In recent years, red tide outbreak in the coastal areas of China and the world has become a major concern of the international community to marine environmental problems and ecological disasters. 70 years since the 20th century onwards, China has recorded 300 times of red tide, nearly 20 years, a sharp rise in the number of occurrences, the occurrence of the scale also showed a trend of rapid expansion, which occurred in 2000 near Zhoushan in East China Sea the original area of red tide dinoflagellate tens of thousands of square kilometers, lasted for nearly a month of time, rare in the world. Red tide on the marine economy, marine environmental hazards and the potential threat to human health has caused widespread concern in society.
What factors will cause bloom?
Occurrence of red tide is a very complex phenomenon, though not yet the real science to understand and master the mechanism of occurrence of red tide, but is generally believed that the red tide occurrence is necessary to the existence of internal red tide organisms, and various environmental factors (external) such as physics, chemistry, biology and climate, the occurrence of red tide plays a regulatory role.
Red tide organisms have been recorded around the world 200 kinds of algae, protozoa and bacteria in addition to a few, but all belong to phytoplankton, including cyanobacteria, diatoms, dinoflagellates, golden algae and Cryptomonas sp and other categories, some of which gradually biological Chek can produce very harmful toxins. Individual small red tide organisms, usually a few to tens of microns, use microscopes to see their shadow, to use electron microscopy to see their face, but some species are difficult to distinguish even if the electron microscope, it is the development of new tools such as molecular biology methods to identify them.
Some red tide organisms, especially dinoflagellates, often developed that can adapt to different environments and with other creatures to survive competition in a series of successful adaptation strategies, such as vertical migration through the competition for sunlight and nutrients priority or can form spores under adverse environmental sediment deposition in the capsule, waiting for the environment suitable for rapid germination and then when the cells formed the dominant group. In addition, the red tide organisms are spread from one area to the original without these species, the sea, filling an empty niche in which to thrive, the formation of red tide. Known routes of transmission are: large-scale ocean water mass movement and circulation of transportation, ocean transport ships carrying ballast water, introduction of cross-sea shellfish and cysts caused by red tide organisms and so on.
Environmental conditions have been red tide organism does not mean that red tide will occur. All kinds of red tide organisms are often present in which it originally among the sea, but between them and between them and other organisms are constantly in a competition with each other and promote each other constraints or situations, and everyone " no problem, "red tide organism," obediently "to play a normal eco-system" ordinary member "role. Only when the external environment conditions, especially for some of the red tide organisms, these red tide organisms will "flatten", from the competition, the rapid proliferation and the formation of red tide.
Environmental factors, including physical (temperature, light, currents, etc.), chemical (nitrogen, phosphorus and other nutrients and iron, manganese and other trace elements and vitamins, etc.), biological (feeding and predation, species interactions, etc.) and climate (rainfall and the greenhouse effect and the El Niño phenomenon), etc., and their synergies are likely to affect its distribution in the occurrence of red tide, red tide occurrence of which play a similar last-minute pull the "trigger" effect is called the "trigger factor . "
Seawater nutrients (mainly nitrogen and phosphorus), trace elements (such as iron and manganese) and some specific organic compounds (such as vitamins, protein) concentration and the existence of a direct impact on the form of red tide organisms metabolism, growth and reproduction. They are the red tide formation and development of physical infrastructure. Temperature is an important red tide of environmental factors, temperature control, directly or indirectly the growth and proliferation of red tide organisms, but also affect the level of red tide organisms and vertical distribution. Occurrence of red tide has also been the wind, streams and other factors. Microscopic algae, and some lack of exercise, organ, and some even moving organs, the migration rate is very small. Thus, to some extent, the distribution of red tide organisms, accumulation and dispersion are directly affected by water movement. In addition, coastal upwelling of nutrients can contain a large number of sub-surface water and bottom water to the surface, for the growth and reproduction of red tide organisms provide the necessary material conditions. It also can be red tide organisms "seed" - cysts (the previously mentioned adverse conditions in the formation and deposition in the sediment) with people and water surface, making it the necessary light and nutrient conditions, and promote germination, while the existence of coastal streams to make it more cysts suspended in water.
Frequency of red tides in recent human factors of various reasons, generally considered the most important is the impact of human activities, such as pollution of the marine environment, particularly in eutrophic waters. With economic development, agricultural and industrial wastewater and domestic sewage discharge increasing coastal eutrophication, the occurrence of red tide provided the material conditions. High incidence of red tide in Bohai Bay, Dalian Bay, Yangtze River Estuary, Fujian coast, Guangdong Dapeng Bay red tide studies have shown that the occurrence of red tide and environmental pollution and human activities are closely linked. However, eutrophication is not simply equated with red tide, there is evidence that the occurrence of red tide and eutrophication of some independent, is not related with the eutrophication eutrophication will certainly happen as long as red tide, such as eutrophication can is the perennial existence of the phenomenon, but the tide will occur at certain times of the year, and that "the main character on stage," may suddenly be replaced.
How serious harm red tide?
