Biomonitoring of pesticides in agricultural river catchments: a case study from two river catchments in tropical Sri Lanka

Monitoring of pesticide pollution in aquatic systems is a complex process and often constrained by high costs and methodical complexities associated with pesticide measurements in many regions of the world. A trait-based Species at Risk (SPEAR) biomonitoring approach has been conducted to test the responsiveness of the SPEAR_(pesticides) index to pesticide effects in two tropical river catchments in Sri Lanka. The effects of pesticide toxicity (TU(D.magna)), water quality parameters, channel quality (CQI), and landuse on SPEAR (pesticides) index and other biotic indices, i.e., family richness of macroinvertebrates (FR) and %EPT (Ephemeroptera, Plecoptera, and Trichoptera) taxa in streams were tested using stepwise multiple linear regression analysis approaches. The analyses revealed that the SPEAR_(pesticides) index and FR respond favorably to the TU(D.magna) and CQI (p < 0.05). % EPT did not significantly respond to any of the measured instream variables. The catchment scale agricultural activities negatively affected the SPEAR_(pesticides) and FR, while riparian forest cover acted to improve both indices. The findings of the study suggest the possibility of using SPEAR_(pesticides) for pesticide impacts assessment in tropical regions.

Automated summary

Monitoring pesticide pollution in aquatic systems is complex and expensive. A biomonitoring approach called SPEAR (Species at Risk, pesticides) was used in two tropical river catchments in Sri Lanka to assess its responsiveness to pesticide effects. The study found that the SPEAR (pesticides) index and family richness of macroinvertebrates responded positively to pesticide toxicity and channel quality. Catchment-scale agricultural activities negatively affected the SPEAR (pesticides) index, while riparian forest cover improved both indices.