Sea Weeding Helps Corals Grow

Volunteers help clean up beaches and ocean waters around the world. But some volunteers are doing a very specialized type of ocean cleaning. This unique group of senior citizen volunteers are cleaning seaweed off of coral reefs to help the reefs regrow and recover.

The sea weeding is part of a project led by  James Cook University senior research officer Hillary Smith and Professor David Bourne (JCU and Australian Institute of Marine Science), according to a press release from the university. James Cook university is located in Queensland, Australia.

The coral renewal project is being conducted jointly with the Earthwatch Institute program, and began in 2018.  The project volunteers are working on two experimental plots on the Great Barrier Reef off the coast of Magnetic Island. The results of the first three years of the project were recently published in  the Journal of Applied Ecology.

How seaweed effects corals
Coral reefs have been suffering from warmer water temperatures, major destructions from cyclones, as well as human intervention from shipping and pollution, according to The Conversation. This leads to the reefs dying off and as corals die, seaweed begins to grow in their place.

When seaweed – a tough algae – starts to grow, it begins to take over the reef and this destroys the fragile ecosystem. Coral larvae cannot thrive because of the chemicals that are emitted by seaweed, so the coral continues to die.  Fish also tend to avoid areas that have dense seaweed.

Many  reefs have been badly damaged by seaweed including some sites on the Great Barrier Reef off the coast of Magnetic island which have been dominated by macroalgae (a form of seaweed). That’s when scientists came up with the idea of weeding the reefs by hand, like weeding a garden, to help restore the areas of the reef that were damaged by seaweed.

The results of the project
The volunteer weeding project in Australia has shown up to a 600 percent coral regrowth, according to the press release. At the same time, there was no change in the coral cover in other sections of the reef that were not weeded.

“We have yet to see a plateau in coral growth within these plots at Magnetic Island, which is characterized as one of the degraded reefs on the Great Barrier Reef,” Smith said in the press release.

“We also found an increase in coral diversity, so this method is benefitting a wide range of different coral types. Every time we return, the seaweed is growing back less and less, so this method could provide [a] lasting benefit without requiring endless effort.”

The project has been so successful that Earthwatch Australia would like to scale up and clean more of the reef. The research team is now scoping out other areas to clean. The senior citizen volunteer project at  Magnetic Island will be running until 2025.

“A project like this enables people to take ownership of their local environment and also makes them aware that there are small things they can do to help our planet,” Smith said.