Does trophic level drive organic and metallic contamination in coral reef organisms?

Metallic and organic pollutants constitute a serious threat for coral reef ecosystems, potentially affecting a great number of species interacting within complex trophodynamic processes. Pesticides, PCBs and trace elements were measured on coral reef communities of three Pacific islands (Moorea, Wallis and New Caledonia) in relation with δ¹⁵N values, a proxy of trophic level. Several potential sources of organic matter, benthic invertebrates and fish belonging to various trophic strategies were sampled at each island. Wallis and New Caledonia displayed, respectively, the highest concentrations of pesticides and trace elements. In the three islands, most trace element concentrations (Cd, Co, Cr, Cu, Fe, Mn, Ni, Pb, and V) decreased when δ¹⁵N was rising (i.e. bioreduction), whereas Hg and Se biomagnified with increasing δ¹⁵N values. Only few trace elements in some islands did not show any significant trend in relation with δ¹⁵N (i.e., Ag in New Caledonia, Zn in Wallis and As plus Zn in Moorea). PCBs concentrations showed a significant bioreduction in New Caledonia and in Moorea, but a significant biomagnification in Wallis. Aldrin and heptachlor were the only pesticides to show a similar significant bioreduction in the three islands. Other pesticides, such as chlordecone, diazinon, endosulfan I and II, heptachlor-epoxide A and B, lindane and pp'-DDE displayed contrasted patterns (e.g. chlordecone significantly biomagnified in New Caledonia, significantly bioreduced in Wallis and did not displayed any significant trend in Moorea). Finally, for unclear reasons, Moorea displayed only negative significant correlations between δ¹⁵N and all pesticides (except pp'-DDT). Our results highlight that trophic level, here assessed through δ¹⁵N values, is a good predictor of metallic trace elements biomagnification or bioreduction in coral reef organisms. However, at large spatial scale, trophic level relevance to predict pesticides and PCBs biomagnification or bioreduction should be considered with caution and studied in close relation with local characteristics.

Levels of organochlorine pesticides in Amazon turtle (Podocnemis unifilis) in the Xingu River, Brazil

Due to the toxicity and high environmental persistence of organochlorine pesticides in aquatic organisms, turtles have been studied as environment biomonitors. These animals are important sources of protein for the riverside and indigenous peoples of the Brazilian amazon. In the present study, organochlorine pesticide contamination was investigated in Podocnemis unifilis. Liver, muscle and fatty tissue samples were removed from 50 specimens collected from five sampling points located in the Xingu River basin. Fourteen organochlorine pesticides were analysed via gas chromatography with an electron capture detector (CG-ECD). Eight organochlorine pesticides were detected with average concentrations of ∑DDT, ∑Endossulfan and ∑HCH which were 26.17 ± 26.35, 14.38 ± 23.77 and 1.39 ± 8.46 ng g^-1 in moisture content, respectively. DDT compounds were the most predominant, with a greater concentration of pp'-DDT in the liver and pp'-DDD in the muscle. Significant differences were noted between the types of tissues studied, and the concentration of OCPs varied between sampling sites.

Accumulation of trace metals in the embryos and hatchlings of Chelonia mydas from Peninsular Malaysia incubated at different temperatures

A variety of trace metals were measured in the egg contents of three clutches of Chelonia mydas collected from Kuala Terengganu state in Peninsular Malaysia. We quantified Mn, Cu, Zn, Se (essential trace metals) and As (anthropogenic pollutant) at several developmental stages obtained by incubating eggs at two different temperatures (27 °C and 31 °C). The incubation temperatures were chosen because they produce predominantly male or predominantly female hatchlings, respectively. The eggs were removed from the sand and washed before being placed in incubators, to ensure that the only possible source of the detected metals was maternal transfer. Other metals: Mo, Co, Ni, Cd, Sn, Sb, Hg, Tl and Pb (all non-essential metals) were detected at concentrations below the lower limit of quantitation (LLOQ). Trace metal concentrations, particularly [Zn], increased during development, other metals (Cu, As, Se and Cr) accumulated to a lesser degree than zinc but no significant differences were observed between the incubation temperatures at any stage of incubation. To date, only a few studies on trace metals in turtle embryos and hatchlings have been reported; this study will provide basic knowledge on the accumulation of trace metals during development at two different incubation temperatures.