Seaweed valued by agriculture more prolific than thought

Scientists have closed the data gap that will transform the cultivation of Asparagopsis, a seaweed set to revolutionise methane reduction in livestock.

Asparagopsis armata is a red seaweed being used as an emerging solution to reduce livestock methane production. The seaweed is endemic to southern Australia and New Zealand and occurs on shallow coastal reefs around Tasmania.

Sea Forest are the only Tasmanian company producing seaweed as a feed supplement for livestock to reduce methane emissions. Researchers from the University of Tasmania’s Institute for Marine and Antarctic Studies (IMAS) have collected data which will assist Sea Forest in identifying target sites that will produce high-quality Asparagopsis.

Over 12 months, scientists collected samples from 15 sites across five regions to determine where it is most abundant and reproductive, the hosts it attaches to and genetic variation. This has established a crucial baseline data set for future management, which was published in an IMAS report released today.

IMAS seaweed ecologist and project lead Associate Professor Jeffrey Wright says it was previously thought the seaweed was seasonal, but the new research has found otherwise.

“Southeastern Tasmania appears to be the perfect place to grow Asparagopsis. Most sites we sampled in the southeast region have Asparagopsis year-round and some sites had consistently high abundance,” he says.

“This has significant implications for management and aquaculture. It suggests there are sites where seed stock could be obtained and grown year-round. This contrasts with most other regions in Australia where Asparagopsis is a spring and early summer ‘annual’ and can only be grown in the ocean during that narrow seasonal window.”

Using an underwater towed video camera, photographs and dive surveys, researchers found southern and eastern regions had higher Asparagopsis abundance compared to the North Coast and Furneaux Group.

“Nearly 95% of Asparagopsis is epiphytic, which means the seaweed will grow on the surface of another ‘host’ seaweed species,” Wright says. “We recorded 56 different seaweeds as hosts, which suggests that maintaining healthy seaweed forests is important for Asparagopsis.”

Researchers also found two distinct genetic lineages of Asparagopsis in Tasmania, genetically separate enough to be considered a different species.

“One lineage is found throughout mainland Tasmania, while the other is specific to the Furneaux Group. This has implications for the independent management of populations within the Furneaux Group and within the rest of Tasmania.”

Sea Forest chief scientist Professor Rocky de Nys says research will provide Sea Forest with key information to inform critical decision making as the company continues to grow.

“Our goal is to create positive environmental outcomes not just through livestock methane abatement but also in the marine environment we rely on,” de Nys says.

Article first published in University of Tasmania News.

It’s not just seaweed being valued on Tasmania’s seabeds