US researcher finds high mercury levels in Mazaruni River

first_imgA Sam Huston State University Professor, conducting research documenting the effects of mercury contamination in freshwater fishes and food webs in the Mazaruni River and tributaries, has found higher than normal levels of mercury in the fishes as well as the water.Dr Carmen Montaña-Schalk from the Department of Biological Sciences has been conducting research in the Mazaruni area for the past two years, and has published some of her preliminary findings over the past week.“Preliminary results by Dr Montaña-Schalk suggest a strong potential for bio-accumulation of mercury in the aquatic food web. For instance, large fish predators contain greater concentrations of mercury.Dr. Montaña-Schalk has also observed that several fishes important in local human diets had Hg (mercury) levels higher (> 1 mg Hg/kg) than the threshold proposed by the World Health Organization (0.5 mg Hg /kg). Therefore, local communities along the Mazaruni River are exposed to dangerous levels of mercury through consumption of fish as well as piscivorous wildlife,” the paper stated.Region Seven (Cuyuni-Mazaruni) is predominantly a mining region, and mercury plays a large part in gold recovery there. The Mazaruni River houses one of the world’s greatest concentrations of freshwater biodiversity, and contains high levels of species endemism, with a number of Amerindian communities relying on those fishes for their food. The Mazaruni area is home to thousands of Amerindians.Dr Montaña-Schalk has said that a major problem facing the freshwater biodiversity in Guyana is habitat transformation via deforestation for gold mining operations and the release of mercury from alluvial gold mining activities into water bodies. She said that although there are studies documenting the presence of mercury in freshwater fishes and alluvial sediments in rivers of Guyana, very little still is known about the synergic effects of gold mining or mercury contamination in all components of the aquatic food web and the pathways for inorganic mercury to be converted into organic methyl mercury.For the last two years, Dr Montaña-Schalk and colleagues from University of Guyana have been surveying tributaries of the Mazaruni River, and documenting fish diversity and mercury accumulation on fishes inhabiting these rivers. She documented that, every year, the effects of gold mining operations are greater.There are more gold dredges in the main channel operating 24/7, but also high inland deforestation to establish inland mining operations. Gold mining activities significantly alter local habitats and downstream waterbodies.“The most noticeable effects in the ecosystem are high turbidity in the water and sediments accumulation. This is particularly concerning, because some species endemic to the Mazaruni Basin appear highly associated with the main channel habitats…post-mining results are having adverse and detrimental effects on natural resources, including biodiversity and the environment. We have observed severely degraded aquatic ecosystems, decline in fish diversity, and mercury accumulation in fishes used as food resources by locals.All of this is of great concern, and requires immediate attention that involves conservation monitoring and restoration initiatives,” she said.Dr Montaña-Schalk will continue her research to serve first-hand information for policy makers to address the threats on fish species in Mazaruni due to mercury contamination.Last week, the Guyana Water Inc announced that the Kaituma River was found to have a high mercury content. GWI Managing Director Dr Richard Van West-Charles had stated that samples had been taken from the river, and the results have shown levels of 0.016mg/L, which are more than the accepted World Health Organisation’s (WHO’s) 0.006mg/L standard.last_img

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