Ribbed Mussels: The hero of our estuarial ecosystem
(Geukensia demissa)
Along the shores of our estuarial environment, at least where bulkheads haven’t been built, there live some truly wonderful creatures you’ve probably never heard of: ribbed mussels. These tough mussels live partially buried in the muck, and don’t look like much. But they play a huge role in the ecosystem that is our precious coastal waters. Here are just a few important facts about this amazing species:
Ribbed mussels play three very important roles in our estuaries — so much so that, in my opinion they should be considered a keystone species. Indeed, on that count they are an underdog, but I’m rooting for them!
The three important roles they play:
Holding the banks together so that they don’t erode, even during a hurricane. Ribbed mussels are very tough. Adult ribbed mussels partially bury themselves in the mucky banks. They pack themselves tightly (up to ~2,000 per square yard) and hang on tight using dense protein bysses (a tuft of tough silky filaments with which they adhere to rocks and other objects.).
Because of this, the grasses are kept from being eroded away during the frequent storms we have here along the coast. They actually attach to the base of the grass stems, keeping them from floating away in a storm. What’s more, as a byproduct of their filter feeding, they deposit fecal material on the surrounding sediment, which stimulates the grass to grow.
If you are walking along a bed full of ribbed mussels, I dare you to try to pick one up. They are simply too strong!
Cleaning the water. One ribbed mussel can filter water at a rate of 6.8 liters an hour. In high tide, they open up and draw in water, filtering out algae and other particles. Here along the coastline, this is especially important because agricultural and increasingly non-permeable surfaces due to development both cause runoff, increasing the nutrients, contaminants, and particles in the water. This filtering allows other species to live within the estuary. They can even be used to restore wetlands that have been compromised.
In a 2011 study conducted by NOAA, researchers used ribbed mussels in an industrial area, not far from a sewage treatment plant. They found that a 20 X 20-foot mussel raft would clean an average of three million gallons of water and remove about 350 pounds of particulate matter daily. And the mussels thrived.
Providing food. Because they do such a great job collecting pollution, they aren’t good to eat, for humans. But blue crabs, clapper rails, willets and dunlins, and raccoons love them and rely on them. So you can thank a ribbed mussel when you sit down to a feast of crab claws.
More facts about ribbed mussels:
They can live for about 15 years. You can count a mussel’s age by counting the annual ridges on its shell.
They grow 2 to 4 inches in length. They have glossy, ribbed shells that vary in color from olive or yellowish brown to black.
They are tough! They can survive extreme water temperatures from -7.6 to 104 degrees F. they can survive salinities from 5 to 100 parts per thousand. They are photosensitive and can respond to the shadows of predators by closing their shells tighter.
Spawning occurs once per summer. During spawning, its gender can be determined by the color of its mantel: females tend to be brownish and males cream or yellowish. Larvae eventually settle and develop.
