The use (and misuse) of sediment traps in coral reef environments: theory, observations, and suggested protocols

Abstract

Sediment traps are commonly used as standard tools for monitoring ''sedimentation'' in coral reef envi- ronments. In much of the literature where sediment traps were used to measure the effects of ''sedimentation'' on corals, it is clear from deployment descriptions and inter- pretations of the resulting data that information derived from sediment traps has frequently been misinterpreted or misapplied. Despite their widespread use in this setting, sediment traps do not provide quantitative information about ''sedimentation'' on coral surfaces. Traps can pro- vide useful information about the relative magnitude of sediment dynamics if trap deployment standards are used. This conclusion is based first on a brief review of the state of knowledge of sediment trap dynamics, which has pri- marily focused on traps deployed high above the seabed in relatively deep water, followed by our understanding of near-bed sediment dynamics in shallow-water environ- ments that characterize coral reefs. This overview is fol- lowed by the first synthesis of near-bed sediment trap data collected with concurrent hydrodynamic information in coral reef environments. This collective information is utilized to develop nine protocols for using sediment traps in coral reef environments, which focus on trap parameters that researchers can control such as trap height (H), trap mouth diameter (D), the height of the trap mouth above the substrate (zo), and the spacing between traps. The hydro- dynamic behavior of sediment traps and the limitations of data derived from these traps should be forefront when interpreting sediment trap data to infer sediment transport processes in coral reef environments.