HANOVER, New Hampshire, May 9 -- Dartmouth College issued the following news: * * * Halo Patterns Around Coral Reefs May Signal Resilience Study models spatial patterns of "grazing halos" around reefs. In coral reefs throughout the world, visually striking bands of bare sand surrounding reefs are often visible in satellite imagery, but their cause remains a mystery. One theory is fear. Parrotfish and other herbivores will leave a reef's shelter to eat algae or the surrounding seagrass, but   more