Plume Dispersion on a Fringing Coral Reef
Nicole Jones, Ryan Lowe, Stephen Monismith and Derek Fong
Environmental Fluid Mechanics Laboratory
Civil and Environmental Engineering
Stanford University

Geno Pawlak
Department of Ocean and Resources Engineering
School of Ocean and Earth Science and Technology
University of Hawaii

A field experiment was conducted on a fringing reef on the South Shore of the island of Oahu, Hawaii, to investigate the dispersion and transport of a nearbed coastal plume. An autonomous dye source released Rhodamine WT fluorescent dye at the sea floor at a constant rate. The horizontal structure of the plume was tracked with a REMUS Autonomous Underwater Vehicle (AUV) [Hydroid, Inc.] with an onboard Turner Designs Cyclops fluorometer (Figure 1a and b; figure 2). The vertical structure of the plume and the ambient stratification was measured using an Ocean Sensors CTD with a Turner Designs Cyclops fluorometer (Figure 3). Experiments incorporated a variety of different surface wave conditions, allowing us to investigate how waves affect cross-reef plume transport (via Stokes' drift) and enhance vertical and horizontal mixing generated by the interaction of the oscillatory flow with the reef roughness.


Figure 1 The Cyclops fluorometer is situated in the nose of REMUS.


Figure 2 Rhodamine WT dye concentration measured by the Cyclops fluorometer. Plume measured centerline vs. that predicted using ADCP data: o's represent measured centerline position. x's represent predicted centerline


Figure 3 Vertical profiles of density and fluorescence illustrate the growth in the height of the plume from roughly 2 m of the bed, 17 m away from the source, to 4 m of the bed, 63 m from the source.