Biomarcadores bioquímicos e elementos-traço em aves aquáticas não passeriformes em áreas úmidas

Abstract

Trace elements exert influence on aquatic ecosystems. Some, such as copper and zinc are essential to living organisms in small concentrations, but they may become toxic at high concentrations. Others, with unknown biological function, such as cadmium and lead are important environmental contaminants. The increased of trace elements in aquatic environments can become harmful to water birds, causing several changes in these organisms. For the study of these relations, we used two approaches, one theoretical and one practical. In the first approach, we performed a systematic review and a meta-analysis on the association between the exposure to contaminated areas to lead in water birds and biochemical biomarkers. For this study, we searched databases such as Web of Science, Scopus Cab among other sources. Biomarkers like delta-aminolevulinic acid dehydratase, protoporphyrin, hematocrit and hemoglobin have been showing satisfactory results of association and detection of lead exposure. Whereas catalase, ceruloplasmin and glutathione reductase are still little explored. We concluded that there are biochemical changes due to the exposure of birds to contaminated areas, but the biomarkers may be affected by several factors. We suggest the proposition of a protocol to measure the biochemical changes to field studies and we advise the use of multiple biomarkers for the detection of the exposure of birds to lead contamination. In the second approach, we did a field study comparing the concentration of trace elements and biomarkers levels in water birds that are found at areas of organic and non-organic irrigated rice cultivation. We tested if: a) there are differences in water birds exposure to trace elements in organic and non-organic rice farming systems; b) there are differences between the aquatic birds that frequent areas of organic rice farming system and non-organic systems regarding the profile of biomarkers of oxidative stress: thiobarbituric acid reactive substances, non-proteic thiols and carbonyl protein in the liver and muscle, and in the activity of superoxide dismutase and catalase in the liver; c) there is an association between biomarkers of oxidative stress and the exposure to trace elements. For this study, we collected aquatic birds with a firearm in two irrigated rice systems. We separated feathers samples (to determine the concentrations of trace elements), liver and muscle (to determine the profile of biomarkers). We observed higher concentrations of cadmium and zinc in feathers of birds that were found at the organic farming systems and higher concentrations of lead and copper in feathers of those that were found at non-organic cultivation systems. We noticed that thiobarbituric acid reactive substances, non-protein thiols and carbonyl protein showed higher levels in organic cultivation system and superoxide dismutase and catalase showed higher activity in non-organic farming system. In this approach, we conclude that the water birds that are found at rice fields presented differences on exposure to trace elements and differences on their biomarkers profile. However, we found no consistent association between the exposure and the biochemical effects. We suggest that various internal and external not controlled factors may affect these relations.