DOI:http://dx.doi.org/10.15446/abc.v23n3.68113 Acta biol. Colomb., 23(3):311-314, Septiembre- Diciembre 2018 - 311 FLOATING Sargassum IN SERRANILLA BANK, CARIBBEAN COLOMBIA, MAY JEOPARDIZE THE RACE TO THE OCEAN OF BABY SEA TURTLES Sargassum flotante en Cayo Serranilla, Caribe colombiano, puede perjudicar la llegada al océano de las tortugas marinas recién nacidas Brigitte GAVIO 1 , Adriana SANTOS-MARTÍNEZ 2 . 1 Departamento de Biología, Universidad Nacional de Colombia, Sede Bogotá. Bogotá, Colombia. 2 Universidad Nacional de Colombia, Sede Caribe. San Andrés Isla, Colombia. *For correspondence. bgavio@unal.edu.co Received: 3 rd October 2017, Returned for revision: 26 th April 2018, Accepted: 23 th August 2018. Associate Editor: Nubia Matta Camacho. Citation/Citar este artículo como: Gavio B, Santos-Martínez A. Floating Sargassum in Serranilla Bank, Caribbean Colombia, may jeopardize the race to the ocean of baby sea turtles. Acta biol. Colomb. 2018;23(3):311-314. DOI:http://dx.doi.org/10.15446/abc.v23n3.68113 ACTA BIOLÓGICA COLOMBIANA http://www.revistas.unal.edu.co/index.php/actabiol NOTA BREVE / BRIEF NOTE Facultad de Ciencias Departamento de Biología Sede Bogotá ECOLOGÍA MARINA ABSTRACT We report for the first time great quantities of floating Sargassum to Serranilla Bank, in the Central Caribbean. The island is an important nesting site for sea turtles, and by the time the Sargassum wave arrived, the baby turtles were disclosing. Due to the thick mat of Sargassum along the beach, the baby turtles may have troubles to reach the ocean. Keywords: baby turtles, floating Sargassum, nesting site. RESUMEN Se reporta por primera vez una gran cantidad de Sargassum flotante en Cayo Serranilla, en el Caribe central. La isla es un sitio importante para anidamiento de tortugas marinas, y al momento de la llegada del Sargassum, los nidos estaban eclosionando. Debido al espeso tapete de algas en la playa, las tortuguas pueden tener problemas en llegar al mar. Palabras clave: Sargassum flotante, sitios de anidamiento, tortugas marinas. Floating Sargassum has been known since Christopher Columbus to occur in the Atlantic Ocean, off the east coast of Florida, in a region named Sargasso Sea (Djakouré et al., 2017). It consists of two pelagic species, Sargassum fluitans and Sargassum natans, which conform a floating ecosystem with a high diversity of species associated to and dependent onto it (Hoffmayer et al., 2005); the Sargasso Sea is unique because it is the only self-sustaining community of holopelagic algae (Trott et al., 2010). Most species associated to Sargassum are highly adapted, with appendages and coloration mimicking the alga (Sterrer, 1992). Ten species of invertebrates and one species of fish are endemic to the Sargasso Sea (Trott et al., 2010). Many other species, including a diverse array of juvenile and migratory fishes, and at least four species of sea turtles, all endangered, use the ecosystem as nursery habitat or as feeding ground (Manzella and Williams, 1991; Mansfield et al., 2014). It has been estimated that the Sargasso Sea harbors about ten million tons of wet biomass (Johnson et al., 2013). Despite the fact that drift Sargassum has historically been reported on the shores along the Gulf of Mexico and the Caribbean Sea (Taylor, 1960), since 2011 the biomass of seaweeds washed ashore has reached unprecedented amounts and has been observed at localities where it was uncommon or unreported before this date (Smetacek and Zingone, 2013; Gavio et al., 2015, Rodriguez-Martinez et al., 2016, Louime et al., 2017). Several hypotheses have been proposed to explain such events, including an excess of nutrient loads, a change in trade currents, and unusually high sea surface temperatures (Lopez et al., 2008; Djakouré et al., 2017). Wrack Sargassum biomass may be beneficial to the environment at moderate densities, because it provides food and shelter to several species, it may help fight beach erosion and provide nutrients to beach habitats (Lopez et al., 2008). However, when biomass is very high, it may have negative effects: the accumulation of algae on the water surface precludes light penetration, and affects corals and benthic macroalgae (Lopez et al., 2008). The drift algae on the beach may become a barrier to nesting turtles and/or to baby turtles finding their way to the ocean (Maureer et al., 2015; Azanza-Ricardo and Pérez-Martín, 2016). Cleaning up the excessive biomass along the beaches may enhance