Page 180 - Hawaii: Diving, Surfing, Pearl Harbor, Volcanoes and More

oral formations are divided into three coral reefs was estimated at $375 billion in deep sea away from continental shelves,
C zones. The Shallow Shore extends from 2002. However, coral reefs are fragile eco- around oceanic islands and as atolls. The
the shoreline to about 30 feet in depth. An systems, partly because they are very sensi- vast majority of these islands are volcanic
excellent example is Bonaire, Netherlands tive to water temperature and typically only in origin. The few exceptions have tec-
Antilles where the reef can extend onto the exist in waters surrounding the Equator. tonic origins where plate movements have
shoreline. Platform Reefs (that we refer to They are under threat from climate change, lifted the deep ocean floor on the surface.
as the Mid Reef ) extend from 30 to 50 feet oceanic acidification, blast fishing, cyanide Healthy tropical coral reefs grow horizon-
and lack the structure of the Edge Reef (The fishing for aquarium fish, overuse of reef tally from 1 to 3 centimeters per year, and
Towering Deep) that can extend to 180 feet. resources, and harmful land-use practices, grow vertically anywhere from 1 to 25
The age of the Mid Reef structure var- including urban and agricultural runoff and centimeters per year; however, they grow
ies between 1,000 and 10,000 years. Edge water pollution, which can harm reefs by only at depths shallower than 150 meters
reefs, characterized by the Great Towering encouraging excess algal growth. because of their need for sunlight, and
Reefs of Cozumel, Mexico and the Cayman cannot grow above sea level. Live coral are
Islands are continuous structures rising ost coral reefs were formed after the small animals embedded in calcium carbon-
into coral peaks high above the edge of the M last glacial period when melting ice ate shells. It is a mistake to think of coral
drop off zone and extending to a depth caused the sea level to rise and flood the as plants or rocks. Coral heads consist of
of 180 feet. Edge Reefs can be hundreds of continental shelves. This means that most accumulations of individual animals called
thousands of years old. They are magnifi- coral reefs are less than 10,000 years old. polyps, arranged in diverse shapes. Polyps
cent structures and safely within range of As communities established themselves on are usually tiny, but they can range in size
the recreational diving. the shelves, the reefs grew upwards, pacing from a pinhead to 30 centimeters across.
rising sea levels. Reefs that rose too slowly
oral reefs deliver ecosystem services to could become drowned reefs, covered by
C tourism, fisheries and shoreline protec- so much water that there was insufficient
tion. The annual global economic value of light. Coral reefs can also be found in the