What are the causes of water pollution

The age of industry

A little history of water pollution

The >> water use shown on the previous page only consumes part of the water, another part is returned to the water cycle, more or less polluted. And water has always been used to wash away waste. As long as the number of people was small and the substances introduced were biodegradable, this was not a problem; However, this changed with the increasing population and later with large amounts of dangerous substances due to the industrial revolution.

Water pollution in Maracaibo Bay (Venezuela): Entry of nutrients into water can lead to excessive growth of algae and other aquatic plants (here: Lemna minor) to lead. Photo: Wilfredo R. Rodriguez H., from wikipedia commons, accessed on July 17, 2009. License: >> GNU FDL 1.2.

Urban water pollution

The already considerable water pollution in the pre-industrial cities (>> more) worsened again with the growing population density. With an improved water supply and the introduction of flush toilets, the situation on the streets improved, but not that of the rivers. In 1858 a session of the British House of Commons had to be broken off because the stench of the Thames was unbearable! Since part of the drinking water was still obtained from these rivers, there were repeated major epidemics of typhoid and (in Europe since 1830) also cholera epidemics; In 1892, 8,600 people died in the last major cholera epidemic in Hamburg alone.

At that time, however, the routes of transmission (salmonella or bacteria in wastewater) were already known, and therefore the first large cities in the rich countries began with the treatment (filtering and, from 1910, chlorination) of drinking water and with the construction of sewage systems, see above about London and Paris. In the 1920s and 1930s, the first cities began building sewage treatment plants. Although it took a while for this to cover most of the houses (in Paris, half of the wastewater still ended up in the Seine in the 1960s, untreated), the wastewater in most large cities in rich countries is now treated at great expense. But the situation is different in poor countries. In Manila, the capital of the Philippines, 9 out of 10 houses are not connected to the sewage system; untreated sewage makes up 70 percent of the water of the Pasig River, which flows into Manila Bay. In China, too, 90 percent of the urban population does not purify wastewater. Half of the world's urban population has no wastewater treatment.

Industrial water pollution

But while the biological water pollution from a large number of people in the industrialized countries was approaching a solution, a new problem arose here: With the >> Industrial Revolution, increasingly difficult to degrade, toxic wastewater was created. The wastewater from the iron and other mines could be very acidic due to the high sulfur content of the ore and contain iron and heavy metals; Iron and steel production produced large amounts of toxic wastewater, including cyanides and heavy metals, and the emerging chemical industry released salts, dyes, and novel and toxic organic chemicals.

John R. McNeill describes what this led to in his book >> Blue Planet: “A royal commission found in 1866 that the water of the Calder River in northern England emits an ink of acceptable quality. To prove it, part of the report was written with calder water. " In Germany, the history of the pollution of the Rhine shows the development: In the 18th century, salmon were so common in the Rhine that servants complained because they had to eat salmon too often. In the 19th century, an industrial area with iron and steel production emerged on the middle reaches of the Rhine, and chemical industry as a result of the good navigability of the river. The Rhine was polluted with heavy metals, salts and organic chemicals; Salmon became rare; the last sturgeon was caught in 1931. Since 1948, phosphorus and nitrogen have been added from detergents and artificial fertilizers; There were almost no fish left in the lower reaches - bathing was no longer an option for a long time.

Example of the Ruhr area

Although the Ruhr was the most important source of drinking water in the Ruhr area (>> water use in the Ruhr area), the fastest growing metropolitan area in the German Empire, this did not prevent the local industrial companies and the municipalities from discharging their wastewater there: faeces were discharged, but also cyanogenic gas washing water from smelting works , Acids and iron sludge from pulp and paper mills and iron pickling plants. But the situation on the Emscher north of the Ruhr was even worse. This had hardly any gradient, and when mining subsidence (>> soil destruction: example of the Ruhr area) occurred, the already existing swamp areas expanded.

