Welcome to the Island - Catalina's Rhodolith Beds

The Isthmus mooring field is a crowded place!

Getting ready for field work is no easy feat, especially when you kick of a 10-day expedition at 4 o’clock in the morning. But that’s just what the Edwards Lab, accompanied by Dr. Ju-Hyoung Kim from Korea, did in the pre-dawn humidity on July 10th. After doing our final checks to make sure all of our equipment was properly stowed, we piled into the lab’s suburban, 21ft dive boat in tow, and headed from San Diego to San Pedro. At around 6:30am we met up with Dr. Diana Steller and another graduate student from Moss Landing Marine Labs (MLML) at the Southern California Marine Institute. There we loaded our gear onto USC’s Miss Christy, the small mainland-Catalina ferry, and prepared to cross the water to Catalina Island.
            During the summers of 2016 and 2017 the Edwards Lab, along with the Konar Lab from the University of Alaska Fairbanks, studied productivity in kelp forests along the Aleutian Archipelago. This time we’re doing a similar study in another kind of algal-dominated community: rhodolith beds. Rhodoliths (rhodo meaning “rose”, but in this case “red algae” and lith meaning “rock”) are rock-like “balls” of coralline red algae that can form massive beds on soft sediments in clear water. These little “tumble weeds of the sea”, as PhD candidate Scott Gabara calls them, can support a rich diversity of marine organisms in nearshore environments (Gabara 2018).

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While the rest of the team headed off to Wrigley on the Miss Cristy, Pike, Dr Edwards and Scotty took the Stillwater Cove

Later that day, Di (red BCD) and Scotty survey the rhodolith bed along a transect

While kelp forests dominate temperate waters on rocky reefs, rhodolith beds thrive in sandy habitats, especially in protected sandy coves. Which, as it turns out, is an excellent place to establish a mooring field for boats. These moorings, where boats tie up overnight, are anchored to the ocean floor (known as the benthos) by heavy chains and massive concrete blocks. Scientists have known for a long time that these mooring chains can crush rhodoliths, turning the once vibrant beds into coralline rubble patches. Scott, who did his Masters on rhodolith beds with Dr. Steller, aka Di, at MLML, showed that benthic diversity is significantly greater inside the beds than outside.
            Which brings us to the purpose of this first of four expeditions to Catalina Island. In conjunction with Dr. Steller and several graduate students from MLML, the Edwards Lab plans on repeating our Collapsible Benthic Incubation Tent (CBIT) experiments inside and outside of rhodolith beds so we can finally understand just how productive these rolling red communities are. Di will be leading SCUBA surveys for diversity, and overall rhodolith community structure, while Ju-Hyoung will be conducting incubation experiments in the lab on individual rhodoliths, and the marine organisms that make their home among the algae.
            Our base of operations is USC’s Wrigley Institute for Environmental Studies, located adjacent to Two Harbors on the west end of Catalina. We’ve got two boats, the 21ft Stillwater Cove, and the 12ft inflatable Kenner (last seen in the Aleutians), 10 scientists and 10 days to learn as much as we can about rhodolith beds, the communities they support, and the consequences of their loss. Be sure to follow along for more rhodolith-related action!