Isotopic studies of food-web properties in Yanga wetlands, NSW Australia

Mazumder, D; Johansen, MP; Kobayashi, Y; Iles, J; Saintilan, N; Knowles, L; Hollins, SE

Isotopic studies of food-web properties in Yanga wetlands, NSW Australia

Date

2009-12-03

Authors

Publisher

Australasian Environmental Isotope Conference

Abstract

Floodplain wetlands provide habitats for a diverse range of species of terrestrial and aquatic biota, and perform important ecosystem functions. Overall productivity and biodiversity of floodplain wetlands is closely linked with water availability and environmental stability. Alternation flow regimes is a major threat to the functioning of food-webs and is responsible for a wide range of ecological responses, including biodiversity loss [1] diversion of energy flow [2] and is suspected to have influenced ecosystem functionality. Changes in land use, flow regulation and diversion for water resources, coupled with climate change have altered energy flow dynamics and structure of aquatic food webs. In the present study stable isotope ratios (δ13C and δ15N) of primary producers, sediment organic matter (SOM) and a variety of invertebrate and fish species are used to gain an understanding of the source of energy and trophic positions for aquatic species at various swamps in the Yanga National Park, lower Murrumbidgee River. A mass balance mixing model [3] was used to determine the fraction of food sources contributing to consumer diet. We also employed probabilistic simulation software (GoldSim) to better understand trends of trophic positions, dietary shifts and varying contributions from sources to consumers in swamps of the Yanga wetlands. We found that energy source varies between swamps in close proximity (in relative contribution of algae). Some trophic links are unaffected by this change (Fig.1) while for others a threshold may be crossed when diet shifts from predominantly benthic organic matter to algae. Over time food chain length is diminished as the floodplain wetland dries, drawing predators into competition. Natural systems are complex and highly variable thereby presenting difficulties and challenges for their effective management. Understanding the variability of the food web properties is important for effective management of the wetlands.

Keywords

Food chains, Wetlands, New South Wales, Australia, Habitat, Species diversity, Water, Environment, Ecosystems, Stable isotopes, Algae, Simulation

Citation

Mazumder, D., Johansen, M., Kobayashi, Y., Iles, J., Saintilan, N., Knowles, L., Hollins, S. (2009). Isotopic studies of food-web properties in Yanga wetlands, NSW Australia. Paper presented to the 10th Australasian Environmental Isotope Conference and 3rd Australasian Hydrogeology Research Conference, Resources and Chemistry Precinct, Curtin University, Perth, Western Australia, 1st – 3rd December 2009. In Grice, K. & Trinajstic, K. (eds), The 10th Australasian Environmental Isotope Conference and 3rd Australasian Hydrogeology Research Conference abstract volume : Resources and Chemistry Precinct, Curtin University, Perth, Western Australia, 1st-3rd December 2009, (pp. 9).