Oysters are delicious and nutritious. They are also a keystone species and an ecosystem engineer, which means that they provide habitat for all kinds of other species, and they filter and clean the water around them, cycle nutrients, and even remove pollutants. Native to many parts of the world, Atlantic oysters are a species found from Louisiana to Maine. Rick Karney is a shellfish biologist and Director Emeritus of Martha's Vineyard Shellfish Group. Alex Friedman is owner of Snows Point oyster farm.