Olive Ridley Sea Turtle Hatching Success as a Function of the Microbial Abundance in Nest Sand at Ostional, Costa Rica

Abstract

Several studies have suggested that significant embryo mortality is caused by microbes, while high microbial loads are generated by the decomposition of eggs broken by later nesting turtles. This occurs commonly when nesting density is high, especially during mass nesting events (arribadas). However, no previous research has directly quantified microbial abundance and the associated effects on sea turtle hatching success at a nesting beach. The aim of this study was to test the hypothesis that the microbial abundance in olive ridley sea turtle nest sand affects the hatching success at Ostional, Costa Rica. We applied experimental treatments to alter the microbial abundance within the sand into which nests were relocated. We monitored temperature, oxygen, and organic matter content throughout the incubation period and quantified the microbial abundance within the nest sand using a quantitative polymerase chain reaction (qPCR) molecular analysis. The most successful treatment in increasing hatching success was the removal and replacement of nest sand. We found a negative correlation between hatching success and fungal abundance (fungal 18S rRNA gene copies g-1 nest sand). Of secondary importance in determining hatching success was the abundance of bacteria (bacterial 16S rRNA gene copies g-1 g-1 nest sand). Our data are consistent with the hypothesis that high microbial activity is responsible for the lower hatching success observed at Ostional beach. Furthermore, the underlying mechanism appears to be the deprivation of oxygen and exposure to higher temperatures resulting from microbial decomposition in the nest.

A preliminary investigation into the early embryo death syndrome (EEDS) at the world’s largest green turtle rookery

“…When nests at Raine Island that have experienced EEDS are excavated at the end of incubation, most of the eggs were in a state of decay and infected with fungus and bacteria [ 2 ], but it is not known if these infections caused embryos to die, or have occurred secondarily after the embryos have died. High nest mortality of sea turtle embryos has been associated with high microbial loads within nests of olive ridley turtle arribada nesting aggregations at Ostional beach, Costa Rica [ 9 , 10 ]. The high microbial load in the sand at these beaches are associated with high concentrations of organic matter in the sand due to hatched eggshells and undeveloped eggs and dead embryos that accumulate in the sand [ 10 , 11 , 12 ].…”

Climate change and temperature‐linked hatchling mortality at a globally important sea turtle nesting site

“…Tropical storms and hurricanes can also reduce hatching success in loggerhead and green turtle nests in Florida (Lindborg, Neidhardt, Witherington, Smith, & Savage, ). In Costa Rica, high abundance of microbes and fungi was negatively correlated with hatching success of olive ridley turtles at a mass‐nesting beach (Bézy, Valverde, & Plante, ). Investigating how these factors are likely to vary in the future and estimating how they will impact sea turtle numbers provides for interesting new research.…”

Distribution and Feeding Behavior of Omorgus suberosus (Coleoptera: Trogidae) in Lepidochelys olivacea Turtle Nests

“…Under natural conditions, many nests have a combination of live eggs with evident development (no perforations) and dead eggs (with perforations) in an advanced state of decomposition, as well as a great quantity of egg shells, apparently the result of intra–specific nest destruction [ 8 ]. This modifies the micro–environmental conditions (i.e., higher CO 2 concentration and increased temperature) within the nests as a consequence of microbial activity [ 45 ], which can facilitate the rapid consumption of the eggs by the beetles. The increased temperature within the nests may explain the greater feeding and reproductive behavior of this beetle, as reported for two species of Omorgus (O .…”