RESUMO

BACKGROUND: Gold mining activities in forested areas across Guyana have been a common practice for more than a century. The intensification of artisanal and small-scale gold mining (ASGM) in recent decades caused by global market demand is contributing to the mobilization of mercury into aquatic systems. Indigenous populations who consume high levels of locally sourced fish are greater at risk for methylmercury poisoning from ingestion of contaminated fish. OBJECTIVES: The aim of the present study was to investigate the levels of mercury contamination and identify the risk factors associated with hair mercury levels in four indigenous communities in Guyana. METHODS: Concentrations of total mercury were measured in hair samples from 99 participants from four indigenous communities in the south Rupununi region in Guyana. The findings of this study were compared with those of previous studies to assess the prevalence of mercury contamination in indigenous communities across Guyana. RESULTS: Hair mercury levels were found to be above the World Health Organization (WHO) reference value for residents who live close to ASGM activities and who consume high quantities of locally sourced fish. Our results are not only consistent with those obtained in previous studies, but also evidence that mercury poisoning has become a generalized problem for indigenous communities in Guyana. CONCLUSIONS: Fish is the main source of protein for many riverine communities and consumption of mercury-contaminated fish poses a serious health hazard for these vulnerable populations. The situation is especially dire for community members of Parabara with 100% of participants showing elevated (>15 µg*g-1) hair mercury levels. It is therefore crucial that Parabara residents be evaluated by relevant health agencies for clinical symptoms related to mercury toxicity. PARTICIPANT CONSENT: Obtained. ETHICS APPROVAL: The study protocol was approved by the Institutional Review Board of the Ministry of Public Health, Guyana. COMPETING INTERESTS: The authors declare no competing financial interests.

RESUMO

Using stable nitrogen and carbon isotope signatures, we investigated the trophic ecology and identified potential prey fish groups supporting the giant Arapaima within floodplain lakes of the Essequibo River basin in southwestern Guyana. Morphological descriptions of feeding structures and digestive tract are presented together with preliminary data on Arapaima diets. Stable isotope results suggest that algivorous/detritivorous and omnivorous fishes contributed most to Arapaima biomass, and generally, that was consistent with what is known about Arapaima diets. Stable nitrogen isotope ratios for piscivorous fishes in these lakes were higher than nitrogen isotope ratios for Arapaima, indicating that piscivorous fishes are unlikely to constitute a major source of energy for Arapaima. This population of Arapaima has an intestine averaging 1.45 times total body length, relatively small teeth, and numerous, closely-spaced gill rakers. These morphological features, together with isotope data, support our inference that Arapaima are secondary consumers and may be better characterized as omnivores and not top predators.

Utilizando firmas de isotopos estables de nitrógeno y carbón, investigamos la ecología trófica e identificamos los grupos de peces que potencialmente mantienen a la Arapaima en los lagos inundables de la cuenca del río Essequibo, al suroeste de Guyana. Presentamos descripciones morfológicas de las estructuras alimentarias y tracto digestivo de la Arapaima, conjuntamente a datos preliminares de sus dietas. Los isotopos estables sugieren que peces algívoros/detritívoros y peces omnívoros son los principales contribuyentes de la biomasa de la Arapaima, y estos resultados son compatibles con lo que se conoce actualmente de la dieta de la Arapaima. A diferencia, las proporciones del isotopo estable de nitrógeno para peces piscívoros en estos lagos resultaron más altas que los valores obtenidos para el isotopo estable de nitrógeno en la Arapaima. Esto indica que es improbable que sean peces piscívoros los que constituyan la fuente energética principal de la Arapaima. La población de Arapaima estudiada presenta un intestino que promedia 1,45 veces la longitud total del cuerpo, dientes relativamente pequeños, y agallas con branquiespinas numerosas y cercanamente espaciadas. Estas características morfológicas, conjuntamente a los datos obtenidos a través del uso de isotopos estables apoyan nuestra inferencia que la Arapaima es un consumidor secundario y que puede ser caracterizada como un pez omnívoro y no como un depredador mayor.

Assuntos

RESUMO

Using stable nitrogen and carbon isotope signatures, we investigated the trophic ecology and identified potential prey fish groups supporting the giant Arapaima within floodplain lakes of the Essequibo River basin in southwestern Guyana. Morphological descriptions of feeding structures and digestive tract are presented together with preliminary data on Arapaima diets. Stable isotope results suggest that algivorous/detritivorous and omnivorous fishes contributed most to Arapaima biomass, and generally, that was consistent with what is known about Arapaima diets. Stable nitrogen isotope ratios for piscivorous fishes in these lakes were higher than nitrogen isotope ratios for Arapaima, indicating that piscivorous fishes are unlikely to constitute a major source of energy for Arapaima. This population of Arapaima has an intestine averaging 1.45 times total body length, relatively small teeth, and numerous, closely-spaced gill rakers. These morphological features, together with isotope data, support our inference that Arapaima are secondary consumers and may be better characterized as omnivores and not top predators.(AU)

Utilizando firmas de isotopos estables de nitrógeno y carbón, investigamos la ecología trófica e identificamos los grupos de peces que potencialmente mantienen a la Arapaima en los lagos inundables de la cuenca del río Essequibo, al suroeste de Guyana. Presentamos descripciones morfológicas de las estructuras alimentarias y tracto digestivo de la Arapaima, conjuntamente a datos preliminares de sus dietas. Los isotopos estables sugieren que peces algívoros/detritívoros y peces omnívoros son los principales contribuyentes de la biomasa de la Arapaima, y estos resultados son compatibles con lo que se conoce actualmente de la dieta de la Arapaima. A diferencia, las proporciones del isotopo estable de nitrógeno para peces piscívoros en estos lagos resultaron más altas que los valores obtenidos para el isotopo estable de nitrógeno en la Arapaima. Esto indica que es improbable que sean peces piscívoros los que constituyan la fuente energética principal de la Arapaima. La población de Arapaima estudiada presenta un intestino que promedia 1,45 veces la longitud total del cuerpo, dientes relativamente pequeños, y agallas con branquiespinas numerosas y cercanamente espaciadas. Estas características morfológicas, conjuntamente a los datos obtenidos a través del uso de isotopos estables apoyan nuestra inferencia que la Arapaima es un consumidor secundario y que puede ser caracterizada como un pez omnívoro y no como un depredador mayor.(AU)

Assuntos