Marine Pollution
Marine pollution is the introduction by humans of substances or energy into the ocean that change the quality of the water or affect the physical and biological environment. There are many different substances which pollute the oceans. We will examine the effects of oil, heavy metals, synthetic organic chemicals, solid waste, and sewage.
Oil
Many different factors determine the effect of an oil spill. The consequences of a spill is determined by its location, the quantity and concentration of the oil, the season of the year, currents, and other factors.
Crude oil spills are usually more frequent and larger in volume. The little components of crude oil that do not dissolve in water, harms juvenile forms of marine organisms, even in small concentrations. The remaining undissolved components, the majority of crude oil, forms sticky layers on the surface which prevents the free diffusion of gases, clogs adult organisms' feeding structures, and decreases the sunlight available for photosynthesis. Most forms of marine life recover within about five years, as crude oil is not as highly toxic and it is biodegradable.
Refined oil near the shore can be more disruptive for longer periods of time. These spills lead to a high number of marine organisms' death and environmental damage which leads to reduced species diversity and fertility. Some areas, after three decades, are not recovered from spills of refined oil.
Although intertidal and shallow water subtidal communities are most sensitive to oil spills, bottom organisms are also affected. Volatile components of an oil spill eventually evaporate into the air, leaving heavier tars behind which forms into tar balls. These balls fall to the bottom and may be assimilated by bottom organisms or incorporated into sediments.
There are many methods to contain and clean up an oil spill, however, sometimes they are dangerous and damageful. Detergents used to disperse oil are especially harmful to living things.
Statistics on sources of ocean oil pollution
45% is due to marine transportation
32% due to routine loading, discharging, and flushing of tanker ships
A mere 8% due to natural seeps
Between 150,000 and 450,000 marine birds killed by routine releases of oil from tankers
Heavy Metals
Heavy metals are a great concern because they enter the food chain. Some dangerous metals being introduced into the ocean are mercury, lead, and copper.
Mercury and lead poisoning cause brain damage and behavioral disturbances in children. Copper is also dangerous to marine organisms, it has been used in marine anti-fouling paints.
Coal combustion, electric utilities, steel and iron manufacturing, fuel oils, fuel additives, and incineration of urban refuse are the major sources of oceanic and atmospheric contamination by heavy metals. Heavy metal contaminated runoff from the land, rain of pollutants from the air, and fallout from shipwrecks pollute the ocean with dangerous metals.
Statistics on heavy metals
Human activity releases about 5 times as much mercury and 17 times as much lead as is derived from natural sources
Synthetic Organic Chemicals
Many different synthetic organic chemicals enter the ocean and become incorporated into organisms. Ingestion of small amounts can cause illness or death.
Halogenated hydrocarbons are a class of synthetic hydrocarbon compounds that contain chlorine, bromine, or iodine are used in pesticides, flame retardants, industrial solvents, and cleaning fluids.
The level of synthetic organic chemicals in seawater is usually very low, but some organisms can concentrate these toxic substances in their flesh at higher levels in the food chain. That is an example of biological amplification. DDT causes this occurrence. Polychlorinated biphenyls (PCB's) also create biological amplification. It was used to cool and insulate electrical devices and to strengthen wood or cement. PCB's may be responsible for the declining fertility and behavioral changes in seals and a deadly viral epidemic among dolphins in the Mediterranean.
To learn more about synthetic organic chemicals
Solid Waste
Plastic is a large amount and danger of solid waste. Plastic is not biodegradable and therefore effects the oceans for long periods of time.
Sea turtles mistake plastic bags for jellyfish and die from internal blockages. Seals and sea lions starve after being muzzled by six-pack rings or entangled by nets.
Statistics on plastic
Six-pack holders will not decompose for 400 years
Each square mile of ocean surface off the North East coast of the U.S. has more than 46,000 pieces of plastic floating
100,000 marine mammals and 2 million sea birds die every year after ingesting or being caught in plastic debris
Adding ingredients to plastics that would hasten decomposition would add 5-7% to costs, but this price increase is unacceptable to industries.
Sewage
Sewage sludge, a mixture of organic matter containing viruses and bacteria, synthetic organic chemicals, and toxic metal compounds, is dumped into the ocean. Sludge can combine with oxygen to produce an oxygen poor environment where few animals can survive. During storms some of this material washes up on local beaches, contaminates shellfish beds and causes disease outbreaks among people.
A ship depositing sewar sludge