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 (Am-241, Cd-109, (CO)-C-57, Cr-51, (CS)-C-134, Mn-54 and Zn-65) 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 parts 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 Cr-51 and 2.5 for Zn-65 and Cs-134, whereas in S. canicula they varied by a much greater factor of 350, with CFs for Cr-51 and Am-241 ranging from ca. 0.4 to 140, respectively. With the exception of Cs-134, all radiotracers were accumulated at a faster rate in S. canicula than in P. maxima, particularly for Am-241 and Zn-65 where the CFs attained during the uptake phase were, two and one order of magnitude greater in S. canicula, respectively. In contrast, Cs-134 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 deputation 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 Am-241, Co-57 and Zn-65. However Zn-65 was also distinctive from Am-241 and Co-57 in its pattern of bioaccumulation in dogfish, with its other body components attaining concentrations of Zn-65 that were comparable to the levels found in its skin. The heightened uptake of Cs-134 in turbot was characterised by a more even percentage distribution among its tissues compared to Am-241 and Co-57, but every tissue of turbot had a higher concentration of Cs-134, 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. (c) 2006 Elsevier B.V. All rights reserved.