Predicting zebrafish spatial avoidance triggered by discharges of dairy wastewater: An experimental approach based on self-purification in a model river

• Published in: Environmental pollution (1987) Vol. 266; p. 115325
• Main Authors: Silva, Daniel C.V.R., Queiroz, Lucas G., Marassi, Rodrigo J., Araújo, Cristiano V.M., Bazzan, Thiago, Cardoso-Silva, Sheila, Silva, Gilmar C., Müller, M., Silva, Flávio T., Montagner, Cassiana C., Paiva, Teresa C.B., Pompêo, Marcelo L.M.
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 01-11-2020
• Subjects: Dairy wastewater; Fish; Habitat selection; Non-forced exposure; Water pollution; Fish; Water pollution; Dairy wastewater; Habitat selection; Non-forced exposure
• ISSN: 0269-7491; 1873-6424
• DOI: 10.1016/j.envpol.2020.115325

Wastewater discharges from dairy industries can cause a range of harmful effects in aquatic ecosystems, including a decline in biodiversity due to species evasion. Therefore, it is important to know the purification potential of rivers for the removal of pollutants released in dairy wastewater (DWW). The hypothesis adopted in this work was that the release of DWW into stretches of the Ribeirão dos Pombos River (São Paulo State, Brazil) might trigger an avoidance response, resulting in fish migrating to other regions, with the response being greater when the self-cleaning potential of the river is smaller. Therefore, the goals of the present study were to: (i) investigate how land use and seasonality of the rainfall regime influence the quality of the water in different areas of the river (P1: river source; P2: urban region; P3: rural region); (ii) assess the potential of the river to purify DWW; and (iii) evaluate the potential toxicity and repellency of DWW to the freshwater fish Danio rerio, using acute toxicity (mortality) and non-forced avoidance tests, respectively. P1 was shown to be the most preserved area. The chemical composition of the river varied seasonally, with higher concentrations of Cl− and SO42− at P3 during the rainy period. The river purification potential for DWW was higher at P2, due to greater microbiological activity (associated with higher BOD). The DWW was more acutely toxic in water from P2. The avoidance response was strongly determined by the concentration of DWW, especially for water from P2. The high capacity for self-cleaning at P2 did not seem sufficient to maintain the stability of the ecosystem. Finally, the non-forced exposure system proved to be a suitable approach that can assist in predicting how contaminants may affect the spatial distributions of organisms.
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•The potential of a river to purify dairy wastewater (DWW) was evaluated.•The repellency of DWW to fish was assessed by avoidance tests in a non-forced system.•Very clean water was less toxic, but less efficient to purify DWW.•The most contaminated area presented higher capacity of self-depuration.•Higher acute toxicity and repellency was recorded in the most contaminated area.
Despite the high capacity for self-purification, the water from the most polluted area presented higher mortality and repellency during the fish exposure period.