Microbial community structure in sand on two olive ridley arribada nesting beaches, Playa La Flor, Nicaragua and Playa Nancite, Costa Rica

Microbial relative abundance, diversity and richness were assessed based on 16S rRNA gene-based TRF community analysis via terminal restriction fragment (TRF) analysis on two olive ridley turtle arribada nesting beaches in Central America, Playa La Flor in Nicaragua and Playa Nancite in Costa Rica. Arribada beaches have very high densities of egg clutches in small areas, and the sand contains numerous broken eggs due to turtles inadvertently disturbing previously laid clutches. The high organic content (broken eggs) in the sand causes microbial build up in clutches, which in return may affect hatching success. Phylotype relative abundance (fragment abundance) differed with nest density and distance from the water at both Playa Nancite and Playa La Flor. Higher relative abundance of certain bacterial species in high nest density areas may have contributed to lower hatching success. Bacterial diversity and richness increased with nest density and were higher in the zones closer to vegetation suggesting that bacterial diversity and richness may be important factors affecting hatching success of olive ridley eggs on these nesting beaches. To better conserve olive ridley sea turtles and manage egg harvest on arribada nesting beaches further studies should focus on identifying bacterial species that are pathogenic to turtle eggs and their effects on hatching success.

► Phylotype relative abundance differed with nest density at two arribada beaches.
► Phylotype relative abundance also differed with distance from the water.
► Bacterial richness increased with increasing nest density in different beach zone.
► Bacterial diversity increased with increasing nest density in different beach zone.