Tracking pesticides from upstream plantations to native bivalves in a tropical wetland habitat in Costa Rica

Mangrove forests are highly productive tropical and subtropical ecosystems providing ecosystem services and supporting local livelihoods, while being influenced by contamination both from land and sea. In the tropics, high temperatures and humidity increase crop susceptibility to pests and pathogens, requiring more frequent pesticide use and raising contamination risks. Costa Rica serves as a key case study, exemplifying the challenges of pesticide management in tropical regions characterized by intensive agriculture. This study identified and quantified pesticide residues in water and sediment samples in the Térraba-Sierpe National Wetland and influence areas. To determine pesticide exposure and its effects, the native bivalve mollusc Anadara tuberculosa was selected as a bioindicator species. Results evidenced the presence of pesticides in the Térraba River waters, the northern Térraba-influenced wetland area, as well as in A. tuberculosa, with diuron, carbendazim, diazinon, and ethoprophos appearing at the highest concentrations in water. Moreover, glutathione S-transferase, cholinesterase, and ethoxyresorufin-O-deethylase biomarkers showed statistically significant differences with a control site (p < 0.05). Considering the geographical distribution of these substances and their utilization in pineapple cultivation, there was a plausible association between this agricultural activity and the observed impact on the wetland aquatic environment. The study supports the potential of A. tuberculosa biomarkers, particularly glutathione S-transferase and cholinesterase activities, to investigate pesticide effects in coastal systems potentially affected by pesticide contamination, develop environmental monitoring and inform pesticide regulations.