Helena A. Kehrig

Mercury in a widely consumed fish Micropogonias furnieri (Demarest, 1823) from four main Brazilian estuaries

We analyzed mercury levels in the white muscular tissue of a fish (Micropogonias furnieri) originated from four Brazilian estuaries during the period between the summer 1990 and spring 1991. Mercury levels were below the maximum permissible limit established for food by the Brazilian legislation (500.0 ng.g-1 wet wt.). The measured mercury concentrations ranged from 17.4 to 266.0 ng.g-1 (wet wt.), for Guanabara Bay 19.5-252.2 ng.g-1 (wet wt.), for Sepetiba Bay 23.0-433.7 ng.g-1 (wet wt.), for Ilha Grande Bay 13.8-296.3 ng.g-1 (wet wt.) for Conceição Lagoon. Positive relationships were observed between mercury concentration in fish and the length and weight of the fishes. Weight normalized concentration showed Guanabara Bay presented the higher levels and the Conceição Lagoon presented the lowest levels. Ilha Grande Bay presented the second highest levels after Sepetiba Bay, although the former is considered a non-contaminated area.

Total and methyl mercury in different species of molluscs from two estuaries in Rio de Janeiro State

-1 dry wt.). This is possible related to their capacity to select particle size and the composition of the ingested food they assimilate, and also reflects the greater ability of mussels to concentrate and excrete methylmercury and also to reflect their environmental conditions.

Total and methylmercury in a Brazilian estuary, Rio de Janeiro.

Guanabara Bay, in Rio de Janeiro state, is impacted by organic matter, oil and heavy metals. The present study evaluated the total mercury (THg) and methylmercury (MeHg) concentrations and the MeHg to THg ratio (%MeHg) in water samples from different points of the bay and in 245 organisms of three different trophic levels sampled between 1990 and 2000. Dissolved mercury concentration in estuarine water samples ranged from 0.72 to 5.23 ngl(-1). THg and MeHg in mussel, ranging from 11.6 to 53.5 microg THg kg(-1) wet wt. and 4.5-21.0 microg MeHg kg(-1) wet wt., varied according to sampling point and water quality. Planktivorous fish and mussel presented similar MeHg concentrations, meanwhile THg in planktivorous fish were lower than in mussel. Carnivorous fish showed higher THg and MeHg concentrations (199.5 +/- 119.3, 194.7 +/- 112.7 microg kg(-1) wet wt. respectively) than organisms from other feeding habits and lower trophic levels. There was a significant difference in the %MeHg among trophic levels: mussel presented lower MeHg percentage (33%) than planktivorous fish (54%) and carnivorous fish (98%).

Methylmercury and total mercury in estuarine organisms from Rio de Janeiro, Brazil.

Guanabara Bay (GB), located in the Rio de Janeiro State, is still a productive estuary on the south-eastern Brazilian coast. It is an ecosystem heavily impacted by organic matter, oil and a number of other toxic compounds, including Hg. The present study aimed to comparatively evaluate the aquatic total mercury (THg) and MeHg contamination, and the ratios of MeHg to THg (% MeHg), in 3 species of marine organisms,Micropogonias furniert — carnivorous fish (N=81),Mugil spp. — detritivorous fish (N=20) andPerna perna — filter-feeding bivalves (N=190), which are widely consumed by the population. A total of 291 specimens were collected at the bay in different periods between 1988 and 1998. THg concentrations were determined by cold vapour AAS with stannous chloride as a reducing agent. MeHg was extracted by dithizonebenzene and measured by GC-ECD. Analytical quality was checked through certified standards. All organisms presented both low THg and MeHg concentrations and they were below the maximum limit of 1,000 μg Hg.kg-1 wet wt. as established for human intake of predatory fish by the new Brazilian legislation. Carnivorous fish showed higher THg and MeHg concentrations, and also % MeHg in muscle tissues, than organisms with other feeding habits and lower trophic levels. The average of THg concentrations in carnivorous fish was 108.9 ± 58.6 μg.kg-1 wet wt. (N=61) in 1990 and 199.5 ± 116.2 μg.kg-1 wet wt. (N=20) in 1998, but they presented different total length and body weights. The average THg content in detritivorous fish was 15.4 ± 5.8 μg.kg-1 wet wt., whereas THg concentrations ranged from 4.1 to 53.5 μg.kg-1 wet wt. for the molluscs. The THg and MeHg contents of mussel varied according to the sampling point and water quality. MeHg concentration in detritivorous fish was similar to MeHg concentration in molluscs, but there was a significant difference in the MeHg/THg ratio: the carnivorous fish presented higher MeHg percentages (98%) than the detritivorous fish (54%) and the molluscs (33%). Weight-normalised average concentration of THg in carnivorous fish collected in 1990 (0.18 ± 0.08 μg.g-1/0.7 kg wet wt.) and in 1998 (0.16 ± 0.09 μg.g-1/0.7 kg wet wt.) presented no significant difference (t=1.34;P < 0.5). In conclusion, the low THg and MeHg concentrations in the organisms from the GB ecosystem, are related to its eutrophic conditions and elevated amounts of suspended matter. In this situation, Hg could be strongly complexed or adsorbed by the particulate, which would dilute the Hg inputs and reduce its residence time in the water column, with a consequent decrease in its availability to organisms.

