River to landscape connections and biodiversity

This project delivered new understanding of the contributions of floodplains to the maintenance of biodiversity and fish biomass in river-floodplain systems, meeting both pure and applied scientific objectives. The outputs of the project can feed directly into wetland management and conservation planning processes, providing end users with methods and tools to quantify the importance of different landscape elements towards overall system biodiversity.

Linkages among habitats and movements of materials across ecosystem boundaries often have major implications for the production of animal and plant biomass and resultant biodiversity.  Fully-aquatic species which typically inhabit the river channel, floodplain billabongs and estuarine waters in the dry season move onto floodplains during the wet season.  As these floodwaters recede, aquatic production that has been assimilated by consumers such as fish is often transferred back into the river systems and exported offshore. These types of subsidies can therefore represent a significant transfer of aquatic carbon and nutrients from floodplains to other parts of the river system and indeed to other aquatic systems over hundreds or thousands of kilometers. Yet it is very difficult to quantify the importance of these linkages and movements.  By measuring sources of energy and trophic level of predators along with underlying sources of production such as algae, and the movement patterns of key fauna species, this project generated ecosystem-level science needed for management.

Project activities involved the following:

Food webs

  • Used stable isotope techniques to trace the chemical signatures of food through the food web.

Remote sensing

  • Mapped long-term seasonal connectivity of flooding and vegetation patterns using remote sensing techniques.

Algal productivity

  • Measured and mapped the sources of algal abundance which support aquatic food webs.

Fish movement

  • Tracked the movement and connectivity of large predators across the aquatic landscape using radio tracking techniques.

For the floodplains of the Alligator Rivers region within Kakadu National Park the project delivered:

  • clarification of the food web implications of water resource development by quantification of the importance of different habitats in sustaining fish and other consumers in river-floodplain systems;
  • remote sensing methods to map, monitor and asses the seasonal connectivity between catchments, floodplains and coastal receiving waters;
  • methods to identify and map seasonally available ‘hotspots’ of floodplain primary productivity that are critical to the maintenance of  food webs, and implications of the loss of such habitats;
  • understanding of the movement patterns of key fauna that use floodplains and the freshwater-saltwater interface in estuaries; and
  • a global context on how the predictability of flood magnitude and timing drives ecosystem responses in tropical floodplain riverscapes.

The project study area comprised the Alligator Rivers Region within Kakadu National Park in the wet-dry tropics along the coastal zone of northern Australia. This region includes the iconic Kakadu National Park which has been designated as internationally important under criteria established by the Ramsar Convention on Wetlands. 

Estuarine crocodiles in a tropical coastal floodplain obtain nutrition from terrestrial prey

Adame F, Jardine T, Fry B, Valdez D, Lindner G, Nadji, J & Bunn S. 2018. Estuarine crocodiles in a tropical coastal floodplain obtain nutrition from terrestrial prey. PLOS ONE. 13. e0197159. 10.1371/journal.pone.0197159.

Gut-content and stable-isotope analyses provide complementary understanding of ontogenetic dietary shifts and trophic relationships among fishes in a tropical river

Freshwater Biology, Pusey, BJ, Jardine, TD, Davis, AM, Blanchett, ML, Pearson, RG, 08/2012

Carbon from periphyton supports fish biomass in waterholes of a wet-dry tropical river

Jardine, T., Hunt, R., Faggotter, S., Valdez, D., Burford, M., & Bunn, S. (2013). Carbon from periphyton supports fish biomass in waterholes of a wet–dry tropical river. River Research and Applications, 29(5), 560-573. doi: 10.1002/rra.2554

Carbon from periphyton supports fish biomass in waterholes of a wet-dry tropical river
Assessing the seasonal dynamics of inundation, turbidity and aquatic vegetation in the Australian wet-dry tropics using optical remote sensing

Ward, D., Hamilton, S., Jardine, T., Pettit, N., Tews, E., Olley, J., & Bunn, S. (2013). Assessing the seasonal dynamics of inundation, turbidity, and aquatic vegetation in the Australian wet–dry tropics using optical remote sensing. Ecohydrology, 6(2), 312-323. doi: 10.1002/eco.1270

Assessing the seasonal dynamics of inundation, turbidity and aquatic vegetation in the Australian wet-dry tropics using optical remote sensing
Productivity, disturbance and ecosystem size have no influence on food chain length in seasonally connected rivers

Warfe, D., Jardine, T., Pettit, N., Hamilton, S., Pusey, B., Bunn, S., Davies, P. and Douglas, M. 2013. Productivity, Disturbance and Ecosystem Size Have No Influence on Food Chain Length in Seasonally Connected Rivers. PLoS One,8(6):1-11. doi: 10.1371/journal.pone.0066240

Understanding and overcoming baseline isotopic variability in running waters
Omnivory and opportunism characterize food webs in a large dry-tropics river system
Organic matter sources and size structuring in stream invertebrate food webs across a tropical to temperate gradient
Kakadu Floodplain Inundation Frequency Map
A guide to sharks of Kakadu Rivers
Largetooth sawfish information sheet

Overall the project was led by Professor Stuart Bunn from Griffith University who led the food web component.  The remote sensing and algal productivity components were led by Dr Douglas Ward from Griffith University with input from Dr Neil Pettit from the University of Western Australia.  The fish movement work was led by Dr David Crook from Charles Darwin University.

The research team included researchers from Griffith University, Charles Darwin University, the University of Western Australia and the Environmental Research Institute of the Supervising Scientist.

The research team would like to acknowledge the support and involvement of Park’s Australia’s staff at Kakadu National Park and traditional owners from the Alligator Rivers region.

Project Leader:
Prof Stuart Bunn
Australian Rivers Institute
Griffith University
[email protected]