Background
The frequency and severity of extreme events such as marine heatwaves, cyclones and flooding along Australia’s West Coast is increasing, however, the impact of such events on marine ecosystems cannot be determined without sufficient baseline data. For example, 36 percent of the total seagrass area in Shark Bay is thought to have died in the catastrophic marine heatwave of 2011, however there is uncertainty around these figures due to the lack of available baseline data.
Baseline information on the distribution, structure and function of macroalgal forests and seagrass meadows in Shark Bay is needed to measure the impact and cumulative effect of extreme events, when they occur.
Seagrass and macroalgae provide habitat and refuge for numerous organisms and comprise the basis of marine and coastal food webs. They also sequester and store large amounts of carbon, so understanding the relationships between their density, species composition and carbon stocks (vegetative parts such as leaves and fronds, as well as soil) is vitally important.
To generate baseline data on the distribution, structure and function of benthic macrophyte dominated systems (macroalgal forests and seagrass meadows) in Shark Bay, Western Australia. The project is a collaboration between CSIRO and the Department of Biodiversity, Conservation and Attractions (DBCA) who are the agency responsible for managing the marine protected areas comprising the Shark Bay World Heritage Area.
Voyage
Priority areas across Denham Sound (Shark Bay) were surveyed, many for the first time, collecting fundamental data to improve our understanding of the structure and function of seagrass and algal habitats.
Drone mapping and seagrass health assessments; experiments (seagrass flux measures), and data collection (seagrass biomass, sediment cores, invertebrate samples, and soil carbon cores) was undertaken at each of the five sampling locations visited on the 5 days voyage.
Outcomes
The collected data comprises a much-needed baseline of benthic vegetated ecosystems in Shark Bay and will advance scientific understanding about the role of benthic diversity, carbon cycling and the consequences for extreme events, such as Marine Heatwaves. Indeed, there are currently two manuscripts in preparation that are expected to be published in the second ½ of 2024 or early 2025.
The science spanned broad fields of research including carbon sequestration, habitat distribution and post heatwave recovery, biogeochemistry and the habitat and nutritional function of seagrass meadows for invertebrate and fish communities. The selected sites included priority areas (identified by CSIRO and DBCA) that have been difficult to access with existing resources (due to distance and costs) and hence the program greatly advanced the scale and scope of seagrass ecosystem research in Shark Bay.
