|Title||The relative importance of top-down and bottom-up control on primary production in a dryland-tropical river|
|Publication Type||Conference Participation|
|Year of Publication||2010|
|Authors||Faggotter, SJ, Burford, MA, Balcombe, SR|
|Keywords||4: Material Budgets|
The ecological integrity of northern Australia’s pristine rivers are under increasing anthropogenic pressure from stressors such as water regulation and abstraction which impact on natural flow regimes. These flow alterations have the potential to impact ecosystem function, including nutrient cycling and productivity. With the aim of better prediction of ecosystem responses to flow regime changes, this study examined the relative importance of top-down versus bottom-up control of primary productivity. The study site was located within a dryland river system in tropical northern Australia which is characterised by vast floodplains in the monsoon period and disconnected waterholes within the dry season. Chlorophyll a concentrations in the water column and periphyton increased over the dry season in a nutrient-depauperate system. Conversely, fish biomass was high soon after flooding but decreased substantially over the same period. Increased algal biomass may be the result of decreased grazing pressure and decomposition of grazers providing an additional nutrient source. The productivity of these systems is therefore sensitive to changes in water regimes, and increased nutrient loads.