Novel optical techniques for detecting and classifying toxic dinoflagellate Karenia brevis blooms using satellite imagery

Abstract

Karenia brevis (K. brevis) blooms are of great interest and have been commonly reported throughout the Gulf of Mexico. In this study we propose a detection technique for blooms with low backscatter characteristics, which we name the Red Band Difference (RBD) technique, coupled with a selective K. brevis bloom classification technique, which we name the K. brevis Bloom Index (KBBI). These techniques take advantage of the relatively high solar induced chlorophyll fluorescence and low backscattering of K. brevis blooms. The techniques are applied to the detection and classification of K. brevis blooms from Moderate Resolution Imaging Spectroradiometer (MODIS) ocean color measurements off the Gulf of Mexico. To assess the efficacy of the techniques for detection and classification, simulations, including chlorophyll fluorescence (assuming 0.75% quantum yield) based on K. brevis blooms and non-K. brevis blooms conditions were performed. These show that effective bloom detection from satellite measurements requires a threshold of RBD>0.15W/m(2)/microm/sr, corresponding to about 5mg/m(3) of chlorophyll. Blooms can be detected at lower concentration by lowering the RBD threshold but false positives may increase. The classification technique is found most effective for thresholds of RBD>0.15W/m(2)/microm/sr and KBBI>0.3*RBD. The techniques were applied and shown to be effective for well documented blooms of K. brevis in the Gulf of Mexico and compared to other detection techniques, including FLH approaches. Impacts of different atmospheric corrections on results were also examined.

A new approach to discriminate dinoflagellate from diatom blooms from space in the East China Sea

“…Besides these efforts that provide key information on distributions and transport of algal biomass, techniques for species or group-level remote detection of HABs have also been developed and applied to satellite ocean color measurements with some successes [e.g., Amin et al, 2009;Cannizzaro et al, 2008;Siswanto et al, 2013;Tomlinson et al, 2009;Wynne et al, 2008]. One classification technique to detect toxic Karenia brevis (dinoflagellate) blooms in the Florida coastal water was developed based on its low particulate backscattering features compared to other high chlorophyll waters [Cannizzaro et al, 2008].…”

Hourly turbidity monitoring using Geostationary Ocean Color Imager fluorescence bands

“…The RBD algorithm was developed for relatively low backscattering blooms such as dinoflagellates 3,4 by taking advantage of the chlorophyll fluorescence emission centered on 685 nm. Since there is nothing else in the water that fluoresces in the red region, the RBD easily identifies and separates chlorophyll rich regions from false chlorophyll-like features generated by CDOM plumes, sediment plumes and bottom reflectance.…”

“…The RBD approach has been used to detect low backscattering algal blooms, particularly dinoflagellates, using MODIS and MERIS imagery. 3,4,[32][33][34] In this study, the RBD approach was applied to GOCI imagery for the first time to detect relatively low backscattering blooms such as dinoflagellates, which are known to occur in the studied region. [35][36][37] Since FLH cannot discriminate between bloom and sediment rich waters, we used FLH and RBD together to separate the two types of waters.…”

“…1,2 Polar-orbiting satellite sensors such as the Moderate Resolution Imaging Spectroradiometer (MODIS) and the Medium Resolution Imaging Spectrometer (MERIS) have been widely used for ocean color studies. 3,4 However, those sensors have limitations in monitoring dynamic variation such as daily or hourly variations of the ocean surface. These sensors typically collect one image per day at about 1 km resolution.…”

“…We also attempted to track the features using hourly GOCI imagery and assess their movement through comparisons with predicted ocean currents derived from the navy coastal ocean model (NCOM). Since MODIS RBD and FLH results have been validated, 3,4 we used MODIS to validate GOCI results and then assess the high frequency dynamics from the hourly imageries in the coastal waters of the Korean Peninsula.…”