Back in the Water: LAW Divers Hunt Alien Seaweed

What we’re seeing and how we plan to remove it!

Author: Ian Jacobson, Dive Program Coordinator

LA Waterkeeper’s Dive Program has had a busy year. We’ve undergone a total transformation—shifting our focus from kelp forest restoration to addressing the invasion of the alien seaweed Sargassum horneri.

S. horneri, non-native algae that crept across the Pacific and invaded the giant kelp forests along the Southern California coast. Photo by Adam Obaza (NOAA).

After years of collaborative restoration efforts, how could we stand by as the “devil weed” S. horneri threatened the integrity of our kelp forests? We decided to take action—we launched a new dive project, centered on researching, mapping and eliminating sargassum from our coastline.

Our hard work paid off. We were awarded grants from the National Oceanographic and Atmospheric Agency (NOAA) and the Edgerton Foundation to help fund our project through 2018. We secured permits from the California Department of Fish and Wildlife that allow our dive team to remove sargassum. We launched a major outreach campaign and generated unprecedented public interest. And we’re back in the water.

Community Outreach

Our outreach efforts have raised awareness throughout Southern California about the dangers of the sargassum invasion. Local press got word of our efforts to thwart the invasive species and published an informative article following our inaugural dive.

LAW volunteers at Divers Day offer tips & tricks to correctly identifying Sargassum horneri

LAW volunteers at Divers Day offer tips & tricks to correctly identify S. horneri

Perhaps most importantly, our outreach focuses on training community members in identifying our target species.

Through our iNaturalist campaign, concerned citizens-turned-scientists can contribute to sargassum tracking efforts that have been underway since 2003.

Anyone can upload photos of their observations, which are then added to a map that includes data from the past 13 years. iNaturalist allows anyone the opportunity to contribute to this important research, and we can supply resources and tools to help community members identify the specific species on our radar. Our dive team frequently attends local events like “Divers Day” at the Aquarium of the Pacific, where we bring S. horneri specimens for show-and-tell.

Hitting the Water

LAW volunteer scientific divers prepare to conduct surveys to assess the spread of sargassum at potential removal site

LAW volunteer scientific divers prepare to conduct surveys to assess the spread of sargassum at potential removal site

Excellent dive conditions tend to follow the onset of the fall season, and we have certainly been taking advantage of them!

In September, LA Waterkeeper’s dive team was busy preparing to tackle the invasive algae S. horneri in the field. Our reconnaissance of Palos Verdes revealed that the more protected areas—that is, those that are less exposed to waves, like Malaga Cove—had significantly more sargassum adjacent to our native kelp forests. Since our goal is to determine how effective removing sargassum will be in the “fringe” areas where it has become abundant, we determined that Malaga Cove is an ideal location to carry out our experiment.

In October, we hit the water with full force: establishing our sites and collecting our first round of data that will be used to track the abundance of sargassum, plus a selection of native indicator species, through the duration of this project.

hannasurvey

Volunteer Hannah Ake surveying her quadrat in our Kelp Forest Reference Site. Photo by Adam Obaza (NOAA).

Our scientific divers headed out with transect tapes, quadrats, and data sheets in hand to survey the benthic community in both our removal and reference plots. As we continue to monitor our sites, we will be gearing up to begin removals in early 2017. We will be using the “Super Sucker” to allow us to efficiently remove sargassum without instigating any additional spreading. Once we remove sargassum from our sites, we will continue to track and monitor through 2018 to measure our effectiveness.

Stay tuned for more updates!

Questions? Contact Dive Program Coordinator, Ian Jacobson, at ijacobson@LAwaterkeeper.org

We have been seeing Green Abalone in our site and sometimes in our quadrats! Photo by Chris Glaeser.

We have been seeing Green Abalone in our site and sometimes in our quadrats! Photo by Chris Glaeser.

Contact Us

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

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

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