A multibiomarker evaluation of urban, industrial, and agricultural exposure of small characins in a large freshwater basin in southern Brazil

Abstract

Iguaçu River is the second most polluted river of Brazil. It receives agrochemicals and contaminants of urban and industrial sources along its course. A multibiomarker approach was employed here to evaluate the health of a small characin (Astyanax spp.) at two sites along the river, sampled during a dry (autumn) and a rainy (spring) season. Biomarkers were condition factor and somatic indices (gonads and liver); genetic damage (comet assay and micronucleus test); enzyme activities such as hepatic catalase (CAT) and glutathione S-transferase (GST), lipoperoxidation (LPO), branchial and renal carbonic anhydrase (CA), acetylcholinesterase (AChE) in the muscle and the brain, histopathology of the liver and gills, and concentrations of polycyclic aromatic hydrocarbons (PAHs) in bile. There were no consistent differences in biomarker responses between the two study sites. Some biomarkers revealed greater potential impact in the rainy season, when increased amounts of contaminants are washed into the river (combined CAT inhibition and LPO increase, CA upregulation). Other biomarkers, however, revealed potential greater impact in the dry season, when contaminants potentially concentrate (GST induction, AChE inhibition, and liver histopathological alterations). Although of a complex nature, field experiments such as this provide rich data for monitoring protocols and assessment of general risk of exposure to pollutants of river systems.

Bioavailability of pollutants sets risk of exposure to biota and human population in reservoirs from Iguaçu River (Southern Brazil)

“…bifasciatus reflected the environmental quality better than G. brasiliensis and C. iguassuensis A. bifasciatus represented a good bioindicator of biomonitoring study to the Iguaçu River, since its biological responses reflected the environmental quality better than the other two fish species in the current study. The same conclusion had been reported by Freire et al (2015) for this species. A. bifasciatus is widely distributed in the Iguaçu River (Daga and Gubiani 2012;Pie et al 2009), and studies in different regions of Brazil and South America also describe the gender Astyanax sp.…”

In vivo effects of Aphanizomenon flos-aquae DC-1 aphantoxins on gas exchange and ion equilibrium in the zebrafish gill

“…Furthermore, this is also supported by the ultrastructural damage observed in the chloride and epithelial cells of zebrafish gills following exposure to aphantoxins in the current study. In addition, the increase in CA activity observed after 1 h of treatment may reflect a response to oppose the sudden influx of toxins, similar to previously reported observations (Freire et al, 2015). Based upon previous studies, the current study indicates that aphantoxins or PSPs trigger a decrease in CA activity by decreasing CA synthesis and/or advancing its consumption in an effort to eliminate the toxin and prevent injury in the zebrafish gill.…”

Histopathological alterations in Astyanax bifasciatus (Teleostei: Characidae) correlated with land uses of surroundings of streams

“…It should be noted that low levels of dissolved oxygen (DO), higher temperature, electrical conductivity and pH are closely linked to the conversion of ammonia into the most toxic form (Pereira, Mercante, 2005), which may alter water quality. These physiological changes potentiate the action of possible contaminants present in the aquatic environment, increasing the presence and frequency of histopathological alterations (Freire et al, 2015).…”

“…Despite being fundamental for the water supply of various cities and agricultural areas (Pereira, Scroccaro, 2010) as well as presenting high endemism of its fauna (Nogueira et al, 2010;Baumgartner et al, 2012), the Iguaçu River basin is highly impacted. At its higher and medium parts, the pollutants are derived mainly from urban and industrial sewage (Yamamoto et al, 2016), while in its lower part, the western part of the state, the principal contaminants are agricultural pesticides based on organophosphates and carbamates (Freire et al, 2015). In this sense, the biomonitoring of water bodies in order to assess environmental quality becomes extremely important, since these xenobiotics can pass by biotransformation in individuals or biomagnification in levels of the food web, thus compromising the entire ecosystem (Silva et al, 2013).…”

“…The histological changes in fish tissue can be used as a tool to detect effects of chemical compounds on target organs (Freire et al, 2015). In this aspect, the gills, as they are in direct contact with the water, become an important histological biomarker of fishes exposed to contaminants (Gomes et al, 2012;Ayadi et al, 2015).…”