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Trophic ecology of an abundant kelp forest echinoderm, the bat star Patiria miniata

Daniel M. Cryan*, Natalie H. N. Low, Steven Y. Litvin, Craig W. Osenberg, Fiorenza Micheli

*Corresponding author:

ABSTRACT: Echinoderms often play key roles in structuring marine ecosystems. The bat star Patiria miniata is an abundant kelp forest echinoderm whose trophic ecology has been understudied. Understanding Patiria’s trophic role is important given the recent declines of many sea star populations due to wasting disease. Patiria was largely unaffected by these outbreaks and could potentially fill the trophic niches left by other ecologically important sea star species. In this study we used a combination of feeding experiments and stable isotope analysis to provide new insights into the trophic ecology of Patiria miniata. Given Patiria is considered an omnivorous generalist, we conducted a series of feeding experiments in which we quantified consumption rates for a wide range of reported prey items. Consumption rates were highest for different types of carrion, lower for sessile invertebrates, and negligible for all species of macrophytes. In a series of follow-up experiments we found that food deprivation did not lead to demonstrable consumption of macrophytes by Patiria, but that the presence of epiphytes significantly increased consumption rates (presumably of the epiphytes plus incidental consumption of macrophytes). Finally, we compared Patiria’s isotopic niche with that of a carnivore (the giant sea star Pisaster giganteus), an herbivore (the purple sea urchin Strongylocentrotus purpuratus), and a detritivore (the warty sea cucumbers Parastichopus parvimensis) and found that Patiria occupied the highest relative trophic level and was isotopically most similar to Pisaster. Altogether, our results suggest that Patiria’s diet is narrower and more carnivorous than previously expected.