Australian biologists finally found the cause of mass mortality events. It turned out that their kills sea water pollution with organic substances, including anthropogenic origin. Especially dangerous is the situation with the reefs located near the resorts, as holidaymakers, as it is known, do not care much about the cleanness of the environment.

It should be noted that the mass mortality of corals on many reefs of the World ocean is one of the most serious problems of the present. As we remember, corals are not only natural builders Islands, but the creators of unique ecosystems and biocenoses of coral reefs. And they are the Champions in species diversity on our planet. However, representatives of the species found mainly very small and in other ecosystems can not live. So if you disappear corals, it will disappear and all their neighbors.

The cause of mass mortality of coral polyps are still not clear. Expressed by many version - global warming, anthropogenic pollution of the sea water, the change of acidity in the oceans, viral infections, etc. However after detailed consideration of each of them found out that she is not particularly convincing. For example, if we assume that the cause of all troubles that befell corals, only anthropogenic pollution, then it should be observed mass destruction and other inhabitants of the reef, for there is such a poison that could kill corals purposefully. But this is not happening - die only polyps.

Recently, a group of zoologists from the Australian Institute of marine biology in Townsville proposed a new version. Scientists decided that perhaps coral kills a large number of organic matter in the water. To check this assumption, there was an interesting experiment: in the courtyard of the Institute scientists have found several rows deep tanks with circulating sea water, were put there by corals, to which was attached a lot of sensors. When corals are comfortable in new dwellings in the water poured suspension sea fine-grained sediment (simply put, silty sand). Then waited until haze settles began to watch what happens to the corals.

The results showed that organic really bad effect on the growth and development of polyps. When its concentration in water was low, coral nothing really noticed. But when a large number of organic molecules from polyps immediately began necrosis of tissues. In the end, the colony quickly died. And what else is interesting parallel scientists have caught the sharp decrease in the number of oxygen and increased levels of hydrogen sulphide in the water. In addition, sediment around the corals themselves began to podcasts.

So, the direct murderers of corals is acidic pH, sulfide, and oxygen deficiency. To find out who this "Trinity" the most dangerous, scientists have put a number of control experiments. At first they checked how the corals affected by lack of oxygen. The polyps were placed in sealed dark boxes (they are darkened in order to deprive symbiotic coral, algae, zooxanthellae capability to produce oxygen). The boxes were filled with water with dissolved nitrogen. What is most surprising - corals quite normally have moved this "torture". As it turned out, in nizkokalorina atmosphere they are quite able to survive and easily recover after they have placed in normal conditions. At the same time, zooxanthellae continued to photosynthesize.

Scientists continued the "fun" over the polyps. In the following experiment they, placing corals in nizkokalorina atmosphere, slightly lowered pH environment, from eight to seven (that is, with slightly alkaline to neutral). And there are already about a day began death polyps. After the water has added the sulfide - and here corals began to die within three hours. Moreover, it was found that the hydrogen sulfide started the process with positive feedback. When you add the intensified activities of bacteria sulfatereducing living in muddy sediments. And its product was a new hydrogen sulphide. Moreover bacteria began to use as a source of necessary sulfur dying tissue polyps and, respectively, multiplied.

So, after these experiments, the picture was quite clear: when in water and sediment increases the content of organic matter, begins the rapid growth of colonies of bacteria sulfatereducing. At the same time sufficiently fast spent all the oxygen near the polyps, and instead highlighted organic acids and hydrogen sulfide. In the end, the conditions for the existence of corals become very depressed and starts killing them. And the dead tissues begin to form new colonies of sulfatereducing, killed the entire area of the reef.

It also emerged that in normal conditions corals can regulate the number of dangerous bacteria. The fact that the polyps secrete certain antibiotic own production, which prevents the growth of colonies of sulfatereducing. However, to make it "medicine" is possible only under normal oxygen content in water. Developing antibiotic requires a lot of energy, and in nizkokalorina environment, it is simply nowhere to take. So when Kislorodmontage little, corals and no longer can defend themselves.

Conclusions from the work of Australian scientists, unfavourable: the death of corals provokes sea water pollution with organic substances, including anthropogenic origin. To stop it will be possible only when people stop Samusocial oceans their waste and oil products. But, you know, to do this very, very difficult. Especially dangerous is the situation with the reefs located near the resorts, as holidaymakers, as it is known, do not care much about the cleanness of the environment.

However, if we want to preserve the unique coral community, we have "cleanliness" in the seas. Because their disappearance impact not only on the tourist industry. Microscopic algae called phytoplankton, also love living near coral reefs, because there are a lot of natural fertilizers. So if you disappear corals will die out and a significant part of phytoplankton. But in fact it is the main supplier of oxygen in the atmosphere. That is, without it we will all several sights...