Moored Sensor Monitoring Program for Nutrients
The indications of decreased Bay resilience to high nutrient loads have come to the fore at a time when the availability of resources to continue assessing the Bay’s condition is uncertain. Since 1969, a USGS research program has supported water‐quality sampling in the San Francisco Bay. This USGS program collects monthly samples between the South Bay and the lower Sacramento River and measures salinity, temperature, turbidity, suspended sediments, nutrients, dissolved oxygen and chlorophyll a. The USGS data, along with sampling conducted by the Interagency Ecological Program, provide coverage for the entire San Francisco Bay-Delta system. The San Francisco Bay Regional Monitoring Program (RMP) has no independent nutrient‐related monitoring program, but instead contributes approximately 20% of the USGS data collection cost. Thus, there is currently an urgent need to lay the groundwork for a locally‐supported, long‐term monitoring program to provide information that is most needed to support management decisions in the Bay.
While most of the historic and current data being generated by the USGS and IEP research programs are derived from ship-based measurements, there is a growing recognition that moored multi-sensor platforms can provide valuable temporally-intensive data. A number of large estuaries in the US (e.g., Chesapeake Bay,
http://mddnr.chesapeakebay.net/eyesonthebay/index.cfm; Columbia River, http://www.stccmop.org/datamart/observation_network; Caloosahatchee Estuary, http://recon.sccf.org/) have well-established moored sensor networks that are integral components of monitoring efforts and provide a strong complement to ship-based monitoring. At a recent RMP-sponsored nutrient conceptual model technical meeting, the technical team recommended that pursuing a pilot project with moored sensors would be a valuable step that should be taken in the early stages of planning the next-generation monitoring program for the Bay. This group further advised that the RMP invest sufficiently in person power, beyond the cost of the hardware, to ensure the success of this effort and to allow ample time for sensor platform selection, operation and maintenance, and data analysis, so that the effort contributes to monitoring program development.
Applicable RMP Management Questions
- Is there a problem or are there signs of a problem in the Bay? Are anthropogenic nutrients currently, or trending towards, adversely affecting beneficial uses of the Bay
- What are appropriate guidelines for assessing SF Bay’s health with respect to nutrients and eutrophication?
The first task in this project focuses on sensor platform selection. The LOBO system (http://www.satlantic.com/lobo) is the most likely option, because of its robust sensors (good track record based on other estuaries), including the considerable attention paid to minimizing biofouling. However other sensor platforms will be considered. The proposed LOBO sensor package includes conductivity, temperature, depth, dissolved oxygen, chl-a, turbidity, and nitrate, and both logs data and telemeters data via the cellular network to a manufacturer-provided web-interface for real-time data visualization (this will likely be most useful for tracking sensor drift or failure; however it could also be useful for detecting short-lived events, such as blooms, and triggering a focused field sampling campaign). The SUNA nitrate sensor (http://www.satlantic.com/suna) that is part of this package is a state of the art sensor and has sufficiently low detection limits (1-5 uM) relative to typical Bay conditions (~20-80 uM).
Next, the LOBO system will be calibrated and tested in the lab, and then field tested for ~1 month at the Redwood City dock near USGS Menlo Park. The system will then be deployed on a bridge piling at Dumbarton Bridge in June 2013, in collaboration with David Schoellhamer (USGS) whose group currently deploys and maintains turbidity, conductivity, temperature, and dissolved oxygen sensors at this site. The overlap in sensor capabilities is helpful because it will allow for continuous and co-located validation during the early stages of this pilot project. Maintenance schedules will coordinate with Schoelhamer’s group; they have agreed to collaborate on maintenance, which will allow both groups to leverage funds from various sources to support field work. Data will be collected continuously from June-December 2013, with on-going QA/QC. Discreet water samples will be collected periodically (bi-weekly) adjacent to the sensor and measured for the suite of parameters to validate sensor operation. An operation and maintenance manual will be developed. Finally, a technical memo will be produced that presents initial data analysis and synthesis, and just as importantly describes lessons learned during year 1 and recommendations for next steps with moored sensor applications.
This project will be led by David Senn of SFEI and Emily Novick of SFEI
Programs and Focus Areas:
Clean Water Program