Olive Ridley Sea Turtle Hatching Success as a Function of Microbial Abundance and the Microenvironment ofIn SituNest Sand at Ostional, Costa Rica

Vanessa S. Bézy,Craig J. Plante,Roldán A. Valverde

doi:10.1155/2014/351921

Vanessa S. Bézy, Craig J. Plante + Show 1 more

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https://doi.org/10.1155/2014/351921

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Abstract

Sea turtle hatching success at mass nesting beaches is typically lower than at solitary nesting beaches, presumably due in part to high rates of microbial metabolism resulting from the large input of organic matter from turtle eggs. Therefore, we tested the hypothesis that hatching success varies across areas of the beach in conjunction with differences in the physical nest environment and microbial abundance of in situ olive ridley sea turtle nests at Ostional, Costa Rica. We marked natural nests in high-density, low-density, and tidal-wash nesting areas of the beach and monitored clutch pO2and temperature throughout the incubation period. We quantified hatching success and collected samples of nest sand during nest excavations. We quantified microbial abundance (bacteria and fungi) with a quantitative polymerase chain reaction (qPCR) analysis. Hatching success was lower in nests with lower pO2, higher temperatures, higher organic matter content, and higher microbial abundance. Our results suggest that the lower oxygen within the nest environment is likely a result of the high microbial abundance and rates of decomposition in the nest sand and that these factors, along with increased temperature of clutches in the high-density nesting area, are collectively responsible for the low hatching success at Ostional.

Highlights

The olive ridley sea turtle (Lepidochelys olivacea) is listed by the IUCN as a vulnerable species
Nest density for the entire beach at the time of excavation was 3.6 ± 0.4 nests m−2 and overall hatching success for nests laid on the main nesting beach during the August arribada was 34 ± 5.4%
Two nests were excluded from the analysis due to unforeseeable factors that likely caused a change in the variables that we attempted to control in this study

Summary

Introduction

The olive ridley sea turtle (Lepidochelys olivacea) is listed by the IUCN as a vulnerable species. The major threats to this species include fisheries bycatch, habitat degradation, and the unsustainable harvest of eggs [1]. This species is characterized by a nesting behavioral polymorphism, with some females nesting solitarily and others nesting en masse. Mass nesting events at Ostional, Costa Rica are some of the largest in the world, with events (or arribadas) estimated at up to approximately 500,000 nesting females [2]. While nest density can adversely affect hatching success (due to competition between developing embryos for physiological requirements), the mean nest density at Ostional is not high enough to reduce hatching success to the drastically low levels observed [4, 5]

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