A new sea otters and seagrass study reveals that the otters aren’t just swimming around out there looking cute. The adorable crab-eating marine mammals also protect the health of vanishing seagrass meadows in at least one California estuary.
The Santa Cruz Sentinel talked to one of the researchers who worked on the sea otter and seagrass study in Eklhorn Slough in North Monterrey County, California. According to ecologist and doctoral candidate Brent Hughes, the discovery that sea otters preserve seagrass was unexpected.
Many coastal waters in California and around the nation are threatened by agricultural runoff. Fertilizer causes algae to bloom, killing the seagrass. Then the fish don’t have any seagrass nurseries where they can lay their eggs.
Yet Elkhorn Slough is still supporting plenty of seagrass.
And crab-eating sea otters seem to be the reason why. According to a Los Angeles Times report, the crabs would normally eat sea slugs. But when the numbers of crabs are controlled by the otters, then there are more sea slugs.
And it turns out that the sea slugs eat algae off the seagrass leaves, allowing them to thrive despite the high levels of agricultural runoff in the estuary.
At one point in the early 20th century, sea otters were hunted nearly to extinction for their fur. By the early 1980s, the seagrass had nearly vanished because of competition from algae fed by the fertilizer runoff.
However, the US Fish and Wildlife said that sea otters — and seagrass — began to return to Eklhorn Slough around 1984. So their data would seem to support Brent Hughes’ findings.
Sea otters are now poised to expand even further. It will be interesting to see if the rise in sea otter numbers leads to a rise in the seagrass nurseries in other areas offshore California.