However, this was not a benefit for nature, because the water was highly contaminated with industrial waste water: more than half of the water in the Emscher consisted of waste water; 90 percent of the wastewater came from industry. But even cities like Oberhausen did not purify their wastewater, since it was routed into a completely dirty river anyway. Typhus mortality was twice as high as the Prussian average in 1887-1900. In 1901 around 500 people died of a typhus epidemic in Gelsenkirchen, a hygienist wrote: "I examined the hygienic conditions in Naples, Palermo and Constantinople during the ... cholera epidemics and saw ... bad sanitary conditions. ... but like that Dangerous conditions with regard to drainage, sewage and faeces disposal ... as in the areas of the Emschertal affected by typhus I have not found anywhere "(50). It was legally difficult to assert oneself against the polluters (1345). Even if the plaintiffs won, the judgments were often not implemented: When the municipality of Altenessen reached a ban on the discharge of wastewater from the city of Essen into the Berne in 1897, the mayor of Essen refused to do so on the grounds that he would then have to put his city under wastewater.

Attempts to find a legal regulation ran into problems. The mine owners wanted permission to discharge their sewage into private rivers without having to pay compensation (as provided for in Saxon mining law), but this was rejected by the Prussian ministries and the large landowners, for whom the compensation had become an important source of income. In 1899 a Emscher Cooperative was founded, the tasks of which were laid down in a law in 1904: essentially, it was supposed to ensure that the wastewater was discharged in order to ensure the economic use of the Emscher area. However, treatment of the wastewater according to the state of the art at the time was not planned - in addition to the costs, one argument was that it ended up in the Rhine, which was also so polluted that it would not cause any damage there (52). The implementation started in 1906 Emscher regulation: the Emscher and its tributaries were converted into open sewers. The cleaning of industrial wastewater from sludge, which could make it difficult to discharge the wastewater, as required by the law on the Emschergenossenschaft, was left to industry for a long time, but had to find out that it hardly took place. Soon the Rhine fishermen complained that fish that stank of carbolic up to 20 kilometers below the mouth of the Rhine were unsaleable: the reason was the introduction of phenols (see also >> Soil pollution: example of the Ruhr area) from the wastewater from tar, ammonia and benzene production from coke oven gas .

Phenols had already caused problems in the Ruhr, where they had appeared in drinking water (e.g. in Essen 1925) - because the chlorination of drinking water increased the carbolic odor, a hotline was set up between waterworks and collieries so that they would not discharge phenol water when the hygiene situation was good required chlorination. From 1926, the Emschergenossenschaft therefore began to try to treat phenol water - and found a profitable method of washing out the phenol; In 1928 it was decided to build 11 plants (which were supposed to hold back around 5,000 of the 10,000 tons produced at that time in the year, for the rest the plants were considered uneconomical). In addition, since the industry could still not be induced to purify its wastewater, the construction of large mechanical sewage treatment plants was started as an emergency measure at the mouths of the "particularly polluted" inlets to the Emscher. However, due to the amount of sludge produced, these proved to be hardly effective, so that a central river sewage treatment plant was finally built near Bottrop in 1927. This held back 250,000 tons (dry weight) of sludge annually. In order to master these quantities, a wide variety of experiments were made - ultimately it was found that the dried sludge could be ground and used as coal dust. Negotiations with the Rheinisch-Westfälische Elektrizitätswerk led to the fact that it built the Karnap power station, which was commissioned in 1937.

It was not until the Water Resources Act of 1957 that an effective legal basis was created for laying down requirements for wastewater discharges. However, since the authorities did not know the extent of many discharges and the companies were happy to threaten to close down operations if illegal discharges were prohibited, it took a long time for the regulations to take effect. It was not until the environmental movement in the early 1970s that effective sewage treatment plants were built; By the early 1980s, 118 sewage treatment plants were built on the Ruhr, 75 percent of the wastewater was treated biologically (and this led to a new version of the Water Management Act in 1976). On the Emscher was a 1976 to 1978 Estuary sewage treatment plant built in Dinslaken that biologically treated the wastewater. But large quantities of heavy metals such as lead, cadmium and chromium were also discharged into the Rhine. In the 1990s, wastewater treatment was converted to four central sewage treatment plants, including the expanded and modernized estuary sewage treatment plant. Some of these are part of a project started in 1992 for Renaturation of the Emscher and its tributaries, In future, the wastewater will be transported in underground sewers (including a central Emscher sewer that runs parallel to the river).

