Zombies of the Nearshore: Metabolic Depression in Sea Urchin Barrens Associated with Food Deprivation

Abstract

Sea urchins can decimate coastal macroalgal forests, creating barren seascapes that can persist for decades or even centuries. The bioenergetic adaptations that allow urchins to persist in food-depauperate barrens remain poorly understood. We hypothesized that urchins reduce resting metabolism to increase energetic efficiency when faced with starvation. We compared energy reserves and mass-specific metabolic rate of red urchins, Mesocentrotus franciscanus, in barrens vs. kelp forests. Barren urchins had not only depleted energy reserves, but also depressed their metabolism by roughly 50% compared to nearby kelp forests. These observations suggest urchins utilize multiple energetic strategies to survive in food-limited barrens.