Occurrence of red tide is not only a serious threat to mariculture and marine fisheries resources, destruction of marine ecological balance, deteriorating marine environment, damage to coastal tourism, but also may lead to consumption of contaminated seafood populations of red tide toxin poisoning and even death. Therefore, the red tide has become the world's coastal countries facing a serious problem of the marine environment, causing widespread concern.
Red tide marine aquaculture and fishing industry, aquaculture internal bay sometimes devastating harm, can culture all died within a short period objects. Tide may also interfere with the migratory routes of marine fish, feeding activities affecting the marine fishing industry. At the same time, out of the red tide-affected zone produced seafood safety management requirements, toxic red tide occurred in the period, the relevant departments will order the ban, seafood market and export the area, all of these to the mariculture industry and the fishing industry brought huge economic losses.
First, the marine environment and marine life, red tides affect the water pH and light intensity, and changes in pH of water, living in the water bound to affect the various physiological activities of marine organisms, leading to changes in the structure of biological populations; Secondly, because of red tide bio-mass propagation and the surface aggregation of the first to absorb sunlight and sheltered waters, so that other organisms do not have adequate underwater sunlight, affect other marine life and reproduction; again, some of red tide organisms can secrete mucus, or in the death of decomposition resulting from mucus, mucus and the mucus of red tide organisms with adhesion to the gills of marine animals, marine animals of the treatment or impede the process of respiration, so that they died of suffocation. Some also contain toxic red tide organisms, fish, shrimp, shellfish and other food intake after these toxic red tide organisms, can cause poisoning or death. In addition, after the death of a large number of red tide organisms, which consume a lot of debris decomposition of dissolved oxygen in sea water, marine environment caused by severe hypoxia, causing fish, shrimp, shellfish and so many deaths.
Human health, sometimes of red tide shellfish biotoxins and will not cause lethal effects of fish, but will be digested in their bodies, absorb and accumulate these as human consumption of seafood with toxins after the red tide, it can cause poisoning, ranging from disease, while in fatal. Toxins produced by the red tide organisms very different structure, and show different biological activities. Based on these symptoms caused by toxins, can be toxic to shellfish as transmission media into paralytic shellfish poisoning, diarrhetic shellfish poisoning, amnesic shellfish poisoning, neurotoxic shellfish poisoning, and other fish as transmission media The West fish poison.
Paralytic shellfish poisoning is by far the most widely distributed, the most damaging kind of red tide toxins, mainly from the dinoflagellate Alexandrium genus of some species produce toxins, including saxitoxin and its derivatives nearly 30 species of paralysis shellfish poisoning the main symptoms of the face, knee-side numbness, because of severe respiratory muscle paralysis leading to death.
Mainly from the diarrhetic shellfish poisoning dinoflagellate genus Dinophysis in the Prorocentrum genus and its main symptoms of poisoning as vomiting, diarrhea, and its active ingredient field okadaic acid is a strong carcinogen, and therefore special attention should be long-term toxicity effect.
Amnesic shellfish poisoning mainly intended nitzschia diatoms are some of the species, the poisoning showed intestinal symptoms and neurological disorders, severe with short-term memory loss phenomenon.
Neurotoxic shellfish poisoning mainly generated by the short Gymnodinium, human poisoning by eating way to show neurotoxic disease-like, by way of toxic aerosols into the respiratory system caused by poisoning symptoms similar to asthma.
West fish poisoning orderly living in the tropics by the dinoflagellate, it is usually by the fish as the medium, cause human poisoning, poisoning showed symptoms of neurotoxicity.
Red tide can be controlled and prevented?
Objectively speaking, we are not yet capable of truly large-scale red tide control and prevention, because we understand the mechanism of occurrence of red tide was not enough, especially in different waters at different times of the different critical moment of the red tide occurrence to "trigger" the role of "trigger factor" knowledge is still very unclear. Therefore, in a large-scale red tide control and prevention, we now can do macro and may do a good job about one thing: control the eutrophication of waters. Although we can not be simply equated with eutrophication and red tide up, but the eutrophication of waters, after all, prepared for the occurrence of red tide conditions sufficient nutrients. Sea eutrophication control the government's macro decision-making needs, from the reduction of major rivers, land and marine aquaculture areas ground source nutrient input to proceed, gradually reduce the eutrophication of waters. Rex the Inland Sea of Japan in reducing the extent of eutrophication occurrence of red tide significantly decreased the number is a good example.
Although the scientific prediction, prediction of the occurrence of red tide can not do yet, but after the occurrence of red tide to minimize the harm it has a lot of attempts. Such as red tides and from the perspective of ocean dynamics to predict its success stories has been that the aquaculture industry can avoid the red tide and ocean management action plan to provide valuable response time. If the red tide occurred in the closed bay or sea-intensive farming areas, in emergency situations, has been trying to use the spray to suppress the red tide clay or loess, thus reducing the dangers of red tide on the culture object.
We believe that as our understanding of the mechanisms of the occurrence of red tide continues to deepen, we will ultimately find a scientific method of effective control and prevention of red tide.