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The Human Presence in the Ocean

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  1. The Human Presence in the Ocean

  2. 15-1 Pollution: What is it? Pollution is the introduction by man, directly or indirectly, of substances or energy into the environment resulting in deleterious effects such as harm to living resources, hazards to human health, hindrance of marine activities, including fishing, impairing quality for use of sea water and reduction of amenities. • In studying pollution it is important to have a baseline from which to measure man’s impact upon the environment because some of what is considered to be pollution may be occurring naturally and not caused by man.

  3. 15-1 Pollution: What is it? • Pollution tends to be concentrated in three parts of the ocean environment: the sea floor, the pycnocline, and the neuston layer. • Pollutants are eventually broken down by various oceanographic and biological processes.

  4. 15-2 Hydrocarbons in the Sea Petroleum is a complex mixture of hydrocarbons, combinations of hydrogen and carbon with various amounts of nitrogen and metals. • Oil as it comes from the ground is called crude oil or petroleum. • Only a small fraction of the oil in the sea comes from major oil tanker accidents. • Once in the environment, an oil spill begins to be altered. • The rate at which the oil is dispersed and dissipated depends upon the weather, composition of the crude and the waves and currents.

  5. 15-2 Hydrocarbons in the Sea • All oil is toxic at all levels of the food chain, but degree of damage depends upon the type of petroleum and upon the specific habitat and ecosystem. • There are several methods employed in attempting to clean a spill: Floating booms, Chemical dispersants, burning the oil at the surface, skimming, and bioremediation

  6. 15-3 Municipal and Industrial Effluent Each year humans produce over 20 billion tons of wastes, much of which is disposed of in the ocean. • Most of the wastes come from farmland, cities and industrial areas and enter the sea by way of rivers. • Wastes tend to be concentrated in harbors, bays and estuaries. • All bodies of water have a natural capacity to clean themselves of a certain amount of pollution, but dense populations can produce so much pollution that the self-cleaning capacity is exceeded. • As pollution enters the sea, it can be greatly diluted depending upon the waves and currents.

  7. 15-3 Municipal and Industrial Effluent • Various pollutants behave differently depending upon their temperature, density and solubility. • As effluents are released, they form a contaminant plume which increases in size with distance as the pollutant is diluted by surrounding water.

  8. 15-3 Municipal and Industrial Effluent Municipal and industrial wastes in the ocean can be divided into three general categories: sewage, metals and artificial biocides. • Sewage consists of mostly human waste sludge or organic and inorganic chemicals. • Heavy metal is a term loosely applied to a collection of elements such as lead, mercury, cadmium, arsenic and copper that normally occur in trace amounts in the ocean, but become toxic in larger dosages. • Artificial biocides are man-made toxic chemical compounds that do not occur naturally.

  9. Hypoxia on Louisiana Shelf 1. Areal extent: Largest oxygen-depleted waters in west Atlantic Ocean (up to 16,000 km2 to 18,000 km2 of hypoxic water recorded, Rabalais, 1998) 2. Seasonality: From late Feb. to early Oct., and peaks in middle Summer when stratification is most severe 3. Severity and duration of hypoxia depends on the amplitude and phasing of discharge from the Mississippi/Atchafalaya rivers (Justic et al, 1993; Rabalais, 1996, 1998)

  10. <> Epidemiologic Notes and Reports Toxigenic Vibrio cholerae 01 Infections -- Louisiana and Florida

  11. What is cholera? • Cholera is an acute, diarrheal illness caused by infection of the intestine with the bacterium Vibrio cholerae. The infection is often mild or without symptoms, but sometimes it can be severe. Approximately one in 20 infected persons has severe disease characterized by profuse watery diarrhea, vomiting, and leg cramps. In these persons, rapid loss of body fluids leads to dehydration and shock. Without treatment, death can occur within hours.

  12. How does a person get cholera? • A person may get cholera by drinking water or eating food contaminated with the cholera bacterium. In an epidemic, the source of the contamination is usually the feces of an infected person. The disease can spread rapidly in areas with inadequate treatment of sewage and drinking water. The cholera bacterium may also live in the environment in brackish rivers and coastal waters. • Shellfish eaten raw have been a source of cholera, and a few persons in the United States have contracted cholera after eating raw or undercooked shellfish from the Gulf of Mexico. • The disease is not likely to spread directly from one person to another; therefore, casual contact with an infected person is not a risk for becoming ill.