The process of nitrogen loss is taking place seriously in the Arabian Sea

Marine microbial scientists at the Max Planck Research Institute in Germany, and colleagues, have discovered that the process of denitrifying bacteria is the main pathway to severe nitrogen loss in the Arabian Sea. Arabic.

The Arabian Sea is part of the Indian Ocean and is surrounded by India, Pakistan, Oman and Somalia.

The process of biochemical nitrogen (a two-step process) begins with ammonia being converted to nitrite by Nitrosomonas bacteria, then nitrite is oxidized to nitrate by Nitrobacter bacteria, then the microorganisms are able to the ability to use nitrogen sources from nitrites and nitrates for respiration (denitrification) and for growth.

Nitrogen is an essential nutrient and a finite element for all life on our planet. It is present in proteins and DNA. In oceans, biological processes that regulate concentrations and concentrations of related bio-nitrogen compounds such as ammonia, nitrite and nitrate frequently occur to provide nutrients to marine life. A large amount of nitrogen gas is released into the atmosphere, derived from the food chain of marine life. The factors to balance this system are much more complex than previously thought.

Currently, marine microbiologists from Max Planck Research Institute, Germany and colleagues have taken a new look at biological processes in the Arabian Sea.

The food chain of marine organisms contains huge amounts of organic carbon compounds. The carbon cycle is interactive with both molecules of dissolved oxygen (O ₂ ) and nitrogen cycle.

The consequences of global warming have reduced the amount of dissolved oxygen , in addition to the waste water flowing into the oceans containing organic compounds from human civilization that continue to work. attenuation of dissolved oxygen. Therefore, oxygen-deficient waters or oxygen-free areas (OMZ), which at the time of discovery only account for less than 1% of the dissolved oxygen mass of the global oceans, but these areas are the culprits. The main responsibility for losing up to 30-50% of nitrogen exists in the global oceans.

Oxygen-deficient waters or minimal oxygen areas (OMZ) have been spreading worldwide over the past few decades. This will lead to more loss of nitrogen in the near future.

The ports in the Arabian Sea act as one of the three largest oxygen regions (OMZ) in the world and cause a loss of about 10-20% of the total amount of nitrogen loss at all sites. positive on a global scale. So far, the process of denitrifying bacteria is the main pathway to the loss of nitrogen in the Arabian Sea, through a step-by-step reduction of the chemical conversion process of nitrate to nitrite. Then there is nitric oxide, nitrous oxide and finally reduce the amount of nitrogen produced.

Previous studies from other authors claim that low oxygen areas and high nitrite concentrations are also a manifestation of ongoing denitrification, but these actual activity measurements are still very limited. . To solve this problem, researchers from Marine Planck Institute, Germany, including: Phyllis Lam, Marlene Jensen and Marcel Kuypers, have collaborated with scientists from Kiel, Oldenburg, Hamburg. , Aarhus (Denmark), Nijmegen (Netherlands) and Princeton (USA) to monitor individual reaction steps in the nitrogen cycle through the identification of compounds with stable isotopes of nitrogen 15N. In addition, the researchers also identified the microorganisms responsible for and expressed the activity of the corresponding biomarker gene.

This new finding is unexpected, because the central area in the northeast of the Arabian Sea, which is believed to be a stronghold, has been shown to have almost no activity causing nitrogen losses in previous studies. The scientists explained that high nitrite concentrations found here are due to the slowing down of nitrate intake and the restriction in ammonia oxidation . Both of these reactions can take place in low oxygen conditions and produce nitrite as a final product. Satellite data during the past 10 years show that the growth of surface phytoplankton in this area is below average. The reason is that the disappearance of organic matter makes the amount of nitrite no longer reduce. Along with too slow water circulation makes nitrite accumulated in the area of ​​the Arabian Sea.

On the contrary, in the northwest part of the Oman coast, where previously thought of no loss of nitrogen, the researchers now found very high nitrogen loss activity. As shown in the publications of scientists, the two reactions in the nitrogen cycle play a decisive role: anammox reaction (anaerobic ammonia oxidation) and alteration of catabolism of nitrate to ammonia (DNRA) . Like in a detective story, scientists found evidence of the presence of stable isotope compounds of nitrogen (15N). When doubled (15N), nitrogen gas is formed from nitrite through a combination of anammox reaction and DNRA reaction. The DNRA reaction provides the ammonia needed for the anammox, ammonia and nitrite reactions required for the process of forming nitrogen gas. More evidence from gene expression studies showed that bacterial genes were actively involved in these processes. It is the bacteria that bridge the two DNRA-anammox reactions. There are also some individual anammox reactions. This explains the loss of large amounts of nitrogen in these waters.

Dr. Marcel Kuypers, director of the Max Planck Research Institute in Germany, said: " Our findings are consistent with our previous research results in other areas of OMZs with minimal oxygen, such as seas. Off the coast of Peru, Chile and Namibia, where we also found anammox reaction plays a major role in the loss of nitrogen, high nitrite concentrations in the northeastern region of the Arabian Sea are probably the last traces. of previous events that are currently leveling off. "

Dr. Phyllis Lam from the Max Planck Institute in Germany added, " In the future, the Arabian Sea is still our main research area, because the chemical reactions there have a strong impact on weight. By global nitrogen, it is not possible to confirm that the amount of nitrogen produced in nature remains the same throughout the year on a seasonal basis and the increasing amount of nitrogen loss will continue to reduce the amount of nitrogen released into the bulb. the atmosphere and the earth The main reason is because of activities that harm human nature, unfortunately, piracy activities will not allow expeditions to study further in the area. this in the future ".