Development of cost-effective strategies for environmental monitoring of irrigated areas in Mediterranean regions: Traditional and new approaches in a changing world

• Pesticide and PhACs pollution was detected in the area of study.
• Preliminary risk characterisation predicts moderate or even high risk for the evaluated groups.
• New microbioassays are able to detect expected toxicological effects.
• New microbioassays show toxic effects of irrigation waters, not detected on risk assessment.

A series of reliable and cost-effective microbioassay-based techniques for routine water quality monitoring were developed and tested on a recently developed irrigation area in western Spain. Results from these assays were compared to a screening-level risk characterisation based on pesticide concentrations in water samples from the study area. The levels of 147 pesticides were measured in irrigation channels, fluvial water and selected animal (Red swamp crayfish, Procambarus clarkii) and plant (Willow, Salix spp. and Holm Oak, Quercus ilex) tissue. The presence of 59 human and veterinary pharmaceuticals in the watershed was also explored. Mitochondrial activity (tetrazolium salts reduction), lipid peroxidation (thiobarbituric acid method), chlorophyll content (autofluorescence) and total amount of DNA (Hoechst fluorimetry) were evaluated in fern (Soft shield fern, Polystichum setiferum) spores and gametophytes as markers of effects on plant development. Lipid peroxidation was assessed as a measure for acute animal toxicity in zebrafish embryos (Danio rerio). Pollution by pesticides (atrazine, diuron, molinate and oxadiazon) and pharmaceuticals (caffeine, cotinine, ivermectine, nicotine and paraxanthine) was detected in water courses receiving irrigation drainage. Pesticide traces were detected in red swamp crayfish (oxadiazon), and Holm oak leaves (oxadiazon, terbutilazine) but not in willow leaves. Preliminary risk assessment described potential moderate or high risk in the lower waters of both studied rivers. The battery of bioassays was able to detect toxicity in the waters of the lower Gargáligas as well as toxic effects on the waters from the irrigation channel. Such methods could both cut costs and improve the prognostic capability of current monitoring programmes.