Project number: 2017-056
Project Status:
Completed
Budget expenditure: $199,990.00
Principal Investigator: Justin Brookes
Organisation: University of Adelaide
Project start/end date: 30 Jun 2017 - 30 Dec 2018
Contact:
FRDC

Need

The National Carp Control Plan (NCCP), operating within the Fisheries Research and Development Corporation (FRDC), is developing a plan for the potential release of the virus known as Cyprinid herpesvirus 3 (CyHVto control invasive common carp, Cyprinus carpio, in Australian freshwater environments.
If the carp virus is approved for release, major carp mortality events are likely and the degradation of carp carcasses is likely to release a considerable amount of nutrients into the water column. Given the enormous biomass of carp in the Murray Darling Basin it is unlikely that this biomass will all be removed in a ‘clean-up’. Consequently, a strategy will be required to ensure this increase in nutrients does not become problematic. Of particular concern is ensuring that these nutrients do not fuel cyanobacterial blooms, which can compromise water quality by the production of toxins, and compounds that taint the taste and odour of water.

Preliminary work has been carried out at the University of Adelaide measuring the remobilisation rate of phosphorus from decaying carp tissue. This work needs to be expanded and incorporated into prediction of phytoplankton growth in the Murray Darling System to determine how this will support algal growth. Nutrients will interact with flow to determine phytoplankton abundance, species dominance and succession. The bloom forming cyanobacteria in the Murray Darling Basin tend to dominate under warm, stable stratified conditions. Consequently flow can be used as a strategy to ensure mixed conditions in the rivers and a greater likelihood that nutrients will be directed into phytoplankton species other than cyanobacteria.

Objectives

1. The aim of this work is to:1. Determine the flux rate and mass of nutrients (nitrogen and phosphorus) from decaying carp2. Determine the flow conditions in a range of rivers in the Murray Darling that allow temperature stratification to develop so that a flow and mixing criterion can be developed3. Use the hydrodynamic-biogeochemical to predict 4. Conduct a whole wetland experiment to assess DO, water quality and cyanobacteria risk

Final report

Author: Justin Brookes
Final Report • 2019-10-18 • 25.69 MB
2017-056-DLD.pdf

Summary

This investigation was undertaken by the University of Adelaide and the University of Western Australia as a part of the research priorities for the National Carp Control Plan. While proposed biological control agents to reduce carp numbers may have positive impacts to aquatic ecosystems, it is possible that wide-spread carp mortality may present considerable risks to the quality of water in Australian wetlands and waterways that need to be managed. Specifically, large-scale carp mortality in aquatic systems will lead to the generation of: 

  • High oxygen demand
  • A pulse of fish-derived nutrients

There is a concern that these impacts will generate water quality risks for humans and ecosystems associated with persistent low oxygen (hypoxia and anoxia), excessive levels of ammonia, and the build-up of cyanobacteria blooms, including the associated challenges of cyano-toxin release, and further deoxygenation during bloom collapse. This study modelled risks to water quality that could arise from carp inputs to a representative set of Australian waterways using data from field and laboratory trials.

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