Abstract
The chronic toxicity of mercury essentially derives from its strong tendency to biomagnify along food webs. For this reason, the European regulatory framework establishes an environmental quality standard for Hg based on the total Hg concentration in prey fish to protect top predators. A considerable part of the Hg burden of prey fish can come from the ingestion of benthic organisms that, in the presence of contaminated sediments, may remobilize substantial amounts of Hg towards the pelagic food webs. The present study evaluated whether Hg accumulation in assemblages of indigenous chironomids and oligochaetes could be predicted using standardized laboratory bioaccumulation tests with Chironomus riparius and Lumbriculus variegatus. Indigenous chironomids and oligochaetes were recovered at different sites in a lake suffering from legacy Hg pollution and analyzed for total Hg content. Sediment aliquots from the same sites were used to assess Hg bioaccumulation using laboratory-reared C. riparius and L. variegatus. Mercury concentrations in indigenous versus laboratory organisms showed a good correlation (p < 0.05; Spearman correlation test) only in the case of C. riparius versus indigenous chironomids, suggesting the possibility of using linear regressions to predict Hg accumulation by these benthic invertebrates. Further research needs and caveats as to the applicability of the present results to other aquatic systems are identified and discussed.
Highlights
Mercury is a persistent environmental contaminant that can severely threaten human and environmental health
The present study evaluated whether Hg accumulation in assemblages of indigenous chironomids and oligochaetes could be predicted using standardized laboratory bioaccumulation tests with Chironomus riparius and Lumbriculus variegatus
Standardized laboratory tests with the model organism C. riparius suggested the possibility to predict Hg bioaccumulation in indigenous chironomids collected from a deep subalpine lake suffering from legacy Hg pollution
Summary
Mercury is a persistent environmental contaminant that can severely threaten human and environmental health. Because of its peculiar environmental chemistry, characterized by the presence of a gaseous species (Hg(0)) and of organic complexes (mainly monomethylmercury—MMHg), mercury is ubiquitous and tends to bioaccumulate and biomagnify strongly in food webs [1]. Protection of top predators from secondary poisoning via ingestion of contaminated preys must, be the primary focus of Hg risk management. These specific management needs are reflected, inter alia, in the current European regulation that establishes an Environmental Quality Standard for Hg based on concentration in prey fish [3]. As much as 65% of the diet of non-piscivorous fish can come, directly or indirectly, from benthic sources with sediment-dwelling organisms representing a crucial link between primary producers, detrital deposits
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