Often rivers even caught fire. The Cuyahoga River burned in Ohio on June 22, 1969, and that fire broke the barrel in the United States: 20 million people demonstrated against the pollution on Earth Day on April 22, 1970, and in 1972 the Nixon government passed under that pressure the Clean Water Act, a law to keep waters clean. In Germany, the Water Management Act of 1957 became the Water Protection Act, primarily through an amendment from 1976. On the Rhine, too, international agreements and the construction of sewage treatment plants slowly brought improvement in the 1970s; from 1976 the fish population increased again - in 1992 a salmon was caught again.

In developing and emerging countries, industrial water pollution is even more severe thanks to older technology and a lack of wastewater treatment: In China, 80 percent of the major rivers are so polluted that fish no longer live in them; on the banks of many rivers are “cancer villages” - so called because many people die prematurely here (>> environmental pollution in China). In India the situation is hardly better; not only the holy Ganges is an open sewer. In Africa, Lake Victoria threatens to tip over, into which Kenya, Tanzania and Uganda discharge untreated household and industrial wastewater; There are hardly any fish left in the rivers Senegal and Niger.

>> Air pollution also has an influence on water quality. For example, sulfur and nitrogen oxides can form acids with water that lead to Acid rain lead, who acidified waters. Since acidic water also releases toxic aluminum ions from the soil, the acid rain in the USA and Scandinavia led to fishless lakes; in the woods it caused damage to trees. The reduction of sulfur and nitrogen emissions led from the 1990s in North America and Europe to an improvement in the situation and to the recovery of the waters; in East Asia the problem remains acute and in Southeast Asia it is of increasing concern.

Agriculture pollution

Since the 1940s, agriculture increasingly used artificial fertilizers (>> industrial agriculture): Runoff from fields and pastures led to large amounts of Phosphorus and nitrogen got into waters. Here, however, a lack of phosphorus and nitrogen is often the limiting factor for the growth of bacteria and plants; with the entry, the limit was lifted, bacteria and aquatic plants grew excessively. The problem: when they die, the decomposition process consumes oxygen, which other living beings then lack. Nutrient intake can kill all life due to a lack of oxygen. This process, known as eutrophication, is a problem especially in lakes, as the water here is not constantly exchanged as in rivers. With increasing intensification and specialization of agriculture, nutrient intake gained a new dimension, since now animal manure It became more and more concentrated and could no longer be used directly in the countryside without problems. 600 cattle produce an organic pollution of the wastewater like 1000 humans, but their wastewater is usually not treated by a sewage treatment plant. And nitrogen increasingly found its way into the groundwater - and in the form of the easily soluble, harmful nitrate. In Germany, the nitrate values ​​in the groundwater are still above the limit value for drinking water (50 mg / l) at more than half of the official monitoring measuring points (further information >> here [Federal Environment Agency]); In 2013 the EU Commission initiated infringement proceedings against Germany because the EU Nitrates Directive was inadequately implemented. Intensive agriculture also contributes to water pollution in another way: Ammonia emissions (54 million tons of nitrogen annually worldwide) are converted to ammonium in the atmosphere and enrich water bodies with nutrients; after nitrification, they contribute to the acidification of water bodies.

Another aspect of agricultural water pollution is ingress of Pesticides in water.Around 10,000 different pesticides are used in agriculture around the world. In Germany there is a limit of 0.1 micrograms / l; this is occasionally exceeded. The most commonly found pesticides such as atrazine or bromacil are now banned here - their discovery is proof of the longevity of this pollution.

