Bioaccumulation of trace metals in Neoechinorhynchus buttnerae and in its fish host tambaqui (Colossoma macropomum) from fish farms.

Fish parasites are excellent bioindicators of environmental contamination because they respond quickly to water pollutant chemicals, and they can accumulate high concentrations of trace metals compared to their hosts. Here, we investigated the bioaccumulation pattern of the following: Cd, Ca, K, Na, Mg, Fe, Al, Zn, Ba, Mn, Cu, Pb, Cr, Ni, and Co. We investigated the presence of trace metals in the acanthocephalan parasite Neoechinorhynchus buttnerae, and the bioaccumulation factors (BAFs) of metals were tested in the food, muscle, and liver of its host fish Colossoma macropomum (tambaqui). We used samples from four commercial fish farms that also conduct other agribusiness activities. Tissues of the fish along with their parasites were subjected a trace metal concentration analysis by inductively coupled plasma optical emission spectrometry. Most of metals showed significantly higher presence in N. buttnerae than in tambaqui (p < 0.05), with increased level of Na, Pb, Ca, Mn, Zn, Al, and Fe in fish muscle and that of Cr, Ni, Zn, Al, Ca, and Ba in fish liver. Considering all the fish farms, the highest values of BAF were observed for Fe, Al, Zn, and Mn with concentrations up to 35.63, 26.88, 14.12, and 6.66 times higher in acanthocephalan tissues than in the fish muscle, respectively. Moreover, Ba, Ca, and Al showed concentrations up to 18.11, 12.18, and 11.77 times higher in acanthocephalan than in the liver of tambaqui. Our results indicate that the higher the levels of these metals in the parasite, the lower their concentrations in the muscular and hepatic tissues of the fish. Therefore, we suggest that N. buttnerae can directly influence the concentrations of trace metals in the fish tissues and accumulate both essential trace (Fe, Zn, Mn, and Ca) and toxic elements (Al, Pb, and Ba) in the host.

Influence of environmental conditions on the mercury levels of the sediment along the Balbina Reservoir, Brazilian Amazon.

Mercury dynamics in hydroelectric reservoirs have been studied worldwide. In tropical reservoirs, especially in those of the Amazon, the influence of geochemistry on Hg levels along this aquatic system is not well understood. The main objective of the present study was to assess the influence of environmental conditions (physical and chemical water parameters, trace element concentrations of sediment and sediment geochemistry) on mercury levels of sediment along the Balbina Reservoir (Amazon basin, Brazil). Sediment was collected along the reservoir and in the main tributaries in May 2015 (n = 10). These samples were assessed for labile iron (LFe), manganese (LMn), aluminum (LAl) and mercury (LHg) concentrations, total mercury (THg) concentrations, organic matter (OM) content, and granulometry. Concentrations in the sediment were 4-212 (LFe), 2-460 (LAl), 180-613 (LMn), < detection limit-256 (LHg), and 12-307 µg kg-1 dry weight (THg). In general, these concentrations decreased along the reservoir from upstream to downstream, reaching the lowest concentrations in the middle of the lake, and they increased in the sampling points near the dam. The lability and concentrations of mercury were influenced by the concentrations of LFe, LMn, LAl, and the granulometry and OM content of the sediment. Altogether, THg concentrations of sediments of the Balbina Reservoir encompass the range of concentrations of other reservoirs or natural lakes in the Amazon basin (from ten to a few hundred µg kg-1 dry weight).

Potential of Bacterial Isolates from a Stream in Manaus-Amazon to Bioremediate Chromium-Contaminated Environments.

Igarapé do Quarenta (IgQ), a stream located in the Manaus-AM, BR, has directly experienced the impacts of urban expansion over the last five decades, which contributed for its contamination. As an affluent of Rio Negro, IgQ also affects the water quality of this important river that bathes Manaus. However, the stress caused by the prolonged exposition to chemical agents may have selected microorganisms that exhibit great bioremediation potential. In the present study, bacteria isolated from four distinct sites of the IgQ were identified, and their potential to degrade hexavalent chromium (Cr(VI)) was investigated using the s-diphenylcarbazide method. Among the investigated isolates, 14 exhibited resistance against Cr(VI) at a concentration of 300 mg/L and eight isolates reduced over 50% (53.5-97.4%) chromium ratios after 72 h of incubation. Those isolates were identified by gene sequencing and classified in 10 genera (Acidovorax sp., Acinetobacter sp., Alicycliphilus sp., Bacillus sp., Comamonas sp., Enterobacter sp., Micrococcus sp., Proteus sp., Serratia sp., and Vagococcus sp.). Under control conditions, the isolate of Vagococcus sp. genus, in only 24 h of incubation, reduced 96.8% of the rate of Cr(VI) added to the culture medium at the concentration of 10 mg/L. Obtained results indicate that the Vagococcus sp. exhibits a great potential to be used in the bioremediation of areas contaminated with chromium. The mechanisms of action of microorganisms should be investigated for more specific applications in the decontamination of effluents and direct use of its by-products to bioremediate polluted environments.

In situ selective determination of methylmercury in river water by diffusive gradient in thin films technique (DGT) using baker's yeast (Saccharomyces cerevisiae) immobilized in agarose gel as binding phase.

Saccharomyces cerevisiae immobilized in agarose gel as binding phase and polyacrylamide as diffusive layer in the diffusive gradient in thin films technique (DGT) was used for selective determination of methylmercury (MeHg). Deployment tests showed good linearity in mass uptake up to 48 h (3276 ng). When coupling the DGT technique with Cold Vapor Atomic Fluorescence Spectrometry, the method has a limit of detection of 0.44 ng L(-1) (pre concentration factor of 11 for 48 h deployment). Diffusion coefficient of 7.03 ± 0.77 × 10(-6) cm(2) s(-1) at 23 °C in polyacrylamide gel (pH = 5.5 and ionic strength = 0.05 mol L(-1) NaCl) was obtained. Influence of ionic strength (from 0.0005 mol L(-1) to 0.1 mol L(-1) NaCl) and pH (from 3.5 to 8.5) on MeHg uptake were evaluated. For these range, recoveries of 84-105% and 84-98% were obtained for ionic strength and pH respectively. Potential interference due to presence of Cu, Fe, Mn, Zn was also assessed showing good recoveries (70-87%). The selectivity of the proposed approach was tested by deployments in solutions containing MeHg and Hg(II). Results obtained showed recoveries of 102-115 % for MeHg, while the uptake of Hg(II) was insignificant. The proposed approach was successfully employed for in situ measurements in the Negro River (Manaus-AM, Brazil).