Daily monitoring of marine mucilage using the MODIS products: a case study of 2021 mucilage bloom in the Sea of Marmara, Turkey

Climate change and global warming along with human activities have caused abrupt changes in the atmosphere, marine, and terrestrial ecosystems. One of these changes is the rising number of mucilage events in marine ecosystems. During the recent two decades, mucilage blooms have begun to appear more frequently in the Sea of Marmara in Turkey, surrounded by seven densely populated cities with various anthropogenic activities including household pollution, heavy industrialization, agricultural pollution, commercial fishing, shipyards, and specialized marine terminals with high maritime traffic density. In Spring 2021, a massive mucilage event observed in the Sea of Marmara plagued the entire ecosystem and raised awareness among the government and the public to detect and monitor this phenomenon. In this research, daily monitoring and detection of mucilage formations from the coarse spatial resolution MODIS products were investigated during the 2021 bloom period. The results were validated with the reference mucilage datasets derived from Sentinel-2A imagery and in situ spectroradiometer measurements over mucilage formations. The results revealed that the MODIS surface reflectance profiles were highly correlated with the field spectral measurements and estimated mucilage formations were spatially overlapped with Sentinel-2A. Overall, the produced maps accurately depicted the mucilage-covered areas despite the limitations of unreliable estimates along the land–water transition lines, and no-data areas due to the low-quality observations and high cloud coverage.