Red tide detection in the Strait of Hormuz (east of the Persian Gulf) using MODIS fluorescence data

Abstract

A monstrous red tide appeared on October 2008 and expanded to the west on November 2008 off the Iranian coasts in the Hormuz Strait (east of the Persian Gulf). MODIS satellite data, hydrographic and bio-optical field measurements were used to detect the red tide. MODIS fluorescence line height (FLH in w m⁻² μm⁻¹ sr⁻¹) data showed the highest correlation with near-concurrent in situ chlorophyll concentration of 0.74 (100(FLH))^1.23 (r = 0.9, n = 44). In contrast, the band-ratio Chlorophyll product of MODIS showed more inconsistency with in situ chlorophyll data due to the interference of other water constituents. High FLH value patches >0.18 were confirmed to be located at the medium to high (10⁴–10⁶ cells l⁻¹) concentrations of Cochlodinium polykrikoides, and also showed a chlorophyll anomaly >1 mg m⁻³, which means the potential of red tide occurrences. The FLH imagery also showed that the bloom started in early September along Bandar-Abbas port, and developed and moved to the west along the coastal regions. The results revealed that MODIS FLH and enhanced RGB (ERGB) imagery plus in situ data are adequate tools for red tide monitoring.