Assessment of mercury contamination in Brycon falcatus (Characiformes: Bryconidae) and human health risk by consumption of this fish from the Teles Pires River, Southern Amazonia

Cascade reservoirs affect mercury concentrations in fish from Teles Pires river, Brazilian Amazon

Hydroelectric reservoirs favor mercury contamination in biota, but the contamination in cascade reservoirs is not yet clear. We investigated total mercury (THg) contamination in fish in four cascade reservoirs in the Brazilian Amazon between August 2022 and April 2023. Overall, downstream predatory fish showed higher mercury concentrations than those upstream. Mercury concentrations in predatory fish collected upstream increased in the reservoirs along the river. Downstream, these concentrations were consistently high, with no variation between reservoirs. Non-predatory fish did not exhibit a clear spatial trend in mercury concentrations. Considering that the synergistic effect of cascade reservoirs was evident in predatory fish, and that the species Serrasalmus rhombeus is widely distributed and important for regional fishing, we suggest it as a target species for future studies on thi issue in the region.

Histopathology and genotoxicity alterations in high Andean catfishes from the Upper Orinoco River Basin, Colombia

Freshwater ecosystem pollution has motivated an extensive list of studies due to deleterious impacts becoming a threat to aquatic organisms that inhabit these environments. This is the first approach to water pollution impact derived from human activities on native ichthyofauna in the Garagoa river basin in Boyacá (Colombian Andes). Therefore, the aim of the present study was to evaluate the occurrence of mercury and arsenic in catfishes and armored catfishes from the Garagoa River basin and the presence of hepatic alterations and genotoxicity in peripheral blood. Biomarkers of effect were analyzed in fishes caught in eight tributaries from Garagoa river basin. The increased presence of lesions in the hepatic architecture and nuclear abnormalities in peripheral blood erythrocytes in Dolichancistrus fuesslii, Chaetostoma joropo, Astroblepus latidens and Trichomycterus cf. knerii individuals could be associated with exposure of pollutants. The tissue alterations observed compromise the fish health, due to the biotransformation processes of xenobiotics such as mercury and arsenic and probably other contaminants. We need to increase surveillance in the Garagoa River to ensure ecological health, recognize hematological and tissue effects in native fishes, and develop effective monitoring strategies to mitigate sources of pollution.

Systematic Review and Spatiotemporal Assessment of Mercury Concentration in Fish from the Tapajós River Basin: Implications for Environmental and Human Health

This study reviews the literature on mercury (Hg) pollution in the Tapajós River basin from 1992 to 2022, focusing on the bioaccumulation in fish and the associated health risks to humans via ingesting contaminated species. Variability in Hg bioaccumulation was analyzed from both spatial (sub-basins) and ecological (trophic levels) perspectives. Mercury concentrations in fish muscle tissue and spatial differences in Hg levels were analyzed using nonparametric Kruskal-Wallis ANOVA and mapped with Inverse Distance Weighting. Additionally, a risk assessment of mercury contamination was conducted using the Target Hazard Quotient (THQ) and Maximum Safe Consuming Quantity (MSCQ) indices. Results indicate that Hg contamination is pervasive across the basin, with piscivorous fish showing the highest Hg levels, particularly in the middle Tapajós, upper Tapajs óand Teles Pires sub-basins, identified as contamination hotspots. Piscivorous species exhibited high Target Hazard Quotients (THQ), suggesting health risks for local consumers. The MSCQ values indicated that 75% of the fish species analyzed should be consumed in quantities lower than the current consumption daily average to avoid health risks.

Mercury Contamination as an Indicator of Fish Species' Trophic Position in the Middle Araguaia River, Brazil

This study evaluates the use of mercury (Hg) concentrations in fish muscle tissue to determine a species' trophic position (TP) in its environment. A campaign conducted in 2019 along 375 km in the middle Araguaia River basin, Brazil, resulted in 239 organisms from 20 species collected. The highest total mercury (THg) concentrations were found in Pellonacastelnaeana (6.93 µg·g-1, wet weight) and in Triportheus elongatus (3.18 µg·g-1, wet weight), whose TPs were different according to the FishBase database. However, they occupied the same trophic level in this study. The intra-specific comparison showed a difference in Hg concentrations between individuals captured in distinct sites. The study of the biota-sediment accumulation factor (BSAF) showed that spatiality interferes with a species' TP. Statistical analyses revealed that when we used a predicted species' TP based on each individual's size, it explained 72% of the variability in THg concentration across all fish species. Multiple regression analysis confirmed that standard length and FishBase values are positively associated with THg (R2 = 0.943). These results point to Hg as a viable indicator of a fish species' TP since it reflects regional, biological, and environmental factors, as demonstrated here for the middle Araguaia River.

Exposure Assessment of methyl mercury from consumption of fish and seafood in Peninsular Malaysia

