Biomagnification of Mercury in Fish from Two Gold Mining-Impacted Tropical Marshes in Northern Colombia

Selenium-to-mercury ratios in popularly consumed Colombian fish: A comprehensive risk-benefit assessment

To understand the benefits and risks associated with the interaction between selenium (Se) and mercury (Hg), it is crucial to gather more information on the factors influencing the variability of their molar ratio. We analyzed Se and Hg concentrations, calculated selenium-to-mercury (Se:Hg) molar ratios, and assessed the health benefit values of selenium (HBV-Se) in commercially important fish (n = 309) from various aquatic environments in northern Colombia. Median Se concentrations were significantly higher (162.4 µg kg-1, U = 355, p = 0.01) compared to Hg concentrations (89.05 µg kg-1). Molar ratios values were greater than 1 for all 28 fish species, indicating a protective effect of Se against Hg. However, considerable variation in Se:Hg values was observed between species and sampling sites. All fish had Se:Hg values greater than 1 except for Astyanax magdalenae, Eugerres plumieri, Trachelyopterus sp. and Oreochromis niloticus. The HBV-Se values were also favorable (>1) for most species. Pelagic species had the lowest Hg concentrations (81.3 µg kg-1) but the highest Se:Hg ratios (6.4), while benthopelagic (908 µg kg-1, 5.2) and demersal species (712 µg kg-1, 3.7) showed higher Hg levels with lower Se:Hg values. There was a strong correlation between Hg levels, size (r2 = 0.94, p = 0.001) and trophic level of the fish (r2 = 0.99, p = 0.001). Similarly, Se levels showed a strong association with size (r2 = 0.96, p = 0.001) and trophic level (r2 = 0.94, p = 0.001). The findings of this study indicate that although the Se:Hg ratios suggest a protective action of Se against Hg toxicity, these values were not consistent. Variations in these ratios could have implications for assessing and managing risks associated with consuming Hg-contaminated fish. Therefore, it is crucial to continue evaluating health benefits and risks, especially in different ecosystems, including tropical ones.

Presence of Nematodes, Mercury Concentrations, and Liver Pathology in Carnivorous Freshwater Fish from La Mojana, Sucre, Colombia: Assessing Fish Health and Potential Human Health Risks

Fish provide high-quality protein and essential nutrients. However, environmental pollution can lead to the accumulation of toxic substances such as mercury (Hg), with known negative impacts on human consumers. The aim of this study was to assess fish health and potential human health risks by analyzing the presence of nematodes, Hg concentrations, and liver pathology in freshwater fish from La Mojana, Colombia. For this purpose, 326 specimens were collected. Parasitic infection was evaluated using parasitological indices. Total Hg (T-Hg) was quantified using a direct mercury analyzer. Liver pathology was assessed through histopathological examination. Risk-based fish consumption limits were established by calculating the hazard quotient (HQ) and safe consumption limits. The overall prevalence and abundance of nematodes (Contracaecum sp.) were 46% and 2.72 ± 0.47 parasites/fish, respectively. Sternopygus macrurus exhibited the highest prevalence (100%) and parasite abundance (13.5 parasites/fish) during the rainy season, whereas Hoplias malabaricus demonstrated the greatest prevalence (100%) and abundance (14.8 parasites/fish) in the dry season. The average T-Hg was 0.31 ± 0.01 µg/g ww. During the rainy season, S. macrurus had the highest T-Hg levels (0.46 ± 0.08 µg/g ww); in the dry season, Cynopotamus magdalenae showed the highest T-Hg concentration (0.54 ± 0.03 µg/g ww). Significant positive relationships were recorded between T-Hg and parasite abundance, while these were negative with the condition factor. All specimens exhibited hepatic alterations. The HQ and Hg values suggest potential health risks from frequent fish consumption, especially in fish-dependent communities. These findings highlight the need for precautionary measures by health and environmental authorities to safeguard human and ecosystem health.

