A Case Study of Europium with Aplysina cavernicola.
abstract: In the ocean, complex interactions between natural and anthropogenic radionuclides, seawater, and diverse marine biota provide a unique window through which to examine ecosystem and trophic transfer mechanisms in cases of accidental dissemination. The nature of interaction between radionuclides, the marine environment, and marine species is therefore essential for better understanding transfer mechanisms from the hydrosphere to the biosphere. Although data pertaining to the rate of global transfer are often available, little is known regarding the mechanism of environmental transport and uptake of heavy radionuclides by marine species. Among marine species, sponges are immobile active filter feeders and have been identified as hyperaccumulators of several heavy metals. We have selected the Mediterranean sponge Aplysina cavernicola as a model species for this study. Actinide elements are not the only source of radioactive release in cases of civilian nuclear events; however, their physicochemical transfer mechanisms to marine species remain largely unknown. We have targeted europium(III) as a representative of the trivalent actinides such as americium or curium. To unravel biological uptake mechanisms of europium in A. cavernicola, we have combined radiometric (γ) measurements with spectroscopic (time-resolved laser-induced fluorescence spectroscopy, TRLIFS, and X-ray absorption near-edge structure, XANES) and imaging (transmission electron microscopy, TEM, and scanning transmission X-ray microscopy, STXM) techniques. We have observed that the colloids of NaEu(CO3)2·nH2O formed in seawater are taken up by A. cavernicola with no evidence that lethal dose has been reached in our working conditions. Spectroscopic results suggest that there is no change of speciation during uptake. Finally, TEM and STXM images recorded at different locations across a sponge cross section, together with differential cell separation, indicate the presence of europium particles (around 200 nm) mainly located in the skeleton and toward the outer surface of the sponge.
authors: Institut de Chimie de Nice, Université Côte d'Azur and Centre National de la Recherche Scientifique , 06108 Nice, France.|Commissariat à l'Énergie Atomique, Direction des Applications Militaires, DIF , F-91297 Arpajon, France.
authors: Melody
authors: M
authors: Maloubier
authors: Chemical Sciences Division, Lawrence Berkeley National Laboratory , Berkeley, California 94720, United States.
authors: David K
authors: DK
authors: Shuh
authors: Chemical Sciences Division, Lawrence Berkeley National Laboratory , Berkeley, California 94720, United States.
authors: Stefan G
authors: SG
authors: Minasian
authors: Chemical Sciences Division, Lawrence Berkeley National Laboratory , Berkeley, California 94720, United States.
authors: Joseph I
authors: JI
authors: Pacold
authors: Synchrotron Soleil , L'Orme des Merisiers, BP 48, Saint-Aubin, F-91192 Gif-sur-Yvette Cedex, France.
authors: Pier-Lorenzo
authors: PL
authors: Solari
authors: Institut de Chimie de Nice, Université Côte d'Azur and Centre National de la Recherche Scientifique , 06108 Nice, France.
authors: Hervé
authors: H
authors: Michel
authors: Monaco Environment Laboratory, International Atomic Energy Agency , 4 Quai Antoine Ier, 98000, Monaco.
authors: François R
authors: FR
authors: Oberhaensli
authors: Monaco Environment Laboratory, International Atomic Energy Agency , 4 Quai Antoine Ier, 98000, Monaco.
authors: Yasmine
authors: Y
authors: Bottein
authors: Commissariat à l'Énergie Atomique, Direction des Applications Militaires, DIF , F-91297 Arpajon, France.
authors: Marguerite
authors: M
authors: Monfort
authors: Commissariat à l'Énergie Atomique, Direction des Applications Militaires, DIF , F-91297 Arpajon, France.
authors: Christophe
authors: C
authors: Moulin
authors: Institut de Chimie de Nice, Université Côte d'Azur and Centre National de la Recherche Scientifique , 06108 Nice, France.
authors: Christophe
authors: C
authors: Den Auwer
mesh_terms: D000576:Americium; D059001:Aquatic Organisms; D003476:Curium; D005063:Europium; D011868:Radioisotopes
chemical_list: D011868:Radioisotopes; D005063:Europium; D003476:Curium; D000576:Americium