In recent years Sargassum has increasingly been seen as a pest, washing up in vast quantities on beaches on both sides of the Atlantic. There are two species of Sargassum involved in this phenomenon - Sargassum natans and Sargassum fluitans. They are both examples of the free-floating variety that characteristically form the large algal rafts found in the Sargasso Sea.
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Something happened in 2011 to produce an ocean-wide explosion of Sargassum that stretched from the Caribbean to the coast of Africa. Unprecedented quantities of seaweed came ashore on coastlines on both sides of the Atlantic. Previously there had been sporadic episodes of the seaweed washing up on beaches, but nothing before on this scale.
Similar events have been observed since the 2011 great Sargassum pileup. There is uncertainty about whether the “golden tides”, as they are often referred to, will be an annual occurrence. However 2015 has seen a severe influx of Sargassum on both sides of the Atlantic, similar in magnitude to the 2011 event. Learn more about Sargassum in this Story Map.