Development of automated surface seawater nitrate mapping systems for use in open ocean and coastal waters

Uncertainty concerning the cycles and budgets of the major bioactive chemicals in the sea is partially a function of undersampling in relation to the actual spatial and temporal variability. However, technologies are becoming increasingly available for development of inexpensive devices for the continuous measurement of ocean properties. We have leveraged on these technologies and built two versions of a nitrate mapping system that is designed to operate with minimal operator intervention and provide near real-time surface seawater nitrate data. The analyzers are based on microprocessor-controlled Kloehn syringe pump modules operating in a batch mode. A rapid response nitrate analyzer uses two syringe pump modules and is capable of a 2-min sampling rate, allowing high temporal/spatial resolution. A simpler system which uses a single syringe pump and provides nitrate data every 20 min has also been built. Both systems can be integrated with other sensors (e.g. fluorometers) and navigation data to either display real-time maps or a scrolling display of multiple parameters. These systems have been deployed for extended periods on coastal and open ocean cruises.