The basal food sources for Murray cod (Maccullochella peelii) in wetland mesocosms

• Published in: Journal of freshwater ecology Vol. 35; no. 1; pp. 235 - 254
• Main Authors: Growns, Ivor, Ryder, Darren, Frost, Lindsey
• Format: Journal Article
• Language: English
• Published: Philadelphia Taylor & Francis 01.01.2020; Taylor & Francis Ltd; Taylor & Francis Group
• Subjects: Agricultural management; Algae; Aquatic ecosystems; Aquatic invertebrates; Aquatic plants; Biomarkers; Birds; Chlorophyta; Consumers; Cyanobacteria; Diatoms; Ecosystems; Environmental management; Fatty acids; Fish; Flooding; floodplain wetland; Floods; Food; Food chains; Food sources; food web; Food webs; Freshwater; Hydrologic regime; Hydrology; Inland water environment; Invertebrates; Larvae; Maccullochella peelii; Marine microorganisms; Mesocosms; Murray Darling Basin; Prey; Soil; Water use; Wetland management; Wetlands; Zooplankton
• ISSN: 0270-5060; 2156-6941
• DOI: 10.1080/02705060.2020.1779140

The use of freshwater for human consumption and agriculture has resulted in many wetland ecosystems being some of the most seriously impacted ecosystems in the world. In attempts to rehabilitate wetland ecosystems environmental flows are used to restore parts of the hydrological regime altered by human water use. The use of environmental water intends to improve ecosystem health, but frequently aims to have specific outcomes for populations of higher-order consumers such as iconic fish and bird species. To date, research and monitoring has mainly focused on understanding 'flow-ecology' relationships, without investigating the mechanisms underlying them. We sought to understand the importance of different basal food sources to the growth of the endangered Murray cod in temporary wetland systems using fatty acid biomarkers. We flooded replicate mesocosms with two different wetland soils to produce sufficient zooplankton prey to sustain and grow Murray cod larvae for approximately 2 weeks. The fatty acid profiles of Murray cod and percentages of different biomarkers were compared at the start and finish of the experiment and our results suggest that the most important basal food source is green algae. However, the biomarkers of diatoms, cyanobacteria and bacteria also increased and differed between wetlands with different hydrological regimes. It is unclear if our results can be extended to other wetland systems and we encourage further research both into the relationship between length of wetland flooding and invertebrate densities in other systems. We also encourage research into the mechanistic pathways in which green algae carbon is transferred through food webs to higher order consumers in wetland systems to help generalise our results to other wetlands and support the management of wetlands through the timing and duration of flooding from environmental water.