Carbendazim is a widely used broad spectrum benzimidazole fungicide; however, its effects to non-target aquatic organisms are poorly studied. The aim of this study was to investigate the toxic effects of carbendazim to zebrafish early life stages at several levels of biological organization, including developmental, biochemical and behavioural levels. The embryo assay was done following the OECD guideline 236 and using a concentration range between 1.1 and 1.8mg/L. Lethal and developmental endpoints such as hatching, edemas, malformations, heart beat rate, body growth and delays were assessed in a 96h exposure. A sub-teratogenic range (from 0.16 to 500μg/L) was then used to assess effects at biochemical and behavioural levels. Biochemical markers included cholinesterase (ChE), glutathione-S-transferase (GST), lactate dehydrogenase (LDH) and catalase (CAT) and were assessed at 96h. The locomotor behaviour was assessed using an automated video tracking system at 120h. Carbendazim (96h-LC50 of 1.75mg/L) elicited several developmental anomalies in zebrafish embryos with EC50 values ranging from 0.85 to 1.6mg/L. ChE, GST and LDH activities were increased at concentrations equal or above 4μg/L. The locomotor assay showed to be extremely sensitive, detecting effects in time that larvae spent swimming at concentrations of 0.16μg/L and thus, being several orders of magnitude more sensitive that developmental parameters or lethality. These are ecological relevant concentrations and highlight the potential of behavioural endpoints as early warning signs for environmental stress. Further studies should focus on understanding how the behavioural disturbances measured in these types of studies translate into fitness impairment at the adult stage.

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During the last century the increase in the mean global temperatures has been shown to impact on freshwater physicochemical parameters such as pH, dissolved oxygen, or ultraviolet (UV) light abundance. Changes in these parameters could modify the toxicity of environmental pollutants. Therefore, in the present study, the authors studied the tolerance (survival and sublethal endpoints) of zebrafish (Danio rerio) embryos to variations in pH (3-12), dissolved oxygen (3.9-237 μmol/L) and UV intensity (55-467 mW/m ) using selected endpoints. Sublethal endpoint assessment included the quantification of hatching success, developmental delay, reduction of body length, frequency of edema, and morphological abnormalities. Median lethal concentrations (LC50s; 96-h) of 3.68 and 10.21 were determined for acid and alkaline pH, respectively. Embryo survival appeared to be relatively resistant to oxygen depletion with a 96-h LC50 of 0.42 mg/L. However, concentrations of 6 mg/L and below caused edema and developmental retardations. Continuous exposure to UV radiation affected zebrafish development by reducing survival and hatching rate and triggering a series of developmental abnormalities such as pericardial edema and deformities. A 72-h LC50 of 227 mW/m was derived from intensity-response modeling. By generation of concentration-response parameters the authors' data provide a basis for the subsequent assessment of combined effect of environmental stress parameters and chemicals. Environ Toxicol Chem 2017;36:682-690. © 2016 SETAC.

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