Dead zones and poisonous algal blooms

The water from the rivers, but also direct discharges from coastal cities and tourist centers, ends up (together with nitrogen from the air) in the ocean, and at first glance it seems to be hardly polluted thanks to its enormous amounts of water. They meanwhile show that this is not the case over 400 dead zones (54), which are located permanently or seasonally on coasts (mostly in front of shallow estuaries) or in inland seas. The cause is that Supply of nutrients. What used to provide rich fishing grounds in front of the estuaries has changed with the increase in the population and especially since the introduction of artificial fertilizers such as in the lakes (see above): Now so much algae grew that the (often overfished) oysters , Mussels and fish could no longer eat them; and dead algae sank into the deep water and there used up the already scarce oxygen: animals that can swim leave the area; bottom animals such as mussels and shrimp die off. The largest dead zones were formed in the Baltic Sea, the Adriatic Sea and the Black Sea, in the Long Island Sound off New York and in the Gulf of Mexico (Mississippi Delta) and the Chesapeake Bay near Washington.

Of course (as has been suggested by some industry representatives) there is nothing in that. Algal blooms in spring and early summer are normal, especially in temperate and polar latitudes, where winter storms stir up nutrients. Dead zones only appeared after the Second World War, as was the case with sediment investigations in, for example Gulf of Mexico showed (56). In the Mississippi, which drains 40 percent of the contiguous 48 U.S. states, sediment loads increased in the early 19th century when the prairies were turned into farmland, and in the early 20th century when dams were built (which held back the silt load), off again. The use of artificial fertilizers can be seen in the number of diatoms (a group of phytoplankton) in the sediment, which increases from the 1950s - and only then did a small but clearly large dead zone in the Gulf of Mexico regularly form from the 1970s. Today it is over 20,000 square kilometers in size.

The dams and the reduced amount of water in many large rivers (>> here) due to withdrawals for irrigation also contributed to the creation of dead zones: the decreased flow of rivers can no longer help to mix oxygen-rich surface water and oxygen-poor deep water, as usually happens in estuaries. Sometimes the nutrient enrichment does not have to lead to a dead zone, but can also be directly harmful to health if the algae, which increase due to nutrient enrichment, produce toxic substances. This happens for example with the regular "red tides"off Florida that of the kind Karenia brevis to be triggered. These produce brevetoxins, a cocktail of neurotoxins which are the main killer of manatees (a species of manatee) and which can cause sore throats, eye irritation and respiratory problems in humans. However, not all species suffer from nutrient enrichment and a lack of oxygen: jellyfish get along well with this. Since overfishing has made animals such as dogfish and sea turtles that eat jellyfish rare and jellyfish can tolerate increasing acidification well, the 21st century could be one of the Jellyfish become.

Long-lasting organic pollutants

With the sewage and rivers, however, not only nutrients but also dangerous pollutants get into the oceans. A group that long-lived organic pollutants (the "POPs", in English persistent organic pollutants), have the unpleasant property of accumulating in marine organisms because they are "lipophilic" - fat-loving - and are stored in adipose tissue. An example are the >> polychlorinated biphenyls (PCBs) that act like hormones and impair the development of embryos (such substances are "endocrine disruptorsThe accumulation begins on the surface of the water: The uppermost layer of the oceans, stabilized by the surface tension, is rich in fats and fatty acids, and therefore many microorganisms, fish eggs and fish larvae also live here. And this is where the fat-loving POPs also accumulate, At the end of the food chain, the concentration is highly harmful to health. In one species of dolphins, the bottlenose dolphins, it has already been shown that the PCB content in the mother's milk of the young animals in Sarasota Bay in Florida endangered (58).

Another example is Tributyl tin (TBT), which was used in underwater protective paints for ships until 2008 - where it prevents the hulls from growing with algae, barnacles and mussels, which increase water resistance. TBT acts like a hormone on sea snails and affects the snails' reproductive organs so badly that the animals become sterile. Barren snails can now be found all over the world, especially in harbors and along sea routes, over 100 species of marine snails are threatened with extinction. Even if the use of PCBs has been significantly restricted and that of TBT has been banned - the substitutes are not always better: brominated flame retardants for example, those used in furniture, electronic devices and synthetic fiber clothing are also suspected of being endocrine disruptors. The concentration of chlorinated hydrocarbons in adipose tissue, especially of subtropical and tropical marine animals, is also still increasing.

