Mesocosm Experiment Photos: Darren Ryder, University of New England

Food Web Research

The Basin Plan objectives include the protection and restoration of ecosystem functions in recognition of their importance to sustaining the health of water dependent ecosystems. There are a number of ecosystem functions including food webs, connectivity, and nutrient cycling. While all ecosystem functions are important, there is growing evidence to suggest that flow modification has affected production and availability of food to support native fish and waterbirds. As a consequence, protection and restoration of water dependent ecosystems will be improved if we understand how flows influence the amount and type of food.

When an animal eats a plant or another animal, it is consuming them to gain energy. Food webs describe how this energy moves through an ecosystem. The main purpose of the Food Web Theme is to improve our understanding of how environmental flows may be used to influence both the productivity of important energy sources (plants, algae and microorganisms) and the transfer of this energy through the food web to consumers, particularly to fish and birds. Research into food webs is inextricably linked with each of the other research programs.

Research focus

The research will investigate which environmental flow regimes can best support the food webs necessary for successful breeding and independent survival of waterbirds and fish (known as ‘recruitment’), and whether there are any clear spatial or temporal patterns.

The research seeks to understand the influence of water flow on food webs and whether there are ‘hotspots’ in the landscape that may be critical to protecting native fish or waterbird populations. It is expected that the influence of flow and ‘hotspots’ may vary between sites and, in recognition of this, the project will seek to understand how flow responses vary across the Basin.

It will also identify other stressors that might disproportionately affect food-web processes related to fish and waterbird recruitment. These will encompass land-use change, invasive species, water turbidity and suitable substrates.

Our approach

To uncover the gaps in current knowledge of food-web dynamics in the Murray–Darling Basin, the Food Webs research team consulted environmental water managers and scientists through structured meetings and informal communications, and also reviewed existing published knowledge.

The project seeks to answer two broad questions. First, what energy resources (plants, algae, microorganisms) support the production of food for larval fish and waterbird chicks. This question will be addressed through analysis (isotopes, fatty acids and amino acids) of the diets of important food sources. Once we have an understanding of the critical energy sources we will be able to address the second question concerning the presence of ‘hotspots’. This question will be addressed through our current understanding of the influence of flow on production, but also field sampling and analysis of remotely sensed images.

The Food Web research program will carry out field and experimental tests to clarify the relative magnitude of the various energy (food) pathways related to fish and waterbirds, and identify changes over time.

What will the research be used for?

Improved understanding of food web responses to environmental flows will enable managers to:

  • Improve quantification of waterbird and fish recruitment water requirements.
  • Identify groups that are critical to energy flows along food chains supporting fish and waterbird recruitment.
  • Identify ecosystem components or habitats that are critical to achieving environmental flow outcomes.
  • Predict the outcomes of a range of scenarios and management interventions.

Research Activities

Our field researchers will use a number of techniques to collect empirical data, including:

  • Laboratory studies to determine energy production and transfer through the food web. This will involve assessing a range of substrates (such as leaf litter, woody debris, plants) to identify the critical basal resources supporting zooplankton productivity in lowland rivers. Experiments will be undertaken in replicate 75 L tanks which will be stocked with natural communities of zooplankton from the Murray River.
  • Field sampling to identify critical energy pathways to taxa of interest, reveal spatial and temporal variability in productivity, and identify important areas.

Field sampling Photo: Jessica Davison

  • Field work and laboratory-based experiments to assess the potential role of stressors (invasive species, water quality, habitat loss) in determining productivity of different habitats in relation to water flow.

PDFFact sheet 8. Work summary (2030 KB)