Potential Impacts of Sargassum Blooms on Resident Mobile Fauna

Nova Southeastern University, Davie, Florida, USA

Objective. This study was conducted to examine effects of sargassum blooms on the resident mobile fauna. Background. Pelagic forms of the brown algae (Phaeophyceae) Sargassum spp. form large mats over areas of open ocean and constitute an important habitat, harboring a diverse array of marine life. The Sargassum species S. Fluitans and S. Natans provide a nutrient rich environment, exploited by juvenile forms of economically and recreationally important fish species. Since 2011 massive sargassum blooms have occurred, resulting in large mats blanketing areas of the Caribbean sea, Gulf of Mexico and the Atlantic ocean. In 2019, the bloom reached proportions equal to or greater than prior years. These patterns are expected to continue due to climate change, deforestation, and other causes. Methods. Sargassum clumps of equal displacement volume were collected from May 2019 through August 2019 using established methods at nearshore, intermediate, and offshore locations. Samples were divided by Sargassum species, and mobile fauna were identified , categorized , and then released. Results. Reductions in both numbers of a given species and species diversity were observed as compared to prior studies . This trend continued into the late summer months. Conclusions. Although further studies are required , these preliminary findings suggest a trend that may have far reaching impacts on important fish species , and the pelagic environment.