Calibration and performance of a new in situ multi-channel fluorometer for measurement of colored dissolved organic matter in the ocean

The development of multispectral in situ fluorescence instruments greatly enhances the study of the optical properties of Colored Organic Matter (COM). Here, we tested the inter-instrument variability of three WetLabs, Inc. SAFIres using quinine sulfate standards. As with any fluorometer, intensity and spectral biases in fluorescence output due to properties of the SAFIreʹs optical components necessitate corrections. Low response of the instrument to quinine sulfate and lack of an excitation/emission channel at the fluorescence maximum of this standard precluded direct spectral calibration. Calibrations conducted using seawater as a secondary standard provided an acceptable alternative. The field performance of the SAFIre from two experiments is presented here. Time series contour plots show that the instrument has the ability to detect small differences in COM optical properties, and observed fluorescence emission ratios are indicative of changes in sources of the material over the course of the study. The SAFIre was found to extend multispectral measurements to include high spatial and high temporal resolution.