The response of sandy beach meiofauna to nutrients from sea turtle eggs

Abstract

Organic matter transfer across ecosystem boundaries strongly influences consumer populations and food web dynamics. Consequently, it is hypothesized that sandy beaches, which are organic matter-limited ecosystems and almost exclusively subsidized by allochthonous inputs, should respond to pulses of organic matter. Large quantities of organic matter in the form of eggs are deposited on the high shore of tropical and subtropical beaches during the turtle nesting season. This study quantifies the response of meiofauna to the decomposition of turtle eggs over time. Meiofaunal densities were first measured in predated nests. Second, the response of meiofauna to organic matter inputs over time were quantified experimentally, in situ, by comparing meiofauna communities from five artificially predated pseudo-nests with those from five control pseudo-nests, sampled daily at three depths for 3weeks. There was a strong temporal response of the meiofauna in the experimental treatment compared to that in the controls. After 5days, the meiofaunal communities in the experimental treatment were significantly different to those in the control treatment, with abundance of all taxa higher in the experimental treatments, particularly nematodes. The peak of the response (maximum nematode abundance: 2.5×105ind·cm3) was observed after 7days. Thereafter, their abundance declined until it returned to the background density (<100ind·cm3) after 20days. Given the large quantity of turtle eggs deposited above the high tide mark, these seasonal inputs represent a pulsed resource with a significant contribution to the energy budget of sandy beach/dune ecosystems. Turtle nesting may thus play a key ecological role in structuring meiofaunal communities of sandy beach ecosystems.