Resumen:
Degradation of freshwater ecosystems by uncontrolled human activities is a growing concern in the tropics. In
this regard, we aimed at testing an integrative framework based on the IFEQ index to assess freshwater ecosystem
health of river basins impacted by intense livestock and agricultural activities, using the Muchacho River Basin
(MRB) as a case study. The IFEQ combine multiple lines of evidence such as riverine hydromorphological
analysis (LOE 1), physicochemical characterization using ions and pesticides (LOE 2), aquatic macroinvertebrate
monitoring (LOE 3), and phytotoxicological essays with L. sativa (LOE 4). Overall, results showed an important
reduction in streamflow and an elevated increase in ion concentrations along the MRB caused by deforestation
and erosion linked to agricultural and livestock activities. Impacts of the high ion concentrations were evidenced
in macroinvertebrate communities as pollution-tolerant families, associated with high conductivity levels, represented 92 % of the total abundance. Pollution produced by organophosphate pesticides (OPPs) was critical in
the whole MRB, showing levels that exceeded 270-fold maximum threshold for malathion and 30-fold for
parathion, the latter banned in Ecuador. OPPs concentrations were related to low germination percentages of
Lactuca sativa in sediment phytotoxicity tests. The IEFQ index ranged from 44.4 to 25.6, indicating that freshwater ecosystem conditions were “bad” at the headwaters of the MRB and “critical” along the lowest reaches. Our
results show strong evidence that intense agricultural and livestock activities generated significant impacts on
the aquatic ecosystem of the MRB. This integrative approach better explains the cumulative effects of human
impacts, and should be replicated in other basins with similar conditions to help decision-makers and concerned
inhabitants generate adequate policies and strategies to mitigate the degradation of freshwater ecosystems.
