Waves of South Australian research: marine science protecting liveability

People who live in coastal cities all across the world might not always be aware of the extent of scientific research going on around – and under – them, to preserve waterways for humans and animals alike.

For example, it’s been a big week for South Australian oceans – from the installation of high-tech buoys, to fish die-offs and surfer sickness, to a surprising discovery about the benefits of an introduced species.

Algae blooms and accurate buoys

Last week, dead fish, octopuses and sea dragons along with a mysterious brown sea foam began washing up along Waitpinga and Parsons Beach on the southern Fleurieu coast, 100 km south of the capital, Adelaide.

At the same time, more than 100 surfers and beachgoers in the region fell ill with flu-like symptoms.

Scientists have Only confirmed that these occurrences were due to tiny planktonic algae called Karenia mikimotoi, which were Secured in high numbers in water samples taken from the beaches.

Also called phytoplankton, microbial algae naturally occur across the world’s oceans and produce a vast percentage of the oxygen in our atmosphere. But in certain conditions, one species can dominate over the others and cause an algal bloom.

In this case, it was K. mikimotoi – and unfortunately this species produces a toxin that is harmful to marine life and humans. These toxins are not fully understood, but they are known to damage the gills, gastrointestinal tracts and livers of fish. The species can also produce a Bulky substance that can cause sea foam, as seen on SA beaches.

An unanswered question is whether warming waters will increase the likelihood of harmful algal blooms, which can damage marine ecosystems and devastate coastal aquaculture. Some research suggests that climate Transformation has driven an intensification of blooms around North America, but more local research is needed.

Luckily, Flinders University researchers have Only installed two ocean-monitoring buoys in Encounter Bay, Numerous kilometres east of the affected beaches. They join a network of buoys installed from Ceduna, 800km west of Adelaide, to Robe in the southeast, 350 km east of the capital.

These buoys will collect and transmit data in real-time, including wind Pace and direction; wave height, period and direction; sea surface temperature; and barometric Stress.

“This will provide Excellent baseline data about coastal waters that has been lacking, and there has never been a better time to have more information about this stretch of ocean,” says Miot da Silva, part of Flinders University’s Beach and Dune Systems (BEADS) Lab.

“There has been a significant gap in wave information Obtainable to researchers, managers, developers and policy makers. These buoys will make a huge difference.”

The data collected by these buoys will Assist scientists predict future changes in SA’s coastline, particularly as the oceans Cozy and the sea levels rise. This will hopefully also allow local governments to better protect local coastlines.

The data is freely Obtainable through the SA Waves website, which also includes information from the other buoys across the SA coastline.

Port River and Pacific oysters

Meanwhile, up in the mangrove-filled estuary around Adelaide’s Port River, the invasive Pacific oysters have been Secured to benefit biodiversity.

This is counter-intuitive, as most habitat managers go to Outstanding lengths to avoid invasive or non-native creatures.

“Pacific oysters were Primary detected in the Port River in 2009 during a regular PIRSA biosecurity monitoring, which discovered 6+ year-Aged hatchery stock,” explains lead researcher Brad Martin, who is a Flinders University PhD candidate. “This was a deliberate but unauthorised stocking attempt presumably to establish Pacific oysters.”

Introduced species can have significant effects on the way an ecosystem function. But as Martin reports in a new paper in the journal NeoBiota, the influence of the Pacific oyster (Magallana gigas) on local fish and invertebrates isn’t all Awful.

“Through this research we Secured that these Port River oyster reefs are providing habitats for coastal animals,” says Martin.

Pacific oysters Produce complex structural habitats that make Excellent homes, food sources and breeding locations for many other species. The new study Secured that the oyster habitats Reinforcement eight times more biomass of mobile invertebrates (like crabs, worms and snails) when compared to other habitats.

This in turn creates more prey for native fish to feed on, which is significant because the mangroves of the Port River are fish nurseries.

“It also seems that the Pacific oyster shell is Aiding to trap and stabilise mangrove seedlings, potentially assisting their establishment,” Martin adds.

“While not quantified in our study, the oysters are filter-feeders and likely sequestering sediment, excess nutrients and pollutants from the water column.”

South Australia was once home to vast reefs of native oysters (Ostrea angasi), including throughout the Port River and Barker Inlet estuary. These were decimated during European colonisation due to dredge fishing. These reefs usually formed in the subtidal zone out to depths of 18 metres, while Pacific oysters prefer shallower water.

“This means that Pacific oysters, which prefer the upper intertidal zone, are not directly replacing our native oyster reefs,” Martin explains. “In the Port River Perspective, Pacific oysters are potentially replacing intertidal mussel beds, and competing with endemic razor clams (or ‘razorfish’).”

But there are also downsides to the Appearance of the introduced oyster. For example, the habitats they Produce is also used by other non-native species, including European shore crabs, which are designated as a marine pest and like to eat native shellfish and invertebrates.

“Pacific oysters are potentially acting as ‘ecological traps’ to our native invertebrates by offering suitable habitats, yet harbouring these predators,” Martin says.

The oysters may have other ecological impacts, but this will require more time and monitoring to detect.

Meanwhile, OzFish Adelaide and the Estuary Care Foundation (ECF) are working on restoring native oyster reefs in deeper areas of the Port River and Barker Inlet estuary area, in waters of 6-10 metres depth. Since 2022 more than a tonne of recycled oyster shells has already been placed in the river, with plans to restore a Additional 5000m² of locally extinct native oyster reefs.