Sargassum landings have not compromised nesting of loggerhead and green sea turtles in the Mexican Caribbean.

The Mexican Caribbean is a vital nesting destination for loggerhead (Caretta caretta) and green (Chelonia mydas) sea turtles. Since 2015, massive periodical landings of pelagic Sargassum species (sargasso) have affected coastal ecosystems. Dense accumulations of sargasso on the shoreline may preclude access to sea turtles' preferred nesting areas and compromise hatching. In this study, we assess whether the number of nests and hatches of loggerhead and green sea turtles has been affected by the massive influx of sargasso. We compare data from before (2010-2014) and after (2015-2019) the first sargasso event, obtained from the same 17 marine turtle camps, which collectively account for 72.3 km of sampling distance over a 210 km section of shoreline. No differences in preferences on nesting beaches were recorded between periods for the two species. The mean number of nests per kilometer of coastline remained without statistically significant changes between periods in 16 camps and increased significantly in one camp for each species. Overall, the mean annual number of nests per kilometer of beach was 37% higher in the period after massive landings of sargasso began. The mean number of hatchlings increased significantly in one camp for C. mydas and in three for C. caretta. Periodical massive landings of sargasso from 2015 to 2019 do not appear to have compromised nesting and hatching of loggerhead and green sea turtles along the Mexican Caribbean coast.