Toxic metal(loids) levels in the aquatic environment and nuclear alterations in fish in a tropical river impacted by gold mining

The Atrato River basin was protected by Colombian law due to anthropogenic impacts, mainly from illegal gold mining, which triggered a critical environmental health problem. In this study we quantified mercury (Hg), methylmercury (MeHg) and arsenic (As) concentrations in aquatic environmental matrices, and explored for the first-time nuclear degenerations in fish from the Atrato River. The median concentrations (μg/kg) for T-Hg, MeHg and As in fish were 195.0, 175.5, and 30.0; in sediments (μg/kg) 165.5, 13.8 and 3.1; and in water (ng/L), 154.7 for T-Hg and 2.1 for As. A 38% and 10% of the fish exceeded the WHO limit for the protection of populations at risk (200 μg Hg/kg) and for human consumption (500 μg Hg/kg); while As concentrations were below the international standard (1000 μg/kg) in all fish. The percentage of MeHg was 89.7% and the highest accumulation was observed in carnivorous fish (336.3 ± 245.6 μg/kg, p < 0.05) of high consumption, indicating risk to human health. In water, T-Hg concentrations exceeded the threshold effect value of 12 ng/L, whereas As concentrations were below the threshold of 10,000 ng/L, established by USEPA. On the contrary, 33% of the sediments exceeded the quality standard of 200 μg/kg for Hg. We found that Prochilodus magdalenae was the species with the highest susceptibility to nuclear alterations in its order, nuclear bud (CNB, 3.7 ± 5.4%), micronuclei (MN, 1.6 ± 2.5%) and binucleated cells (BC, 1.6 ± 2.3%). These results indicate that the species appears to be a good predictor of genotoxicity in the Atrato River. Fulton's condition factor (K) indicated that 31.7% of the fishes had poor growth condition, suggesting that the Atrato River basin needs to be monitored and restored in accordance with the agreements reached in the Minamata Convention on Mercury.

Genotoxicity effects in freshwater fish species associated with gold mining activities in tropical aquatic ecosystems

The main aim of this study was to investigate total mercury (THg), methylmercury (MeHg) and arsenic (As) concentrations, and their genotoxic effects on fish species in freshwater habitats impacted by gold mining activities in the Mojana and Bajo Cauca regions (Northern Colombia). A total of 255 individuals of Prochilodus magdalenae (PM) and Hoplias malabaricus (HM) were collected in different areas of northern Colombia, 205 in the exposed groups: Mojana 1 (61), Mojana 2 (81) and Bajo Cauca (63); and 50 individuals in the control group. Dorsal muscle was analysed for pollutants and blood to perform micronucleus (MN) and erythrocytic nuclear alterations (ENA) tests. The results of the MN revealed statistically significant (p < 0.05) genetic damage in both PM (Mojana 1 = 29.7 ± 14.2; Mojana 2 = 25 ± 6.25; Bajo Cauca= 26.6 ± 10.6) and in HM (Mojana 1 = 17.7 ± 7.8; Mojana 2 = 20.4 ± 6.3; Bajo Cauca= 20.8 ± 9.8) compared to the control group (PM= 10.5 ± 3.6; HM= 9.1 ± 3.9). Likewise, the frequency of ENA was statistically higher in the exposed groups compared to the control group (p < 0.05). On the other hand, the concentrations of THg, MeHg and As found in tissue samples were significantly higher (p < 0.05) compared to the control group, being the Bajo Cauca region the area of highest risk due to high concentrations of THg (651.2 ± 344.5 μg/kg for HM and 678.5 ± 983.9 μg/kg for PM) and MeHg (504.6 ± 220.9 μg/kg for HM and 606.8 ± 886.4 μg/kg for PM). Results showed that mean THg values for both species in Bajo Cauca exceeded the WHO maximum limit (set in 500 μg Hg/kg) in fish for human consumption. Results suggest that DNA damage in erythrocytes is associated with the presence of Hg, MeHg and As, coming from mining activities.

Health Risk Assessment for Human Exposure to Heavy Metals via Food Consumption in Inhabitants of Middle Basin of the Atrato River in the Colombian Pacific

