ibclogo XVI International Botanical Congess


Abstract Number: 2081
Session = 20.9.7


TROPHIC STATE CRITERIA FOR BENTHIC ALGAE IN STREAMS


Barry J. F. Biggs (NIWA, Box 8602, Christchurch, New Zealand)


Algae are an important indicators of water quality. However, they also have their own importance in environmental management, particularly when they form nuisance growths in streams and rivers. There is currently a major effort worldwide to establish defensible biomass and nutrient criteria to reduce the occurrence of benthic algal blooms in streams. I describe the derivation of benthic algal biomass criteria, then link these to soluble nutrient concentrations for prevention of problem growths. A sliding scale of critical nutrient values is proposed to accommodate different probabilities of flood disturbance. This will give greater flexibility in catchment management strategies. Biomass criteria also need to be set within the natural constraints of the stream. Some 'ideal' biomass levels may never be attained because of natural enrichment (e.g., geological enrichment).


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