Marine Biology
A major source of coastal pollutants, human sewage fouls bays and beaches
with
both toxic and nontoxic pollutants. Although billions of dollars have
been
invested in sewage treatment plants to treat wastewater, new and growing
coastal
communities have increased the amount of discharge into oceans and
estuaries.
The United States Office of Technology Assessment has
identified thirteen
hundred major industries and six hundred municipal
wastewater treatment plants
that discharge into coastal waters of the United
States. Many toxic substances
enter the sea through the sewer systems, but
others originate as industrial
discharges. For many toxic substances, we do
not yet know how to determine their
extent or fate in the marine environment
or to evaluate their effects on marine
life. Some of the better-known trace
metals and toxic chemicals include mercury,
copper, lead, and chlorinated
hydrocarbons. Chlorinated hydrocarbons, synthetic
chlorine-containing
compounds, are created for use as pesticides or are
by-products of the
manufacture of plastics. Oil is a very dangerous thing when
it comes to oil
spills into the ocean. These catastrophic oil spills engender a
concern for
the marine environment as no invisible containment can. Spilled oil
floats on
seawater and provides a constant reminder of its presence until it is
washed
ashore, sinks, or evaporates. Large volumes of oil suffocate
benthic
organisms by clogging their gills and filtering structures or fouling
their
digestive tracts. Marine birds and mammals suffer heavily as their
feathers or
fur become oil soaked and matter, and they lose insulation and
buoyancy. Until
recently, marine debris was considered to be of minor
importance when compared
to other pollutants. Problems caused by marine
debris, however may rival or
exceed those resulting from some better known
pollutants, including oil. By
definition, marine debris is any manufactured
object discarded in the marine
environment. When dumped, it may sink to the
sea floor, remain suspended at
mid-depths, or float at the surface and
eventually be carried ashore by winds
and waves. Plastics constitute as great
an environmental threat as all the other
kinds of debris, combined. Although
plastics may break up into smaller pieces,
they degrade much more slowly than
most other kinds of debris, and most plastics
float. Concentrations of
plastics tend to be highest in the Northern Hemisphere,
where vessel traffic
is the heaviest, where most plastics manufacturers and
fabricators are
located, and where more intensive recreational use is made of
beaches and
coastal waters. Hopefully, as we approach the twenty-first century,
we can
learn to leave some old and wasteful habits behind. It will not be easy
or
simple, but each one of us must develop a sense of stewardship toward
the
world ocean and its resources that is reflected in our personal as well
as our
political decisions.