Sea urchin intestinal bacterial communities depend on seaweed diet and contain nitrogen-fixing symbionts.

Kelp deforestation by sea urchin grazing is a widespread phenomenon globally, with vast consequences for coastal ecosystems. The ability of sea urchins to survive on a kelp diet of poor nutritional quality is not well understood and bacterial communities in the sea urchin intestine may play an important role in digestion. A no-choice feeding experiment was conducted with the sea urchin Strongylocentrotus droebachiensis, offering three different seaweeds as diet, including the kelp Saccharina latissima.