Monitoring of selected wetlands associated with Lock 8 and 9 weir pools on the Murray River, Final Report

"June 2009".

Project Number: Monitoring of wetlands disconnection in New South Wales: Locks 8 and 9 weir pool manipulation - M/BUS/252.

MDFRC item.

1 of 2 reports associated with project see (Weir Pool Manipulation (In-channel and wetland effects) - Report on Pre-drawdown Monitoring: Weir Pools & Wetlands).

The Murray-Darling Freshwater Research Centre (MDFRC) was engaged by the former Murray-Darling Basin Commission, to undertake ecological monitoring of nine wetlands connected to Locks 8 and 9 weir pools on the Murray River. These two were under consideration to be drawn down as a water saving measure during the drought which would result in disconnection of the wetlands from the Murray River. The aim of the monitoring program was to (i) identifying water quality threats; (ii) monitor the response of fish and macrophytes in response to the disconnection; (iii) assessing the response of tree condition to changing water levels. The MDFRC undertook monitoring of fish, aquatic and riparian vegetation and water quality within the nine wetlands between December 2007 and December 2008. During this period the expected drawdown of the weir pools did not eventuate and disconnection of the wetlands from the Murray River did not occur. This report summarises the data obtained from the monitoring program, however, interpretation of the data needs to consider that only four sampling events occurred within the 12-month period. Conclusive comments on the communities associated within and between wetlands cannot be made given the limited number of sampling events and short time frame, any statistical analysis undertaken would not detect any differences. Any differences observed could be through natural variability due to seasonality or life cycle processes. Key findings from this monitoring are: -Sediment within five of the wetlands had low pH (<4.5) indicating the presence of sulfidic sediments. -The water quality parameters measured were within expected levels for wetlands. -An abundant and relatively diverse native fish community exists within the wetlands -- Nine native fish species and four introduced species were recorded. -- Two of the native fish (Silver perch and Murray cod) are listed under either State or Federal legislation as vulnerable. -A total of 55 aquatic plant species were recorded from all wetlands. -In general, the condition of tree canopy condition across all sites was moderately stressed.