Assessing the occurrence, social vulnerability, and legal implications of sargassum influxes in Puerto Rico using a social-ecological systems approach

Sargassum spp. influxes are causing significant alterations to both natural and human systems in the Wider Caribbean Region. To understand and respond to this situation, a holistic approach is needed that considers the distribution and dynamics of pelagic sargassum and the impacts and feedback between the natural and human systems. This research aimed to provide information for the decision-making processes regarding sargassum accumulations on the coasts of Puerto Rico. Remote sensing techniques implemented in Google Earth Engine were used to detect and spatiotemporally assess sargassum accumulations along the shoreline. The model developed was able to identify both fresh and decomposing sargassum, as well as Sargassum-brown-tide generated from decomposing sargassum. A combination of a participatory exercise and surveys were used to assess the social vulnerability of an impacted coastal community and to identify factors to reduce their social sensitivity and improve their adaptive capacity, such as establishing mitigation actions to reduce the exposure of residents to toxic gases and improving access to sargassum information. Lastly, legal barriers to implementing effective mitigation strategies and agencies jurisdictions in the permitting process were clarified using a co-production approach with local and federal agencies. Recommendations provided include the development of a territory-wide and priority areas response plans and the continuation of meetings with agencies to clarify legal aspects of sargassum mitigation actions including its disposal on land. This dissertation provides much needed information for household, community, and national decision-making. Methods and findings of this dissertation can also be applied to inform decisions in other coastal areas in the region affected by these recurrent events.