Brent Hughes, a doctoral candidate in ecology and evolutionary biology at the University of California at Santa Cruz, and colleagues have proven that sea otters provide a vital link to the recovery of seagrass beds in environmentally endangered estuaries in the Aug. 26, 2013, issue of the journal Proceedings of the National Academy of Sciences.
Sea otters were reintroduced to Elkhorn Slough in 1984. At that time no seagrass grew in Elkhorn Slough. By 2013 the seagrass had returned to levels of growth seen before 1984.
Sea otters eat crabs. As the population of crabs is reduced by sea otters, the number of sea slugs began to grow. Sea slugs are the primary food source for crabs. Sea slugs eat algae. The overabundance of algae was caused by runoff from farms and urban areas. The nitrogen nutrients in the runoff promoted algae growth in preference of seagrasses. The presence of a growing sea otter population reversed the effects of pollution on segrass beds.
About 100 sea otters were responsible for the 30 year recovery of the seagrass beds in Elkhorn Slough.
The researchers plan to use this evidence to promote the reintroduction of sea otters to other depleted estuarial areas improving both the life expectancy of the endangered sea otter and the seagrass beds.