Heavy metals

Pollutants that enter the oceans via rivers and air also include Heavy metals. Is particularly critical mercury, which comes to a large extent from the emissions of coal-fired power plants - and whose content is rising again with the coal boom, especially in Asia. Large predatory fish at the end of the food chain such as swordfish and tuna are particularly affected; in the United States, 40 percent of the mercury content in the human body comes from tuna. There, the food authority advises pregnant women and women of childbearing age to limit the consumption of fatty fish. The worst case of marine mercury pollution occurred in Minamata Bay, Japan (see box).

The environmental disaster in Minamata Bay

After cats went mad in the Japanese city of Minamata in the 1950s and danced like drunk before they finally died, the first brain damage in children occurred here in 1956. In autumn, researchers identified the high mercury content of the fish from Minamata Bay as the cause of the disease. The cause was immediately suspected to be mercury-containing wastewater from the acetaldehyde production of the local company Chisso. This initially denied any connection. When the fishermen of Minamata occupied the factory several times in 1959, the case became known nationwide. But only after many years, and after the case was documented by the photographer W. Eugene Smith and in 1972 by his book "A warning to the world ... Minamata ”became known worldwide, there was a 1973 court ruling that the company had to pay $ 100 million in damages to the victims. In 1984 the bay was dredged over 14 years for a total of $ 400 million to clear the pollution. As far as we know today, around 3,000 people died from this in the Minamata region Mercury poisoning.

A second mass poisoning of mercury occurred in 1964 on the Agano River in Niigata prefecture, the cause was the same production process. Both events are now among the “four great environmental poisonings” in Japanese history.

Most of the pollutants in the oceans come from wastewater discharges on the coasts and rivers and are concentrated around estuaries and ports; In addition, there is the waste that is thrown into the sea from oil rigs and ships. Even worse was prevented because the "Dump”(Dumping) of litter into the seas is now largely illegal. It was mainly used for liquid industrial waste (dilute acid from the production of titanium dioxide, but also sewage sludge) and radioactive waste. But we managed to pollute the oceans over a large area: the cause is the plastics, of which we now produce 300 million tons every year - and process a third of it into disposable packaging.

Plastic waste on a beach on the Red Sea. Photo: Vberger, from >> wikipedia commons (accessed July 12, 2014), public domain.

Plastic waste

Thor Heyerdahl already reported how he kept drifting on his Atlantic crossing in 1970 Plastic waste bumped. This now also makes up a large proportion of the floating debris lining the world's beaches (if they are not cleaned in the morning before the tourists arrive - regular beach cleanings are a must for holiday resorts these days). But above all, it gathers in huge rubbish stains in the oceans. The fact that the plastic waste collects here is due to the >> surface circulation of the oceans in interaction with the >> wind: In the center of the oceans, huge, as Ocean eddy designated circular currents. Seafarers have long known that floating objects accumulate in their center: so much seaweed of the species accumulates in the Atlantic vortex Sargassumthat it became known as Lake Sargasso. Today in these eddies lie the great rubbish spots of the world's oceans. The eddies rotate at different speeds - the orbital times range from a good three to 13 years - and with each orbit, it is estimated that around half of the plastic waste ends up at the edge of the eddy (and finds its way to the coast over time).

The location of the garbage spots in the ocean. Own illustration according to Figure 4 in >> Roberts 2013 (and there after Curtis Ebbesmeyer).

Stomach contents of a dead albatross boy, taken in the Midway Atoll National Wildlife Refuge in the Pacific Photo: Chris Jordan, US Fish and Wildlife Service, from >> wikipedia commons (accessed July 12, 2014), license: >> cc 2.0.

The biggest problem with these garbage stains: marine animals don't know plastic and think of it as food. Sea turtles, for example, apparently mistake plastic bags for jellyfish: two and a half kilos of plastic bags have already been found in dead sea turtles; More than 500 pieces of plastic were found in the body of dead young albatrosses. Even sperm whales have died from plastic constipation. In the garbage stains there are not only large plastic parts, but also many small particles: Part of this plastic granulate, which was lost in accidents, is partly the product of the decomposition of plastics (probably a larger part), or a product - the cosmetics industry, for example, uses skin creams to exfoliate small plastic particles that are so small that they can be Sewage treatment plants are not filtered out. The pollutants accumulate on such particles in the surface layer, and since a third of all plankton-eating fish today have plastic particles in their intestines, they enter the food chain in a particularly concentrated form - little is known about how and to what extent they pass from the plastic to the animals.


