Schematic of nutrient removal by mussels. Source: American Chemical Society

Algal blooms, oxygen depletion and reduced ecosystem diversity are attributed to nutrient enrichment in coastal waters. The use of native shellfish to filter excess nitrogen from such impacted waters was demonstrated by researchers from the U.S. National Oceanic and Atmospheric Administration (Milford, Conn.), Shellfish R&D (Damariscotta, Me.) and Rocking the Boat (Bronx, N.Y.).

The ribbed mussel (Geukensia demissa) was tested for its water purification prowess in an urban environment. Specimens were suspended from a commercial mussel raft in a section of the Bronx River Estuary of New York City, N.Y., closed to shellfish harvest due to bacterial contamination.

Naturally occurring populations of these mussels were observed to be healthy and resilient in this highly urbanized environment. Those grown suspended in the water column contained substantially lower concentrations of heavy metals and organic contaminants in their tissues than blue mussels (Mytilus edulis) collected at a nearby benthic site.

The researchers estimate that a fully stocked raft would clean an average of 3 million gallons of water and remove about 350 pounds/day of particulate matter. Almost 140 pounds of nitrogen were also potentially removed when the animals were harvested.