Page 306 - French Polynesia

owever, in the face of other human- of algae, which smothers reefs by cutting
H induced pressures, corals have become
vulnerable. In many cases, bleached coral
colonies die. In the past few decades, the
amount of carbon dioxide in the air has in-
creased by one-third. This is harmful to cor-
als because increased amounts of carbon
dioxide are dissolving into the water, which
appears to be dissolving the skeletons of
corals. As a result, coral in waters with large
amounts of carbon dioxide form weaker
skeletons, making them more vulnerable to
damage from waves, careless tourists, and
destructive fishers.
S cientists have identified pollution as
one of the leading causes of coral reef
degradation. This threat comes from a
variety of sources. For example, oil, gas and
pesticide contamination poisons coral and
marine life. Reefs are harmed when human,
animal waste and/or fertilizer is dumped
into the ocean or when river systems carry
these pollutants to reef waters. These
pollutants increase the level of nitrogen
around coral reefs, causing an overgrowth
artificial prawn farms.
off their sunlight. Trash also kills coral reef
animals. Floating trash can cover reefs,
blocking off sunlight that polyps need to
survive. Turtles often mistake plastic bags
for jellyfish and eat them. Plastic blocks
the turtle’s digestive tract, causing them to
starve to death. Lost or discarded fishing
nets - called “ghost nets” - can snag on reefs
and strangle thousands of fish, sea turtles
and marine mammals.
C onstruction along coasts, inshore con-
struction, mining, logging and farming
along coastal rivers can all lead to erosion.
As a result, particles end up in the ocean
and cover coral reefs. This ‘smothers’ coral
and deprives it of the light it needs to sur-
vive. Mangrove trees and sea grasses, which
normally act as filters for sediment, are
also being rapidly destroyed. This has led
to an increase in the amount of sediment
reaching coral reefs. Mangrove forests are
often cut for firewood or removed to create
open beaches. They are also destroyed by
prawn harvesters to open up areas to create
M ining also destroys coral. Sometimes
coral pieces are removed for use as
bricks or road-fill. Or, sand and limestone
from coral reefs are made into cement
for new buildings. But corals aren’t only
removed from their habitat for construc-
tion; they are also sold as souvenirs. Coral
curios and jewelry are often sold to tourists
and exporters in the markets of developing
countries.
T ourist resorts that empty their sewage
directly into the water surrounding
coral reefs contribute to coral reef degra-
dation. Wastes kept in poorly maintained
septic tanks can also leak into surrounding
ground water, eventually seeping out to the
reefs. Careless boating, diving, snorkeling
and fishing can also damage coral reefs.
Whenever people grab, kick, walk on, or stir
up sediment in the reefs, they contribute
to coral reef destruction. Corals are also
harmed or killed when people drop anchors
on them or when people collect coral.