Oil spills are still making headlines: dying, oily birds and other animals are attracting public attention. With increasing oil consumption and the concentration of oil deposits in a few places (>> more), the transports and thus the risk of accidents increase (see box). But tanker accidents are only responsible for about five percent of the oil that ends up in the sea: 10 percent comes from natural sources, the rest comes from pipelines, drilling rigs, ships, but for the most part (around two thirds of the total in the US) from rivers washed into the sea. However, this oil can hardly be seen because it does not collect on the surface of the water; Nevertheless, it has consequences for marine organisms - oil contains very toxic “polycyclic aromatic hydrocarbons” (PAHs). In contrast to many other pollutants, oil also occurs in nature, and there are organisms that break down oil, which somewhat reduces its harmfulness.

Black Death - Oil Spills and Their Consequences

Torrey Canyon, 1961: The tanker operating for BP ran into a reef off the coast of Cornwall due to a navigational error; 100,000 tons of crude oil leaked and polluted 190 km of English and 80 km of French coast.

Amoco Cadiz, 1978: The tanker driving for Amoco Oil rammed a rock off Brittany after a failure of the steering gear; 223,000 tons of crude oil polluted 150 km of coastline.

Exxon Valdez, 1989: The ExxonMobil tanker rammed a reef off Alaska while its captain lay drunk in the cabin. 40,000 tons of crude oil leaked and polluted over 2,000 kilometers of coast in a particularly sensitive ecosystem (>> more).

Sea Empress, 1996: The tanker sailing under the Liberian flag ran into a rock at the entrance to the harbor due to a pilot's error in South Wales; 72,000 tons of crude oil leaked and polluted 200 kilometers of coastline, most of which belong to the Pembrokeshire Coast National Park (official investigation report on the consequences >> here).

Erika, 1999: The tanker broke in front of Brittany in wind force 10 and 14 meters high waves and sank; in the process he lost 17,000 tons of oil. The client TotalFinaElf, the owner and the classification society were sentenced to a fine and damages because they knew that the ship was not seaworthy. As a result, the EU banned the use of single-hulled tankers by 2015 at the latest.

Prestige, 2002: The tanker registered in the Bahamas wrecked off the coast of Galicia (north-west Spain) and broke; 64,000 tons of oil polluted 2,900 kilometers of coastline in Spain and France, 250,000 seabirds died. The captain, who knew of the ship's structural weaknesses and had overloaded it, as well as the ship owner Mare Shipping and his insurance company P&I Club were convicted.

Deepwater Horizon, 2010: In April 2010, the Deepwater Horizon oil rig, operated by BP, exploded in the Gulf of Mexico after an uncontrolled gas leak at the well. 11 employees died, and fireboats could not stop the fire, so that the oil rig went down two days later. The pipeline and the oil well broke

April 2010: The Deepwater Horizon oil rig burns in the Gulf of Mexico, 670,000
Tons of oil ended up in the water. Photo: U.S. Coast Guard.

and drilling rig connected. The "Blowout preventer«, A safety device that is supposed to prevent the uncontrolled leakage of natural gas and / or oil, failed, and the oil was able to escape unhindered for almost three months. By the time BP managed to stop the oil spill, the US government estimates that 4.9 million barrels of oil had been released.