The Atrato river basin is one of the world's most biodiverse areas; however, it is highly impacted by mercury gold mining, which generates air, water, and soil pollution. (1) Background: The concentrations of persistent heavy metal pollutants, mercury (Hg), lead (Pb), cadmium (Cd), and arsenic (As) in the fish, fruits, and vegetables most consumed by the riverside inhabitants of the middle basin of the Atrato river represent a danger to public health; (2) Methods: A total of 154 samples of different fruits and vegetables and 440 samples of fish were analyzed by atomic absorption spectroscopy. A sample of 446 people were surveyed to evaluate food consumption and carcinogenic and non-carcinogenic risk; (4) Conclusions: High concentrations of As, Hg, Pb, and Cd were identified in fish, fruits-tubers, and vegetables-stems commonly consumed by inhabitants of the middle basin of the Atrato River, which exceeded the Codex limits and the limits established by the WHO/FAO, especially for carnivorous fish species. A high carcinogenic and non-carcinogenic risk was evidenced amongst inhabitants of the middle basin of the Atrato River due to the consumption of fish contaminated with high concentrations of As, MeHg, and THg. The risk due to the consumption of vegetables was very low.

Drivers of biomagnification of Hg, As and Se in aquatic food webs: A review

Biomagnification of trace elements is increasingly evident in aquatic ecosystems. In this review we investigate the drivers of biomagnification of mercury (Hg), arsenic (As) and selenium (Se) in aquatic food webs. Despite Hg, As and Se biomagnify in food webs, the biomagnification potential of Hg is much higher than that of As and Se. The slope of trophic increase of Hg is consistent between temperate (0.20), tropical (0.22) and Arctic (0.22) ecosystems. Se exerts a mitigating role against Hg toxicity but desired maximum and minimum concentrations are unknown. Environmental (e.g. latitude, temperature and physicochemical characteristics) and ecological factors (e.g. trophic structure composition and food zone) can substantially influence the biomagnification process these metal (oids). Besides the level of bioaccumulated concentration, biomagnification depends on the biology, ecology and physiology of the organisms that play a key role in this process. However, it may be necessary to determine strictly biological, physiological and environmental factors that could modulate the concentrations of As and Se in particular. The information presented here should provide clues for research that include under-researched variables. Finally, we suggest that biomagnification be incorporated into environmental management policies, mainly in risk assessment, monitoring and environmental protection methods.

EL LEGADO DEL ARSÉNICO Y MERCURIO EN EL COMPLEJO CENAGOSO RAMSAR DE AYAPEL, (CÓRDOBA, COLOMBIA): APROXIMACIÓN A LA MACROCUENCA MAGDALENA-CAUCA

Colombia, país localizado al norte de Suramérica, afronta diferentes conflictos socioambientales y es uno de los más contaminados por mercurio en el mundo, situación que amenaza la riqueza natural y la biodiversidad del neotrópico, reconocida por sus altos niveles de endemismos. El complejo de humedales de Ayapel (Sitio Ramsar) ubicado al norte del país, reporta el desembarco del 23 % de la producción pesquera de la macrocuenca Magdalena-Cauca y a su vez sufre alta presión por minería de aluvión. Este trabajo evaluó la presencia de dos disruptores endocrinos, mercurio (Hg) y arsénico (As), en peces de consumo humano, agua y sedimentos, colectados en las ciénagas central de Ayapel, Escobillas y Paticos. En el sedimento y en el agua se registraron concentraciones de arsénico no reportadas previamente, y al ser un cancerígeno, es un hallazgo relevante ya que también puede estar presente en los cultivos de arroz, lo que aumenta el riesgo toxicológico para los pobladores de la región. Adicionalmente, el 96 % de los peces presentaron simultáneamente Hg y As con diferencias estadísticamente significativas entre las especies. El blanquillo (Sorubim cuspicaudus) fue el más contaminado por ambos polutantes y el bocachico (Prochilodus magdalenae) registró el nivel más alto de Hg en los últimos 15 años para la zona. Los niveles de Hg en la ictiofauna de la macrocuenca (1993-2020) alertan sobre los impactos no monitoreados en las redes tróficas y la urgencia de acciones intersectoriales para proteger la biodiversidad y la salud humana.

