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MEPS prepress abstract   -  DOI:

El Niño events and chlorophyll levels affect the reproductive frequency but not the seasonal reproductive output of East Pacific green turtles (Chelonia mydas)

Helena Ramírez*, Verónica Valverde-Cantillo, Pilar Santidrián Tomillo

*Corresponding author:

ABSTRACT: The El Niño-Southern Oscillation (ENSO), which includes El Niño and La Niña phases, affects oceanographic conditions and primary productivity of marine ecosystems at a global scale. During El Niño events, warm temperatures in the central and eastern tropical Pacific decrease primary productivity, affecting the biology of many species including sea turtles. We aimed to determine the effect of ENSO (as a global index) and primary productivity in the foraging areas (as a local index) on remigration intervals (number of years between nesting seasons) and seasonal reproductive output (clutch size and number of clutches in a season) of green turtles (Chelonia mydas) in North Pacific Costa Rica, an area highly influenced by ENSO. We used the multivariate ENSO index (MEI) and mean values ​​of alpha chlorophyll from previously identified feeding areas for this population over different time periods (up to three years before the nesting season). Alpha chlorophyll levels in foraging areas and MEI strongly influenced the reproductive frequency of green turtles. Variability in the remigration intervals was better explained by models that included MEI conditions two and three years before the offset of the nesting season and chlorophyll levels in the last three years. Models using global and local indexes were equally good at predicting changes in the remigration intervals. Positive values of MEI (El Niño phase) and lower levels of alpha chlorophyll, corresponded to longer remigration intervals. No statistically significant relationships were found between seasonal reproductive output and MEI or alpha chlorophyll levels. As El Niño events may become more frequent and last longer due to climate change, the lifetime reproductive output of green turtles in this area may be compromised in the future.