Sea Otters Help Seagrass Meadows Thrive

Sea otters are iconic members of Pacific coast habitats. They are frequently associated with kelp forests where they feed on predatory urchins, but are lesser known for living among seagrasses. Now, a new study shows that these otters not only help foster more diverse seagrass beds, but that the duration of their presence does as well.

When otters are in seagrasses, they dig around in the mud for food items like clams, leaving cavities in their wake. These mud pits are attractive spots for new seagrass shoots to grow. Essentially, sea otters are creating prime real estate for seagrass meadows to prosper.

What is especially important about the indirect benefits of sea otters is that their presence changes the way that seagrasses are reproducing. Just as strawberries are known for doing, seagrasses can effectively produce runners that result in clones of themselves that grow up close to the parent plant.

Alternatively, they can release reproductive cells (gametes) and produce offspring with the help of other seagrasses. This latter option – sexual reproduction – is what likely results in seagrasses occupying the pockmarked mud left behind by the otters and ultimately leads to more genetically diverse seagrass beds.

This study shows that large animals can impact their surrounding habitat in ways that benefit not only themselves, but the other species they share it with.

Lead author Erin Foster describes these findings as a “rediscovery”, as it seems that Indigenous Seri people have long known to harvest seagrass from beds that otters had disturbed.

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