A new nitrate continuous observation sensor for autonomous sub-surface applications: Technical design and first results

Nitrate as one of the chemical parameters of major interest in marine biogeochemistry is detectable by means of its optical absorption in the ultra violet spectrum, given appropriate algorithms to correct for other seawater constituents. The presented work outlines the potential and technical requirements to adopt this new instrumentation in autonomous sub-surface applications. First results from laboratory experiment as well as from a flow-through application onboard RV POSEIDON cruise P347 in the North Atlantic are used to characterize the sensitivity of the method. Having long term deployment in mind, different antifouling strategies are reviewed and evaluated in the context of an optical sensor.