Abstract

Sargassum is a floating, holopelagic, macroalgae that occurs in continental shelf and offshore waters across the Gulf of Mexico (GOM). It often accumulates in mats and windrows to form a structured habitat and is a source of food and refuge for a diverse assemblage of fish and invertebrates.Yearly differences in the abundance and distribution of pelag-ic Sargassum may contribute to the variation observed in recruitment of some marine fishes. Long-term temporal data on distribution and abundance of Sargassum in the GOM is lacking, but there is a time series of occurrence of Sargassum associated with ichthyoplankton surveys conducted by NOAA, National Marine Fisheries Service under the Southeast Area Monitoring and Assessment Program (SEAMAP). From that data set, the monthly percentages of ichthy-oplankton samples associated with Sargassum were calculated for square degree areas of longitude and latitude across the region of the Gulf of Mexico in U.S. territorial waters (USGOM). Presence of Sargassum was compared under differing climatological regimes using a nonparametric two-related-samples test (Wilcoxon signed ranks test). The warm phase of the Atlantic Multi-decadal Oscillation (AMO) and the negative phase of the decadal North Atlantic Oscillation (NAO) were significantly correlated with occurrence of Sargassum across the area of study. These regimes are associated with weather-related hydrographic characteristics in the North Atlantic, neritic zones of Central America, and the GOM that influence rates of reproduction, growth, and dispersion of pelagic Sargassum.

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