Scuba diving scientists delve into underwater seagrass meadows to sample the health of Geographe Bay

Scuba diving scientists delved into underwater seagrass meadows last month to sample the health of Geographe Bay’s ecosystem.

Scientists from Edith Cowan University and divers from the Department of Biodiversity, Conservation and Attractions dived into seven seagrass sites across Geographe Bay to build on more than a decade of research.

The researchers measure seagrass health by laying metal quadrats down in the seagrass and counting the shoots within the square.

Measuring shoot density over time gives an indication of whether seagrass meadows in the bay are improving or declining in condition.

They also measure the algal growth on the seagrass leaves and take samples to process for nutrient content.

The scientists said they were pleased with preliminary results after two days of diving and sampling with the underwater ecosystem looking to be bouncing back from a slump in 2023.

In the 2023 report, researchers said six of the seven sites showed a decline in shoot density, with Busselton Jetty and Port Geographe decreasing more than 20 per cent.

However, this trend reversed last year with only the Dunsborough site seeing a small decline.

Edith Cowan University research fellow Ankje Frouws said shoot density for all seven monitoring sites had increased or stayed the same as 2024 as per early assessments.

“We saw significant increases in shoot density for the Vasse Diversion Drain and Busselton Jetty seagrass meadows, and also a reduction in algal cover at many sites,” he said.

Seagrass meadows also provide an important nursery ground for fish, protect the coast from erosion and act as carbon sinks.

ECU Associate Dean of Research and program lead Kathryn McMahon said having long-term sites and annual monitoring was crucial to ensuring declining trends are noticed.

“Having the ongoing sponsorship from Water Corporation is critical to the success of the program and helps ensure early detection of any changes to seagrass health,” she said.