Concentraciones de metilmercurio en Prochilodus magdalenae (Teleostei: Curimatidae) y Hoplias malabaricus (Teleostei: Erythrinidae) en la cuenca baja del río Cauca-Magdalena, norte de Colombia

Las emisiones de mercurio (Hg) a partir de actividades de minería afectan los recursos pesqueros, los cuales son importantes en la alimentación proteínica de las poblaciones humanas. El objetivo de este estudio fue analizar las concentraciones de MeHg (metilmercurio) en Prochilodus magdalenae (Bocachico) y Hoplias malabaricus (Moncholo) en hábitats continentales de la región de La Mojana y en la parte baja del río Cauca (Norte de Colombia), sitios que han sido afectados por actividades de minería aurífera. Un total de 160 ejemplares fueron colectados para su respectivo análisis, 130 en el grupo expuesto: Mojana 1 (n=36), Mojana 2 (n=56) y El Bajo Cauca (n=38), y n=30 en el grupo control. Se realizaron las determinaciones de MeHg mediante análisis directo con un Analizador Directo de Mercurio DMA 80, cromatografía líquida y espectrometría de absorción atómica. Las concentraciones de MeHg encontradas en muestras de tejido del músculo dorsal de los peces procedentes de los lugares expuestos, fueron significativamente mayores comparados con el grupo control (p< 0.05), siendo la región del Bajo Cauca la más afectada por altas concentraciones de MeHg. Los resultados indican que la presencia de MeHg en los peces es consecuencia de las actividades de minería aurífera ampliamente desarrolladas en la zona. Estas concentraciones MeHg representan un riesgo mortal para la salud humana y animal.

Mercury species in fish from a tropical river highly impacted by gold mining at the Colombian Pacific region

This study was carried out in the Atrato River basin, a tropical ecosystem in northwestern Colombia, highly impacted by gold mining. The aim of this study was to show how these activities have deteriorated the quality of fish species, and how their intensity has influenced the distribution of mercury (Hg) pollution in the Atrato River basin. Results showed that total mercury (THg, n = 842) ranged between 32 ± 53 μg kg^-1 (Cyphocharax magdalenae) and 678.5 ± 345 μg kg^-1 (Agneiosus pardalis); 38% of the samples exceeded the WHO limit for the protection of populations at risk, and 15% surpassed the WHO maximum limit of THg in fish for human consumption. A significant positive correlation (p < 0.001) was found between THg with total fish length and trophic level, indicating bioaccumulation and biomagnification of mercury in fish, respectively. Using the non-migratory and carnivorous fish species Hoplias malabaricus and Caquetaia kraussii, Hg contamination was found distributed from high mining activity zones (Rio Quito, Medio Atrato, and Murindó & Vigía del Fuerte - upstream zones) to low activity areas (Rio Sucio & Carmen del Darién, and Ciénaga de Ungía & Tumaradó - downstream zones). In the first-ever performed methylmercury (MeHg) measurements in 520 fish muscle samples analyzed from the Atrato River basin, a high MeHg/THg ratio (91% of the THg) in species such as A. pardalis and H. malabaricus were recorded. Results indicated that the environment and the fish species in the Atrato River basin had been greatly affected by gold mining activities practiced on the river and its tributaries. Therefore, environmental authorities must take protection measures for the inhabitants of the area as well as for the environment.

Mercury biomagnification in an ichthyic food chain of an amazon floodplain lake (Puruzinho Lake): Influence of seasonality and food chain modeling

Mercury (Hg) biomagnification in fish food chains is a relevant subject due to the high fish consumption of the Amazonian population and the high toxicity of this metal. In the Amazon, floodplain lake hydrodynamics change considerably along the four seasons of the hydrological cycle (rising water, high water, falling water and low water), which can influence Hg bioaccumulation in fish. The main aim of this study was to evaluate if Hg biomagnification is influenced by seasonality in a floodplain lake (Puruzinho Lake) in the Brazilian Amazon. Additionally, the influence of food chain modeling on measurement of Hg biomagnification was tested. Hg concentrations and stable isotope signatures (carbon and nitrogen) were estimated in four species, Mylossoma duriventre (herbivorous), Prochilodus nigricans (detritivorous), Cichla pleiozona (piscivorous) and Serrasalmus rhombeus (piscivorous). The "trophic magnification slope" (TMS) of the food chain composed by the four species was calculated and compared among the four seasons. There was no significant seasonal variation in TMS among rising water, high water, falling water and low water seasons (p = 0.08), suggesting that Hg biomagnification does not change seasonally. However, there was significant variation in TMS among different food chain models. Lower TMS was observed in a food chain composed of detritivorous and piscivorous fish (0.20) in comparison with a food chain composed of the four species (0.26). The results indicate food chain modeling influences TMS results.

