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The relative importance of top-down and bottom-up control on primary production in a dryland-tropical river | TRaCK: Tropical Rivers and Coastal Knowledge

TRaCK: Tropical Rivers and Coastal Knowledge

Science and knowledge that governments, communities, industries for sustainable use of Australia's tropical rivers and estuaries

The relative importance of top-down and bottom-up control on primary production in a dryland-tropical river

TitleThe relative importance of top-down and bottom-up control on primary production in a dryland-tropical river
Publication TypeConference Participation
Year of Publication2010
AuthorsFaggotter, SJ, Burford, MA, Balcombe, SR
Keywords4: Material Budgets
Abstract

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.

URLhttp://aslo.org/santafe2010/