ISUS Nitrate sensor.

Abstract

Since November 2004, a Satlantic ISUS nitrate sensor has been integrated with a Seabird 911+ CTD-Rosette system deployed on CalCOFI cruises. Cruises typically occupy 75 stations, collecting approximately 1400 discrete seawater samples throughout the water column. The discrete seawater samples are analyzed at-sea for nitrate, nitrite, silicate, phosphate and ammonia within 24 hours of collection. The ISUS voltage data are processed along with other sensor data using Seabird’s SBE Data Processing Suite. Processed CTD-ISUS data are merged with bottle data. The ISUS voltages are plotted versus corresponding nitrate data, generating a voltage-to-nitrate regression. These regression coefficients are applied to all ISUS voltages, converting voltages to estimated nitrate.