Biomarcadores de toxicidade em Loricariichthys anus (Valenciennes, 1835) e Geophagus brasiliensis (Quoy & Gaimard, 1824): influência de variáveis abióticas e da poluição agrícola

Abstract

Limnic environments are threatened worldwide, receiving loads of pollutants from various anthropogenic activities. Brazil is one of the largest consumers of agrochemicals, especially pesticides. These will eventually enter the aquatic systems via several mechanisms and may be dammed, as in the reservoirs, affecting directly or indirectly their dwellers. Toxicity biomarkers are widely used in ecotoxicology to verify deviations from the normal function. However, biomarkers may fluctuate seasonally due to abiotic/biological factors, such as the temperature that governs the physiology of ectothermic animals. In this study, two species of fish (Loricariichthys anus and Geophagus brasiliensis) were collected seasonally along with abiotic variables during one year at six sites in the Passo Real reservoir, in the Upper Jacuí basin, southern Brazil. Eight pesticides were detected in the water. As temperature is the key factor for physiological regulation, comparing biomarkers data from L. anus collected in the summer and in the winter, it can be seen that in the winter there were major changes in the liver (increase of GST and GPx) and in the gills in the summer (elevation of GST, GPx and TBARS). Increased AChE in brain and muscle in the winter was associated with carbonylation of proteins. As the variables act concomitantly on the organisms, a redundancy analysis was performed for both species, considering the biochemical responses and data of pesticides, metals and abiotic factors of the four seasons. In this way, it was evident that not only the pesticides affect the biomarkers response, but also ammonia, nitrite, electrical conductivity and temperature. Seasonality was clearly fundamental for both species. Although it is difficult to separate the normal fluctuations of biomarkers from those related to the exposure of pollutants, in a long-term, these can cause indirect effects to the populations of these species by reducing food resources or affecting fitness by diverting energy to produce antioxidant defenses, reducing investment in other activities such as reproduction.