The PI's request funding to develop reliable, accurate, stable in situ nutrient sensors for long-term ocean observing. WET Labs has been developing a core set of technologies to utilize optical detection techniques for determination of nutrient concentrations using low volume, reagent-based reaction chemistry. This development has been ongoing in partnership with SubChem, focusing on the in situ measurement of phosphate concentration and has led to a mature prototype sensor. Evaluation of the in situ data obtained using this system has shown that the measurement technology is robust, and that the sensor provides stable and accurate readings. In addition, the PI?s will develop an Ammonium sensor using a similar technology as the Phosphate sensor. This will likely involve one more reagent and hence pump, and possibly fluorometric detection, which will require redesign the manifold for this purpose.
Broader Impacts:
Dissolved nutrient dynamics broadly affect issues related to public health, ecosystem status, and resource sustainability, including impacts of climate variability, eutrophication, harmful algal blooms, carbon cycling, and species composition among others. The need for in situ, autonomous, real-time nutrient monitoring capabilities has been clearly documented in several national reports on ocean observing and water quality monitoring. The development and commercialization of long-term, reliable, traceable phosphate and ammonium in situ sensors would enable enhanced monitoring of nutrient inputs (natural and anthropogenic) into the coastal zone. Nutrient additions have been postulated to contribute to algal blooms when the effluent rises sufficiently high in the water column to intersect with the euphotic zone and may promote harmful algal blooms (HABs). Providing a long-term nutrient monitoring capability would allow scientists, environmental managers and regulators to better understand the role of nutrient discharges in contributing to blooms and their effects on the phytoplankton community.
The goals of this research were complete the development of a reagent-based, wet chemistry in situ phosphate analyzer for commercial use, develop a methodology to measure ammonium based on the same fluidic platform design, and to assess the feasibility of adapting the fluidic platform for determining harmful algal/toxin concentrations. The development and commercialization of the phosphate anaylzer, termed the CYCLE-PO4 sensor, was successfully completed, and is available through WET Labs, Inc. An extensive field testing and validation program was completed, and results show that the system is accurate to 0.03 +/- 0.2 microMolar phosphate. Several of the CYCLE-PO4 systems are now in use, ranging from freshwater streams to coastal estuaries. We have also completed development of an in situ ammonium analyzed, termed the CYCLE-NH4 sensor. Several prototypes of the CYCLE-NH4 have undergone field testing and initial results indicate 0.1 microMolar detection limit is achievable. Initial field validation efforts showed several hundred nanoMolar offsets, and as a result, improvements in the calibration methodology and in reagent stability have been made. Finally, we successfully demonstrated the feasibility of adapting the CYCLE platform technology to detect the presence of harmful algal/toxin substances by implementing an immunoassay within the system. We completed demonstration of a benchtop prototype which utilized magnetic beads as the antibody substrate, and developed a sensitive detection system to determine the concentration of the analyte of interest. A complete assay was developed for domoic acid.
