Corals & Coral Reefs Index
Scientific Classification
Habitat & Distribution
Physical Characteristics
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Adaptations
Diet & Eating Habits
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Anatomy & Physiology
Coral Reefs
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CORALS & CORAL REEFS
Longevity & Causes of Death
 
LONGEVITY
1.

Little is known about the lifespan of corals. Generally, coral colonies may live for several decades to centuries.
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PREDATORS
1.

Coral polyps face many predators including parrotfishes, butterflyfishes, and sea stars.
   
2.

During the larval stage, corals are particularly subject to predation. They may also drift into areas where the substrate isn't suitable for coral growth.
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HUMAN INTERACTION
1.

Ocean pollution poisons coral polyps. Pollution takes on many forms including oil slicks, pesticides and other chemicals, heavy metals, and garbage.
   
2.

Fertilizer runoff and untreated sewage introduce added nutrients to coastal ecosystems. These elevated nutrient levels promote algae growth. Unfortunately, high concentrations of algae or solid sewage can overwhelm and smother the polyps. Under normal conditions, herbivores fish and some invertebrates keep the algae population in check.
   
3.

Deforestation degrades more than just land habitats. When tropical forests are cut down to clear land for agriculture, pasture, or homes, topsoil washes down rivers into coastal ecosystems. Soil that settles on reefs smothers coral polyps and blocks out the sunlight needed for corals to live.
   
4.

Coastal development and dredging ravages reefs. This development includes building seaside homes, hotels, and harbors.
   
5.

Fishing with dynamite, cyanide, or bleach has killed coral reefs in the Indo-Pacific region. Between 1986 and 1991, half of the coral reefs in the Philippines have been demolished by these and other destructive fishing methods.
   
6. Besides fishes, fishermen harvest a variety of exotic seafood from the reef including conchs and lobsters. Overharvesting could lead to these species' demise. Careless handling of nets, lines, and lobster traps has led to some reef damage.
   
7. International seashell and aquarium trades have put a strain on coral reefs and reef inhabitants. Excessive collecting decimates reef species and upsets the balance of the reef ecosystems. Careful monitoring of these trades will help make sure that the demand for reef species doesn't exceed the sustainable supply.
•

The souvenir trade has created an international market for coral skeletons, shells, sponges, and other reef animals. In 1990, the world consumption of corals for the souvenir trade was estimated at 2,200 tons a year. Coral skeletons are used for decoration aquariums, or fashioned into jewelry and sculptures.
• Coral skeletons are also sold as "live rock". Live rock is popular in home saltwater aquariums because it is permeated with living bacteria and algae and acts a natural biological filter.
• The tropical fish trade has created a demand for reef fishes. These attractive fishes are popular in saltwater aquariums.
   
8. Careless water recreationist damage reefs. Divers and snorklers that stand on, sit on, or handle corals can injure the delicate polyps. Dropped boat anchors can gouge the reef and crush corals. (Boaters should be very careful when navigating around the coral reefs. Anchors shouldn't be dropped directly on the reef, but on a near-by sandy area. Divers should rest by floating or standing on the sandy bottom. They should be very careful not to grab on to any coral formations.)
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NATURAL DISASTERS
1.

Changes in sea level are detrimental to established corals and reefs.
•

A drop in sea level exposes corals.
• A rise in sea level decreases the amount of available sunlight and may inhibit growth. Added emissions of carbon dioxide and other trace gases (called greenhouse gases) into our atmosphere may be causing a gradual warming of our planet. This warming could cause the polar ice caps to melt, thereby raising sea level.
• Rises in sea level can also release nutrients trapped in soil.
   
2.

Coral diseases can wipe out entire strands of coral reefs. Diseases may be connected to the sea level rise and nutrient level increase.
   
3.

Coral bleaching occurs when coral expels its symbiotic zooxanthellae. As a result, the coral loses its coloration. Without zooxanthellae, the coral polyps have little energy available for growth or reproduction. Scientists aren't sure why bleaching occurs. Hypotheses include elevated water temperatures, ultraviolet radiation, and diseases or viruses affecting the zooxanthellae.
   
4.

Major tropical storms can strip corals from miles of reef habitat.
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