A snapshot of sediment dynamics on an inshore coral reef

Authors: Jodie Schlaefer, Sterling Tebbett, Casey Bowden, William Collins, Stephanie Ducec, Christopher Hemingson, Victor Huertas, Michalis Mihalitsis, Juliano Morais, Renato Morais, Alexandre Siqueira, Robert Streit, Sam Swan, Jessica Valenzuela & David Bellwood

Abstract:

Sediments are ubiquitous on coral reefs. However, studies of reef sediments have largely focused on isolated reservoirs, or processes, and rarely consider hydrodynamic drivers. We therefore provide a quantitative snapshot of sediment dynamics on a coral reef. Across a depth profile, we simultaneously examined: suspended sediments, sediment deposition and accumulation, and hydrodynamic and biological movement processes. We reveal the marked potential for the water column to deliver sediments. Currents carried 12.6 t of sediment over the 2,314 m2 study area in 6 days. Sediment traps suggested that a surprisingly high percentage of this sediment was potentially deposited (5.2%). Furthermore, wave-driven resuspension and reworking by parrotfishes separated a highly dynamic sediment regime on the shallow reef flat (3 m), from a more stagnant reef slope (4.5 m–12 m). This study provides a comprehensive model of how hydrodynamic forces and on-reef processes may shape sediment dynamics on a coral reef.