<title>Multisensor in-situ fiber optic fluorometer</title>

Abstract

A prototype in situ multi-sensor fiber optic fluorometer is described which was designed to acquire long term time-series fluorescence measurements. The multi-sensor system uses dual detectors with four excitation sources, thereby providing for independent measurements at eight sensor locations. Strobe excitation light of wavelength < 500 nm is passed through one of each pair of optical fibers and stimulated chlorophyll fluorescence is carried back to a photomultiplier tube. The excitation and detection hardware are enclosed in a pressure case along with a battery operated 500 kHz data acquisition/storage system. Aspects of the design of the fiber optic sensor are described which were intended to optimize detection of fluorescence signals and minimize interference by ambient light. An illustration of the utility of fiber optics for fluorescence measurements was made by comparing a prototype fiber optic profiling fluorometer with a commercial fluorometer. Time series fluorescence measurements were made with the multi-sensor fluorometer in the Gulf of Mexico, and revealed chlorophyll variability in the benthic boundary layer.