<MAN and the OCEAN ENVIRONMENT
1. Marine Pollution
2. Low O2, high temp., dredging, wastes
3. Removal of marsh lands and wet lands
4. Benefits of the sea
5. Uses of ocean to man
Throughout history the ocean has played a vital role in the development and growth of civilization, and humans have considered the ocean to be an unlimited source of food and a bottomless garbage dump. With a population of 5.5 billion most fisheries are fully exploited and ocean dumping is causing measurable contamination of the food supply.
Some negative influences of man...
1. The use of pesticides and other agricultural chemicals to help crop yield on land has harmed food production in the ocean.
2. A process called BIO-MAGNIFICATION, concentrates toxins such as DDT, PCB'S and mercury in tissues of consumer organisms...many of which are used for human consumption.
3. Alternates to ocean dumping must be sought to prevent further contamination of the food supply.
4. Economic and ethical issues of commercial whaling works these animals toward extinction.
5. Destruction of marshlands by draining and dredging and attempts to control beach erosion in spite of a world wide rise in sealevel.
POLLUTION
For the past 100 years, contaminants like oil, PCB, DDT, heavy metals, radioactive wastes, sewage sludge and garbage is introduced into the sea .
OIL due to tanker accidents, oil rig blowouts, daily oil washed off roadways into sewers and into water, ships pumping waste oil from bildges/ballast, seepage from garbage dumps and natural seepage from the ocean bottom. (the largest discovered off trinidad at 100m /100m thick and contains 1 megaton of oil)
Oil harms the environment by
1. covering or poisining
2. birds die of starvation because they can't fly and no insulation
3. injest oil from feathers while trying to clean
4. damage the liver and vital organs
Crude oil released into the sea usually floats although some sinks .
Oil in intertidal zones...tides bring a new blanket of oil to cover oysters, clams, mussels etc interfering with feeding and breathing. The devastation usually occurs initially but recovery usually occurs with time. More serious than the oil itself has been the various chemicals used such as detergents used to break it up or disperse the oil into the water.. The Torry Canyon disaster in 1967 the chemicals were shown to cause more mortality to marine organisms than the oil itself.
Pelagic...eggs and larva drift in oil slicks, they can't swim and there is less photosynthesis.
Pelagic tar...some components evaporate or dissolve but lots sink to the bottom to be trapped in sediments.
Right whales injest floating tar and sperm whales feed off bottom sediments (complete with tar!)
Sewage and Garbage
The discharge of human sewage and garbage into the coastal waters is practiced throughout the world. The sewage may or may not have had some treatment before discharge. It adds a large volume of small particles to the water and also large amounts of nutrients. In small volumes and with adequate diffusing pipes, it is difficult to detect long-term effect on the communities of the open coast. In large volumes and in semienclosed embayments, the effect can be devastating.
Two examples...
Southern California..LA area discharges 330 million of sewage per day at the Whites Point outfall off the Palos Verdes Penn. Studies around the outfall and others in the area revealed that sewage has caused significant degradation in benthic invertebrate communities in areas near the outfall, kelp beds disappeared near the outfall, more urchins, diseased fish more prevalentand about 4.6% of the Southern Cal. mainland shelf has been changed or degraded as a result of sewage discharge from 4 major outfalls.
Hawaii-Kaneohe Bay on Oahus east side was subjected to a 10-fold increase in population and the bay was subjected to massive domestic sewage discharges, siiltation from runoff during storms and resulted in the total destruction of the once beautiful coral reefs of this shallow bay. Once the discharges were eliminated from the bay, a renmarkable recovery of corals and water clarity was reported!
In addition to sewage, large amounts of garbage are dumped into the ocean every year.
And then there is New York. The city dumps dredge spoils, sewage, chemicals, garbage, construction materials, which are dumped in such large numbers its visbale from satellites. Sewage alone the 127 municipal discharges contribute 2.6 x 109 or 2,600,000,000 billion gallons per day. The dumping has dropped O2 levels near zero over extensive bottom areas off New Jersey, led to massive fish and shellfish mortalities, and even though most are dumped many miles offshore, some returns to contaminate bathing beaches (needles).
CHEMICALS
Worse than oil or sewage, which are at least visible, are various toxic chemicals produced by the industrialized nations which find their way into the oceans ecosystems.These chemicals are often transfered through the food chains in the sea and exert their effects in animals and places removed in time and space from its source. Certain marine organisms also enhance the toxic effects of many chemicals because of their ability to accumulate the substances in their bodies far above that found in the surrounding water. Another factor that tends to increase the effects of chemicals on living systems is biomagnification in which the chemical increases in concentration in the bodies of organsisms with succeeding trophic level....this can lead to very high concentrations in the top predator...sometimes man!
Example..in the late 1930's, the Chisso Corp. of Japan established a factory on the shores of Minimata Bay to produce vinyl chloride and formaldehyde. By-products from the plant contained mercury and were discharged into the bay. Through biomagnification, the marine fishes and shellfish accumulated high concentrations of the toxic compound methyl-mercury chloride. The fishes and shell fish were in turn consumed by the inhabitants of the area. About 15 years after the dumping of the mercury into the bay began, a strange permanently disabling neurological disorder began to appear among the inhabitants, especially the children. It was called Minimata Disease. The cause was diagnosed as mercury poisoning in 1959 but it took until the early 60's to discover the source from the factories. and until the 1970's before Japan to stop dumping mercury into the sea.
DDT and Pelicans etc Radioactive wastes
Channel Dredging
Channels are dredged deeper and wider so boats won't run into each other or run aground and until the day comes when (1) no more boats are built, (2) they don't increase in length, beam and draft or (3) moving water stop dumping silt into channels, they will continue to be dredged.
Dredging can damage by tearing up marine habitat by releasing silt which smothers shellfish and cuts down sunlight penetration into the water, changes water current patterns,, creates deep holes in an otherwise shallow and even bottom and the holes can collect detritus and form low oxygen conditions and the worse is the dredged material is usually dumped on the protective marshlands. Deeper channels can also allow denser salt water to travel further up the estuary increasing the salinitys and bringing predators to an otherwise low salinity environment which can then feed of the oysters etc.
Mariculture...farming the sea can add to world food production. (growing aquatic is aquaculture).
History...The japanese/chinese raised fish and japan raised fish and the Japanese grew seaweed on ropes but the main problem with mariculture is
1. lack of suitable domestic organisms
2. gaps in knowledge of nutritional requirements and life cycles (larva stages)
3. need to duplicate the natural environment
4. lack of knowledge in relation to diseases of marine organisms.
Instead of trying to find all these, a way around it is to work out some, which can be done by interupting the natural stages and leave the rest to nature.
There are 2 broad types of mariculture.
1. Duplicate environment artificially
2. Grow more effectively in the natural environment
1. Artificial settings are used in growing lobsters, shrimp, fish.
2. Ranching--rear young from artificially fertilized eggs and release 3 year old fish to ocean.
(most mortality occurs during 1st year of life)