Murray-Darling Basin Environmental Water Knowledge and Research Project: Food Webs Theme Research Report

The EWKR food web theme identified that the relationship between flow variability and the provision of resources for consumers at critical life stages was a key knowledge gap in the management of environmental flows. The first phase of the EWKR food web theme (the conceptualisation phase) reviewed existing conceptual models and empirical research to assess our current knowledge status and the knowledge gaps surrounding the influence of flow on lowland river food webs. This work generated three scientific manuscripts that identified a framework for monitoring the effects of hydrological regimes on food webs, evaluated a range of analytical methods suitable for their assessment and highlighted that consideration of food web-hydrology interactions will improve environmental flow planning.
Empirical research carried out within the EWKR food web theme set out to address knowledge gaps identified within the conceptualisation phase. This work was undertaken at three scales: 1) mesocosm (an outdoor experimental system that examines the natural environment under controlled conditions) 2) river and 3) basin. Mesocosm experiments showed that green algae are a key basal resource for consumers, providing a high-quality food source. Essential fatty acids were traced from green algae through Food Webs from invertebrates to fish. Dissolved organic carbon (DOC) based Food Webs by contrast, provided the lowest invertebrate density, richness and lowest fish growth and survival.