Methylmercury in a predatory fish (Cichla spp.) inhabiting the Brazilian Amazon

This research tested whether limnological conditions, biological characteristics of fish and anthropogenic impacts influenced the assimilation of methylmercury into the muscle of a sedentary piscivorous fish, Cichla spp., from three rivers (Negro, Madeira, Tapajós) and two hydroelectric reservoirs (Balbina, Tucuruí) within the Brazilian Amazon. Methylmercury in this fish ranged from 0.04 to 1.43microgg(-1) w.w. across sites. No significant differences were observed in the methylmercury concentrations between males and females, or for different morphotypes of this species. Positive correlations were found between methylmercury and fish body weight. No differences were found between the weight normalized methylmercury (MeHg) concentrations or its percent of total mercury in fish from the three rivers; weight normalized MeHg was highest in one of the two reservoirs. In Rio Tapajós, where gold mining and deforestation cause high water turbidity, fish showed the highest MeHg and concentrations were different across the four sites examined. In all sampling areas, the %MeHg was found to be higher than 70.

Methylmercury in hair samples from different riverine groups, Amazon, Brazil

The present study was aimed to evaluate comparatively the levels of methylmercury (MeHg) in human hair, collected from different groups of Amazonian populations exposed to contamined fish. The study was undertaken in fishing villages and gold mining areas, mainly in the Tapajos and Madeira river basins, two of the main tributaries of Amazon river. The study population included 125 hair samples, chosen from a collection of over one thousand samples collected in different periods. Hair analyses were conducted with a new efficient extraction technique and measured with ECD-gas chromatographer. This analytical method presented good accuracy and precision when compared with standard hair samples from IAEA. A highly significant correlation was found at the interlaboratory exercise between National Institute for Minamata Disease and our laboratory at Federal University of Rio de Janeiro. The results of the present study showed, through hair analysis, a relationship between environmental contamination by mercury and methylmercury and dietary habits of the Amazon population. The highest levels of MeHg in hair samples were found in riverine population from upper Tapajos river and in riverine population from some tributaries of Madeira river, followed by population of fishing villages from Madeira river. Majority of the women of child-bearing age presented high MeHg concentration in hair samples (10 mg.kg-1). On the other hand, Yanomami Indians presented MeHg concentration below the limit tolerable of 6 mg.kg-1.

Mercury and Nitrogen Isotope in a Marine Species from a Tropical Coastal Food Web

The present study raised the hypothesis that the trophic status in a tropical coastal food web from southeastern Brazil can be measured by the relation between total mercury (THg) and nitrogen isotope (δ15N) in their components. The analysed species were grouped into six trophic positions: primary producer (phytoplankton), primary consumer (zooplankton), consumer 1 (omnivore shrimp), consumer 2 (pelagic carnivores represented by squid and fish species), consumer 3 (demersal carnivores represented by fish species) and consumer 4 (pelagic-demersal top carnivore represented by the fish Trichiurus lepturus). The values of THg, δ15N, and trophic level (TLv) increased significantly from primary producer toward top carnivore. Our data regarding trophic magnification (6.84) and biomagnification powers (0.25 for δ15N and 0.83 for TLv) indicated that Hg biomagnification throughout trophic positions is high in this tropical food web, which could be primarily related to the quality of the local water.

Inorganic and methylmercury: do they transfer along a tropical coastal food web?

Methylmercury (MeHg) and inorganic mercury (Hg(inorg)) were evaluated in the water of a Brazilian estuary, with two size classes of plankton and seven fish species of different feeding habits. Water partition coefficients (PCs) in microplankton were fourfold higher for MeHg than for Hg(inorg); and water PCs in mesoplankton were 26 times higher for MeHg than Hg(inorg). Difference between microplankton and mesoplankton MeHg bioaccumulation factor (BAF) was higher (0.60 log units) than Hg(inorg) BAF (0.24 log units), indicating that trophic transfer of MeHg between planktonic organisms is more efficient than Hg(inorg) transference. MeHg concentrations, proportion of mercury as MeHg and its biotransference factors (BTFs) in the microplankton, mesoplankton and fish increased with increasing trophic level while biotic concentrations of Hg(inorg) and proportion of mercury as Hg(inorg) decreased thus indicating that MeHg was indeed the biomagnified species of mercury. MeHg reflected the vertical trophic guilds distribution, due to the fact that the top predator fish presented the highest concentration (0.77 μg g(-1)d.w.), followed by the less voracious species (0.43 μg g(-1)d.w.); while planktivorous fish presented the lowest concentrations (0.044 μg g(-1)d.w.). Hg(inorg) did not present the same behavior. Results suggest that feeding habits and trophic guild are important parameters, influencing biotransference and biomagnification processes.

Mercury and selenium biomagnification in a Brazilian coastal food web using nitrogen stable isotope analysis: A case study in an area under the influence of the Paraiba do Sul River plume

Mercury (Hg), selenium (Se) and nitrogen (δ(15)N) stable isotope were assessed in a tropical food web of Rio de Janeiros north coast. Isotopic data on muscle suggest a difference related to this parameter along the food web; where top-predators (cetacean and voracious fish) displayed heavier δ(15)N over the entire food web. Both top-predators presented similar δ(15)N values. Cetacean displayed higher Hg and lower Se than voracious fish. Five trophic positions (TP) were found in relation to primary consumer as baseline, ranging from 2.0 to 4.0. Positive relationships were found between trace-element and δ(15)N. The slope of regression equations (0.11 for Se and 0.21 for Hg) and food web magnification factors (2.4 for Se and 5.4 for Hg) showed that Hg presented higher rate of increase over the food web. Simultaneous measurements of trace-elements and ecological tracers emphasize the importance of TP into the trophic structure and distribution of Hg and Se throughout the food web.

Essential (Se, Cu) and non-essential (Ag, Hg, Cd) elements: What are their relationships in liver of Sotalia guianensis (Cetacea, Delphinidae)?

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