Abstract

In 2011, unusually large quantities of pelagic Sargassum washed ashore along the coastlines of eastern Caribbean islands and West Africa. Backtracking using ocean circulation models indicated that the Sargassum had arrived from the North Atlantic equatorial region rather than directly from the Sargasso Sea. The quantity of the Sargassum in the invasion events and the frequency of event occurrence created immense problems for fishery and tourism industries and presented unknown consequences for marine ecosystems. Several north Atlantic climate indices with decadal-scale oscillations reached historical maxima/minima during 2010-2011. A Hypothesis is developed which suggests that climate related circulation changes in the equatorial Atlantic created conditions for increased pelagic Sargassum retention while warm, nutrient-rich conditions aided Sargassum growth and bloom conditions. The invasion events, bloom dynamics, and probable transport mechanisms are examined using ocean models and satellite-tracked ocean drifters. The goal of this study is to provide a fundamental understanding of the recent pelagic Sargassum blooms and invasion events in order to facilitate development of prediction capabilities for the tropical Atlantic nations.

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