The Microbiomes of Sea Turtle Nests in Venice Beach, Florida

Abstract

Sea turtles nest throughout the world’s beaches and the fate of their clutches depends on many factors including the biotic and abiotic properties of the sand.It is well documented how a multitude of sand properties can impact the nest microenvironment and consequentially have a positive or negative effect on incubation. The present study looks at the microbiotic diversity in the sand of four beach areas of varying human traffic on Venice Beach, Florida. Our goal was to document bacterial species presence, relate them to human usage and extrapolate the potential role these bacteria species have on their respective sea turtle nest nest microbiomes.This study was conducted during the sea turtle summer nesting season and samples were collected at four locations in Venice Beach every week from July until October. The locations were a pubic beach, a private beach, a dog beach and an isolated beach. This study design documents changes within the same beach and nesting site. Samples were also collected along the dune and high tide line and at three different depths in the same location to document microbiotic differences across and at different depths of the beach planform, respectively. Sargassum and other macroalgae were collected at random locations and its bacterial fauna identified to see if they could serve as possible bacterial sources for beach sand.Sand samples were incubated in trypic soy broth and then plated in agar that selected for gram positive and negative bacteria. After individual bacterial colonies were isolated, DNA was extracted using standard procedures. The 16s ribosome was target with a primer, DNA was amplified using a PCR, and the DNA was sent for Sanger sequencing.Bacteria species were identified by comparing their DNA sequences against several online databases such as BLAST. Data collected from several biochemical tests (oxidase test, glucose/fructose/lactose fermentation, anaerobic test, MacConkey and Mannitol Salt media, etc) done prior to DNA isolation were used to confirm the bacteria species identified by the database.Our results show that there is diversity in bacterial fauna in the sand samples from the different sea turtle nesting areas of Venice Beach. Although some bacteria species (i.e. Pseudomonas), were found more prevalent in sand from hatched than unhatched clutches we cannot, at this time, state they played a significant role in the fate of the clutch. However, species diversity could not be explained in relation to sand properties and we believe it to be correlated to the level of anthropogenic impact. Further research is needed to test the direct influence these bacterial species have on the incubation of sea turtle eggs.Support or Funding InformationStudy was funded by National University’s Undergraduate Research Opportunity Program