Predator Diet and Trophic Position Modified with Altered Habitat Morphology

Area of Science:

• Ecology
• Marine Biology
• Ecosystem Dynamics

Background:

• Coastal margins are dynamic ecosystems where aquatic and terrestrial systems interact.
• Human development activities are concentrated in coastal areas, impacting ecosystems.
• A dynamic food web approach is crucial for understanding these impacts but is rarely applied at the coast.

Purpose of the Study:

• To model and test ghost crab (Ocypode quadrata) feeding patterns along a beach morphology gradient.
• To predict how dominant prey (Emerita talpoida, Talorchestia sp., Donax variablis) shift with changing beach conditions.
• To assess the implications of anthropogenic disturbance on coastal food webs.

Main Methods:

• Studied 16 Florida beaches, quantifying morphology, wrack, prey, and ghost crab burrows.
• Utilized stable isotope analysis (¹³C/¹²C and ¹⁵N/¹⁴N) to determine ghost crab diet.
• Applied the SIAR mixing model to analyze dietary composition and trophic position.

Main Results:

• Ghost crab diet and trophic position varied significantly with increasing beach width.
• Dietary shifts correlated with the availability of preferred micro-habitats for prey species.
• Ghost crabs exhibited flexible feeding strategies, adapting their diet to habitat morphology.

Conclusions:

• Ghost crab feeding demonstrates a functional response within the food web across different beach morphologies.
• The dynamic food web approach provides a framework for assessing anthropogenic impacts on sandy beaches.
• Findings are critical for managing impacts like beach grooming, nourishment, and human traffic.