Remove Sargassum
Why Are We Removing Sargassum?
The decline of kelp paved the way for the dominance of Sargassum horneri, an invasive algae species. Native turf algae also thrived without the competition and shading effects of kelp. As a result, kelp spores no longer have enough bare rock to settle naturally.
To address this challenge, we’ll evaluate various methods to identify the most efficient approach to removing Sargassum to create an ideal habitat for kelp to grow and thrive.
Step 1: Selectively Clear Sargassum
We've found that the best time to remove Sargassum is from October to early November when it's less than half a meter tall and has not entered its reproductive stage.
During the removal process, each diver is equipped with fine mesh bags that they'll fill one by one until the site is clear. Between November and March, we'll conduct bi-monthly dives to monitor the sites, removing and weighing any new Sargassum growth.
Step 2: Help Existing Kelp Thrive
Despite the spread of Sargassum, some kelp is naturally present at our restoration sites. The stormy weather during the winter of 2023 played a crucial role in dislodging boulders in shallow waters, thereby providing new “real estate” for kelp spore settlement. However, this kelp is struggling to grow in the Sargassum pastures.
We launched a "Kelp Rescue" plan to help new kelp recruits thrive. This plan involves removing Sargassum within one meter of the kelp and turf algae within half a meter of the holdfast at our study sites. After removal, we regularly monitor the area and measure new kelp growth.
Kelp Rescue in Action
Before: A strand of Giant Kelp is surrounded by a sea of Sargassum.
During: The team clears Sargassum and turf algae to conduct the “rescue.”
After: Giant Kelp has suitable habitat to thrive.