Restoring Balance: Dr. Galloway on Predatory Sea Stars and Kelp Forest Regeneration

Welcome to another episode where we dive into the undercurrents of our world's oceans. Today, we're joined by Dr. Galloway, who will share fascinating insights into the ecosystem dynamics of the North American west coast. Recently, a collapse in predatory sunflower sea star (Pycnopodia helianthoides) populations due to Sea Star Wasting Disease (SSWD) has coincided with an explosive proliferation of sea urchin barrens, leading to a concerning decrease in kelp forests. Dr. Galloway's research tackles the potential role that recovering Pycnopodia populations could play in kelp forest regeneration by consuming nutritionally poor purple sea urchins (Strongylocentrotus purpuratus) typical of barrens. Dr. Galloway's experiments reveal that Pycnopodia consume an average of 0.68 S. purpuratus per day, and interestingly, they seem unable to chemically distinguish between starved and fed urchins. They even demonstrate higher predation rates on starved urchins due to shorter handling times. By using a model and sensitivity analysis, Dr. Galloway shows that even minor recoveries in Pycnopodia populations could lead to a reduction in sea urchin densities consistent with kelp-urchin coexistence. These findings emphasize the vital role of Pycnopodia in regulating purple sea urchin populations and maintaining healthy kelp forests through top-down control. Join us as we explore the fascinating world of marine ecosystems, and learn how the recovery of predatory sunflower sea stars could be a key step towards restoring kelp forests at ecologically significant scales. Whether through natural means or human-assisted reintroductions, the return of this important predator might be the ray of hope these underwater forests need.Sunflower sea star predation on urchins can facilitate kelp forest recovery https://doi.org/10.1098/rspb.2022.1897