Good news for giant seaweeds

Just as trees form the backbone of many a terrestrial ecosystem, so too do macroalgae (seaweeds) play a critical role in providing food and shelter for marine organisms. Unfortunately, large canopy-forming seaweeds are in decline. I don’t want to point fingers, but ocean warming, overfishing and coastal urbanization are definitely implicated in those declines. 

These declines are bad news for the many creatures that make their homes or livings in or on the seaweeds. One species of seaweed, Phyllospora comosa, used to be abundant around Sydney, Australia providing resources for many of the local fisheries, including abalone. Unfortunately, the seaweed died off in the 1970s. Coincidentally, there was an excess of sewage discharged into the area at that time. 

Although the water  in the area has since been cleaned, P. comosa has not come back. Alexandra Campbell and her colleagues from the University of New South Wales set about remedying that problem. They attempted to transplant mature P. comosa seaweeds back to Sydney. 

Researcher tying P. comosa plants to the sea floor.

Giant seaweeds like P. comosa attach to the sea floor with their aptly named holdfasts. They don’t have a root system that you can bury in soil like you would if you were planting a tree. Therefore, to reestablish the P. comosa colony, the plants had to be tied to mesh matts with cable ties. In order to determine whether that procedure itself was overly traumatic, some of the plants were removed and then tied down in their original habitats. Other plants were left completely undisturbed.

Survival of algae that were translocated to Sydney was about 70%. This is about the same survival rate as that of totally undisturbed plants, suggesting that moving P. comosa to a new habitat is not harmful. Even more promising, the transplanted algae were able to successfully reproduce at their new site.

It is possible to clean a marine environment so that it’s once again suitable for its original inhabitants. The question is only whether we have the will to do so.


Campbell AH, Marzinelli EM, Vergés A, Coleman MA, & Steinberg PD (2014). Towards restoration of missing underwater forests. PloS one, 9 (1) PMID: 24416198.