Linking catchment management and estuary health
The challenge for ecology is the development of general prediction models that link experimentation and environmental observation into a conceptual framework that allows predictions to be made and tested. The New South Wales Department of Environment, Climate Change and Water and the CSIRO, working in the Logan-Albert Catchment, have achieved this with a prediction model for suspended sediment, nutrients, phytoplankton biomass, and the coupling between the water column and sediment biogeochemistry.
The Logan ERM modelling framework predicts net metabolism in the pelagic and benthic zones along the estuary, and gives estimates of nutrient and suspended sediment loads to Moreton Bay.
eWater Source can be used to predict freshwater flows and sediment-nutrient yields from the catchment, with the Logan ERM bridging knowledge gaps in terms of understanding the impacts on estuarine health as well as the role of estuaries in attenuating pollutant exports to the bay. This allows impacts on estuarine ecological health to be more comprehensively included in integrated catchment modelling.
The focus has been the receiving waters of Moreton Bay, and the work provides an insight into estuarine function at the base of the foodweb, with implications for higher orders of estuary dwellers such as prawns and fish. For example, the model can predict temporal and spatial variation in deposition of organic material, which is one of the primary drivers of detritivore populations — for example, prawns and mudcrabs.
This forms a valuable adjunct to models developed by Queensland Primary Industries and Fisheries that predict prawn and barramundi abundance based on flood occurrence.
This project represents a fruitful collaboration between researchers with very different skills and experience (biogeochemistry, mathematical modelling and software engineering). The modelling framework provides a powerful tool for understanding ecosystem function along estuarine gradients, allows the derivation of system-specific thresholds and guidelines, and can be used in the testing of management scenarios.