PARENT SESSION
Oral Session # 61: Biogeochemistry IV: Al, Ca, P, and DOC.
Presiding: R Fitzhugh
Wednesday, August 6. 1:30 PM to 5:00 PM, SITCC Meeting Room 205.

Nutrient flow from sea turtle nests to dune vegetation.

Plog, Laura^*,1, Weishampel, John¹, Roth, James¹, Ehrhart, Llewellyn¹, ¹ University of Central Florida, Orlando, FL

ABSTRACT- Sea turtles are important biological transporters, bringing nutrients and energy from distant foraging grounds to nesting beaches through egg deposition. Because nesting beaches are typically nutrient-poor, an increase in nitrogen (N) concentrations could be critical for maintaining dune vegetation and promoting stabilization from erosion. The 40.5 km stretch of beach between Melbourne Beach and Wabasso Beach, Florida, supports the worlds third largest nesting population of loggerhead turtles (Caretta caretta) and the largest nesting population of green turtles (Chelonia mydas) in the continental United States. Nest locations of both species exhibit similar clinal patterns, ranging from approximately 100 nests per km in the northern part of the beach to over 1000 nests per km in the southern portion of the beach. To evaluate the contribution of nutrients from sea turtle eggs to dune vegetation, we measured stable-nitrogen isotope ratios ¹⁵N/¹⁴N) of turtle eggs and other marine sources (e.g., drift algae), which are typically enriched in ¹⁵N over terrestrial sources, and compared these to stable-nitrogen isotope ratios of dominant dune plants. Plant samples were collected along a gradient of nesting density parallel to the shore and at three locations on the dune (foredune, middune, and top of dune). Eggs of carnivorous loggerhead turtles were enriched in ¹⁵N by 5.0^o/_oo over eggs of herbivorous green turtles. Isotopic signatures of sea oats (Uniola paniculata) were significantly higher in the area of high sea turtle nest density. Within this area, sea oats at the foredune were enriched in ¹⁵N by 3.1^o/_oo over plants at the top of the dune. Thus, sea turtle nesting may represent an important biogeochemical link between marine and terrestrial environments.

Key words: sea turtle, dune vegetation, isotope, nutrients