During the latest Live Mollusk Count promoted by the National Shell Museum & Aquarium on March 11, organizer and Associate Director of Education Jorden Falker found two complete shells (paired valves) of the Green Mussel (Perna viridis). The shells, found at low tide on the east end of Sanibel Island, were discovered tangled in seaweed. The hinged shell and remnants of the soft bivalves’ bodies inside hint that the mussels died recently and came from a nearby location.
shells from Lighthouse Beach, Sanibel, Florida. Illustration: José H. Leal
The Green Mussel originates from the Indo-West Pacific region, but was introduced, probably via ship hulls and/or ballast water, to the western Atlantic Ocean and other coastal waters of the world’s oceans. The first known occurrence of Green Mussels in the United States was in Tampa, in 1999. Since then, the species has spread along the coast of the Gulf of Mexico and the eastern coast of Florida, apparently never approaching the high densities sometimes observed in its native areas, where they can reach hundreds and even thousands of individuals per square meter.
Perna viridis
on a dock piling at the south end of Marco Island, Florida, 2023. Photo: Amy Tripp
Yet, the Green Mussel is considered an invasive species, as it is not indigenous to the Atlantic Ocean and can certainly have negative impacts on native species and their environment. Invasive species have the potential to compete with and negatively affect local species and, in the particular case of Green Mussels, to foul and clog marine equipment and to introduce parasites and diseases to other marine organisms. Please let us know if you see Green Mussels in your local coastal areas!
shells from Fort De Soto State Park, Pinellas County, Florida; Illustration: James F. Kelly
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