Shellfish aquaculture is gaining acceptance as a tool to reduce nutrient over enrichment in coastal and estuarine ecosystems through the feeding activity of the animals and assimilation of filtered particles in shellfish tissues. This ecosystem service, provided by the ribbed mussel (Geukensia demissa), was studied in animals suspended from a commercial mussel raft in the urban Bronx River Estuary, NY, in waters closed to shellfish harvest due to bacterial contamination. Naturally occurring populations of ribbed mussels were Observed to be healthy and resilient in this highly urbanized environment. Furthermore, mussels 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. Spat collection efforts from shore and within the water column were unsuccessful; this was identified as a key bottleneck to future large-scale implementation. Filtration experiments indicated that a fully stocked G. demissa raft would clear an average 1.2 x 10(7) L of Bronx River Estuary water daily, removing 160 kg of particulate matter from the water column, of which 12 kg would be absorbed into mussel digestive systems. At harvest, 62.6 kg of nitrogen would be sequestered in mussel tissue and shell. These values compare favorably to other resource Management recovery methods targeting agricultural and stormwater nitrogen sources.