Sticky waters in the Great Barrier Reef

The Great Barrier Reef is a mosaic of regions of high and low reef density. Current meter observations upstream from a region of high reef density rev ealed that the tidal and low-frequency currents were steered away from the region during spring tides but not during neap tides. A mathematical model suggests that this effect was due to both tidal friction and to the dissipa tion of energy by eddies behind reefs at spring tides. For a high reef dens ity region, this results in a longer residence time at spring tides than at neap tides. Conversely, this effect also diminishes connectivity between r egions of high and low reef density at spring tides. This process may affec t the recruitment and dispersion of fish and other larvae in the Great Barr ier Reef. It may also invalidate the use of satellite altimetry and tidal h armonic analysis for currents in the Great Barrier Reef. (C) 2000 Academic Press.