Without the presence of sea otters, sea urchins would otherwise overgraze kelp beds, dramatically changing the marine community of which the urchins and otters are a part. for this reason, sea otters are considered a parasite a keystone species a predator an indicator specieswithout the presence of sea otters, sea urchins would otherwise overgraze kelp beds, dramatically changing the marine community of which the urchins and otters are a part. for this reason, sea otters are considered