SAREDA (AERIS/ICARE, MODIS AFAI, Descloitres et al. 2021): daily gridded Sargassum, 2002–2026, 5 km, variable fractional_coverage. Open archive.
USF AFAI (NOAA AOML / USF SaWS, Wang & Hu 2016): 7-day AFAI fields, 2016–present, ~1.6 km, via ERDDAP.
Comparative extent index; absolute calibration to USF percent-cover pending. Sources are government/peer-reviewed.