Abstract
Trace metals (Cd, Cu, Pb and Zn) were analysed in different well-defined mixed copepod and euphausiid samples as well as in individually analysed decapods collected during a cruise on board “RV Walther Herwig III” to the Iberian Deep Sea Plain in March and April, 2002. We found a substantial interspecific heterogeneity with partially high mean Cd levels in the decapods: 1.9 mg kg-1 dry weight in samples of the genus Sergia; 6.1 mg kg-1 in Acanthephyra pelagica (Risso, 1816) and Acanthephyra acanthithelsonis Bate, 1888; 10.7 mg kg-1 in Bentheogennema intermedia (Bate, 1888); 14.9 mg kg-1 in Benthesicymus iridescens (Bate 1881) and 16.3 mg kg-1 in Systellaspis debilis (A. Milne Edwards, 1881). The agreement of these high Cd concentrations with those reported for polar crustaceans, and Cu concentrations (17–56 mg kg-1) that indicate that the total metabolic requirements have probably not been met, support the hypothesis that the frequently reported Cd-anomaly in polar crustaceans might be extended to other relatively deep ocean waters like the Iberian Deep Sea Plain and that this might be related to a corresponding Cu deficiency. Zn concentrations in decapods from this study (52–80 mg kg-1) are within the worldwide range, which indicates that decapods are able to regulate their Zn body concentrations. Our preliminary data on mixed zooplankton samples suggest that Pb concentrations far below 1 mg Pb kg-1 might serve as a regional background value for comparison in biomonitoring studies. Results for Cd, Cu and Zn are largely within the reported range, especially for data from the Central and Southern North Sea.
Highlights
To assess the environmental quality regarding heavy metals in the oceans, the bioavailable fraction is of great importance, since possible toxic effects are largely dependent on the bioavailable exposure concentration in seawater
Limits of detection proved to be adequate for the range of metal concentrations found in this study for marine crustaceans
For Pb, we found distinctly lower concentrations in copepods from the Iberian Deep Sea Plain, probably indicating some regional background value
Summary
To assess the environmental quality regarding heavy metals in the oceans, the bioavailable fraction is of great importance, since possible toxic effects are largely dependent on the bioavailable exposure concentration in seawater. In order to differentiate human impact from natural variability, knowledge of background concentrations of metals and their fluctuations in biomonitor organisms is essential as well as a thorough understanding of accumulation and detoxification strategies. These depend on various aspects, including the biological species and element considered, the applied exposure regime, cation homeostasis mechanisms, life-history status, spatial and temporal scales and other factors (Rainbow and White, 1989; Zauke and Petri, 1993). Regional background values should be established in order to follow possible future trends of metals in biomonitors
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