Mercury distribution and enrichment in coastal sediments from different geographical areas in the North Atlantic Ocean.

This study evaluated mercury (Hg) in three coastal areas in the North Atlantic Ocean (Azores archipelago, Northwest Portugal and Southeast Mexico) and calculated their enrichment factor and geoaccumulation index. Hg presented greater affinity with fine sediment fraction. In all sampling areas the sites with proximity to possible Hg hotspots presented increased [Hg] in fine sediments. However, this fraction only represents less than 1% of the whole sediment, resulting in a significantly lower [Hg] in the total sediment fraction. After comparing [Hg] in the fine fraction and the values established by the Sediment Quality Guidelines, two sites in the Azores exceeded these values. Nevertheless, when considering the total sediment fraction, adverse biological effects are not expected to occur. Finally, both enrichment factor and geoaccumulation index indicated that the Hg present in 86% comes from natural sources and only sampling sites close to potential hotspots showed some degree of enrichment and contamination.

Bioaccumulation and morphological traits in a multi-generation test with two Daphnia species exposed to lead.

Anthropic pressure negatively affects natural environments. Lead (Pb) is a non-essential highly toxic metal that is present in aquatic ecosystems. Two daphnid species from two different latitudes, the temperate Daphnia magna and the tropical Daphnia similis were used as test-organisms to evaluate a long-term Pb exposure. Both species were exposed for nine generations to a chronic concentration of Pb (50 µg/L) and the effects were explored, considering some endpoints not commonly used in toxicity tests: body burden of Pb and presence of granules in the dorsal region of neonates, hemoglobin contents, carapace deformation and morphology, production of males and ephippia (or dormant haploid egg), changes in the eggs' colour and eggs abortion. This multi-generation test was conducted under two food regimes, the usual (3 × 105 cells/mL) and the restricted (1.5 × 105 cells/mL) regime. On generation F6, Pb acclimated neonates were changed to a clean media for three generations, to evaluate exposure retrieval (recovery period). Negative and adverse effects occurred through generations, but no disparity was shown between D. magna and D. similis. The D. magna Pb accumulation showed different patterns regarding food regime. Bioaccumulation was faster under usual food, rapidly reaching a saturation point, whereas a gradual increase occurred under food restriction. A successful retrieval happened regarding Pb in D. magna, since no difference between control and recovering organisms was evidenced regarding their Pb body burdens. Generational Pb exposure led to carapace malformations, Pb aggregation in neonates' dorsal region, reddish extremities, production of males, ephippia (or dormant haploid egg), and aborted eggs, and changes in the eggs' colour (green and white). Food restriction also induced the production of males. Reddish extremities disappeared in recovering organisms and ephippia (or dormant haploid egg) did not occurred during the recovery period. Existent males revealed a shorter lifespan than females (under stress). D. magna and D. similis presented similar responses, for the endpoints analysed; however, it does not mean that this lack of sensitivity difference will be observed when other endpoints (e.g. survival, reproduction) are considered. Bioaccumulation of Pb and adverse effects occurred at the tested concentration of 50µg/L, although higher Pb levels are allowed in the environment as safe concentrations, as reported by the Brazilian legislation and the literature where effects are evidences above 400 µg/L of Pb. Pb effects on reproduction, respiration, malformation, and other adverse effects suggest that a chronic generational exposure can be harmful to both D. magna and D. similis, and that such chronic contaminated environments should not be disregarded when it comes to environmental monitoring.

Pesticide residue analyses and biomarker responses of native Costa Rican fish of the Poeciliidae and Cichlidae families to assess environmental impacts of pesticides in Palo Verde National Park.

Pesticide chemical residues in water samples and biomarker responses in transplanted fish were used to monitor environmental hazards of pesticides in Palo Verde National Park (Costa Rica). The Costarican fish, Parachromis dovii (Ciclhidae) and Poecilia gillii (Poecillidae), were selected as sentinel species. Contaminant analyses detected up to 15 different pesticide residues in water with hexachlobenzene (2261 ng l(-1)), phorate (473 ng l(-1)), epoxiconazole (314) and bromacil (117 ng l(-1)) being the compounds found in higher concentrations. Biomarker responses evidenced impacts on cholinesterase activities in transplanted fish at Barbudal site probably due to the presence of organophosphate insecticides such as phorate. High enzyme activities of glutathione S-transferase and catalase and elevated levels of lipid peroxides were also observed at a site impacted by rice fields (Cabuyo); those effects could be associated with the presence of hexachloro benzene and triazole fungicides. In general, P. dovii biomarkers were affected to a greater extent than those of P. gillii in fish transplanted to sites associated with agriculture, which suggests the former species is a good candidate for future surveys.

In vivo evaluation of three biomarkers in the mosquitofish (Gambusia yucatana) exposed to pesticides.

In this study, the acute toxicity and the in vivo effects of commercial chlorpyrifos, carbofuran and glyphosate formulations on cholinesterase (ChE), glutathione S-transferase (GST) and lactate dehydrogenase (LDH) activities of the mosquitofish (Gambusia yucatana) were investigated. In a first phase of the study, head and muscle ChE were characterized with different substrates (acetylthiocholine iodide, s-butyrylthiocholine iodide and propionylthiocholine iodide) and the selective inhibitors eserine hemisulfate, 1,5-bis(4-allyldimethylammoniumphenyl)-pentan-3-one dibromide (BW284C51), and N,N'-diisopropylphosphorodiamic acid (iso-OMPA). The results obtained suggest that the enzyme present in both head and muscle of G. yucatana is mainly acetylcholinesterase (AChE). Acute toxicity was evaluated by exposing fish to several concentrations of single pesticides and of a mixture of chlorpyrifos/glyphosate. LC50 values were determined after 96 h of exposure, except in the case of carbofuran for which LC50 was calculated after 24 h since almost all the fish died within this period. LC50 values were 0.085 mg/l for chlorpyrifos, 17.79 mg/l for glyphosate, 0.636 mg/l for carbofuran and 0.011 mg/l for the chlorpyrifos/glyphosate mixture. A Toxic Unit approach was used to compare the toxicity of chlorpyrifos and glyphosate when occurring in a mixture with their toxicities as single compounds. Synergistic effects of chlorpyrifos and glyphosate when present in a mixture were found. At the end of each bioassay (24 h for carbofuran, 96 for the other substances/mixture), effects on biomarkers were analyzed. Muscle LDH activity was not altered by any of the three pesticides tested. Gill GST activity was significantly inhibited (40%) by carbofuran after 24 h of exposure to concentrations equal or higher than 0.06 mg/l. ChE muscle and head activity were significantly inhibited (50% and 30%, respectively) by carbofuran at concentrations equal or higher than 0.25 mg/l. Chlorpyrifos induced a significant inhibition of both muscle and head ChE (80% and 50%, respectively) after 96 h of exposure to concentrations equal or higher than 0.05 mg/l. Carbofuran did not induce significant alterations of fish ChE. The ChE EC50 determined for chlorpyrifos/glyphosate mixture (0.070 mg/l) was higher than the correspondent value calculated for chlorpyrifos alone (0.011 mg/l) suggesting an antagonistic effect of glyphosate on ChE inhibition by chlorpyrifos. ChE activity of G. yucatana seems to be a good biomarker to diagnose the exposure of wild populations of this species exposed to anticholinesterase pesticides.