THE GULF OF MEXICO ECOSYSTEM: A COASTAL AND MARINE ATLAS
theorize that it originates in the western Gulf and moves east through the Gulf and into the Atlantic in late summer (Gower & King, 2008). Based on their findings, Gower and King (2008) concluded that the northwest Gulf is a major nursery area for sargassum and that most sargassum plants have a lifespan of one year or less. See related maps and narratives on Sea Surface Currents and Kemp’s Ridley Sea Turtle. Data Compilation and Mapping Methods This map was developed from data provided by the Institute of Ocean Sciences at Fisheries and Oceans Canada (Gower & King, 2008). These data represent a simplified outline of the seasonal average extent of pelagic sargassum during the months of March, May, July and August averaged over the years 2002 through 2007. Pelagic sargassum was detected using the Medium Resolution Imaging Spectrometer aboard the European Space Agency’s Envisat satellite as it orbited the earth, providing global coverage of ocean color every three days. A maximum chlorophyll index provides good data on the extent of floating vegetation in the ocean (Gower & King, 2008). The summarized data in Map 13 are based on the maximum chlorophyll index for the Gulf. Data Quality Data quality for this map is considered good because of the Gulf-wide data coverage at a constant resolution of 1,200 meters (3,937 feet). While interpretation of these satellite-based data, including the inferred seasonal movements of pelagic sargassum, is controversial in the scientific community, these data are the first time-series observations of this habitat type in the Gulf and Atlantic waters. As more studies are published using other satellite-based sensors, such as the Moderate Resolution Imaging Spectroradiometer and field-based genetic research, scientific understanding of the origins and seasonal movements of this pelagic species will continue to expand.
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Synthesis and Conclusion The Gulf has one of the highest concentrations of pelagic sargassum in the world. It floats at the surface in island-like masses and can also be found in widely dispersed clumps or along ocean convergence weed lines. Sargassum is an important habitat for sea turtles, larval and juvenile fish, and invertebrates. Research is needed to support a higher level of resolution to describe and identify the sargassum habitat. It is also necessary to identify and evaluate the existing and potential natural or human impacts on sargassum habitat, such as direct physical loss or alteration, impaired quality or function, cumulative effects from fishing, and non-gear-related fishery activities. Continued monitoring and research on the various effects of the BP Deepwater Horizon oil disaster concerning sargassum mats and associated biological communities will be essential to conservation and preservation efforts in the Gulf.