Spectral characteristics of sea snot reflectance observed from satellites: Implications for remote sensing of marine debris

In 2021, coastal communities in the Sea of Marmara were impacted by large sea snot events. Based on data collected by several satellite sensors, we analyze and present the spectral reflectance characteristics of sea snots in the visible and near-infrared wavelengths. Sea snots often form elongated image slicks in Red-Green-Blue (RGB) or false-colour RGB (FRGB) images. Most reflectance spectra of sea snots show largely featureless spectral shapes, with continuous reflectance increases from the blue to the red, which then become flat toward the near infrared wavelengths. Some reflectance spectra show a local trough around 670 nm, indicating presence of chlorophyll a pigment, and thereby live algae. A 20-year time series of satellite data also reveals large-scale sea snot events in the Sea of Marmara before 2021. These results suggest that it might be possible to develop algorithms to search and map sea snots at a global scale, as sea snot events also occur in other regions. The results also indicate that remote differentiation of sea snots and marine debris using multi-band sensors may be difficult because of the spectral similarity between them. [Display omitted] •Spectral reflectance of sea snots determined from multi-sensor satellite measurements.•Sea snot reflectance mostly featureless, with increases from the blue toward the NIR.•Small reflectance trough found in some sea snot spectra, indicating live algae.•Strong similarity between sea snot and marine debris, making discrimination difficult.•Sea snot events more often and possibly more widespread than previously reported.