Is it a sinker or a floater? And where does it go?
They're the questions AIMS scientists investigated when they recently studied the dispersal of Sargassum seaweed along the Ningaloo Coast in Western Australia.
The field trip was part of the Blue Carbon Seascapes Project , exploring the potential for Sargassum to reduce the severity of climate change by storing carbon in tropical seascapes.
The project is measuring how much blue carbon is flowing from Sargassum into sediment sinks along the coast and in the deep ocean, how long it is stored there, and how we can best protect and enhance this natural process.
AIMS senior research scientist Dr Eric Treml said the team focused on the Ningaloo Coast as a case study to understand the movement of Sargassum in the UNESCO World Heritage site.
"We're studying where the Sargassum travels when it breaks away from the natural meadows inside the lagoon," he said. "We measured Sargassum's buoyancy and mapped the ocean currents to determine where it drifts over time."
AIMS research scientist and co-lead, Dr Ronen Galaiduk, said they used satellite imagery to identify beaches where the seaweed was likely to have accumulated.
"We used satellites, drones and ocean drifters (that measure currents) to map where the algae were found," he said. "We mapped the drifting algal rafts and beach wrack (seaweed on beaches) at high resolution and estimated the sinking rates of detached Sargassum."
The team is creating a computer model to show how the blue-carbon-containing seaweed may move under different conditions and where it would likely end up.
Over eight days in the field, the scientists racked up some impressive achievements:
- 191 in-water observational surveys
- 243 shoreline surveys
- 11 dives
- 100 Sargassum buoyance trials
- three drone beach surveys covering 3ha at 1cm resolution
- Five oceanographic instruments deployed
- 20 bags of sour squirm lollies demolished (diving is hungry work).
The $20 million research project is jointly funded by AIMS and BHP.
