The goal of this project is to develop a robust and cost effective Dissolved Inorganic Carbon (DIC) sensor that can be deployed in combination with the robust moored pCO2 sensor (MAPCO2) previously developed by NOAA�??s Pacific Marine Environmental Laboratory on moorings for up to a year at a time. The sensor is based on the proven technology used in PMEL’s pCO2 sensor, infrared detection of CO2 in a gas stream. In this application a known volume of seawater will be acidified, and the CO2 that is evolved from the sample quantified. This technique has been used successfully to measure DIC on shipboard systems. While this method is fast and reliable, it has not been fully adapted for robust long-term autonomous DIC measurements on a mooring. Over the three years of this project, a prototype moored DIC sensor will be developed and field tested in a location with already existing pCO2 moorings.