Assessing temporal dynamics on pelagic Sargassum influx and its relationship with water quality parameters in the Mexican Caribbean

Abstract Since 2011, massive inflows of pelagic Sargassum have been recorded in the Caribbean region, which has affected coastal ecosystems, mainly water quality and the flora and fauna that inhabit these areas. The aim of this study is to evaluate the temporal dynamics of Sargassum arrival and its relationship on water quality in three sites of the Mexican Caribbean (Mahahual, Xahuayxol and Xcalak). We used remote sensing tools to estimate Sargassum coverage and turbidity to know if these parameters vary throughout the year and are related. We measured in situ water quality parameters to identify variations, depending on the Sargassum quantity and leachate concentration. Our results of 26 Landsat 8-OLI images show higher Sargassum coverage and turbidity during the winter months and a high relationship between Sargassum coverage and turbidity in areas near the coast. Additionally, turbidity calculated from multispectral bands complemented satellite detection of Sargassum, as high turbidity values were identified in near-shore areas where satellite images could not detect the alga. Finally, water quality parameters showed an increase in ammonium concentration and decreased pH and oxygen levels in the areas with higher Sargassum accumulation and leachate concentration. This study provides a better understanding about temporal dynamics of Sargassum influx in the southern Mexican Caribbean and its relationship with water turbidity in order to develop strategies, management plans and harvesting policies that could prevent huge masses of Sargassum reaching the coast.