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Effects Of Heavy Metal Pollution On Biodiversity In Andean Wetlands From Bolivia

Congress: 2015
Author(s): Alejandra Domic (La Paz, Bolivia), Rosa Isela Meneses, Susi Losa, Jorge Molina, Paula Pacheco
Herbario Nacional de Bolivia1, Unidad de Limnologia, UMSA2, Agua Sustentable3

Keyword(s): Sub-theme 11: Key vulnerabilities and security risks,
AbstractIntroduction Wetlands are generally recognized as important sinks of pollutants due to its capacity to retain heavy metals and traces. Once pollutants are absorbed through the organic matter, they can either be retained over long periods or absorbed by plants and then incorporated into the food chain. In the Andes, wetlands are threatened by increasing discharge of pollutants originated from natural processes (geological processes) or anthropogenic activities (mining). However, the effects of contaminants on biota, in particular heavy metals, are poorly studied. In this paper, we present the results from two study cases in Andean wetlands. Firstly, we quantified presence of several pollutants and its relationship with plant and invertebrate diversity from wetlands affected by mining in northwestern Bolivia. Secondly, we evaluated metal (arsenic and boron) accumulation in water, soil, and plants in wetlands from central western Bolivia. Methods We carried out a field survey of plants and macroinvertebrates in 14 wetlands in northwestern Bolivia. Plant diversity was estimated by using transects of 200 m long, where species presence was recorded every 10 cm. Macroinvertebrates were sampled using suber nets (15 x 10 cm and 250 μm mesh aperture) and a corer sampler (7cm diameter) in lentic and lotic areas. Water samples were collected to quantify of several pollutants (As, Cd, Co, Pb and Fe) and physical attributes (pH, electric conductivity, nitrates, nitrites, and oxygen content). In wetlands from central western Bolivia, we collected samples of water, soil, and plants from three Andean wetlands in October of 2013 (dry season) and January 2014 (wet season). Samples were processed according to standard procedures at the Environmental Quality Lab, Universidad Mayor de San Andres. Results and discussion In northwestern Bolivia, water from most of studied wetlands exhibited low levels of several of the pollutants evaluated. Iron was the only metal detected in all the wetlands, in 10% of the cases levels were above permissible limits. Plant and macroinvertebrate diversity decreased significantly with increasing levels of iron. Macroinvertebrates diversity decreased drastically in heavily polluted wetlands as only 8 taxa were found in these wetlands. Hyallela (Amphipoda), Hellobdela (Glossiphonidae), Cricotopus (Orthocladiinae) and Alotanypus (Tanypodinae) were found in the heaviest polluted wetlands, suggesting their resistance to contamination. Wetlands from central western Bolivia exhibited high concentration of arsenic and boron in water, soil, and plants. In most of the cases, concentrations of arsenic and boron were above national and international permissible limits. In the case of arsenic, concentrations were higher in soils, followed by plants and lastly water. In contrast, boron concentrations were higher in plants, then soil and finally water. Plants also showed high tolerance to arsenic and boron concentrations, exceeding toxic levels by far. The maximum concentration of arsenic and boron were 25 and 17 times higher, respectively, than established tolerance levels for plants. Conclusions Pollution constitutes a major threat to Andean wetlands as it changes habitat chemical properties and decreases plant and macroinvertebrates diversity. This two study cases showed that some plants and invertebrates species are able to tolerate high concentrations of specific pollutans. Additionally, it shows that Andean wetlands are able to retain pollutants in the soil, which is partially assimilated by native vegetation. Additional studies are needed to asses bioaccumulation of heavy metals in wildlife and cattle.
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