"The Influence of Rhodolith Algae on Life History of the Painted Urchin, Lytechinus pictus"
A Thesis Defense by Celine de Jong
Live-Stream | May 6th, 2025 at 4:00 pm PDT
Abstract
Rhodolith beds are globally distributed hotspots of diversity and productivity and serve as nursery habitats for some marine invertebrates. Poorly understood is whether rhodolith beds are nurseries because invertebrate larvae actively select them for settlement or migrate to them at later life stages. We studied the nursery role of rhodolith beds for the painted urchin, Lytechinus pictus at Santa Catalina Island, CA, USA. Subtidal surveys showed that in areas with greater live rhodolith cover, urchin density increased as well as mean urchin size. In caged substrate choice experiments, urchins selected rhodolith substrate relative to carbonate sand, supporting the notion that urchins congregate in rhodolith beds after they have settled. To evaluate whether beds also serve as nurseries by inducing settlement, urchin larvae were assessed following exposure to six cues: live and dead rhodolith, biofilm-inoculated sand, GABA, KCl, and filtered seawater. Live rhodolith induced the strongest settlement response across all treatments, initiating 2.5x greater settlement compared to the inducement control of KCl after 24 hours. Larvae also settled faster in the presence of live rhodolith substrate than other treatments. These results highlight the importance of rhodolith beds for multiple life stages of L. pictus, by inducing settlement of larvae and supporting post-larval individuals. Rhodolith beds receive minimal protections globally, due to limited research on their ecological importance. However, recognizing their role as nursery habitats strengthens the case for the inclusion of rhodolith beds in future management decisions.
Bio
Native to the Greater Seattle Area of Washington state, Celine found herself drawn to the sparkling waters of Monterey Bay and earned her BSc. in Marine Biology from the University of California, Santa Cruz in 2018. As an undergraduate, she worked extensively as a scientific research diver and laboratory technician for multiple university-based operations and has contributed data to long-term projects aimed at exploring mechanisms of kelp forest resiliency and ecosystem dynamics - specifically relating to urchin barren patch distribution throughout central California. In addition to her field contributions, she has been actively involved with various community outreach initiatives revolving around marine conservation and science education; notably as a science advisor for the Hydrous and teaching assistant for the Wildlands Studies Big Sur field course, focused on the conservation and preservation of coastal systems.
Co-advised by Dr. Amanda Kahn and Dr. Diana Steller, Celine joined MLML in the Fall of 2021 and investigated nursery potential of rhodolith beds for benthic invertebrates, specifically those on Santa Catalina Island, CA. When not wearing her science hat, Celine can be found tending to her garden, trying new recipes, hiking, camping, diving, or looking for washed up treasures on the beach.
