Marie Anne Eurie Forio

Analysing the effects of water quality on the occurrence of freshwater macroinvertebrate taxa among tropical river basins from different continents

Macroinvertebrates are globally used in environmental monitoring and assessment. However, due to environmental and biological evolution, local adaptations of species might occur. This can contribute to uncertainties in the extrapolation of familyspecific ecological models developed from one region to another. Thus, we aimed to determine if models can be extrapolated to other regions with similar climatic conditions and if a reliable model can be developed from a pooled dataset (consisting of data from different regions). The occurrence of five families was modelled based on physical-chemical water quality variables with classification trees using the data from three tropical river basins (Chaguana in Ecuador, Gilgel Gibe in Ethiopia and Cau in Vietnam). The relevance of each model was tested on complementary data from both the same and other river basins, to test specificity and universality. Furthermore, models with a pooled dataset were developed and tested. Model reliability was assessed based on chance-corrected agreement (Cohens kappa, kappa) and percent agreement (correctly classified instances, CCI). Values of higher than 0.4 (kappa) and 70% (CCI) were used to classify models as good. Only the pollution sensitive taxon (Leptophlebiidae) resulted in reliable models for most cases. In general, responses of macroinvertebrates towards pollution were different among countries except for the pollution sensitive taxa. Thus, extrapolation of ecological models for sensitive taxa to another river basin with similar climatic and environmental conditions is possible. Nevertheless, this type of systematic analyses for all families is necessary to determine and minimize uncertainty in ecological assessment.

Distribution of agricultural pesticides in the freshwater environment of the Guayas river basin (Ecuador)

The rapid increase and transition to more intensive agricultural activities in developing nations are often leading to misuse and overuse of pesticides, making their environment vulnerable for pesticide accumulation. In the present study, the Guayas river basin was taken as a representative case study to evaluate pesticide contamination of the Ecuadorean freshwater environment. Pesticide contamination was determined at 181 sampling sites by a multi-residue method using solid phase extraction (SPE) and pesticide residues were linked with agricultural land use activities to identify the main pollution sources. Moreover, the biological water quality status based on macroinvertebrate communities was determined at every location and the relation with the occurrence of pesticide residues was further investigated. Results showed that pesticide contamination of the freshwater environment was widely present in the Guayas river basin with detections at 108 sampling sites (60%). A total of 26 pesticide products were identified. Most frequently detected pesticides included cadusafos (62 locations), butachlor (21 locations) and pendimethalin (21 locations), with concentrations up to 0.081, 2.006 and 0.557 μg·L-1 respectively. Pesticide residues detected in this study did not significantly influence the biological water quality (p = 0.69), but were observed to be positively correlated with ammonium concentrations, supporting the assumed combined application of chemical fertilizers and pesticides in agriculture. These pesticide residues were also associated with one or more agricultural crops, with in particular the banana and rice industries identified as major pollution sources. Both high consumption rates and non-specific application methods, such as aerial spraying of banana plantations and application directly into the water layer of irrigated rice fields, may attribute to pesticide contamination of the freshwater environment of the Guayas river basin. It is therefore suggested that measures, e.g. legal regulations and awareness campaigns, taken to prevent environmental pollution and accumulation of pesticides primarily focus on these industries.