Program and Agenda

Abstract

FINE-GRAINED SEDIMENT TRANSPORT ON A FRINGING CORAL REEF FLAT AS ELUCIDATED BY SEDIMENT TRACERS AND OCEANOGRAPHIC MEASUREMENTS

To advancing our understanding of the natural controls on fine-grained terrestrial sediment resuspension and advection on ecosystem health and the evolution of high-island coral reef systems, 80 kilograms of synthetic coarse-grained silt with magnetic and fluorescent properties were deployed at a depth of 1 meter on the fringing reef flat of southern Molokai, Hawaii. These sediment tracers were tracked over a seven-day period by using an in situ array of 24 rare-earth magnets attached to poles. The tracers were also sampled with an ultraviolet seabed sediment camera system at preselected grid points; concurrent oceanographic and meteorologic time-series measurements were collected to characterize the physical forcing. The initial plume following deployment was in the form of a narrow - order of meters - concentrated jet, with very little lateral mixing over alongshore dispersal distances of 100s of meters. Subsequent resuspension of the seabed tracer deposit resulted in greater lateral dispersal relative to alongshore dispersal than during the initial deployment. Sediment tracer dynamics estimated from the oceanographic measurements compared well with the patterns of tracer redistribution revealed by the magnets and the seabed camera. The data and resulting analyses indicate that the integration of traditional oceanographic measurements with sediment tracers form a useful tool to evaluate sediment transport pathways in coral reef environments.

Authors

Field, M. E., US Geological Survey, USA, mfield@usgs.gov

Storlazzi, C. D., US Geological Survey, USA, cstorlazzi@usgs.gov

Cacchione, D. A., US Geological Survey, USA, dcacchione@comcast.net

Logan, J. B., US Geological Survey, USA, jlogan@usgs.gov

Rubin, D. M., US Geological Survey, USA, drubin@usgs.gov

Details

Oral presentation

Session #:014
Date: 2/28/2014
Time: 15:30
Location: 313 C

Presentation is given by student: No