Exercise 4
The Pollution of the Oceans
The oceans have long served as a vast dumping ground for all kinds of waste. No one can calculate
the quantity of solid waste that has been dumped in the world’s oceans, but the total certainly exceeds many
millions of tons. For example, from 1880 to 1895, 75 percent of the solid waste from New York City was
dumped untreated into the Atlantic Ocean. Although it is now prohibited by law, the dumping of solid waste,
including wastewater sludge, industrial waste, and high-level radioactive waste were common in the United
States until 1970. Cruise ships and huge floating fishing factories still regularly dispose of their solid were
products directly into the ocean.
The earth naturally recycles water and refreshes the land in what is called the hydrological cycle. The
hydrological cycle not only renews the supply of water, but cleans it as well. The process begins as heat from
the sun causes sea water, 97 percent of the earth’s total water reserve, to evaporate and form clouds. Because
water evaporates at lower temperatures than most pollutants, the water vapor that rise from the seas is
relatively pure and free of the contaminants, which are left behind. Next, water returns to earth as rain, which
drains into streams and rivers and rushes toward the sea. Although the hydrological cycle produces clean water
in the form of rain, it does not remove the pollutants that steadily build up in the oceans.
Chemicals, petroleum products, and other dangerous substances such as radioactive materials remain
in the ocean, polluting it permanently. The polluted ocean water kills fish or makes them dangerous to eat,
posing health problems for those who consume them. It kills the tiny sea creatures that are the source of food
for larger fish, sharks, and whales. It also spoils a source of great beauty and pleasure when some solid waste is
thrown onto beaches during storms. Discharged petroleum products are frequently found on beaches and
they not only ruin the beach, the petroleum residue kills hundreds of shore birds. These are just a few of the
problems caused by using the oceans as dumping grounds.
Some pollutants in the ocean are not dumped there directly. Nonpoint pollutants are dumped into
lakes, rivers, and streams that may be far away from any ocean. However, these pollutants flow, eventually
into the oceans. They can come from a variety of sources, from road salt to agricultural pesticides. One source
of nonpoint pollution is runoff form farming, including fertilizers, manure, and pesticides. Another source is
industrial runoff, including heavy metals, phosphorous, and many other chemicals. Urban runoff (oils, salts,
various chemicals) and atmospheric fallout of airborne pollution are other sources of nonpoint pollutants that
reach the oceans.
Wastewater dumping is yet another major form of ocean pollution. This includes water and waste
from sinks, toilets, washing machines, and bathtubs. The problem with this type of waste is that it provides
massive amounts of nutrients for water plants, such as algae, so that they grow rapidly. This sudden growth
causes concentrations or algae blooms, which use up the oxygen in the water. As the oxygen levels of the water
decline, many organisms suffer and die, and the ocean ecosystem is radically altered. This can be prevented by
the installation of waste treatment plants that prevent waste from entering the sea, but such facilities do not
exist in many poorer countries.