FocusSargassum coverage in the northeastern Gulf of Mexico during 2010 from Landsat and airborne observations: Implications for the Deepwater Horizon oil spill impact assessment

•Most satellite sensors inadequate to provide accurate coverage estimates of pelagic Sargassum due to coarse resolution•Approach developed to scale Landsat observations using less synoptic and frequent but more accurate airborne observations•Mean integrated Sargassum coverage over the northeastern during the four quarters of 2010 estimated•Implications of potential Sargassum injury in contact with oil inferred from these estimates

Using high-resolution airborne measurements and more synoptic coverage of Landsat measurements, we estimated the total Sargassum coverage in the northeastern Gulf of Mexico (NE GOM) during 2010, with the ultimate purpose to infer how much Sargassum might have been in contact with oil from the Deepwater Horizon oil spill. Mean Sargassum coverage during the four quarters of 2010 for the study region was estimated to range from ~ 3148 ± 2355 km2 during January-March to ~ 7584 ± 2532 km2 during July-September (95% confidence intervals) while estimated Sargassum coverage within the integrated oil footprint ranged from 1296 ± 453 km2 (for areas with > 5% thick oil) to 736 ± 257 km2 (for areas with > 10% thick oil). Similar to previous studies on estimating Sargassum coverage, a direct validation of such estimates is impossible given the heterogeneity and scarcity of Sargassum occurrence. Nonetheless, these estimates provide preliminary information to understand relative Sargassum abundance in the NE GOM.