|Throughout history humans have been directly or indirectly influenced
by the oceans. Ocean waters serve as a source of food and valuable minerals,
as a vast highway for commerce, and provide a place for both recreation
and waste disposal. Increasingly, people are turning to the oceans for
their food supply either by direct consumption or indirectly by harvesting
fish that is then processed for livestock feed. It has been estimated that
as much as 10% of human protein intake comes from the oceans. Nevertheless,
the food-producing potential of the oceans is only partly realized. Other
biological products of the oceans are also commercially used. For example,
pearls taken from oysters are used in jewelry, and shells and coral have
been widely used as a source of building material.
is processed to extract commercially valuable minerals such as salt, bromine,
and magnesium. Although nearly 60 valuable chemical elements have been
found dissolved in ocean water, most are in such dilute concentrations
that commercial extraction is not profitable. In a few arid regions of
the world, such as Ascension Island, Kuwait, and Israel, ocean water is
desalinated to produce freshwater.
continental shelves have been exploited as a source of sands and gravels.
In addition, extensive deposits of petroleum-bearing sands have been exploited
in offshore areas, particularly along the Gulf and California coasts of
the United States and in the Persian Gulf. On the deep ocean floor manganese
nodules, formed by the precipitation of manganese oxides and other metallic
salts around a nucleus of rock or shell, represent a potentially rich and
extensive resource. Research is currently being conducted to explore nodule
mining and metallic extraction techniques. Ocean water itself could prove
to be a limitless source of energy in the event that nuclear fusion reactors
are developed, since the oceans contain great quantities of deuterium.
also have become more important for recreational use, as each year more
people are attracted to the sports of swimming, fishing, scuba diving,
boating, and water-skiing. Ocean pollution, meantime, has escalated dramatically
as those who use the oceans for recreational and commercial purposes, as
well as those who live nearby, have disposed of more and more wastes there
(see water pollution).