LAUSR

Multisensor medium-resolution satellite images from Moderate Resolution Imaging Spectroradiometer (MODIS), Visible Infrared Imaging Radiometer Suite (VIIRS), Ocean and Land Color Imager (OLCI), and Medium Resolution Imaging Spectrometer (MERIS) are used to study spatial and temporal distributions of sea snot features in the Marmara Sea between 2000 and 2021. Suspicious image slicks are identified in most years, and spectral diagnostics indicate sea snot features in 2007, 2008, and 2021, with the record-high sea snot event occurring in spring–summer 2021. In other years, when similar image slicks are found, they appear to be from surface scums of red Noctiluca scintillans, a heterotrophic dinoflagellate responsible for red tides. Based on the medium-resolution images, the 2021 sea snot event started from March 14 and ended on June 27, with its peak time around May 4 when the sea snot features are found in the entire Marmara Sea covering an area of 1160 km2. When all sea snots are aggregated together, the estimated areal coverage during the peak time is 50 km2, suggesting significant patchiness in the surface scums.