Bioaccumulation of heavy metals and radionuclides from seawater by encased embryos of the spotted dogfish Scyliorhinus canicula.

Encased embryos of spotted dogfish Scyliorhinus canicula absorbed six radio-isotopes (241Am, 109Cd, 57Co, 134Cs, 54Mn and 65Zn) directly from seawater during short-term experimental exposure, demonstrating the permeability of the egg-case to these contaminants. Embryo to water concentration factors (CFs) ranged from 0.14 for 134Cs to 7.4 for 65Zn. The 65Zn and 57Co CFs increased exponentially with embryo length, whereas the CF for 109Cd declined with length. Among different components of the encased embryo the egg case was the major repository (69-99%) of all six radio-isotopes that were distributed throughout its wall. Egg-case CFs were as high as 10(3) for 57Co and 65Zn, making it the major source of gamma radiation exposure to the embryo and potentially of radio-isotopes for continued absorption by the embryo, following the uptake phase of the experiment. The patterns of uptake by the egg-case approximated linearity for most isotopes and loss rates were isotope-specific; egg-case biokinetics were not greatly affected by the viability of the contained embryo. Within the embryo initial data on radio isotopic distribution show that the skin is their major site of uptake, as previously demonstrated for juveniles

Comparison of the bioaccumulation from seawater and depuration of heavy metals and radionuclides in the spotted dogfish Scyliorhinus canicula (Chondrichthys) and the turbot Psetta maxima (Actinopterygii: Teleostei).

The bioaccumulation of selected heavy metals and radionuclides ((241)Am, (109)Cd, (57)Co, (51)Cr, (134)Cs, (54)Mn and (65)Zn) from seawater was experimentally compared in the Chondrichthyan Scyliorhinus canicula (spotted dogfish) and the Actinopterygian Teleost Psetta maxima (turbot), of comparable size, age and benthic feeding habits. The speciation of these elements in seawater (salinity 38 per thousand, pH 8.1, temperature 16.5 degrees C) was also calculated to determine their potential bioavailability. The uptake rates, measured over 14 days, varied greatly among isotopes and between species. Concentration factors (CFs) in P. maxima varied 5-fold between ca. 0.2 for (51)Cr and 2.5 for (65)Zn and (134)Cs, whereas in S. canicula they varied by a much greater factor of 350, with CFs for (51)Cr and (241)Am ranging from ca. 0.4 to 140, respectively. With the exception of (134)Cs, all radiotracers were accumulated at a faster rate in S. canicula than in P. maxima, particularly for (241)Am and (65)Zn where the CFs attained during the uptake phase were, two and one order of magnitude greater in S. canicula, respectively. In contrast, (134)Cs reached a CF of about 2.5 in P. maxima, which was 5-fold greater than in S. canicula. Patterns of loss from the experimental depuration phase over 29 days showed greater similarities between species, compared to the uptake phase that highlighted the greater differences between elements. The distributions of these seven radioisotopes among six body components indicated that between the two species the skin of the dogfish displayed a greater bioaccumulation potential, particularly for (241)Am, (57)Co and (65)Zn. However (65)Zn was also distinctive from (241)Am and (57)Co in its pattern of bioaccumulation in dogfish, with its other body components attaining concentrations of (65)Zn that were comparable to the levels found in its skin. The heightened uptake of (134)Cs in turbot was characterised by a more even percentage distribution among its tissues compared to (241)Am and (57)Co, but every tissue of turbot had a higher concentration of (134)Cs, compared to dogfish, particularly the muscle and liver. The elevated uptake rates and higher CFs for most radioisotopes indicate that S. canicula is more susceptible than P. maxima to exposure and contamination by these metals and radionuclides in seawater. These experimentally-determined differences between dogfish and turbot in their bioaccumulation characteristics were assessed against a set of criteria erected to evaluate the working hypothesis that they were taxonomically based. The outcomes of this initial assessment were supportive of this hypothesis that warrants further investigation

Distribution of heavy metals in the echinoid <i>Paracentrotus lividus</i> from the Mediterranean <i>Posidonia oceanica</i> ecosystem: seasonal and geographical variations

