Quantifying Nutrient - Algae Relationships in Freshwater Systems; Outcomes of a Workshop held at Monash University on the 8th August 2000

"November 2000".

Project Number: Quantifying Nutrient - Algae Relationships in Freshwater Systems.

MDFRC item.

28 pages. ISBN: 1876810483.

There has been considerable investment in the development and implementation of catchment based nutrient reduction strategies across Australia in response to algal management issues. While most strategies have been based on best available information, key gaps for most strategies are the ability to: Quantify the relationship between nutrient loads, nutrient availability and algal growth in waterways and reservoirs; and Identify the time frame over which reductions in nutrient loads are likely to result in reduced algal bloom frequency and intensity. In simple terms, managers require answers to two key questions: 1. If the load of a limiting nutrient entering a waterbody from the catchment is reduced by x%, what will be the corresponding reduction in algal bloom frequency? 2. How long will it take for the estimated reduction in algal bloom frequency and intensity to occur? The complexity of nutrient-algae relationships (e.g. Harris, 1994) means that there is likely to be only limited information available to directly answer these questions for the range of waterbodies that exist across south-eastern Australia. One way of overcoming this problem is to adopt some form of classification of waters and develop conceptual models for each waterbody type. Computer modelling could then be developed to provide information on nutrient generation and transport processes, the interaction of algae and nutrients in freshwaters, and an assessment of factors or modifiers that might affect the response of algae to available nutrients. This information could then be used for further assessment of the response of algae and cyanobacteria to management actions that reduce nutrient inputs. The CRC for Freshwater Ecology and the Department of Natural Resources & Environment convened a workshop attended by specialists in freshwater ecology, ecological modelling and water resource management (Appendix 1), at which approaches to classifying freshwaters in Victoria and assessing the likely effect of catchment based nutrient management strategies were examined. The workshop, held at Monash University on the 8th August 2000, focussed on in situ effects if the load entering a waterbody was reduced by x%, rather than on how management agencies and others may actually achieve the desired reduction of catchment nutrient load entering waterways. Another aim of the workshop was to scope out the development of a predictive nutrient-algae response model to address the two main questions above, including the organisations and individuals to be involved.