Nitrate

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Shallow Profiler at 30 m Engulfed in Sunlight

The Winched Shallow Profiler engulfed in soft sunlight rises up 30 m beneath the ocean's surface. Located at the Slope Base site it is measuring nutrients, dissolved oxygen and carbon dioxide concentrations, seawater acidity, temperature and chlorophyll concentrations at high temporal and spatial resolution, controlled from >200 miles onshore through the Internet at the University of Washington. Credit: NSF-OOI/UW/ISS; V15.

Nitrate sensors measure the nitrate concentrations in the ocean. Nitrogen is an essential element or nutrient in plant growth in marine environments, of which the dominant labile inorganic form is nitrate.  Nutrients typically have higher concentrations in the deep ocean, while concentrations near surface are often very low due to uptake by phytoplankton during photosynthesis.  The nitrate vertical gradient may be very dynamic, responding to both physical and biological processes.

Nitrate sensors on the Cabled Array are installed on the Science Pods on the Shallow Profiler Moorings at Axial Base (SF03A), Slope Base (SF01A), and at the Endurance Array offshore site (SF01B). Since 2015, the Science Pods have made >27,000 profiles of the coastal and far offshore waters from ~200 m water depth to ~ 10 m water depth.

Nitrate sensors on the platforms are provided by Seabird (ISUS - In situ ultraviolet Spectroscopy) that uses ultraviolet spectroscopy to measure nitrate concentrations. This instrument was developed at Monterey Bay Aquarium Research Institute.