Negative impacts of mining on Neotropical freshwater fishes

Abstract Mining activities have significantly affected the Neotropical freshwater ichthyofauna, the most diverse in the world. However, no study has systematized knowledge on the subject. In this review, we assembled information on the main impacts of mining of crude oil, gold, iron, copper, and bauxite on aquatic ecosystems, emphasizing Neotropical freshwater fishes. The information obtained shows that mining activities generate several different disturbances, mainly via input of crude oil, metals and other pollutants, erosion and siltation, deforestation, and road construction. Mining has resulted in direct and indirect losses of fish diversity in several Neotropical waterbodies. The negative impacts on the ichthyofauna may change the structure of communities, compromise entire food chains, and erode ecosystem services provided by freshwater fishes. Particularly noteworthy is that mining activities (legal and illegal) are widespread in the Neotropics, and often located within or near protected areas. Actions to prevent and mitigate impacts, such as inspection, monitoring, management, and restoration plans, have been cursory or absent. In addition, there is strong political pressure to expand mining; if – or when – this happens, it will increase the potential of the activity to further diminish the diversity of Neotropical freshwater fishes.

Spatial profiles of perfluoroalkyl substances and mercury in fish from northern Lake Victoria, East Africa

There is an acute deficit of data on per- and polyfluoroalkyl substances (PFASs) and mercury (Hg) in the open waters of Lake Victoria, East Africa, relative to nearshore areas. We analyzed stable isotopes (δ¹⁵N and δ¹³C), PFASs and Hg in Nile Perch and Nile Tilapia muscle and liver samples from nearshore and open lake locations from the Ugandan part of the lake. The δ¹⁵N values of Nile Perch muscle indicated a higher trophic level for samples from the open lake than from nearshore locations. Averages of ∑PFAS concentrations in Nile Perch muscle and liver (0.44 and 1.75 ng/g ww, respectively) were significantly higher than in Nile Tilapia (0.24 and 0.50 ng/g ww, respectively). ∑PFAS concentrations in muscle of open lake Nile Perch were significantly higher than for nearshore samples. A similar observation was made for total mercury concentrations in muscle (THg_{_Muscle}) of Nile Perch. THg was dominated by methyl mercury (MeHg⁺, 22-124 ng/g ww) and mercuric mercury (Hg²⁺, <MDL-29 ng/g ww) in Nile Perch muscle. Strong correlation between MeHg⁺ and some PFASs (e.g. PFOS: r = 0.704, P = 0.016) suggested similar exposure routes or factors. Estimated human daily intake values of PFOS from fish consumption were below international limits whereas for MeHg^+, the US EPA reference dose was exceeded.

Human health risk of methylmercury from fish consumption at the largest floodplain in Colombia

Colombia is one of the countries with the highest emissions of mercury (Hg) to the environment, due to its use in gold mining. This study evaluated the human health risk from exposure to Hg through fish consumption in 11 municipalities located in the Mojana region, northern Colombia. The study participants (n = 839) were categorized into three population groups: children (CHD), women of childbearing age (WCHA) and the rest of population (RP). Total Hg (THg) and methylmercury (MeHg) concentrations were evaluated in the top ten most consumed fish species (n = 292). Median concentrations (range: 0.22-0.58 μg/g ww) of the five carnivorous fish species exceeded the reference limit established by FAO/WHO (0.2 μg/g ww) for vulnerable populations. For 6 of the 10 studied fish species, the estimated weekly intake (EWI) in children was above the provisional tolerable weekly intake (PTWI, 1.6 μg/kg bw/week) of MeHg established by JECFA. EWI values for WCHA were above PTWI in 4 fish species, whereas in general, for RP group values were below PTWI (3.2 μg/kg bw/week). Our assessment of potential risks to MeHg exposure indicated that most of the consumed fish could generate negative effects in vulnerable groups, because according to ingestion rate, MeHg permissible is, in some cases, up to 4 times higher than reference limits. Consumption advisories should be a guidance to avoid risk, gain nutritional benefits, and sustain fish populations. Because its high MeHg levels as well as high ingestion, it is recommended that inhabitants of this region should stop eating certain kinds of fish and the whole fish as a single meal. To reduce its harmful intake, we have proposed a didactic strategy based on marbles that control the portion of fish they are eating.

