Diuron and its biodegradation metabolites were recently reported to cause alterations in plasma steroid hormone concentrations with subsequent impacts on reproductive development in fish. Since steroid hormone biosynthesis is regulated through neurotransmission of the central nervous system (CNS), studies were conducted to determine whether neurotransmitters that control hormone biosynthesis could be affected after diuron and diuron metabolites treatment. As the same neurotransmitters and steroid hormones regulate behavioral outcomes, aggression was also evaluated in male Nile tilapia (Oreochromis niloticus). Male tilapias were exposed for 10 days to waterborne diuron and the metabolites 3,4-dichloroaniline (DCA), 3,4-dichlorophenyl-N-methylurea (DCPMU), at nominal concentrations of 100 ng L. In contrast to Diuron, DCA and DCPMU significantly diminished plasma testosterone concentrations (39.4% and 36.8%, respectively) and reduced dopamine levels in the brain (47.1% and 44.2%, respectively). In addition, concentrations of the stress steroid, cortisol were increased after DCA (71.0%) and DCPMU (57.8-%) exposure. A significant decrease in aggressive behavior was also observed in animals treated with the metabolites DCA (50.9%) and DCPMU (68.8%). These results indicate that biotransformation of diuron to active metabolites alter signaling pathways of the CNS which may impact androgen and the stress response as well as behavior necessary for social dominance, growth, and reproduction.

This study aimed to evaluate DNA damage in animal and plant cells exposed to water from the Água Boa stream (Dourados, Mato Grosso do Sul, Brazil) by using bioassays, and to identify the chemical compounds in the water to determine the water quality in the area. Through the cytotoxicity bioassay with Allium cepa, using micronucleus test, and comet assay, using Astyanax altiparanae fish, the results indicated that biological samples were genetically altered. Micronuclei were observed in erythrocytes of A. altiparanae after exposure to water from locations close to industrial waste discharge. The highest DNA damage observed with the comet assay in fish occurred with the exposure to water from locations where the presence of metals (Cu, Pb, Cd, Ni) was high, indicating the possibility of genotoxic effects of these compounds. Thus, these results reinforce the importance of conducting genotoxicity tests for developing management plans to improve water quality, and indicate the need for waste management before domestic and industrial effluents are released into the rivers and streams.

Fipronil is a phenylpyrazole insecticide widely used to control pests in agriculture even 29 though evidence of harmful side effects in non-target species has been reported. A 30 comprehensive study on the effects of dietary administration of Regent®800WG (80% 31 fipronil) in European sea bass juveniles was carried out under two temperature regimes: 32 a) natural conditions, and b) 3 ºC above the natural temperature (an increase predicted 33 for the NW Mediterranean by the end of this century). Fipronil was added to the fish 34 food (10 mg fipronil /Kg feed) and the effects were studied at several time points 35 including right before administration, 7 and 14 days after daily fipronil feed and one-36 week after the insecticide withdrawal from the diet (depuration period). A wide array of 37 physiological and metabolic biomarkers including feeding rate, general condition 38 indices, plasma and epidermal mucus metabolites, immune response, osmoregulation, 39 detoxification and oxidative-stress markers and digestive enzymes were assessed. 40 General linear models and principal component analyses indicated that regardless of 41 water temperature, fipronil resulted in a significant alteration of several of the above 42 listed biomarkers. Among them, glucose and lactate levels increased in plasma and 43 decreased in epidermal mucus as indicators of a stress response. Similarly, a depletion 44 in catalase activity and higher lipid peroxidation in liver of fipronil-exposed fish were 45 also indicative of an oxidative-stress condition. Fipronil induced a time dependent 46 inhibition of Cytochrome P450-related activities and an inhibition of phase II 47 glutathione-S-transferase. Moreover, fipronil administration was able to reduce the 48 hypo-osmoregulatory capability as shown by the increase of plasmatic osmolality and 49 altered several digestive enzymes including trypsin, lipase, alpha amylase and maltase. 50 Finally, analyses in bile and muscle confirmed the rapid clearance of fipronil but the 51 persistence of the metabolite fipronil-sulfone in bile even after the 7-day depuration 3 52 period. Altogether, the results reveal a notable impact of this compound on the 53 physiological condition of the European sea bass. The results should be considered in 54 future environmental risk assessment studies since fipronil could be hazardous to fish 55 species, particularly those inhabiting estuarine ecosystems exposed to the discharge of 56 agriculture runoffs where this pesticide is mainly used.

Anthropic activities are directly related to the contamination of aquatic ecosystems owing to the release of numerous chemicals from agricultural and urban waste. These contaminants cause environmental degradation and a decrease in the availability of water quality. The objective of this search was to evaluate the efficiency of physicochemical, chemical, and microbiological tests; extraction of chlorophyll a; and genetic parameters to identify anthropic activities and weather condition effects on the stream water quality and the consequences of its use by the population. The physicochemical parameters were within the limits allowed by the Brazilian law. However, contamination by metals (Cd 0.510 mg L, Co 0.405 mg L, and Ni 0.316 mg L) has been found at various collection points to be more than the allowable values. The antibiotic oxytetracycline was detected in stream water in quantities of up to 89 μg L. In relation to microbiological contamination, Escherichia coli and Pseudomonas spp. have been isolated. The averages of chlorophyll a were up to 0.15558 mg cm. Genetic tools identified greater number of micronuclei and DNA damage in periods that showed lower rainfall rates and lower amounts of metals. The analysis used for monitoring was efficient to verify the interference that animal breeding and planting of different cultures have caused on that stream. Thus, the continued use of this water for drinking, irrigation of vegetables, and recreational activities makes the population susceptible to contamination by bacteria and creates conditions for the development of genetic alterations in the long run.

Water quality monitoring is used to determine the impact of human activities on the environment. We evaluated water quality in the Água Boa stream, located within the municipality of Dourados, State of Mato Grosso do Sul, Brazil, by analyzing physico-chemical, chemical, and microbiological parameters, as well as chlorophyll concentrations. Five sets of water samples were collected between December 2012 and November 2013 from three locations within the stream. The results showed the presence of Escherichia coli and antibiotic-resistant Pseudomonas spp. strains and high concentrations of organic matter (total dissolved solids), inorganic species (Mg, Ca, and Fe), and agrochemical residues (thiamethoxam). The main stream water contaminants are derived from urban, industrial, and agricultural activities within the watershed. Given the presence of contaminants, it is important that such findings are disseminated in order to highlight the risks that contact with this water may pose to human health. To preserve the environment and improve site conditions, people would need to participate by demanding that normative national and international standards be respected and that the situation be supervised by the competent governmental agencies; this would make it possible to reverse or minimize contamination problems within the Água Boa stream.