Abstract

Since 2011, unprecedented strandings of pelagic Sargassum have occurred over broad areas of the North Atlantic basin and Caribbean Sea. These strandings, characterized by excessive biomass, are considered to be harmful algal blooms (HABs) as they have a detrimental impact on both the environment (fish kills, dead zones, toxic H2S) and the tourist-based economies of affected coastal areas. Similar high biomass strandings of Sargassum increased during the 1980s and 1990s in the Gulf of Mexico (GOM), impacting coastlines along both Texas and Florida. Research in the late 1980s documented the importance of boundary current circulation between the GOM, Gulf Stream, Sargasso Sea, and Caribbean region to nutrition, productivity and growth of pelagic Sargassum. Tissue C:N, C:P, and N:P ratios were significantly lower in neritic (western Caribbean, Florida Current, Gulf Stream) compared to oceanic waters (Sargasso Sea), indicating the importance of land-based nutrient enrichment (Lapointe 1995). The relatively nutrient-enriched plants in the neritic areas also had two-fold higher productivity and much shorter doubling times, indicating nutrient-enhanced growth (Lapointe et al. 2014). Considering the increased strandings of Sargassum, the question that arises is: are the increased strandings of Sargassum linked, in part, to nutrient enrichment and eutrophication in the GOM?

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