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Sustaining measurements of water quality parameters in sensitive watershed habitats is challenging, particularly during critical periods such as spring blooms, and major run off events. Direct, in situ measurements of nitrate have been difficult to obtain until the development of the ISUS (In Situ Ultraviolet Spectrometer, Johnson & Coletti 2002) and more recently the next generation SUNA (Submersible Ultraviolet Nitrate Analyzer). These chemical-free optical sensors have now been operating in a wide range of challenging environments over the past five years. Performance evaluations of these instruments, lessons learned, and environmental insights obtained will be discussed, as well as results from these sensors under the recent ACT (Alliance for Coastal Technologies) Nutrient Sensor Technology Demonstration Program.

The Land/Ocean Biogeochemical Observatory (LOBO) system was initially developed by MBARI under the NSF Biocomplexity program to monitor the land/ocean interface for coastal zone management. The system utilizes highly robust and accurate sensors to provide sustained monitoring of critical watershed habitats in challenging environmental conditions in real time. With the incorporation of novel anti-fouling technology developed by WET Labs, the system has an unprecedented six week maintenance cycle, greatly reducing operational costs while providing high quality data sets. LOBO measurements include nitrate, dissolved oxygen, conductivity, temperature, chlorophyll fluorescence, turbidity and CDOM. A LOBO was deployed in the Northwest Arm of Halifax Harbour in January of 2007 and has been monitoring the biogeochemical parameters continuously since (see http://lobo.satlantic.com ). Despite heavy icing at -20degC, heavy winds, and sea ice the system reported data every hour where the detailed nature of the annual spring phytoplankton bloom was recorded at high resolution. The coincident and continuous record of nutrients, phytoplankton and other physical and chemical parameters is unique, and provides a robust means to base predictive coastal ecosystem models in sensitive marine areas.