Biologia

Human Impacts on the Oceans
We still don’t know everything about the oceans, one of the most unknown regions of our planet. While we do not reside in the ocean, our lives and societies greatly impact the happenings under the sea. With the huge population boom which has occurred in the last few centuries, humans have had an increasingly large impact. Agricultural technologies have led to oceanpollution, and over-fishing has altered the composition of the ecosystem. According to an international consortium of researchers, less than 5% of the world’s oceans are currently unaffected by human activities (Halpern, Science, 949 ). Humans have had enormous negative effects on the oceans, but there are ways to reverse the damage.
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A global map of the overall impact that 17 differenthuman activities are having on marine ecosystems (Halpern Science 949).
One of the major ways the humans have negatively affected the ocean is fishing. This is a more recent problem due to modern technology; in fact, the equipment used by humans throughout history has been so inefficient that even as late as the 1880’s scientists such as T.H. Huxley believed that major fisheries wereinexhaustible (Nybakken 500). This does not mean that fishing had no impact on marine life before then, for example, as early as the 1300s the inshore fish populations in northwestern Europe had been slightly but noticeably reduced. In the last hundred years, however, ships and equipment have been improved, including devices used for detecting fish, resulting in massive fish population reductions. Theincreasing human population is only encouraging the use of modern fishing equipment.
Pollution is another harmful human effect on the oceans. 80% of ocean pollution is land based, such as runoff from agricultural farms and auto waste from roadways (Kostigen, 144). This causes disease and death to coastal fish populations as well as to their food supply, and results in degradation of the coastalwaters.
Eutrophication is when excess nutrients are released into coastal waters (Nybakken, 529). These nutrients generally come from fertilizers on agricultural land that is washed into the ocean. This can lead to red tides and foams, slimes, and slicks tinted green or yellow. These are all signs of an excess of phytoplankton growth. Eutrophication can result in dead zones. Dead zones areoxygen-starved areas that do not have enough oxygen to sustain marine life.
Oil spills from offshore rigs and tankers are a major source of pollution as well. Unfortunately, detergents and other agents used to treat the spills can often worsen the effects, as noted by Nelson-Smith about the Torrey Canyon disaster of 1967 (Nybakken 520). Oil spills can cause disruption of habitats with no recovery foryears. The Amoco Cadiz, a supertanker lost off the coast of France in March 1978, spilled two hundred twenty thousand tons of oil. By 1985, studies showed that there was still a significant difference in the affected area and the same area before the spill.
It has been a common global practice to dump human sewage and garbage into surrounding waters, which in large amounts can have negativeeffects. In the Pacific Ocean, there is a single mass of garbage that is twice the size of Texas. (Kostigan 143). Sewage can create massive plankton blooms, which obliterate other ocean life (Nybakken 524). It also causes deoxification, which suffocates ocean life. Chemical wastes such as DDT and mercury have been proven to cause harmful effects to both sea creatures and humans. Absorbed by creatures atthe bottom of the food chain, their effects are magnified by the time they get to the top of the food chain, the kinds of fish humans eat. As these chemicals are not naturally excreted, they build up into ever-increasing concentrations. DDT is a pesticide now banned by the US, but when its use was common, sea birds absorbed it from runoff into the oceans, and it made their eggshells so thin...