Research Highlights Role of Sunflower Sea Stars in Kelp Forest Restoration

SANTA CRUZ, Calif. — A recent study conducted by ecologists and undergraduate students at the University of California, Santa Cruz, has revealed the potential role of sunflower sea stars (Pycnopodia helianthoides) in the revival of kelp forests, which have been severely impacted by overgrazing from sea urchins. Published on July 9, 2023, in the Proceedings of the Royal Society B, the research indicates that the presence of sunflower sea stars may create a 'landscape of fear' that deters red sea urchins from consuming kelp, thus aiding ecological recovery efforts.

Kelp forests serve as critical marine ecosystems, providing habitat for a myriad of species and contributing an estimated $500 billion annually to the global economy through various industries, including pharmaceuticals and food production. However, these underwater forests have been declining significantly since 2013, a period marked by the local extinction of sunflower sea stars due to a catastrophic wasting disease. The loss of these stars has been linked to the explosion of sea urchin populations, leading to extensive kelp bed degradation along the Californian and Oregon coasts.

In the study, lead author Rae Mancuso and her team utilized scientific diving techniques to investigate whether sunflower sea stars could effectively deter sea urchins from feeding on kelp. The research was conducted in the waters near Sitka, Alaska, where the team set up experiments involving cages containing kelp and either sunflower sea stars or left empty as controls. Results showed that red sea urchins kept a distance of approximately six feet from kelp in the presence of sunflower sea stars, contrasting sharply with green sea urchins, which displayed no such avoidance.

Kristy Kroeker, a professor of ecology and evolutionary biology at UC Santa Cruz and senior author of the study, emphasized the significance of the findings, stating, "These are very hungry urchins that are dissuaded enough by the scent of a sea star to deter grazing on kelp forests, which is promising for thinking about their role in kelp-forest recovery." The study suggests that reintroducing or conserving sunflower sea stars could be a viable strategy for kelp forest restoration without necessitating manual removal of urchins by divers.

The research team, which included contributors from Oregon State University and the University of Oregon, highlighted the need for further studies to explore the broader implications of sunflower sea stars on other urchin species, particularly the purple sea urchin, known for its destructive grazing habits. Kroeker noted, "While our results are promising, there remain many unknowns that need to be addressed before we can generalize about the reintroduction of Pycnopodia for kelp-forest recovery."

The study was funded by the Nature Conservancy and the National Science Foundation, underscoring the collaborative efforts in marine ecological research aimed at restoring crucial ecosystems. As kelp forests continue to face threats from climate change and overgrazing, this research provides valuable insights into potential natural solutions for their revival and highlights the interconnectedness of marine species in maintaining ecological balance.

This finding not only contributes to the growing body of literature on marine ecology but also emphasizes the importance of conservation efforts for sea stars, which could play a pivotal role in the health of marine ecosystems. The work of UC Santa Cruz students in this research exemplifies the potential for undergraduate involvement in significant scientific discoveries, fostering a new generation of ecologists committed to environmental stewardship.