Abstract
The aim of the present work was to investigate the response of zebrafish to the effects of widely-used organophosphates roundup and chlorpyrifos and putative effectiveness of chlorella in terms of decreasing pesticides toxicity. Studied organophosphate pesticide roundup and chlorpyrifos in ecologically relevant concentrations, both individually and in a mixture, evoked the prominent suppression of catalase and total antioxidant capacity in the liver of Danio rerio which were consistent with higher levels of lipid peroxidation, protein carbonylation, and DNA strand break. Also, both roundup and chlorpyrifos provoked endocrine disorders registered as induction of vitellogenin and depletion of triiodothyronine as well as neurotoxicity appeared as inhibition of acetylcholinesterase after individual action or activation after combined action. The rate of apoptosis observed by caspase 3 activity was decreased, but in different manner depends on the exposure. The potency of toxicity followed the order: roundup > chlorpyrifos > roundup + chlorpyrifos (due to some kind of antagonistic action between chlorpyrifos and roundup in the binary mixture). Based on the results of CART analysis triiodothyronine, TBARS and caspase 3 were determined as the most significant indices for discrimination of the studied groups. The introduction of Chlorella vulgaris in the amount of about 100 thousand cells L-1 into the environment did not show a significant bioremediation effect on the harmful effect of studied pesticides for Danio rerio, which does not exclude the positive impact of algae on the functioning of the ecosystem as a whole and requires further comprehensive research.
Highlights
In case of complex pollution, inherent in natural fresh water reservoirs, the measurement of hydrochemical parameters, as well as the determination of the toxicant concentration in organisms may not be sufficient criteria for hazards assessment [1]
The antioxidant parameters namely total antioxidant capacity and catalase activity in Danio rerio liver were significantly decreased after exposure by organophosphate pesticides when compared with the correspondent control (Fig. 1)
Studied chemicals provoked an increase in lipid peroxidation and protein carbonylation level with the most prominent changes found in the R-group
Summary
In case of complex pollution, inherent in natural fresh water reservoirs, the measurement of hydrochemical parameters, as well as the determination of the toxicant concentration in organisms may not be sufficient criteria for hazards assessment [1]. As of 2019, Ukraine ranks 6th in the world in terms of pesticide use (https://www.worldometers.info/foodagriculture/pesticides-by-country/). Due to their cumulative properties and long half-live (e.g. 45-60 days for roundup) most pesticides circulate in ecosystems and can be accumulated in non-target organisms and be included in food chains, showing signs of toxicity [2]. Promotion of green growth strategies and action plan for sustainable use of pesticides that contributes to further risk reduction all over the world, studies conducted by US Environmental Protection Agency showed the presence of micromolar amounts of atrazine and roundup in about 30% of 154 analysed river water samples (https://toxics.usgs.gov/highlights/glyphosate02.html). Roundup exists in rivers (0.1-0.7 mg/l), sediments (0.0-4.9 mg/kg) and soil (0.5-4.3 mg/kg), sometimes even at concentrations close to toxic [3]
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