Page 35 - Coral Reef Teachers Guide

Coral Forest Teacher’s G u i d e What and Where are the Coral Reefs?

How Coral Reefs Coral reefs deliver ecosystem services
to tourism, fisheries and shoreline pro-
Form tection. The annual global economic
value of coral reefs was estimated at
$375 billion in 2002. However, coral
reefs are fragile ecosystems, partly be-
Coral reefs are underwater structures made cause they are very sensitive to water
from calcium carbonate secreted by corals. temperature and typically only exist in
They are colonies of tiny animals found in ma- waters surrounding the Equator. They
rine waters that contain few nutrients. Most are under threat from climate change,
coral reefs are built from stony corals, which oceanic acidification, blast fishing, cya-
in turn consist of polyps that cluster in groups. nide fishing for aquarium fish, overuse
The polyps belong to a group of animals known of reef resources, and harmful land-use
as Cnidaria, which also includes sea anemo- practices, including urban and agricul-
nes and jellyfish. Unlike sea anemones, coral tural runoff and water pollution, which
polyps secrete hard carbonate exoskeletons can harm reefs by encouraging excess
which support and protect their bodies. Reefs
grow best in warm, shallow, clear, sunny and algal growth.
agitated waters. Often called “rainforests of
the sea”, coral reefs form some of the most di-
verse ecosystems on Earth. They occupy less
than 0.1% of the world’s ocean surface, about
half the area of France, yet they provide a
home for 25% of all marine species. Coral reefs
flourish even though they are surrounded by
ocean waters that provide few nutrients. They
are most commonly found at shallow depths in
tropical waters.

Coral formations are divided into three
zones. The Shallow Shore extends from
the shoreline to about 30 feet in depth.
An excellent example is Bonaire, Nether-
lands 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 varies between 1,000 and
10,000 years. Edge reefs, characterized
by the Great Towering Reefs of Cozumel,
Mexico and the Cayman Islands are con-
tinuous 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 Most coral reefs were formed after the last
years old. They are magnificent structures glacial period when melting ice caused the
and safely within range of the recreational sea level to rise and flood the continental
diving.
shelves. This means that most coral reefs
are less than 10,000 years old.

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