A combination of chemical and biological studies demonstrated extensive surface water contamination, the occurrence of pesticides in sediments, especially near the banana plantation areas, and biological impacts. Pesticides were even found in the downstream waters of the Tortuguero conservation area, a highly diverse wetland that protects several endangered species.
The frequency of observation and the found concentrations were higher closer to the banana plantation areas. Peak concentrations were observed following application of ground and aerially applied pesticides. The fungicides used in packing plants (imazalil and thiabendazole), as well as several insecticide-nematicides (chlorpyrifos, diazinon, cadusafos, carbofuran, ethoprofos and terbufos) were detected in concentrations that have the potential to damage aquatic life. Acute and chronic toxicity tests with effluent water from the packing plant indicated increased mortality as well as sublethal effects on the cladoceran Daphnia magna and the cnidarian Hydra attenuata. Changes in protein patterns and respiration rates of the indigenous cichlid fish Cichlasoma dovii and the mussel Anodontites luteola were observed in the laboratory at ecologically relevant environmental levels of pesticides, before any mortality could be observed.
Community richness and composition measures such as the percentage of EPT, ratio EPT/Chironomidae abundance, community loss and the Jaccard similarity index allowed detection of differences between the benthic community in the forested area streams of the reference sites from that of the disturbed banana plantation area. Multivariate analysis (non-metric multi-dimensional scaling, MDS) revealed that terbufos, cadusafos and carbofuran applications resulted in significant community changes at all the studied banana plantation sites and that these changes were similar (i.e. the same genera were affected, among them Microcylloepus sp., Leptohyphes sp., Leptonema sp. and Cf. Pseudochironomus sp.) at all sites and for all pesticides. The study of the macrobenthic community was more sensitive in distinguishing pesticide effects than the used toxicity tests, the multivariate analysis used (MDS) was also more sensitive than the richness and composition measures. Community studies, however, would benefit from a better understanding of natural variability in wet tropical areas.
The use of biomarkers and field and laboratory toxicity tests with relevant native organisms could help clarify the relationship between chemical stress and effects on invertebrate populations. An integrated approach combining chemical exposure evaluations, bioassays and including the biological assessment methods used in this thesis, seem to be more appropriate for ecological risk assessment of banana production, than the use of chemical analysis and laboratory bioassays only.
Stockholm: Stockholm University, 2000. , 24 p.