The concentration of meHg in freshwater fish and seafood was investigated, as well as the consumption patterns of fish and seafood by different demographic groups (age, ethnicity, gender). A potential alarm for human health hazards was also assessed, and the results were compared to the provisional tolerable weekly intakes (PTWIs) and the hazard quotient parameter (HQ). The results showed that meHg levels of 67 species ranged from 0.013 to 0.252 mg/kg of wet weight (WW) with significant differences between different fish and seafood groups (χ2KW = 49.09; p < 0.001). Median concentrations of meHg in fish and seafood groups in descending orders are as follows: demersal fish (0.1006 mg/kg WW) > pelagic fish (0.0686 mg/kg WW) > freshwater fish 0.045 mg/kg WW) > cephalopods (0.0405 mg/kg WW) crustaceans (0.0356 mg/kg WW). The results revealed that older population (> 40 years old) consumed significantly (p = 0.000) more fish compared to younger generations and the elderly consumed the highest amounts of fish (104.0 ± 113.0 g/day). The adolescents (10-17 years old) consumed more than double of amount for both cephalopod and crustacean compared to the older populations (p < 0.05). Malay ethnic (96.1 ± 99.6 g/day) consumed significantly (p = 0.000) higher amounts of fish and seafood compared to other ethnicities, similar to male subjects (95.2 ± 102 g/day; p = 0.026) when compared to the female (86 ± 96.3 g/day). The estimated weekly intake (EWI) values showed results below 1.6 µg/kg BW/week, the tolerable levels recommended by the Joint FAO/WHO Expert Committee on Food Additives (JECFA) for all different demographic factors except for higher consumers at 75th percentile and above. Consumption of marine fish contributed to a higher value of PTWI to all different demographic groups (the estimated weekly intake (EWI) range: 0.2988-0.6893 µg/kg BW/week) but for the adolescents, where from the consumption of crustaceans (0.3488 µg/kg BW/week or 21.8% of PTWI) and cephalopods (0.504 µg/kg BW/week or 31.5% of PTWI). The results from this study also revealed the HQ value for overall consumption of fish and seafood by the adolescents and elderly exceeded one. This was contributed from the consumption of demersal fish and cephalopods, thus indicating the nonacceptable level of noncarcinogenic adverse health effects.

Assessing the short-term response of fish assemblages to damming of an Amazonian river

The enormous biodiversity of tropical freshwater combined with a considerable increase in the construction of reservoirs urges to understand the ecological effects caused by damming. Using rarely available data obtained before (one year) and after (four years) the filling of a hydroelectric plant on the Teles Pires River (Amazon River basin), the effects on abundance, biomass, and diversity of the fish assemblage were evaluated using two complementary approaches: a BACI (before-after-control-impact) design with mixed models and analyses of covariance. Significant Before-After × Control-Impact interactions in abundance, biomass, and species richness were observed, with decreases of abundance and species richness and more stable biomass after filling. Some abundant species, such as Jupiaba polylepis, Jupiaba acanthogaster, Knodus cf. heteresthes, and Moenkhausia lepidura among others, declined in abundance or disappeared from the impact sites. However, temporal and particularly spatial variation independent of damming explained more variation in all the response variables analyzed, including species composition, and analyses of covariance demonstrated general negative trends irrespective of damming. This study illustrates the usefulness of BACI designs to assess the effects of damming but also that other statistical approaches are complementary, given the difficulty of identifying control sites and the short length of most ecological time series. The results also suggest that preserving tributaries upstream of reservoirs and natural regimes of spatial and temporal environmental variation might help to mitigate the impacts of damming in tropical ecosystems.

Mercury in neonatal and juvenile blacktip sharks (Carcharhinus limbatus). Part II: Effects assessment

As apex predators, blacktip sharks (Carcharhinus limbatus) are highly susceptible to biomagnified mercury (Hg) particularly in the Gulf of Mexico (GOM), which is known to contain fishes and invertebrates with elevated Hg levels. Blacktip sharks occur in the GOM year-round and are heavily fished both commercially and recreationally, but little is known about how Hg affects the species. In this study, blood, muscle, liver, and kidney samples were collected from neonatal (n = 57) and juvenile (n = 13) blacktip sharks in Charlotte Harbor, Florida. Hg concentrations in neonates and juveniles were found to be elevated in muscle (mean ± SE = 0.59 ± 0.23 mg kg^-1), liver (0.39 ± 0.29 mg kg^-1), kidney (0.56 ± 0.25 mg kg^-1), and blood (0.059 ± 0.041 mg kg^-1) compared to other local shark species and conspecifics from other areas. Blood plasma chemistry, hematology, and liver histology were evaluated to assess the relationship between Hg and tissue damage. Plasma chemistry parameters alanine aminotransferase (ALT) and phosphorus (PHOS) were not correlated with tissue Hg or liver condition index. Hematological effects were also not correlated with tissue Hg. However, melanomacrophage presence and lipid deposition, evaluated as part of histopathological analysis, were found to exhibit a statistically significant association with concentrations of Hg in tissue and ALT levels. These results suggest that Hg exposure potentially had a negative effect on the livers of the blacktip sharks evaluated in the present study.

Trace metals in estuarine organisms from a port region in southern Brazil: consumption risk to the local population

Metal contamination is a threat to estuarine environments. They can accumulate in the food chain and cause toxic effects on aquatic organisms and human health. This study evaluated the concentrations of metals (Cd, Cr, Cu, Fe, Ni, Pb, and Zn) in aquatic organisms of Antonina Bay (southern Brazil) to analyze whether the metal concentrations were in accordance with Brazilian food legislation and estimate the human risk of local seafood consumption. All analyzed organisms (Centropomus parallelus, Mugil curema, Genidens genidens, Crassostrea brasiliana, and Xiphopenaeus kroyeri) showed traces of metals in their tissues with different metal concentrations among species. Metal concentrations were generally higher in oyster C. brasiliana, and biomagnification was not observed. Cr and Zn concentrations were above the limits established by legislation for all species in at least one sample. The concentrations of the other metals were within permitted levels. However, concentrations of Cd, Cr, Fe, and Zn posed a human consumption risk. In general, the C. brasiliana oyster presented the highest risk for human consumption, probably due to its filtering habit. Thus, the results indicated that metal concentrations in the tissues of the Antonina Bay seafood can pose a risk to human health, and this chronic exposure to metals also can cause toxic effects on local aquatic biota.