This project developed a shellfish biosensor monitoring system to complement existing long-term water quality monitoring and provide real-time feedback on estuary conditions.

The Project

Southern California’s estuaries can experience large swings in water quality due to events like freshwater inflow, sewage spills, and estuary mouth closures. The Tijuana River NERR (TRNERR) monitors several estuaries in San Diego County to better understand how biological communities respond to changes in water quality. While this biological monitoring produces detailed, high-quality data, the labor associated with this monitoring is significant and imposes limits on the frequency of monitoring. Regional partners, including the TRNERR and California State Parks among other intended users, expressed a need for improved monitoring techniques to detect when water quality conditions threaten the biotic community. Automated monitoring of biological communities could provide real-time feedback about biological response to changes in water quality while reducing the frequency of in-person monitoring.

Through an iterative process with TRNERR and other users, this project team co-developed a biosensor monitoring system that uses shellfish (oysters and mussels) as biosentinels. Alongside state and local land managers and other wetland and aquaculture professionals, the team designed an open-source electronic sensor that attaches to shellfish and monitors gaping behavior and heart rate. These metrics that can be used as indicators of physiological stress in response to environmental changes. The team deployed shellfish outfitted with these sensors in three field locations in San Diego. The deployed shellfish provided a real-time data stream of gaping behavior and heart rate, associated with a variety of changing water quality conditions, including frequent salinity and oxygen fluctuations in Tijuana River Estuary and mouth closure events in Los Peñasquitos Lagoon. Periods of low salinity associated with rainfall or possible sewage outflows in Tijuana River were accompanied by group closures of shells and lower heart rates, and similar patterns were observed for periods when dissolved oxygen was now.

The project demonstrated the successful design and deployment of a low-cost, long-duration biosensor system. Ongoing refinement of this open-source hardware and software will help enhance monitoring capacity in Southern California and beyond, allowing for targeted deployments of biosentinels in the short term as well as their incorporation into routine long-term monitoring. The real time data stream provided by biosentinels will help managers adapt to changing conditions and inform locally relevant decision making for events that pose significant threats to wildlife and habitat like estuary mouth closure and sewage spills. The biosensor system also holds potential value to other coastal areas and sectors, for example, long-term biosentinel performance data can inform siting for aquaculture or living shoreline projects.

The Impact

• Developed innovative hardware and software tools for an open source biosensor system that can be used and modified by other groups.
• Demonstrated the function of real-time data reporting of oyster and mussel behavior in three estuaries across San Diego County.
• Complemented existing water quality monitoring efforts and enhanced monitoring capacity at TRNERR.