Sargassum Abatement

Tom Boyd-S.horneri

Photo by Tom Boyd

There is a growing number of non-native species being introduced into the marine environment. Today, we are faced with Sargassum Horneri, an invasive species that has proliferated along the California coastline that is displacing native habitat, and threatening to undermine the kelp forest restoration we have worked so hard to accomplish. In 2003, this algae was introduced to our coastal waters in Long Beach harbor and has since spread as far north as Santa Barbara, south into Baja, and is now found on many of the Channel Islands. Originating in the warm waters of Japan and Korea, Sargassum’s distribution and persistence along the West Coast has generated concern as it poses a potential serious threat to our native ecosystems.

Continuing LA Waterkeeper’s mission to protect and restore our marine resources through community action and fieldwork, Waterkeeper launched a new dive project in 2015 to contribute to the understanding of how sargassum is impacting our nearshore ecosystems.

In Phase I of this effort, LAW:

  • Utilized our team of experienced scientific divers to document and assess the impacts of the invasive algae Sargassum horneri on rocky reefs along the Los Angeles coastline, prioritizing the region’s most ecologically sensitive areas;
  • Educated and engaged the local community, including recreational divers, boaters, and beachgoers, to increase their awareness and participation in the documentation of horneri; and
  • Worked with our partners to develop recommendations on how to effectively reduce the impact of horneri along the Los Angeles coast.

Through our Phase I efforts, LAW combined existing data and more detailed SCUBA surveys of S. horneri along the Los Angeles coast; evaluated locations for control; empowered an informed public who can contribute to monitoring efforts through I-naturalist; and provided the public and decision-makers with information needed to slow the spread of S. horneri.

Phase II involved hands-on removal efforts from fall 2016 through spring 2018.

LAW also aims to work with like-minded groups across Southern California and collaborate on strategies that address S. horneri along the entire Southern California Bight. Developing a model for invasive species control and prevention in conjunction with establishing a network of organizations and trained divers from the community will allow us to rapidly respond to future non-native invasions.

Have you seen any sargassum?

Help contribute to tracking efforts that have been underway since 2003. Click here to upload photos of your observations to our iNaturalist sargassum tracking map!


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LA Waterkeeper
120 Broadway, Suite 105
Santa Monica, CA 90401

Phone: 310-394-6162
Fax: 310-394-6178

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