Abstract

Sargassum macroalgae biomass spiked to unprecedented quantities in 2011 and has been increasing since (Schell et al. 2015, Wang and Hu 2016). As a result, seaweed has been episodically inundating western Atlantic shorelines, especially on windward coasts. These Sargassum arrivals often occur on the same beaches that serve as essential habitats for protected species such as marine turtles. On Long Island, Antigua, Sargassum arrivals are impacting a regionally important nesting population of hawksbill sea turtles (Eretmochelys imbricata; Maurer et al. 2015). Large quantities of the macroalgae pose a potential threat to females coming ashore to nest and to hatchlings leaving the beach (Figure 1), but these impacts remain mostly unassessed for any sea turtle species. We quantified the effect of Sargassum accumulation on hawksbill nesting ecology during the 2015 nesting season. Specifically, we tested two hypotheses: i) The spatial distribution of nesting crawls (emergence onto the beach to nest) would vary according to Sargassum presence, with more Sargassum associated with fewer crawls, and ii) Beach zones most heavily affected by Sargassum in 2015 would receive a lower proportion of total seasonal crawls than the same zones in nesting seasons when little to no Sargassum was present.

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