What’s been happening in the wetlands?

Scientists presented their findings from experiements they have been conducting in the Geographe waterways at a community forum on Friday.
Scientists presented their findings from experiements they have been conducting in the Geographe waterways at a community forum on Friday.

A forum was held on Friday to update the community on science projects that were being conducted in the Vasse-Wonnerup Wetlands and Lower Vasse River.

The projects were undertaken as part of work being conducted by the Vasse Taskforce and the Revitalising Geographe Waterways program.

Eight scientists from the Department of Water, Department of Parks and Wildlife and Murdoch University presented findings from their projects in the waterways.

Many of the scientists found what was done at the floodgates had an impact on the Vasse Estuary. Department of Water mathematical modeller Peta Kelsey worked with a team that used hydrodynamic models to help manage the Vasse estuary.

The team trialled opening the flood gates and fish gates to monitor the salinity levels in the water and found the longer they were opened the further it pushed a salt wedge into the estuary.

The team found this gave pollutants more time to come out of the sediment, but when the fish gates were only opened for 20 per cent of the time they found it improved the water quality by prolonging stratification.

In another experiment, scientists found when the water warms phosphate is removed from the water and the phytoplankton population increases, which could cause algae blooms to occur.

The algae blooms could be caused by human disturbance including fertiliser from farms, urban mulch and septic tanks, and when blooms occurred in high numbers it could cause problems for fish deaths.

Scientists found 88 species of of phytoplankton in the estuary during summer, a high proportion of these were harmful and said it would not be practical to have different management actions for each species.

Another trial which had a positive outcome for the water quality was using oxygentation technology upstream of the Vasse surge barrier.

Department of Water environmental officer Ryan Kam said oxygenating water ensured the sediment was aerobic, reduced nutrients and odour and degraded organic matter. It also provided oxygen for fish to live.

Mr Kam said similar techniques used in the Swan River showed if water was oxygenated long enough it would get back to a healthy state requiring less oxygenation.