California’s Changing Ocean: Curious Observations in 2020

By Maxwell Seale, Reef Check California’s Central Coast Volunteer Coordinator

This year, Reef Check divers made several important observations beyond the data that they collected during over 100 surveys along the coast. Together these are a sign of how California’s coastal ecosystems are changing. At the beginning of this survey season, Reef Check Volunteer Melanie Moreno reported the first-ever evidence of Sargassum horneri in the Monterey Bay. Sargassum horneri, also known as Devil Weed, is an invasive species of seaweed native to the coasts of Japan and Korea. It was first found in Southern California in 2003, and a northward expansion of this algae could spell dire straits for Central California’s kelp forests already under heavy pressure from growing urchin barrens and increasing ocean temperatures. A new urchin barren was reported in the Point Buchon State Marine Reserve, in the shallows of Montana De Oro.

In addition to Sargassum, another continued range expansion was documented this year. Several crowned urchins were observed in a number of locations along the Monterey Peninsula where we reported the first known observation of Centrostephanus coronatus north of the Northern Channel Islands in 2016. Continuous sightings of this urchin could indicate the Central Coast is undergoing “Tropicalization.” This process describes a poleward shift of the distributions of species as the temperature of the ocean is rising due to climate change.

Further evidence that the Central Coast is undergoing Tropicalization is the continued observation of the Finescale Triggerfish, Balistes polylepis. Reef Check Volunteer Claes Nordahl observed this Triggerfish hiding in an urchin barren along the Monterey Peninsula. Rarely observed along the Central Coast, this species has a wide range but is generally associated with warmer waters. 

The Central Coast is not the only place where evidence for Tropicalization is growing. In Southern California, divers have also reported large schools of this Triggerfish in abundances greater than previously observed. This year on surveys around Catalina Island, Reef Check divers observed four sea turtles over just a single week! In recent years, the Eastern Pacific Green Sea Turtle, a species common off the coast of Mexico, has expanded its range into San Diego and the Channel Islands. In the same week, the team also observed massive schools of Pacific Barracuda, Sphyraena argentea. This historically overfished stock is now abundant in the Santa Barbara Channel again.

Beyond changing oceanographic conditions, many species are still struggling to survive a variety of ecosystem pressures. Tristin McHugh, North Coast Regional Manager along with Kelp Forest Restoration Program Staff Morgan Murphy-Cannella and Ian Norton documented the continued persistence of the sea star wasting disease occurring on a large, predatory Sun Star Solaster stimpsoni. The team observed this star in the Van Damme State Marine Conservation Area (SMCA) with the same disease that brought the largest sea star in the world, Pycnopodia helianthoides, to the brink of extinction. The now critically endangered Sunflower Star has been added to the IUCN Red List this month and Reef Check divers have not seen any individuals of this once abundant species along the California coast in recent years.   

All these sightings add to the growing body of observations that indicate the impacts of a changing climate on California’s kelp forests and the need to protect and conserve our coastal ecosystems.