In situ calibration of biofouling-prone oceanographic sensors in the framework of the POSEIDON project

Abstract This work presents the in situ calibration procedures developed for the sensors of conductivity, dissolved oxygen and chlorophyll-α, attached to eleven Oceanor Seawatch-type buoys deployed since 1999 in the Aegean Sea. The sensors are deployed in the upper 50 m of ocean, where bio-fouling is a significant cause of measurement error. The limited resources in instrumentation and the cost of ship-time have dictated the development of parallel procedures allowing the calibration of 4–5 CT sensors, one chlorophyll-α fluorometer and one dissolved oxygen sensor within two hours. Through our calibration we have achieved significant improvement of the chlorophyll and conductivity measurements.