The ecosystem services provided by marine species have been well-documented, with nutrient cycling driving the movement of massive quantities of elements essential for stable ecosystems. Loggerhead sea turtles have been shown to improve the quality of nutrient-poor beaches through nesting and egg deposition. These services contribute many net benefits to soil quality and vegetation nutrient uptake through nutrient influxes of nitrogen, phosphorus, and potassium. Prior studies have aimed to map the entire spectrum of nutrients and organic material contributed from sea turtle nesting. We quantified nutrient deposition by loggerhead sea turtles at eight nests between June 2015 and August 2016 to add to the existing knowledge regarding ecosystem service contributions of loggerhead sea turtles. Nitrate and nitrite concentrations (NOx) were examined due to their contribution to sand dune vegetation growth and their relative measurement reliability compared to concentrations of other compounds. Samples were taken at various time and location intervals to account for spatial and temporal heterogeneity. Sand samples adjacent to incubating nest cavities and directly below hatched nest cavities were collected and analyzed for NOx concentration by spectrophotometry. Overall, this analysis was conducted to provide quantitative insight into one of the major ecosystem services provided by loggerhead sea turtles.
Results/Conclusions
Samples taken adjacent to incubating nests had NOx concentrations of 0.693 ± 0.39 mg/L (mean ± SD), and samples taken from hatched nest cavities had NOx concentrations of 2.95 ± 4.96 mg/L. While an ANOVA of the NOx concentrations does not indicate a significant increase after the hatching of sea turtle nests (p = 0.105), this may be attributed to a small sample size and low statistical power. The methodology used in this analysis was adapted from several sources, and thus provides a detailed method for approximating nutrient concentrations in sand dune ecosystems. NOx analysis reveals a fraction of the true contribution of nutrient deposits, though the preliminary results from this study provide relative nutrient comparisons that capture the value that loggerhead sea turtles provide to sand dune ecosystems. The results from this analysis provide information that could be used to better understand the benefits that loggerhead sea turtles directly confer to sand dune vegetation. These contributions underscore the value that nutrient deposits from hatched and unhatched sea turtle eggs allocate to soil quality, vegetation uptake, and erosion mitigation due to increased vegetation growth.