Project Title: In-Situ Nutrient Monitoring in Estuaries
Principal Investigator(s): Jane M. Caffrey, Hans Jannasch, Mark Silberstein

Accomplishments
Scheduled Tasks:
The tasks scheduled for completion include: Adapt phosphate chemistry to analyzer. Make necessary changes to manifold (e.g., add heater) and electronics/software. Purchase parts and assemble four more analyzers. Test phosphate analyzers in Elkhorn slough. Publish results in peer reviewed literature.

Progress on Tasks
Dr Chapin with collaboration from Drs. Jannasch and Caffrey has submitted the first of several manuscripts describing the nitrate Digi-Scanners and the results from the Outfall and Azevedo Pond deployments to Limnology and Oceanography. A second manuscript is in preparation. The results from the deployments in Weeks Bay and Apalachicola Bay were presented at the February Ocean Sciences meeting in Honolulu, HI, the May Gulf Estuarine Research Society meeting in New Orleans, and invited seminars at Florida State University and the University of Maryland.

The work on a DigiScan phosphate analyzer is rapidly progressing. The analytical manifold is based on the standard manual phosphate method utilizing ammonium molybdate, potassium antimony tartrate, and ascorbic acid as the reductant. In the tests to date, the system appears to be quite stable and doesn't have the anticipated color coating problem on the flow cell. A quick estimate of the detection limit would be on the order of 0.1 uM. The biggest problem that we have encountered so far is the formation of bubbles in the manifold and we are working on solving that problem with the addition of surfactants and deploying the instrument deep enough to eliminate air bubbles. Assuming there are no problems with reagent lifetime, which will require long-term testing, we're ready for field testing deployments.

Difficulties Encountered
We have no concerns or difficulties at this time

Anticipated Success in Meeting Project Objectives in Scheduled Project Period
We anticipate meeting the project objectives.

Preliminary Results
The manuscript submitted to Limnology and Oceanography revealed how deep water from Monterey Canyon was being advected into Elkhorn Slough on spring tides. Peak nitrate concentrations occurred on rising tides associated with a temperature and salinity signature characteristic of deep Monterey Bay (Figure 1). We were also able to use the Digi-Scanners to discriminate the sources of runoff into Azevedo Pond, whether from farm fields adjacent to the pond or from runoff into the upper Slough. Peak nitrate concentrations at low tide indicated that runoff must have been from the adjacent farm fields, while peak nitrate concentrations at high tide could only have come into the pond from water from the upper Slough (Figure 2). The second manuscript focuses on using statistical techniques such as harmonic regression and fourier analyses to explain the variations in nitrate concentrations in Elkhorn Slough. Tidal, lunar and daily components can explain between 40 and 90% of the variation in nitrate concentrations from individual deployments (Figure 3).

Tasks and activities for next reporting period

Tasks for the next reporting period
The tasks for the next report period include testing of the phosphate Digi-Scanners and ISUS sensors in Elkhorn Slough. We will continue processing and analyzing data in a timely fashion. We will continue preparing of manuscripts for publication describing the monitoring results from Azevedo Pond and the outfall. We will begin preparing manuscripts on the results from Weeks Bay and Apalachicola Bay deployments.

Work plan to accomplish tasks
Based on the results from laboratory testing of phosphate Digi-Scanners, testing in Elkhorn Slough will begin. The second paper describing statistical methods of analyzing this kind of data will be prepared for submission to Estuarine Coastal and Shelf Science. Analysis of Weeks Bay and Apalachicola Bay data will continue.

Concerns or difficulties
We have no concerns or difficulties at this time.

Expenditures
Expenditures were within the expected range.