Development, testing and use of functional indicators for river health assessment in New Zealand

River health assessment has traditionally concentrated on structural measurements related to abundance and community composition.  However, a complete assessment of river health requires information on both structural and functional components of the ecosystem.  Efforts to incorporate ecosystem function measures in river health monitoring in New Zealand began with a project that reviewed potential indicators, summarized their response to a variety of impact types, and provided guidance on when and where these indicators may improve biomonitoring.  The approach focused on ecosystem metabolism and organic matter decomposition and was tested with local government staff to develop simple protocols that were suitable for regular monitoring programmes.  Criteria for distinguishing between healthy and unhealthy streams were also determined.  Functional indicators are now part of regular monitoring programmes in some regions of New Zealand, but uptake has been limited in other areas.  Uptake was best when additional information could be obtained from existing data collection (e.g. continuous DO records allowing metabolism calculation) and in large rivers where problems with traditional approaches were apparent.  Further research looking at responses of various functional and structural indicators along stressor gradients will provide improved guidance on which indicators suit specific stressors and how to interpret indicator results.