Horse Mussel Reefs in the Bay of Fundy

Horse mussel (Modiolus modiolus) reefs are formed when the shells of dead mussels mix with sand and mud to form mounds, on top of which live mussels grow. Images of the seafloor show multiple rows or mussel reefs that are up to 4m high, 40m wide and 1km long...that's higher than the ceiling in the average room and larger in area than an average city block!The Bay of Fundy is the only place on earth where reefs of this size formed by horse mussels have been found

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Similar to coral reefs, mussel reefs can provide habitat for other species. They also help in nutrient exchange by filtering food from the well-mixed waters of the Bay of Fundy, and then supplying nutrients in the form of waste products to the seafloor.

The main threat to horse mussel reefs is damage from physical impacts such as trawling, dredging or aggregate extraction.


In Canada, absolutely no protection measures have yet been implemented to ensure that these globally significant and little-known features off the Bay of Fundy seafloor are maintained.

Much remains to be known and many questions remain to be answered about the horse mussel reefs and the role they play in the Bay of Fundy ecosystem. However, we do know that these reefs are a unique, and significant marine feature, and they play an important ecological role in the marine environment of the Bay of Fundy. Because of this, it is important to ensure that we can maintain these reefs and ensure that they are not significantly damaged or destroyed.