Nutrient Mitigation

Quartermaster Harbor on Vashon Island is a shallow, circulation-restricted bay with development within the watershed and along its shoreline. The poor circulation of the bay combined with a suite of waste and stormwater inputs has led to low oxygen conditions creating a eutrophic marine system. As a result, this condition has altered habitat and species diversity and reduced estuary function causing the Department of Health to close most of the harbor to shellfish harvest.

PSRF is working with the community of Vashon to build a creative strategy that mitigates for the chronic nutrient inputs in Quartermaster Harbor, engages Vashon residents in the recovery of healthy marine resources, and develops market-based mechanisms for cleaning Puget Sound. In the spring of 2011, PSRF installed an experimental field station in Quartermaster Harbor to culture native mussels as a method that could provide a cost-effective and feasible means of mitigating nitrogen inputs in Quartermaster Harbor.  The station itself is a small raft, 8 x 30 feet, with instrumentation that will measure water motion and quality. Onsite data collection and biomass samples will be analyzed to determine the amount of nutrient sequestration by the mussels and associated marine biomass. 

The raft

Once the shellfish are grown, they will be removed through two market-based disposal options that will redistribute the sequestered nutrients back into the watershed. Both methods have been successfully implemented elsewhere in the world..They are:

  • Composting of mussels to create a value-added soil amendment.
  • Processing of mussels to create an animal feed additive.


Completion of this 18-month project will also help develop a conceptual model for a nitrogen trading system that could potentially be applied to other parts of Puget Sound. However, even if the mussels prove to be effective at removing excessive nutrients, the long term health of Quartermaster Harbor will depend on reducing nutrient input and the continued commitment of island residents to improve water quality.  If you would like to get involved in this effort, please contact Brian at or call 206.780.6947. 

Dinner, dancing... and a face full of baby mussels. Think you've been on some weird dates? Well, meet Michael and Susan, two freshwater mussels looking for the perfect match.