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Presented at the NABS Annual meeting, Pittsburgh, Pennsylvania, 2002
in Current and Future Approaches for Using Benthic Algae to Monitor and Assess Aquatic Ecosystems I
EUTROPHICATION OF STREAMS AND RIVERS: HIERARCHICAL RIVER ENVIRONMENT CLASSIFICATION TO IDENTIFY AND MAP REFERENCE CONDITIONS AND STATE OF IMPAIRMENT.
B.J.F. Biggs1, T. Snelder1, M.A. Weatherhead1, K. Niven1, and A. Elosegi2. 1NIWA, P.O. Box 8602, Christchurch, New Zealand, 2Department of Plant Biology and Ecology, Science Faculty, University of the Basque Country, P.O. Box 644, 48080 Bilbao, Spain.
Eutrophication is of fundamental concern in managing streams and rivers world-wide. Degree of impairment (e.g., oligotrophic, mesotrophic, eutrophic states) will depend not only on human induced enrichment, but on natural environmental constraints operating over a range of scales. Indeed, ‘reference’ conditions will vary naturally among streams as a function of landscape properties (e.g., climate, topography, geology) and this should influence our expectations of, and management responses to, perceived impairment. A GIS rule-based, “top-down”, river environment classification that codifies models of instream biotic responses to physical environments has been developed and applied in New Zealand. We use this classification to illustrate how environmental variability can be partitioned, mapped as a network from reach to regional scales, and used to identify reference and impaired reaches for stream eutrophication. We demonstrate the efficacy of this approach using periphyton community and nutrient data. The nutrient data are analysed in relation to flow regimes and predicted maximum periphyton biomass and then degree of impairment mapped back to the landscape from first through to sixth order channels.
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