A major source of coastal pollutants, human sewage fouls bays and beaches withboth toxic and nontoxic pollutants.
Although billions of dollars have beeninvested in sewage treatment plants to treat wastewater, new and growing coastalcommunities have increased the amount of discharge into oceans and estuaries. The United States Office of Technology Assessment has identified thirteenhundred major industries and six hundred municipal wastewater treatment plantsthat discharge into coastal waters of the United States. Many toxic substancesenter the sea through the sewer systems, but others originate as industrialdischarges. For many toxic substances, we do not yet know how to determine theirextent or fate in the marine environment or to evaluate their effects on marinelife.Order now
Some of the better-known trace metals and toxic chemicals include mercury,copper, lead, and chlorinated hydrocarbons. Chlorinated hydrocarbons, syntheticchlorine-containing compounds, are created for use as pesticides or areby-products of the manufacture of plastics. Oil is a very dangerous thing whenit comes to oil spills into the ocean. These catastrophic oil spills engender aconcern for the marine environment as no invisible containment can.
Spilled oilfloats on seawater and provides a constant reminder of its presence until it iswashed ashore, sinks, or evaporates. Large volumes of oil suffocate benthicorganisms by clogging their gills and filtering structures or fouling theirdigestive tracts. Marine birds and mammals suffer heavily as their feathers orfur become oil soaked and matter, and they lose insulation and buoyancy. Untilrecently, marine debris was considered to be of minor importance when comparedto other pollutants. Problems caused by marine debris, however may rival orexceed those resulting from some better known pollutants, including oil. Bydefinition, marine debris is any manufactured object discarded in the marineenvironment.
When dumped, it may sink to the sea floor, remain suspended atmid-depths, or float at the surface and eventually be carried ashore by windsand waves. Plastics constitute as great an environmental threat as all the otherkinds of debris, combined. Although plastics may break up into smaller pieces,they degrade much more slowly than most other kinds of debris, and most plasticsfloat. Concentrations of plastics tend to be highest in the Northern Hemisphere,where vessel traffic is the heaviest, where most plastics manufacturers andfabricators are located, and where more intensive recreational use is made ofbeaches 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 easyor simple, but each one of us must develop a sense of stewardship toward theworld ocean and its resources that is reflected in our personal as well as ourpolitical decisions.Biology