Page 66 - Melanesia

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