Since 2011, unusually large quantities of pelagic Sargassum fluitans and S. natans (sargasso) have been washing ashore along the coasts of some African countries and the Greater Caribbean, impacting ecosystems and economies. We estimated biomass and composition of sargasso arriving to a Mexican Caribbean coast from September 2016 until May 2020. In 2016, the beached masses comprised S. natans VIII and S. fluitans III. S. fluitans III was the predominant form throughout the study period, comprising on average >60 % of total wet biomass. The relative abundance of S. natans VIII decreased in time from 2016 to 2019 (41 to 3 %), although it became prevalent again in the first months of 2020. The third morphological form, S. natans I, was not registered until February 2018, and its relative abundance increased from 23 % in 2018 to 31 % in 2019. The initial composition of Sargassum species and morphotypes of the beached sargasso in Mexico differed from that commonly reported in the Sargasso Sea. The total biomass of beached sargasso varied considerably among years and seasons, with peaks during the summer months of 2018 and 2019. Seasonal variations in biomass were explained by 1) presence of sargasso in the Yucatan Current and 2) prevailing trade winds. This study is the first report on biomass and species composition of beached sargasso in the Western Caribbean and may help to understand patterns of the massive influxes; which will aid in the management of this new phenomenon.

自2011年以来，一些非洲国家和大加勒比海沿岸的海岸上浮游动物海藻和长臂猿S. natans（海藻）异常大量地冲上岸，影响了生态系统和经济。我们估计了从2016年9月至2020年5月到达墨西哥加勒比海沿岸的藻类的生物量和组成。2016年，滩涂质量包括纳丹链球菌VIII和沙门氏菌III。在整个研究期间，S。fluitans III是主要形式，平均占总湿生物量的> 60％。纳丹链球菌VIII的相对丰度从2016年到2019年的时间减少了（41％到3％），尽管它在2020年的前几个月中再次盛行。第三个形态形式，即纳坦葡萄球菌I，直到2018年2月才被注册，相对丰度从23增加％，2018年的31％在2019年的初始组合物，马尾藻墨西哥滩涂藻类的物种和形态类型与藻类海中通常报道的不同。滩涂藻类的总生物量随年份和季节变化很大，在2018年和2019年夏季达到峰值。生物量的季节性变化可通过1）尤卡坦海流中存在藻类和2）主流贸易风来解释。这项研究是关于西加勒比滩涂藻类的生物量和物种组成的第一份报告，可能有助于了解大量涌入的模式。这将有助于管理这种新现象。