Even countermeasures such as burning off the oil on the surface of the water or the use of chemicals that should decompose the oil so that it can be more easily absorbed by bacteria (and also less visible ...) could not prevent significant amounts of oil from reaching the coast, including the Mississippi River Delta and the Louisiana Marshes. Around 25,000 marine mammals, 6,000 turtles and 82,000 sea birds died in the Gulf of Mexico. The subsequent investigation into the accident showed that the main cause was a failure of the safety and emergency management: Since the well was behind schedule, central tests such as the test of the cement layer, which the well was supposed to complete by the start of production, were not carried out for cost reasons; In addition, there were numerous possible errors on the (actually considered "fail-safe") Blowout preventer known, which also did not match the technical drawings. In addition, there were no specific contingency plans in the event of such an uncontrolled escape - it was simply declared impossible. BP was convicted as the main culprit by a US court in 2014; Supreme Court dismissed BP appeal against reimbursement; the total cost to BP is estimated at around $ 40 billion. However, the long-term ecological consequences of the degradation products that have sunk to the seabed, including the toxic chemicals and heavy metals from the drilling mud, will hardly be able to be precisely determined, as the state of many animal and plant species before the disaster was not precisely recorded and is therefore not known .

>> DER SPIEGEL online on the oil spill in the Gulf of Mexico
>> National Geographic Society: Gulf Oil Spill
>> DIE ZEIT on the use of Correxit in the Gulf of Mexico

Since the oil production are increasingly shifted into the deep sea, binding international safety rules are urgently needed. So far, as Deepwater Horizon has shown, our ability to prevent a disaster if something goes wrong has lagged significantly behind the funding opportunities. In order to increase motivation for more safety, the >> Global Ocean Commission, for example, also demands that those who cause damage to the marine environment are liable.

If tanker accidents make up only a small - albeit spectacular - part of the oil pollution of the oceans, it represents Shipping It is also a burden in other respects. For one thing, most ships burn Heavy oil with a high sulfur content for propulsion - a kind of hazardous waste incineration at sea. Ships cause around half of all sulfur emissions in Europe today! (Incidentally, also in the port, where the motors for the power supply continue to run.)


Sound travels faster and much farther underwater than on land; and because in some areas - for example in front of river mouths with high sediment loads - and in the depths, orientation with the eyes is difficult, Sound has a completely different meaning under water than on land: For example, some whales use echolocation to find their prey; other whales can use sounds to communicate with each other over hundreds or even thousands of kilometers. Nobody really knows what effects man-made noise has on the world underwater. But after tests of military sonar systems, whales have stranded and perished several times with all signs of decompression sickness; The noise of the more than 50,000 ships that transport eighty percent of international goods traffic across the seas considerably reduces the ability of whales to communicate (the noises of fin whales, for example, are drowned out from a distance of 10 kilometers). Some researchers suspect that some whales hardly recover even after the end of the >> whaling because males and females can hardly find each other due to the noise in the oceans. Fish kept in aquariums react - like humans - to noise with increased cortisol production - a sign of stress.

Introduced species

As on land, >> introduced species also pose a threat in the sea. Most species become carried away with the ballast water of ships. Most of the species introduced in this way die at the destination, but some cause great damage: This is how the American comb jellyfish became with ballast water Mnemiopsis brought into the Black Sea and caused billions in damages; In the Baltic Sea, the shipworm, which originated in Asia, causes damage worth millions every year. In the Caribbean, the Pacific lionfish (probably released by aquarists in southern Florida) has increased explosively and is wreaking havoc among the reef fish; The seaweed species from southwest Australia overgrows in the Mediterranean Caulerpa racemosa Seagrass meadows, sponges and native seaweed species, which are much richer in fish, crustaceans, starfish, sea urchins and other species.

Such introduced species are likely to benefit from the weakening of original ecosystems through pollution and overfishing; species-poor ecosystems appear to be significantly more sensitive than species-rich ecosystems. Such "biological pollution" can hardly be reversed (even on land this is only possible with a great deal of effort, as has been shown, for example, in the attempt to control rats introduced on islands); Prevention is therefore the best protection. For example, the problem of species being carried over in ballast water could easily be solved with the help of waste heat from the engines or with UV light. In the USA, Australia and New Zealand it is at least already stipulated that the ballast water is changed on the high seas, where it causes less damage, and no longer near the coast.

The greatest impairment of the >> ocean as a habitat today, however, is >> overfishing - and the ocean is also threatened by climate change.

