Abstract
The biotic integrity of the Guayas River basin in Ecuador is at environmental risk due to extensive anthropogenic activities. We investigated the potential impacts of hydromorphological and chemical variables on biotic integrity using macroinvertebrate-based bioassessments. The bioassessment methods utilized included the Biological Monitoring Working Party adapted for Colombia (BMWP-Col) and the average score per taxon (ASPT), via an extensive sampling campaign that was completed throughout the river basin at 120 sampling sites. The BMWP-Col classification ranged from very bad to good, and from probable severe pollution to clean water based on the ASPT scores. Generalized linear models (GLMs) and sensitivity analysis were used to relate the bioassessment index to hydromorphological and chemical variables. It was found that elevation, nitrate-N, sediment angularity, logs, presence of macrophytes, flow velocity, turbidity, bank shape, land use and chlorophyll were the key environmental variables affecting the BMWP-Col. From the analyses, it was observed that the rivers at the upstream higher elevations of the river basin were in better condition compared to lowland systems and that a higher flow velocity was linked to a better BMWP-Col score. The nitrate concentrations were very low in the entire river basin and did not relate to a negative impact on the macroinvertebrate communities. Although the results of the models provided insights into the ecosystem, cross fold model development and validation also showed that there was a level of uncertainty in the outcomes. However, the results of the models and sensitivity analysis can support water management actions to determine and focus on alterable variables, such as the land use at different elevations, monitoring of nitrate and chlorophyll concentrations, macrophyte presence, sediment transport and bank stability.
Highlights
IntroductionWater quality monitoring involves the measurement of different water quality variables, including physical and chemical conditions, sediment and the biological composition of an aquatic system
Water quality monitoring involves the measurement of different water quality variables, including physical and chemical conditions, sediment and the biological composition of an aquatic system.Monitoring allows managers to maintain a good water quality by enabling them to make necessary decisions and to take actions prior to ecosystem degradation
High BMWP‐Col values were witnessed at sites where dissolved oxygen (DO) concentrations ranged from 6 to 10 mg/L, turbidity values were witnessed at sites where DO concentrations ranged from 6 to 10 mg/L, turbidity was lower than 20 Nephelometric Turbidity Units and flow velocity was higher than or equal to was lower than 20 Nephelometric Turbidity Units and flow velocity was higher than or equal to 0.2
Summary
Water quality monitoring involves the measurement of different water quality variables, including physical and chemical conditions, sediment and the biological composition of an aquatic system. Monitoring allows managers to maintain a good water quality by enabling them to make necessary decisions and to take actions prior to ecosystem degradation. As it is more sustainable to keep a clean environment compared to restoring a polluted one [1], monitoring plays a crucial role in water quality management. Agriculture, urban settlements, irrigation and industries are examples of anthropogenic threats that may change the ecological water quality [2,3]. Agricultural land use and hydromorphological alteration negatively affect species richness and the ecological quality of aquatic communities. Agriculture can alter rivers and riparian integrity, habitat quality and bank stability
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