Up and down the California coast, purple sea urchins have devastated kelp forests. In Southern California, hundreds of acres of the underwater giant kelp forests, Macrocystis pyrifera, have been devoured, leaving bare rock coastal terrain devoid of habitat for lobsters and high-value fish species, such as bass and sheepshead.
Jeremy Claisse, associate professor of biological sciences, and Chelsea Muñoz Williams (’21, master’s in biology) are coauthors on a new study, published in the April 15 issue of the Marine Ecology Progress Series, that provides strong evidence that deliberate efforts to remove urchins can be a key strategy in bringing back giant kelp forests and the high-value commercial marine species they support.
The research included a decade of annual surveys off the Palos Verdes Peninsula starting in 2011, led by the Vantuna Research Group based at Occidental College. Claisse helped develop the project while he was a postdoctoral researcher and adjunct faculty at Occidental. Muñoz Williams joined the team as an undergraduate.
After the initial surveys, purple urchin culling on test sites began in 2013. Halfway through the study, in 2015, a local outbreak of a bacterial infection known as “black-ring disease” nearly wiped out the purple urchin in both the test and control plots, making it possible to study what would happen if human efforts to reduce urchin populations were equally successful. In just six months after the first signs of urchin die-off, rocky reefs returned to a kelp-dominated condition and stayed vigorous until the end of the study.
The positive result demonstrates that human culling efforts of purple urchin can be successful in pushing urchin-devastated rocky reef ecosystems back over their ecological tipping point and allow giant kelp forests to flourish.
Nearly one-quarter of all California marine organisms depend on giant kelp forests for some portion of their life history. Among the fish whose populations have rebounded with kelp restoration is the bright orange Garibaldi, the official state marine fish of California. Other species include kelp bass, sheephead, lobsters, abalone and red sea urchins, which produce roe (known as uni) that is often used in sushi.
The increased red urchin population has greater roe production and returns to being viable for the fishery. This provides motivation for commercial urchin fishermen to become involved in restoration efforts and actively contribute to ecosystem restoration, researchers noted in the study.
In addition to Muñoz Williams, Austin Pyles (’17, environmental biology; ’21, master’s in biology)) and Jacob Eagleton (’16, biology; ’21, master’s in biology) collected data for the study as scientific divers for the Vantuna Research Group’s kelp forest monitoring team for the last three years. Muñoz Williams estimates that she dives more than 200 times a year on ocean monitoring projects.
Cal Poly Pomona students interested in marine biology and scuba training have great opportunities on campus. In addition to marine biology and ecology classes, students earn their initial “Open Water” recreational diver certification at a discount through the BRIC, which also offers an Advanced Open Water course and, in normal years, scuba trips during spring break.
“Within the CSU, it’s really unusual to have a robust recreational scuba training program like we do at the BRIC,” said Claisse.
Both Pyles and Eagleton began their scuba certifications this way and then earned their American Academy of Underwater Sciences (AAUS) scientific diver certification through the CSU Ocean Studies Institute, which enabled them to participate on the kelp forest monitoring team.
“Our students have the opportunity to work as marine biologists while they are getting their degrees,” said Claisse. “We have partnerships with many nonprofit groups and state and federal agencies and work to create opportunities for our undergrad and graduate students to gain experience and then find employment as marine biologists in Southern California.”
Undergraduates can take a variety of field biology classes where they can go out on boats and collect data, learn about aquatic sampling or take a spring break trip to Hawaii or Panama.
Muñoz Williams is a research associate and grants manager with the Vantuna Research Group, and Eagleton was recently hired full-time as a research associate. Ben Grime (’21, master;s in biology), who worked in Claisse’s marine lab and wrote his thesis research focused on how sea urchins have fared in the restored kelp forest sites, is now a marine program manager for the Bay Foundation, a Los Angeles-based non-profit working to restore coastal marine environments.
Claisse is also associate director of the Vantuna Research Group which has conducted the longest continual time-series studies of rocky reefs in the world and the largest spatial-scale studies of reefs in the Southern California Bight. He joined the group in 2009 as a post-doctoral researcher.