The concentrations of Zn, Pb, Cd, Fe, Cr, Cu, and Ti were measured in specimens of the echinoid Paracentrotus lividus from three Posidonia oceanica meadows in the NW Mediterranean (Marseille, France; Ischia, Italy; Calvi, Corsica). Investigated metals were selectively distributed among the echinoid body compartments (i.e. body wall, Aristotle's lantern, digestive wall, and gonads); their concentrations were influenced by season. The present work emphasises the need to consider both body compartment and sampling period as important factors in studies intending to use P. lividus as a biomonitor species. In particular, digestive wall and, secondarily, body wall and gonads are recommended for use in biomonitoring programmes, though with some restrictions for gonads. Concentrations of most metals differed significantly in the echinoid body compartments according to the seagrass meadow considered. However, these differences were generally of low amplitude, except for Fe and Ti contaminations by these two metals showed significant departures from background concentrations in echinoids from Ischia). Results suggest that the meadows of Calvi and Marseille, although subject to different pollution status (the meadow of Calvi is considered as a reference meadow while the Marseille meadow is exposed to intense domestic and industrial discharges), showed similar patterns of metal contamination

Bioaccumulation of inorganic Hg by the juvenile cuttlefish Sepia officinalis exposed to 203Hg radiolabelled seawater and food

Uptake and depuration kinetics of inorganic mercury (Hg) were investigated in the juvenile common cuttlefish Sepia officinalis following exposures via seawater and food using a sensitive radiotracer technique (203Hg). Cuttlefish readily concentrated 203Hg when exposed via seawater, with whole body concentration factors >260 after only 10 d of exposure. The total Hg accumulated from seawater was depurated relatively fast with a radiotracer biological half-life (Tb1/2 of 17 d. During both exposure and depuration periods, accumulated Hg was mainly (>70%) associated with the muscular parts of the cuttlefish. However, the proportion of the whole-body Hg content associated with the digestive gland increased during exposure and depuration phases, suggesting that the metal was transferred from the muscles towards this organ for detoxification. When fed with radiolabelled food, cuttlefish displayed high assimilation efficiency (>90%) and the metal was found to be mainly located in the digestive gland (60% of the whole Hg content). Nevertheless, high depuration rates resulted in short Tb1/2 (i.e. 4 d), suggesting that this organ has a major role in Hg detoxification and depuration. Whatever the exposure pathway, a low proportion of Hg (<2%) was found in the cuttlebone. Assessment of the relative contribution of the dietary and dissolved exposure pathways to inorganic Hg bioaccumulation in juvenile cuttlefish revealed that Hg was mainly accumulated from food, which contributed 77 ± 16% of the global metal bioaccumulation

The brown alga Lobophora variegata, a bioindicator species for surveying metal contamination in tropical marine environments

Uptake and depuration kinetics of Cd, Co, Cr, Mn, Ni and Zn were determined in the brown alga Lobophora variegata exposed to realistic concentrations of these metals, using highly sensitive radiotracer techniques. The experiments were designed to assess the possible influence of varying dissolved metal concentrations on the capacity of metal bioconcentration and retention in the alga. Results indicate that the alga takes up Cd, Co, Cr, Ni, and Zri in direct proportion to their ambient dissolved concentrations over the entire range of concentrations tested (three orders of magnitude). In contrast, Mn was taken up in proportion to its dissolved concentration only over a concentration range of 2 orders of magnitude (up to 250 ng Mn L-1, i.e. 4.55 nM), then at higher concentrations its accumulation efficiency slightly decreased. Overall, L. variegata appears to be a reliable bioindicator species that shows a rapid response time in metal uptake (uptake rate constants ranging from 60 to 1,023 d(-1)) and has a suitable potential to furnish valuable information on the bioavailable contamination levels occurring in New Caledonian areas affected by land-based mining activities. Furthermore, due to its wide geographical distribution, L. variegata could be considered as a useful bioindicator species for surveying metal contamination in many other tropical areas

Marine environment and radioecology radiotracer techniques for studying pollutant bioaccumulation in marine organisms.

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