Some of the important sources of marine pollution are as follows:
The pathogenic materials are the living organisms that can produce sickness or biological imbalance in either plants or animals within the ocean itself or in humans who either come into contact with oceanic waters or eat the organisms caught in the water. These include a wide variety of bacteria, protozoa, viruses and fungi.
The most common of these are normally found in sewage. However, other pathogens may occur in non-waste disposal areas where environmental conditions are such that the proper conditions exist for growth and reproduction.
Sediments are always present to some extent in the marine environment. These sediments have a marked effect on plant growth because they block out a large portion of the light normally reaching greater depths and therefore decrease photosynthetic activity. In some case rooted plants get completely destroyed by this process.
As sediments are deposited on the bottom they will cover up bottom dwelling organisms (benthos) such as oysters and may even smother them under extreme conditions.
The deposited sediments tend to make the water shallower so that, in regions traversed by ships, periodic dredging is needed.
3. Solid Waste:
The disposal of solid waste has been a critical urban problem because areas suitable for the dumping of these voluminous materials are becoming scarcer. Due to this reason the ocean has been used as a dumping ground for solid waste.
The solid waste most frequently marine dumped is sludge material left over as a by-product from domestic sewage treatment. However, the unused products of industry and the used-up products of society are also put into the sea.
If the product discharged at sea contains materials which may be leached into the oceanic environment, a serious problem could arise especially when the materials are toxic. However, when the solid materials are inert, a little forethought may result in some benefit to the marine environment. Artificial fishing reefs, for example, have been found to be very successful in certain areas, serving to enhance the habitat area, especially for small fish.
4. Excess Heat:
Excess heat, if added to the marine environment, alerts ambient conditions, and these changes may be detrimental to the organisms present.
The amount of heat that is detrimental and the extent of the degradation is determined by a number of factors.
The primary source of this heat has been of course, from electrical generating plants, whether they are fossil fueled or nuclear powdered.
5. Fresh Water and Brine:
Although fresh water may be in great demand ashore, too much of it in the ocean obviously will produce a marked environmental change within a small area.
This change may occur due to poorly designed storm drainage systems, wear diversion networks associated with dams, and effluent of some industrial processes. Excessive fresh water usually is not a critical problem.
The introduction of brine into the marine environment is similar in its effect to that of fresh water except in the opposite direction. The organisms acclimated to a particular salinity now find themselves in a more saline environment which could make permanent damage. Brine is a byproduct of desalination plants.
Toxic inorganic material are commonly used in industry, many of them are relatively harmless; however, in larger quantities they may be quite destructive.
There are perhaps, 35 to 40 commonly used toxic in organics and these should be very closely controlled by the user.
The toxic organics have been the most disturbing of the modern day chemicals commonly discharged either purposefully or accidently into the marine environment.
These include the biocides such as fungicides, herbicides, insecticides, rodenticides, and also the additional organics including halogenated hydrocarbons, petroleum’s and industrial chemicals.
The most disturbing toxic organics have been the pesticides such as DDT and ketone which have the unfortunate, characteristic of being more soluble in oil than in water so that they tend to collect within the fatty tissues of marine organisms.
They have been also very stable compounds which do not deteriorate very easily over a long period of time. These find their way into the ocean both as manufacturing effluent and as runoff after utilization. Their long-term effects are unknown upto this fine.
Although petroleum may be classed as a toxic organic, it is a naturally occurring material and is biodegradable, given enough time. Its effects are not too well known. Petroleum enter into the marine environment due to accidents such as tanker damage or transfer loss, natural seepage, offshore production losses, losses associated with refineries, from runoff originating as drippings or disposal of used automobile lubricants, and unburned hydrocarbons emitted into the atmosphere as internal combustion exhaust.
Nutrients (commonly called fertilizers) are those chemicals which are required by plants. The activities of man have added to the total nutrient load of almost all coastal areas. When nutrient levels becomes out of hand, plants grow unchecked so that decaying plants exist in such great numbers that the oxygen supply becomes rapidly depleted.
These nutrients are present in domestic sewage effluents, agricultural runoff, and the little understood but apparently important non-point source runoff from urban areas.
Radioactive material have been not only discharged to the marine environment by nuclear power plants, nuclear power plant fuel production and reprocessing plants, and uranium activities of all sorts, but also result from more common activities of burning of coal.
When coal is burned it gives out radioactive particles to the atmosphere which are then washed into the sea at a greater rate than any known nuclear power plant at this time. Other sources of radioactivity include the natural background, weapons testing, mine drainage, accidental spillage, and a few isolated industries.
One of the partially unsolved problems associated with the use of nuclear energy for electrical power has been the long-term storage or disposal of spent fuels. This storage must be in an area such there have been no pathways back to man, and the deep oceans have been suggested as meeting this criterion.
10. Oxygen Demand:
Oxygen demand materials have been those which need oxygen for degeneration and therefore steal oxygen which would normally be utilized by marine animals. Thus, if too many oxygen demand materials are kept in the marine environment, the animal population will be markedly decreased due to the lack of oxygen.
Sewage sludge and any other organic waste material, even that resulting from excessive plant growth due to an oversupply of nutrients have examples of common oxygen demand materials.
11. Acids and Base:
The discharge of acid and bases to the marine environment is quite disturbing to the natural ecological balance of the system. The normal pH of oceanic water has been somewhere around 8.0, slightly basic.
This is maintained by the carbonate system. If a large amount of acid or base is introduced into the system, the carbonate reactions will be offset and an important element of the environment will get affected. In addition, there are large synergistic effects associated with pH. Most toxic materials, for example, increase their toxicity under conditions of low pH.
The sources of acidic or basic material have been primarily industrial with some of this material reaching the marine environment from accidental discharges and the rupturing of tankers.
12. Aesthetic Considerations:
Aesthetically, displeasing material includes all the stuff one finds in the ocean which is unpleasant to look at or to smell. Tar balls, floatables, gas (often hydrogen- sulphide) producing materials, and coloring agents are some examples, of pollutants offending the senses.
Although in some cases these materials do not pose any real threat to the ecology of an area, when the area is being used for recreation, the quality of the surroundings becomes somewhat important.