Spatial Variation in Mercury Bioaccumulation and Magnification in a Temperate Estuarine Food Web

Estuaries are renown sinks or repositories of contaminants and reflect historical pollution of persistent compounds. In particular, mercury (Hg) contamination is widespread in coastal environments and occurs in both inorganic (THg) and highly toxic organic forms (OHg) with high bioaccumulation potential. Trophic magnification factors have been increasingly used to quantify biomagnification and represent the average rate of change in contaminant concentration throughout a food web. Here, we assessed small-scale spatial variation in THg and OHg concentrations, as well as variations in local trophic magnification factors in three segregated areas of the Tejo estuary. Selected sites covered a gradient of contamination from industrial Hg hotspots to a natural reserve area, and are key nursery areas for multiple fishes. We analyzed concentrations in sediment and biota, representing the entire local food webs. Samples included sediments, primary producers (salt marsh plants), primary consumers (macrobenthic invertebrates) and top consumers (fish muscle and liver), and the trophic web structure was characterized via SIAR mixed-modeling of nitrogen and carbon isotopic ratios. Spatial variation in Hg concentrations was observed in sediment and biota (but not for all species), with highest concentrations in the area near historical mercury input. Hg concentrations increased with trophic level, and so did the OHg fraction (% of OHg relative to THg), with mean maximum values up to 48.7 and 94.9% in invertebrates and fish, respectively. Trophic magnification factors were positive for all sites (p < 0.05 for all regressions), ranging between 1.56 to 1.76 and 1.78 to 2.47 for THg and OHg, respectively. Overall, rates of mercury bioaccumulation were similar across sites with variations in biota Hg concentrations reflecting baseline differences in site environmental levels. Understanding mercury bioaccumulation and magnification in estuarine biota is critical to safeguard the multiple ecologic functions and economic benefits estuaries provide

Spatial Variation in Mercury Bioaccumulation and Magnification in a Temperate Estuarine Food Web

Estuaries are renown sinks or repositories of contaminants and reflect historical pollution of persistent compounds. In particular, mercury (Hg) contamination is widespread in coastal environments and occurs in both inorganic (THg) and highly toxic organic forms (OHg) with high bioaccumulation potential. Trophic magnification factors have been increasingly used to quantify biomagnification and represent the average rate of change in contaminant concentration throughout a food web. Here, we assessed small-scale spatial variation in THg and OHg concentrations, as well as variations in local trophic magnification factors in three segregated areas of the Tejo estuary. Selected sites covered a gradient of contamination from industrial Hg hotspots to a natural reserve area, and are key nursery areas for multiple fishes. We analyzed concentrations in sediment and biota, representing the entire local food webs. Samples included sediments, primary producers (salt marsh plants), primary consumers (macrobenthic invertebrates) and top consumers (fish muscle and liver), and the trophic web structure was characterized via SIAR mixed-modeling of nitrogen and carbon isotopic ratios. Spatial variation in Hg concentrations was observed in sediment and biota (but not for all species), with highest concentrations in the area near historical mercury input. Hg concentrations increased with trophic level, and so did the OHg fraction (% of OHg relative to THg), with mean maximum values up to 48.7 and 94.9% in invertebrates and fish, respectively. Trophic magnification factors were positive for all sites (p < 0.05 for all regressions), ranging between 1.56 to 1.76 and 1.78 to 2.47 for THg and OHg, respectively. Overall, rates of mercury bioaccumulation were similar across sites with variations in biota Hg concentrations reflecting baseline differences in site environmental levels. Understanding mercury bioaccumulation and magnification in estuarine biota is critical to safeguard the multiple ecologic functions and economic benefits estuaries provide.info:eu-repo/semantics/publishedVersio

An international proficiency test as a tool to evaluate mercury determination in environmental matrices

We report on an international proficiency test (PT) scheme for mercury (Hg) determination in soil, sediment, fish and human-hair samples (ILAE-Hg-02). For total-Hg determination, 74% of participants had a satisfactory performance (|z-score| ≤ 2), 8% had a questionable performance and 18% required action (|z-score| > 3). The best results were obtained for soil, while fish yielded the most-biased results, reflecting the analytical problems of quantifying Hg at low concentrations. Proficiency in the extraction of organometallic and available metal fractions was an important goal of the ILAE-Hg-02 and it was concluded that most laboratories are still not acquainted with the procedures for Hg fractionation; we therefore discuss their importance and highlight the need for more PT schemes dedicated to this matter, as they are an important tools in the standardization of procedures and for the development of adequate quality control/quality analysis protocols and certified reference materials

Mercury-Induced Chromosomal Damage in Wild Fish (Dicentrarchus labrax L.) Reflecting Aquatic Contamination in Contrasting Seasons

Ria de Aveiro (mainly Laranjo basin, Portugal) has been subjected to mercury contamination from a chlor-alkali plant, currently presenting a well-described mercury gradient. This study aimed to assess mercury genotoxicity in this area by measuring the frequency of erythrocytic nuclear abnormalities (ENA) in the European sea bass (Dicentrarchus labrax), addressing the relation with total mercury concentration in the blood and the modulatory role of seasonal variables. Fish were collected, in warm and cold periods, at three locations differing in their distances to the main mercury source: reference (R), moderately (M), and highly (H) contaminated sites. Genotoxicity was detected in both degrees of contamination (M and H) and in both periods of the year (warm and cold), which is in line with the greater levels of mercury measured in fish blood. No significant seasonal variations were observed for mercury bioaccumulation or ENA frequency. The apparent low imperviousness of ENA frequency to seasonal factors reinforced its consistency as a genotoxicity biomarker, thus enabling a clearer identification of cause-and-effect relationships. Overall, the results reflected a serious environmental risk to native ichthyofauna at Laranjo basin due to mercury contamination, showing a potential of mercury to induce genetic damage in fish blood cells through clastogenic and/or aneugenic actions