Effects of El Niño Southern Oscillation and local ocean temperature on the reproductive output of green turtles (Chelonia mydas) nesting at Tortuguero, Costa Rica

Abstract

In species presenting long intervals between reproductive seasons, atmospheric-oceanic phenomena can affect the yearly number of individuals that become reproductively active. Sea turtles take multiyear intervals between reproductive seasons, which are influenced by environmental processes affecting their nutrition. Atmospheric-oceanic phenomena affect the reproductive output of different sea turtle species and populations. The population of green turtles (Chelonia mydas) nesting at Tortuguero-10.4489° N, 83.5069° W-, Costa Rica, is the largest in the Atlantic Basin and one of the most comprehensively studied. Nevertheless, only one study analyzed the effects of sea surface temperature on the reproductive output of Tortuguero green turtles. We analyzed three decades of data that revealed two likely scenarios: (1) more green turtle clutches were laid at Tortuguero after warm sea surface temperature anomalies during boreal winters and (2) fewer green turtle clutches were laid at Tortuguero 2 years after El Nino and more green turtle clutches were laid 2 years after La Nina events. Atmospheric-oceanic phenomena affect green turtle reproductive output likely through disrupting nutritional pathways, which alters the number of female green turtles that become reproductively active each year. Tortuguero green turtles are herbivorous feeding mostly on seagrass meadows off Nicaragua. As primary consumers, green turtles are tightly constrained by environmental conditions, and if the productivity of seagrass meadows decreased due to elevated sea surface temperature in the Caribbean basin or the altered hydric regime following El Nino events, fewer females would be able to accrue energy for reproduction.