Water quality variables and pollution sources shaping stream macroinvertebrate communities

Area of Science:

• Environmental Science
• Ecology
• Water Quality Management

Background:

• In 2015, over 90% of German rivers did not meet the EU Water Framework Directive's ecological status goals.
• Diffuse pollution (agricultural runoff) and wastewater treatment plants (WWTPs) are suspected major contributors to declining water quality.

Purpose of the Study:

• To evaluate the relative importance of water quality variables and their pollution sources on stream ecological quality.
• To assess the impact of agricultural and urban land use on ecological status.

Main Methods:

• Modeled six macroinvertebrate-based ecological metrics for 184 streams.
• Analyzed responses to water quality gradients, individual variables, and catchment land use/wastewater exposure indices.
• Used indicator substances (carbamazepine, caffeine, herbicides) to link water quality to pollution sources.

Main Results:

• Arable and urban land cover strongly correlated with reduced ecological quality.
• Key in-stream predictors of ecological quality were electric conductivity, oxygen concentration, caffeine, silicate, and pesticide toxicity.
• Caffeine successfully indicated wastewater impact, while herbicides indicated agricultural runoff.

Conclusions:

• Managing diffuse pollution is essential for improving river ecological quality.
• Wastewater treatment plant (WWTP) improvements, particularly reducing poorly treated effluent, are vital for freshwater ecosystem health.