Optical algorithms for assessment of fluorescence sources in sea waters

An optical algorithm, hereinafter called the Red Band Difference (RBD), is proposed and tested using sun induced chlorophyll fluorescence as the primary tool for the detection of relatively low backscattering phytoplankton blooms from space. The RBD technique is found to have potential for improving identification of blooms and their location compared to other algorithms. Since Karenia brevis (K. brevis) blooms are of great interest and have been commonly reported throughout the Gulf of Mexico, I also propose a K. brevis bloom classification algorithm, hereinafter called the K. brevis Bloom Index (KBBI). The KBBI technique is primarily based on the fact that total particulate backscattering associated with K. brevis bloom is different and much lower than that for non-K. brevis blooms. Since K. brevis bloomed water is known to have lower particulate backscattering than the non- K. brevis bloomed waters, the water-leaving radiance signal is much weaker for K. brevis blooms. As a consequence, the KBBI index becomes much larger for K. brevis blooms than for non- K. brevis blooms, thus permitting their distinction. The RBD and KBBI algorithms are capable of detecting relatively low backscattering blooms and classifying K. brevis blooms respectively from Moderate Resolution Imaging Spectroradiometer (MODIS) and Medium Resolution Imaging Spectrometer (MERIS) ocean color measurements. To assess the efficacy of the detection and classification algorithms, simulations, including chlorophyll fluorescence (assuming 0.75% quantum yield) based on the K. brevis and non-K. brevis blooms conditions were performed and thresholds were determined. The approaches were applied to well documented blooms of K. brevis in the Gulf of Mexico and results were compared to other detection techniques such as Fluorescence Line Height (FLH). The application of the RBD was extended to test capabilities for detecting various toxic dinoflagellates blooms around the world. An analysis of impacts of the atmospheric corrections was performed on both of the algorithms.