Integrating measures of ecosystem structure and function to improve assessments of stream integrity

Freshwater ecosystems have been degraded by multiple stressors. To mitigate the effects of multiple stressors on freshwater ecosystems, we must assess the current ecological condition of these systems, diagnose the cause of the environmental impact, and predict how they will respond to future changes in anthropogenic pressures. Most biomonitoring programs use metrics of community structure to quantify ecological condition; however, they do not assess the overall ecological integrity of an ecosystem, including ecosystem function. This series of papers explores how structural and functional aspects of stream ecosystems can respond to different stressors. The use of a combination of structural and functional measures increases the ability to assess degradation of stream ecosystem integrity. We suggest that future studies should focus on development of measures that integrate ecosystem structure and function, such as the identification and refinement of species traits that are clearly associated with important functional properties of species and whose responses to different anthropogenic pressures can aid in informing the specific management activities likely to be most effective in restoring degraded stream ecosystems.