The closest most people get to seaweed is an unsettling brush against the leg during a swim at the beach, or a snagged fishing line while trying to hook a winner.
But the ecological importance of the marine plant should not be ignored, say researchers who warn some species are in decline.
In waters around southern Tasmania, kelp forests which favour cool waters are being impacted by warming, Institute for Marine and Antarctic Studies associate professor Catriona Hurd says.
"What was a major habitat 20 years ago is almost endangered now ... and it shows what could happen in other areas," Hobart-based Prof Hurd told AAP on Tuesday.
Along with being home to thousands of species of invertebrates, seaweed also generates about half of all marine energy.
"Oceans are like a global sinkhole for carbon and seaweed acts like an underwater forest," Prof Hurd said.
Kelp in particular is essential for continued marine life diversity.
"If the kelp is not there to slow the water and provide a conducive environment, you lose the habitat."
The breakdown of seaweed into "flakes" also supplies feed for popular shellfish such as oysters and mussels.
Human action is proving the greatest threat.
"Land use changes increase nutrients from agricultural and urban run-off, and increase sedimentation, thereby reducing light and inhibiting attachment and development of seaweeds," Prof Hurd said.
Foreign species of seaweed introduced by international shipping and other human activities are also invading Australia's marine environment.
As a hot spot for warming, Tasmania's seaweed stocks are being hit hard, with water temperatures having risen by some two degrees celsius, Prof Hurd added.
Some of the 400-plus species of seaweed found in Tasmanian waters are exclusive to the island state.
Five years of research by Prof Hurd has resulted in Tuesday's release of a new textbook - Seaweed Ecology and Physiology - the first in its area of expertise in 20 years.
Including contributions from international researchers, the book looks at how seaweeds respond to local and global environmental change.
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