Macroalgal propagules do not survive digestion by the green sea urchin Strongylocentrotus droebachiensis

Faecal pellets from Strongylocentrotus droebachiensis fed on a diet of fertile macroalgal tissue were cultivated to test the hypothesis that propagules from selected species of macroalgae common in northern Norway survive digestion by S. droebachiensis. This hypothesis was tested on the brown algae Alaria esculenta, Fucus evanescens, and Pilayella littoralis, and the red algae Devaleraea ramentacea and Palmaria palmata. Faecal pellet cultivation from each macroalgal treatment was replicated at least 35 times. Two control treatments, one with fertile algal tissue and one with filtered seawater used to rinse the urchins, were each replicated at least 10 times. Our results indicate that propagules and tissue from the tested macroalgal species do not survive digestion by S. droebachiensis.