Floating marine structures, like the brown macro algae Sargassum, provide essential habitat and support a variety of life history for many marine organisms. However, the fragmentation and persistence of these floating habitats are poorly understood. Extending landscape ecology to seascapes requires new methodologies. I examine Sargassum in a seascape ecology context, exploring 1) structural descriptions of the Sargassum patch seascape, 2) species-habitat relationships between Sargassum and dispersal-stage juvenile sea turtles, and 3) explore whether historical Sargassum patch distribution is represented by delineated proposed and finalized Sargassum-as-a-critical-habitat designations under the US Endangered Species Act. I utilize historical Sargassum data at two spatial scales: a coarse scale (1.6km) and a medium-scale (328m) spatial resolution to determine whether fragmentation processes are occurring at either spatial scale across seven marine regions in the Northern Atlantic Ocean. The seascape fragmentation analysis indicates that over a 6-year period, Sargassum is fragmenting across most of the Northern Atlantic Ocean. The movements of four turtle species were analyzed in relation to nearby Sargassum patches and were found to not significantly select these areas at the patch size ranges that were studied. Lastly, Sargassum patches were found to exhibit a notable increase in occurrence within the proposed green turtle critical habitat designation of Sargassum when compared with the loggerhead critical habitat designation for Sargassum. These data provide valuable insight into Sargassum as an important and highly dynamic seascape that may provide critical habitat for dispersal-stage juvenile sea turtles during their oceanic ‘lost years’.
Alexander Sacco
Dr. Kate Mansfield, Advisor
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