In 2017, the Environmental Water Knowledge and Research food web theme commenced a field program that set out to examine energy pathways among three habitats of a lowland river floodplain – wetlands, anabranches and the river channel. The work was carried out on the Ovens River in Victoria, and the chief objectives were to determine important energy pathways in food webs, as well as to assess the quality of food resources among the three habitats.

Ovens River floodplain anabranch. Photo credit: Catherine McInerney


Why is this important?

Thinking about food webs is useful for thinking about the relationships between different species within an ecosystem. Improving our understanding of how energy, nutrients and other resources are incorporated into food webs will increase our capacity to maximise the benefits of using water for the environment.

The relationship between wetlands, anabranches and rivers are of particular interest due to ongoing management efforts to connect these habitats using environmental flows which are being used to restore critical functional components of natural hydrological regimes.

Examples of the Ovens River system. Photo Credits: Paul McInerney

What we’ve learned so far

The results, recently published in the international journal of Limnology and Oceanology, have important implications for environmental water management in Australia. What we found was that the primary source of energy for animals in all three habitats was seston (planktonic material comprised of detritus, algae, and bacteria floating in the water column).  Interestingly, however, the food quality of seston differed between the three habitats; with floodplain habitats containing higher concentrations of omega 3 fatty acids that are essential for animal growth and survival.

The results suggest that inundation of floodplains and subsequent reconnection to the river could be important for two reasons:

  1. to mobilise high quality food resources from floodplains to the river.
  2. to allow riverine animals the opportunity to access high quality resources by moving onto floodplains.

The research demonstrates the importance of revealing both the quantity and quality of food resources into food webs, and the potential role of targeted environmental flows to re-establish critical energy pathways in riverine ecosystems.

Image: Exploring river and wetland food webs is often best done in mesocosms where we can control environmental factors such as temperature, depth and food sources. Photo credit: Ivor Growns

The work continues…

The work also highlighted a number of knowledge gaps in our understanding of how to improve food quality and quantity using environmental flows. These include optimum floodplain inundation duration and reconnection intervals, the influence of season and flow timing, and the potential limitation of fatty acids for consumers in river channels. These knowledge gaps have informed the generation of the new Flow-MER Food webs and water quality Theme research program, which will seek to improve our understanding in these areas.

Journal Article: Basal resource quality and energy sources in three habitats of a lowland river ecosystem

Published on Wiley Online Library here

In this paper, we demonstrate the importance of estimating the quality of organic matter fluxes into food webs, and the potential role of targeted environmental flows to re‐establish high quality energy pathways in riverine ecosystems.

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