The New York State Office of the Attorney General, through the Bronx River Watershed Initiative, has funded Carter Newell, a commercial shellfish farmer, and Rocking the Boat, a local youth-development organization, to install a raft in the Bronx River with ropes to catch and grow ribbed mussels. These mussels naturally live along the Bronx River shoreline, but have lost most of their salt-marsh habitat as human populations and industry have expanded along the river. Ribbed mussels now exist at much lower abundance than they did historically.
Mussels feed on plankton, and when they grow they incorporate into their shells and meat nutrients that are in excess in the urban waters around New York City. These excess nutrients come from sources such as wastewater and storm runoff. When the mussels are harvested, this harvest will also remove the excess nutrients from the environment that have been incorporated into their shells and tissue, thereby improving water quality for other marine life.
NOAA aquaculture scientists from the Milford Laboratory in Connecticut are helping to evaluate the effectiveness of these mussels at removing nutrients from the Bronx River. Such harvest of cultivated aquatic animals and plants for the purpose of removing nutrients from the environment is referred to as “nutrient bioextraction,” and this project in the Bronx River is one of the first in the region to test the effectiveness of this relatively new technology.
The ribbed mussel raft was installed in August 2011 and mussels were harvested in October 2012. The raft system is still being used as part of the co-located seaweed project.
1. Can ribbed mussels live on a commercial, blue mussel aquaculture raft?
Ribbed mussels naturally live on the shoreline, in salt marshes, and are regularly exposed to the air during low tide. When they are grown on a typical mussel raft they will be constantly underwater, so it was important to determine if this would interfere with their growth. Laboratory experiments with ribbed mussels showed that after three days of submersion, there were no differences in feeding between the intertidal and submerged mussels. These results have been reviewed and published in the scientific journal Aquaculture International (see link here). These results support the use of ribbed mussels for bioextraction purposes using traditional mussel aquaculture techniques.
2. Is mussel health impacted by living in such an urban environment?
The native ribbed mussel populations are being studied by a shellfish pathologist and compared to a population in a suburban environment to look at occurrence of physiological abnormalities and disease.
3. Is the Bronx River a good place to grow mussels?
Researchers from the Milford lab are trying to answer this question using a combination of water testing and experiments with native mussel populations. During the summer of 2012, water was sampled weekly for temperature, salinity, dissolved oxygen, dissolved and particulate nutrients, chlorophyll, plankton abundance and community composition. Once the sample analysis is complete, data can be combined with the monthly physical and chemical data from 2008-2012 sampled at Hunts Point by the New York City Department of Environmental Protection (for NYC DEP monitoring data see link here) to determine if environmental conditions remain within the tolerance ranges of ribbed mussels.
A series of feeding experiments with native mussel populations were performed during the summers of 2011 and 2012. These experiments allow NOAA researchers to determine how quickly and efficiently the mussels consume food that is naturally available in the water. These mussel feeding data can be combined with measurements of mussel growth at the site to estimate the impact of the raft as a whole on the local environment.
4. Are the mussels from the raft contaminated?
Harvested mussels will be sent to a contract laboratory and tested for a wide range of contaminants, including heavy metals, PCBs and flame retardants. These results can be compared to those from the nearby Throgs Neck Bridge, which is a long-term mussel contaminant monitoring site that is part of the NOAA Status and Trends program.
5. What do we do with the mussels once they are harvested?
Ribbed mussels are not eaten by people because of their poor taste, and the waters around Hunts Point are not approved for shellfish consumption. Therefore, alternative uses must be identified for future shellfish production from urban waters such as New York City. The NOAA Aquaculture Program funds an alternative finfish feeds program, based in the NOAA Northwest Fisheries Science Center. Harvested mussels from the raft have been sent to the NOAA Seattle Lab for evaluation as a potential fish feed. Other potential uses of bioextraction-related mussel meat are being explored in Sweden, and include chicken feed and compost.
Maine Shellfish R+D