Article Review--- Olive Ridley Sea Turtle Nesting

Article Review: Olive Ridley Sea Turtle Hatching Success as a Function of the Microbial Abundance in Nest Sand at Ostional Costa Rica. Bézy V.S, Valverde R.A, Plante, C.J. (2015) PLoS ONE 10(2): e0118579. doi:10.1371/journal.pone.0118579

The purpose of this study is to determine if a relationship exists between high microbial loads and embryo mortality caused by overlapping nesting sites in the olive ridley sea turtle, Lepidochleys olivacea.

The study was conducted in Ostional, Costa Rica, which is considered one of the most important nesting sites for this species in the world. These areas are home to mass nesting events known as arribadas, where a high abundance of nests results in overlapping and ultimately breaks eggs. It is known that there is a significant relationship between biotic and abiotic factors that determine the success and survival of turtle nests. So, the study hypothesized that high microbial abundance was responsible for low hatching success on arribada beaches.

Nest conditions and hatching successes were studied in an experimental plot, consisting of removal treatments, topical and control treatments. Removal treatment consisted of a dilution of household bleach in freshwater. The topical treatment consisted of seawater from the ocean. Control treatment consisted of freshwater and no manipulation. These experimental plots were made using a high microbial load in the sand. The pO₂ of each nest was recorded using an oxygen sensor. Nest temperature was monitored and mean daily temperatures were recorded. A qPCR molecular analysis was performed to measure the abundance of bacteria in the sand. Each sample of sand was then homogenized for a DNA extraction.

The results depict how removal treatments had significantly higher hatching success than topical treatments, as depicted in the first graph. The second graph explains how nest sand with no treatment had significantly higher levels of microbial DNA than the sand that underwent removal treatment. Thus, the negative relationship between bacterial abundance and hatching success supports the hypothesis stated above. This study represents the importance of how nesting environments role in the embryonic development of the Olive Ridley. Microbes have been proven to affect the reproductive success of sea turtle species, and it is importance to address this threat to aid in conservation of this species.