TRaCK: Tropical Rivers and Coastal Knowledge

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

Consumer-resource coupling in wet-dry tropical rivers

TitleConsumer-resource coupling in wet-dry tropical rivers
Publication TypeJournal Article
Year of Publication2012
AuthorsJardine, TD, Pettit, NE, Warfe, DM, Pusey, BJ, Ward, DP, Douglas, MM, Davies, PM, Bunn, SE
JournalJournal of Animal Ecolocy
Start Page310
Date Published03/2012
Keywordsbiofilm, energy sources, floodplain, food webs, gut contents, Hydrology, stable isotope analysis

1. Despite implications for top-down and bottom-up control and the stability of food webs, understanding the links between consumers and their diets remains difficult, particularly in remote tropical locations where food resources are usually abundant and variable and seasonal hydrology produces alternating patterns of connectivity and isolation.

2. We used a large scale survey of freshwater biota from 67 sites in three catchments (Daly River, Northern Territory; Fitzroy River, Western Australia; and the Mitchell River, Queensland) in Australia’s wet–dry tropics and analysed stable isotopes of carbon (d13C) to search for broad patterns in resource use by consumers in conjunction with known and measured indices of connectivity, the duration of floodplain inundation, and dietary choices (i.e. stomach contents of fish).

3. Regression analysis of biofilm d13C against consumer d13C, as an indicator of reliance on local food sources (periphyton and detritus), varied depending on taxa and catchment.

4. The carbon isotope ratios of benthic invertebrates were tightly coupled to those of biofilm in all three catchments, suggesting assimilation of local resources by these largely nonmobile taxa.

5. Stable C isotope ratios of fish, however, were less well-linked to those of biofilm and varied by catchment according to hydrological connectivity; the perennially flowing Daly River with a long duration of floodplain inundation showed the least degree of coupling, the seasonally flowing Fitzroy River with an extremely short flood period showed the strongest coupling, and the Mitchell River was intermediate in connectivity, flood duration and consumer–resource coupling.

6. These findings highlight the high mobility of the fish community in these rivers, and how hydrological connectivity between habitats drives patterns of consumer–resource coupling.