I can't give a professional biologist answer here, but having both classes in oceanography and just doing a quick google search, mussel beds are nurseries for fish, and are essentially the intertidal community and are the mainstay reason for metabolic and productivity in the intertidal zones ( because of mussels )

And just like how we can export water, you can also import water to supply a city - I never said refilling Lanier back up, I just said import a water supply so that people can still cook and bathe on a ration system till the rain comes. You can always drink bottled water. In fact, Coca-Cola imports thousands upon thousands of gallons of water daily in from Alabama from artesian wells.

Mussels do serve a purpose, they're the base to a very large ecosystem.