Total and methyl mercury distribution in water, sediment, plankton and fish along the Tapajós River basin in the Brazilian Amazon

Mercury (Hg) is known as one of the major contaminants in the Amazon. The Tapajós River basin, in the Brazilian Amazon, has diverse anthropogenic activities which increase Hg concentrations in the aquatic ecosystem. Moreover, high concentrations of Hg are naturally found in this basin. Distribution of total (THg) and methyl (MeHg) mercury were assessed in unfiltered water (n = 47), suspended particulate matter (SPM, n = 30), superficial sediment (BS, n = 29), plankton (n = 28) and fishes (n = 129) from the Tapajós River basin. Suspended particles were the main carrier of Hg in the water column and sediment. Increased erosion, prompted by anthropic activities, led to higher Hg concentrations in water from the most impacted areas. Hg is transported mainly in particulate matter; thus, anthropic disturbances influence Hg concentrations downstream. Limnological parameters such as organic matter content influenced MeHg concentrations in water, plankton and sediment of the Tapajós basin. Hg methylation in total plankton was more efficient in lakes (13-66%) than in Tapajós River main channel (2-14%). Biotic and abiotic factors interact in a complex way in the aquatic ecosystem, making Hg concentrations to vary in food web. Gold mining and deforestation probably increase Hg levels in the Tapajós basin. Thus, in addition to Hg monitoring, prevention and remediation efforts should be focused on soil and sediment erosion control.

Foraging habits and levels of mercury in a resident population of bottlenose dolphins (Tursiops truncatus) in Bocas del Toro Archipelago, Caribbean Sea, Panama

A small and genetically isolated bottlenose dolphin (Tursiops truncatus) population resides year-round in the Bocas del Toro Archipelago-Panama (BDT). Photo-identification and genetic data showed that this dolphin population is highly phylopatric and is formed exclusively by individuals of the "inshore form". This study aimed to investigate the trophic ecology and mercury concentrations of bottlenose dolphins in BDT to assess their coastal habits. We collected muscle samples (n = 175) of 11 potential fish prey species, and skin samples from free-ranging dolphins in BDT (n = 37) and La Guajira-Colombia (n = 7) to compare isotopic niche width. Results showed that BDT dolphins have a coastal feeding habit, belong to the "inshore form" (δ¹³C = -13.05 ± 1.89‰), and have low mercury concentrations (mean = 1637 ± 1387 ng g^-1dw). However, this element is biomagnified in the BDT food chain, showing a marginal dolphins health risk (RQ = 1.00). We call for a monitoring pollutant program and conservation strategies aimed to protect the dolphin population at BDT.

Mercurio, metilmercurio y otros metales pesados en peces de Colombia: riesgo por ingesta

En 2013 el pescado proporcionó a más de 3100 millones de personas casi el 20 % de la ingesta promedio de proteínas de origen animal per cápita (FAO, 2016). De acuerdo con el Programa de las Naciones Unidas para el Desarrollo (PNUD), en Colombia y, particularmente en las poblaciones ribereñas y costeras, el 90 % del consumo de proteína de origen animal proviene del pescado, como resultado de un acceso muy bajo a otro tipo de proteínas. Colombia enfrenta uno de los mayores problemas por contaminación ambiental a nivel mundial, generado en gran parte por el abuso de sustancias químicas para el aprovechamiento de minerales, mala disposición de aguas servidas y prácticas industriales y agrícolas inadecuadas, en cuerpos de aguas fundamentales para la dinámica poblacional de animales, vegetales y humanos. Como estrategia mundial para reducir los riesgos a la salud humana por consumo de pescado contaminado con metales pesados, se han considerado límites máximos permisibles, propuestos por diferentes entidades; sin embargo, el 31,5 % de los resultados de estudios publicados para Colombia, son superiores al límite permisible recomendado por la OMS (0,5 μg/g). Los resultados presentados en esta revisión evidencian la urgente necesidad de realizar estudios que evalúen el riesgo a la salud que enfrentan pobladores de zonas mineras y no mineras de Colombia, aportará también fundamentos científicos y bases para el establecimiento de ejes estratégicos que permitan la puesta en marcha de nuevos proyectos productivos que ofrezcan el acceso de la población a diversas fuentes de alimentación.