The oceans are getting warmer

The consequences of >> climate change have recently been added to these pressures. Just like the atmosphere, the oceans are also getting warmer, but due to the inertia of the huge amounts of water, they have so far been somewhat slower than the air - the warming has been 0.6 degrees Celsius on the sea surface (compared to 0.9 degrees Celsius of the air). In parts of the polar sea, however, the increase in surface temperature is 3 degrees Celsius. This temperature increase leads to a Increase in sea level (warmer water expands) and a stabilization of the separation and thus Reduction of the exchange of warm surface water and cold (denser) deep water.

The rise in water temperature leads to shift - or, if the species cannot adapt quickly enough, to Destruction - of habitats. Warm water species such as sea bass are more common in the North Sea, while cod, for example, has withdrawn to the north. Species and communities that cannot adapt to temperature changes simply by migrating, such as those that are particularly rich in species Cold water and tropical coral reefs, are particularly endangered by the warming of the water (more on this >> here and here). The stabilization of the stratification of the sea water also has consequences: With the reduced water exchange, less oxygen reaches the depths and fewer nutrients reach the surface. If less oxygen gets into the depths, this means that the breakdown of dead organisms from the productive, light-flooded surface consumes more oxygen than it already does, and hostile, oxygen-poor zones expand.

Another possible consequence of the seawater temperature increase is that Release of the greenhouse gas methane by the decomposition of the abundant methane hydrate there (methane hydrate is a mixture of methane and water that is created under high pressure and at low temperatures; in the sea it occurs in amounts whose carbon content roughly corresponds to that of the world's coal reserves in the deep warmer, some of the methane changes to the gaseous state and some escapes into the atmosphere.)

The oceans are getting more acidic

As a result of the higher carbon dioxide concentration in the atmosphere, the carbon dioxide concentration in the surface water of the oceans is also increasing - the world's oceans have had since the beginning of the industrial revolution 568 billion tons of carbon dioxide released by humans recorded (>> here). Carbon dioxide forms carbonic acid in water, and carbonic acid reacts with carbonate ions in water (206). But they need many types of plankton and other marine organisms such as oysters, mussels, crustaceans, sea urchins and hard corals to keep their calcium carbonate housing

Acid level (pH value) of the ocean over the past 24 million years
and extrapolation up to the year 2100. (The pH value is a logarithmic unit,
i.e. a decrease of 1 means a 10 times higher acid content;
a decrease of 0.1 means an approximately 30 percent higher acidity.) Figure
from Synthesis Report Climate Change: Global Risks, Challenges & Decisions.
Copenhagen 2009, March 10-12, own translation.

or to form the reef-forming calcareous skeletons. The consequences for the biology of the oceans are still being researched, but in addition to a decrease in biodiversity - acidification, for example, are those that are already endangered by the warming of the water Coral reefs Also at risk - the productivity of the seas could also decline because the Plankton species, which form the basis of the food web in the oceans, especially in the polar seas, are damaged. In addition, acidification also makes the absorption of nutrients more difficult: iron, for example - which is often the limiting factor for the growth of phytoplankton in the sea anyway - is less easily absorbed when the acid content is higher. In the medium term, the ocean's capacity to absorb carbon dioxide could also decrease: The formation of calcium carbonate is one of nature's ways of removing carbon dioxide from the >> carbon cycle - dead organisms sink to the bottom and become sediment there . If less calcium carbonate is formed, less carbon dioxide is bound and removed from the cycle.

Recommended websites on the topic

The American marine researcher Benjamin Halpern and colleagues published a current overview map of the adverse effects on the world's oceans in February 2008 in the science magazine Science published - >> report on mirror online.

See on the subject also:
>> The report of the Global Ocean Commission 2014
>> The pillage of the world's oceans

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>> Water use

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>> Overview of the industrial age

© Jürgen Paeger 2006 - 2020

See on this topic also the page: >> Water use by humans.

Therefore, British MPs still enjoy one today Summer break from June to October - at least that is what Callum Roberts claims in his book Man and the Sea.

"A megalomaniac jellyfish ruler striving for world domination would have longed for the changes that are coming in the oceans today just as much." (Callum Roberts, Man and the Sea, p. 193).

On the possible consequences of climate change for the seas, see also:
>> The consequences of climate change