National Geographic : 2001 Jan
continental, or high, islands, which were mountains and hills along Australia's Ice Age coast before the glaciers melted and raised sea levels; the Aborigines' legends of ancient gen erations walking out to those islands are true. In addition there are about 300 low islands, or cays, formed atop coral shoals from reef sed iments. As seabird droppings glue the grains together and colonizing plants build soil, some of those desert isles transform into shadowy woodlands, while storms pound others back into shifting piles of sand. By acting as a buffer against heavy seas, the reef-and-island complex makes possible neigh boring sea grass beds and coastal mangrove forests. Those in turn trap sediments, store nutrients, and serve as nurseries for a number of reef residents. Now add the soft sea bottoms between reefs plus submarine hillocks made entirely of Halimeda, a calcium-hardened green algae. Put all these habitats together with clear azure waters flowing from the Coral Sea and brown, soil-laden waters washing off the con tinent. Mix with currents, daily tides, and sea sonal weather patterns. What you have is the formula for the Great Barrier Reef ecosystem and lifetimes of discovery. T HE BETTER we came to know this off shore nation, the more it resembled a long chain of provinces. Four major sections are widely recognized: Mackay/ Capricorn in the south, where the water first warms enough to encourage coral growth, Central, Cairns, and Far Northern, which is the most remote and, being closest to the Equator, hosts the lushest array of life. Our first destination was the Eastern Fields, a rarely visited atoll that lies outside the Far Northern section near the Gulf of Papua, 200 miles east of Australia's Cape York Peninsula the damsel, whip gobies (below)-less than two inches long-stick close to the thin, polyp-studded coral sea whips that serve as home,feeding ground, and nesting place.