Sedimentation-Construction
along coasts mining, farming and logging of Rainforests
causes soil run off smothers coral reefs blocking sunlight that it needs to
survive.
Soil runoff, Hawaii
National Oceanic and
Atmospheric Administration
Fishing
with explosives -In
depleted fisheries, people resort to desperate tactics to catch the fish
that remain—one of those is dynamite. The explosions send dead fish to the
surface and destroy living reefs.
This
Coca-Cola bottle, found near one of the Capone islands,Philipines
still shows a slightly burned fuse and explosive inside
Dynamite
not only kills the fish that live in the reef, but the reef as well
(Photo courtesy Thomas Heeger: Philippines)
Fishing
with Poisons-Poison fishing
commonly referred to as “cyanide fishing,” is another popular
destructive fishing method. Sodium cyanide and bleach are the two most
commonly used poisons. Other fish poisons, also called icthyotoxins or
piscicides, occur in several related plant species. A variety of chemicals
found in these plants will stun fish when it passes through the gills or
in some cases ingested. The fish then floats to the surface for easy
capture. These practices also poison "non-target" species,
including corals, and can cause a variety of human health problems. The impact of these poisons on the reef ranges from coral
bleaching to death.
Water
Pollution-Petroleum
products and chemicals are lethal to Coral
Reefs.
Massive
Oil Slicks Bahrain NASA Space Shuttle
They
are dumped directly into the ocean or carried by river systems from
sources upstream.
Runoff
from this pipe in the U.S. Virgin Islands spews directly into the ocean
only a few hundred yards from reefs. Photo courtesy of the NOAA Coastal
Programs Division
Some pollutants, such as sewage and runoff from farming,
increase the level of nitrogen in seawater, causing an overgrowth of
algae, which 'smothers' reefs by cutting off their sunlight.
Careless
recreation and collection of coral-Careless
boating, diving and fishing can cause damage to Coral
Reefs. Careless boating, diving, snorkeling, and fishing happens around
the world, with people touching reefs, stirring up sediment, collecting coral,
and dropping anchors on reefs.
Overfishing- This
affects the ecological balance of coral reef communities, warping the food chain
and causing effects far beyond the directly over fished population.
Coral mining- Live
coral is removed from reefs for use as bricks, road-fill, or cement for new
buildings. Corals are also sold as souvenirs to tourists and to exporters
Climate Change/Global Warming-When ocean
temperatures increase the coral polyps lose the symbiotic algae inside them,
causing them to turn white and die.
This is referred to as
"bleaching". In the past several years there has been an unprecedented number
of "bleaching" events world wide.
The
effects of bleaching can be seen already in sections of the Great Barrier Reef
Anthropogenic
Threats to Corals
Human-caused,
or anthropogenic activities are major threats to coral reefs. Pollution,
overfishing, destructive fishing practices using dynamite or cyanide,
collecting live corals for the aquarium market and mining coral for
building materials are some of the many ways that people damage reefs all
around the world every day.
One of the most significant threats to reefs is pollution. Land-based
runoff and pollutant discharges can result from dredging, coastal
development, agricultural and deforestation activities, and sewage
treatment plant operations. This runoff may contain sediments, nutrients,
chemicals, insecticides, oil, and debris .
When some pollutants enter the water, nutrient levels can increase,
promoting the rapid growth of algae and other organisms that can smother
corals .
Coral reefs also are affected by leaking fuels, anti-fouling paints and
coatings, and other chemicals that enter the water . Petroleum spills do
not always appear to affect corals directly because the oil usually stays
near the surface of the water, and much of it evaporates into the
atmosphere within days. However, if an oil spill occurs while corals are
spawning, the eggs and sperm can be damaged as they float near the surface
before they fertilize and settle. So, in addition to compromising water
quality, oil pollution can disrupt the reproductive success of corals,
making them vulnerable to other types of disturbances. .
In many areas, coral reefs are destroyed when coral heads and
brightly-colored reef fishes are collected for the aquarium and jewelry
trade. Careless or untrained divers can trample fragile corals, and many
fishing techniques can be destructive. In blast fishing, dynamite or other
heavy explosives are detonated to startle fish out of hiding places. This
practice indiscriminately kills other species and can crack and stress
corals so much so that they expel their zooxanthellae. As a result, large
sections of reefs can be destroyed. Cyanide fishing, which involves
spraying or dumping cyanide onto reefs to stun and capture live fish, also
kills coral polyps and degrades the reef habitat . More than 40 countries
are affected by blast fishing, and more than 15 countries have reported
cyanide fishing activities .
Other
damaging fishing techniques include deep water trawling, which involves
dragging a fishing net along the sea bottom, and muro-ami netting, in
which reefs are pounded with weighted bags to startle fish out of
crevices. Often, fishing nets left as debris can be problematic in areas
of wave disturbance. In shallow water, live corals become entangled in
these nets and are torn away from their bases . In addition anchors
dropped from fishing vessels onto reefs can break and destroy coral
colonies .
Reef
Check Australia: The Reef Needs You
Natural
Threats to Coral Reefs
Coral
reefs face numerous threats. Weather-related damage to reefs occurs
frequently. Large and powerful waves from hurricanes and cyclones can
break apart or flatten large coral heads, scattering their fragments . A
single storm seldom kills off an entire colony, but slow-growing corals
may be overgrown by algae before they can recover .
Reefs also are threatened by tidal emersions. Long periods of
exceptionally low tides leave shallow water coral heads exposed, damaging
reefs. The amount of damage depends on the time of day and the weather
conditions. Corals exposed during daylight hours are subjected to the most
ultraviolet radiation, which can overheat and dry out the coral's tissues.
Corals may become so physiologically stressed that they begin to expel
their symbiotic zooxanthellae, which leads to bleaching, and in many
cases, death.
Black-band
disease
Corals
face serious risks from various diseases, including black-band disease.
The susceptibility of corals to disease may be on the rise as a result of
human activities.
Increased
sea surface temperatures, decreased sea level and increased salinity from
altered rainfall can all result from weather patterns such as El Niño.
Together these conditions can have devastating effects on a coral’s
physiology . During the 1997-1998 El Niño season, extensive and severe
coral reef bleaching occurred in the Indo-Pacific and Caribbean.
Approximately 70 to 80 percent of all shallow-water corals on many
Indo-Pacific reefs were killed.
In addition to weather, corals are vulnerable to predation. Fish, marine
worms, barnacles, crabs, snails and sea stars all prey on the soft inner
tissues of coral polyps . In extreme cases, entire reefs can be devastated
by this kind of predation. In 1978 and 1979, a massive outbreak of
crown-of-thorns starfish(Acanthaster
planci)attacked the reef at the
Fagatele Bay National Marine Sanctuary in American Samoa. Approximately 90
percent of the corals were destroyed.
crown-of-thorns starfish
Coral reefs may recover from periodic traumas caused by weather or other
natural occurrences. If, however, corals are subjected to numerous and
sustained stresses including those imposed by people, the strain may be
too much for them to endure, and they will perish.
Data
compiled from The British Antarctic Study, NASA, Environment Canada,
UNEP, EPA and
other sources as stated and credited Researched by Charles
Welch-Updated dailyThis
Website is a project of the The Ozone Hole Inc. a 501(c)(3) Nonprofit
Organization
