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Oil
spills account for only about five percent of the
oil entering the oceans. |
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The Coast Guard estimates that for United States
waters sewage treatment plants discharge twice as
much as oil each year as tanker spills. |
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The
most frequently found item in beach cleanups is pieces
of plastic. The next four items are plastic foam, plastic
utensils, and pieces of glass and cigarette butts. |
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Lost
or discarded fishing nets keep on fishing. Called "ghost
nets," this gear entangles fish, marine mammals, and sea
birds, preventing them from feeding or causing them to
drown. As many as 20,000 northern fur seals may die each
year from becoming entangled in netting. |
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When
nitrogen and phosphorus from sources such as fertilizer,
sewage and detergents enter coastal waters, oxygen depletion
occurs. One gram of nitrogen can make enough organic material
to require 15 grams of oxygen to decompose. A single gram
of phosphorus will deplete one hundred grams of oxygen.
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The
zebra mussel is the most famous unwanted ship stowaway,
but the animals and plants being transported to new areas
through ship ballast water is a problem around the world.
Poisonous algae, cholera, and countless plants and animals
have invaded harbor waters and disrupted ecological balance.
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There
are 109 countries with coral reefs. Cruise ship anchors
and sewage, by tourists breaking off chunks of coral,
and by commercial harvesting for sale to tourists are
damaging reefs in 90 of them. |
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One
study of a cruise ship anchor dropped in a coral reef
for one day found an area about half the size of a football
field completely destroyed, and half again as much covered
by rubble that died later. It was estimated that coral
recovery would take fifty years |
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Egypt's
High Aswan Dam, built in the 1960s to provide electricity
and irrigation water, diverts up to 95 percent of the
Nile River's normal flow. It has since trapped more than
one million tons of nutrient rich silt and caused a sharp
decline in Mediterranean sardine and shrimp fisheries.
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More
on Ocean Pollution.... |
