|Title||Seasonal contrasts in carbon budgets and ecological processes on a tropical floodplain river in Northern Australia, Coast 2 Coast Conference, Darwin 2008|
|Year of Publication||2008|
|Authors||Pettit, NE, Warfe, DM, Bayliss, P, Davies, PM, Douglas, MD, Bunn, SE|
|Keywords||5: Foodwebs and biodiversity|
Tropical floodplains are highly productive ecosystems and flooding replenishes water supplies on the floodplain which boosts primary productivity. For floodplain rivers in the wet-dry tropics of northern Australia, predictable seasonal changes in hydrology are associated with dramatic increases and seasonal shifts in primary productivity. This review proposes a carbon budget for the Magela Creek floodplain to identify the important ecological processes and contrasting conditions between the wet and dry seasons. The quality of the autotrophic food source is important in aquatic systems and many studies have suggested a dominant role for algae in river food webs over other sources of carbon such as macrophytes. In tropical seasonal rivers, macrophytes produce more than half of the primary production on floodplains, but only contribute small fractions of the total carbon assimilated by consumers. What then happens to this large amount of carbon produced on the floodplain in the wet season? For much of the wet-dry tropics of northern Australia fire is a major consumer of plant biomass. For example, between 1996 and 2000, 25% of floodplains within Kakadu NP where burnt. For macrophyte biomass not consumed in fires the labile dissolved organic carbon leaches out and is quickly consumed by microbes and the remaining refractory material is probably consumed by microorganisms without being directly utilized in the upper food web. Epiphytic algae are most likely the predominant energy source for aquatic consumers and emergent macrophytes provide suitable substrate for these epiphytes. Macrophytes on the floodplain can however be an important source of energy for water birds. A generalised food web contrasting the wet season and dry season for Magela Creek, as a representative seasonal flooplain river in tropical northern Australia, is presented. This includes best guess estimates of the major sources, producers and consumers of carbon as well as important knowledge gaps.
Seasonal contrasts in carbon budgets and ecological processes on a tropical floodplain river in Northern Australia, Coast 2 Coast Conference, Darwin 2008