If you live in the city like me, you are a standard office worker from 9 to 5. Every day, it is so painful to worry about the impact of human activities in the ocean surrounding this island. Although the issue of suspended particles in the ocean has attracted more and more attention recently, most people's attention is mostly focused on "pollution of plastic particles", rather than the earth and rocks that wash away the sea water when heavy rains hit.
The soil and rocks are washed away. As long as it is not hit on your own house and exiled to the sea water, and wait for precipitation? It is not that simple. In addition to causing optimum eutrophication, these earth and rocks that wash into seawater are also related to the generation of greenhouse effect gases.
After agricultural or other development activities, excessive fertilizer or sewage generated by humans in the soil will be washed away by heavy rain, and heavy rain will carry the nutrients from the soil into the lake or ocean. When nutrients rich in nitrogen and phosphorus enter the water, the algae and plankton that were originally in the water grow in large quantities in a short period of time due to these nutrients. This is the most familiar phenomenon of eutrophication.
However, the living cycle of algae is short. When the algae settles and dies, a large number of bacteria will breed to decompose the algae's debris, consume oxygen in the water, and reduce the dissolved oxygen level, which makes other organisms unable to survive in this environment. Especially at the interface between freshwater and saltwater in marginal sea areas, the surface and the atmosphere are in contact with freshwater with higher oxygen content, which is not easy to mix with seawater with higher density below, making the bottom seawater particularly prone to hypoxia. In severe cases, it will cause a fearful phenomenon - Dead zones.
Dead zone formation: (1) In spring, freshwater with higher temperatures flows from the Mississippi River into the Gulf of Mexico, forming a barrier that blocks the seawater below for oxygen exchange. (2) The nitrogen and phosphorus nutrients from fertilizers and sewage promote the growth of a large number of algae. After the algae dies, the body will settle down to the seawater below and be decomposed by bacteria, which consumes a lot of oxygen. (3) The oxygen concentration in the sea water below is getting lower and lower and oxygen exchange cannot be carried out, so the dead zone is formed. Image source: Nola.com(image Credit:Dan Swenson)
In the 1950s, scientists first noticed the hypoxia in the dead zone in the Adriatic sea in the Mediterranean region, and then appeared in the northwest continental shed of the Black Sea and the Kattegat Strait in the Atlantic North Sea. By 2008, dead zones had spread across more than 400 regions around the world (Figure III), with an impact of more than 245,000 square kilometers. The most serious example is the Gulf of Mexico in North America. In 2011, the floods of the Mississippi River caused a large amount of fresh water with rich nutrients to flow into the Gulf of Mexico, causing the area of dead zones in the local waters to reach 17,534 square kilometers, which is like half a Taiwan, seriously threatening the ecology and fishery of the Gulf of Mexico.
Currently known global distribution map of dead zones (white circles); human development activities (percentages) are marked on the map in different colors. Image source: Diaz and Rosenberg, 2008.
Ocean dead zone refers to an area where the dissolved oxygen content of seawater is less than 2 ml/L. In the dead zone, benthic organisms begin to have abnormal behavior, such as leaving their caves and moving to the sediment-water interface. When the dissolved oxygen in the water is less than 0.5 ml/L, it will cause a large number of organisms to die. In recent years, most dead zones have occurred in the continental shed areas, such as the Bering Strait, the Katgart Strait, the Black Sea, the Gulf of Mexico and the East China Sea, and these areas are also major fishing grounds. Therefore, dead zones are seen as the main threat affecting marine ecosystems.
is really not sure if the butterfly effect (refers to something that seems to be unrelated and very small on the surface, which may bring huge changes), or should we use the law of Mayfa (everything that may go wrong will go wrong) to describe this matter. Perhaps the above two words are not enough to describe the complex relationship between human behavior and the earth's environment.Recent research has found that in addition to affecting regional marine ecology, dead zones are also closely related to global climate change.
greenhouse effect gas is a greenhouse effect gas that absorbs infrared rays, so that heat retains the greenhouse effect gas in the local surface atmosphere. In the atmosphere, there are many types of this type of gas, including water vapor, carbon dioxide (CO2), ozone (O3), methane (CH4) and nitrous oxide (N2O), etc. Among them, nitrous oxide, the greenhouse effect it produces, is more than 153 times higher than that of the well-known carbon dioxide (calculated in a 500-year period).
N2O is more likely to be generated in environments with low oxygen concentration, and the expansion of ocean dead zones is one of the reasons for increasing N2O release to the atmosphere.
then returns to the soil washed into the water body, which is also one of the driving forces that promote the formation of N2O. These soils are washed into the water to form suspended particles in the water, and their structure also provides an oxygen-deficient microenvironment. When these suspended particles enter the optimum eutrophied water body, it is possible to promote the production of N2O.
Dr. Xiao Songyun from the Environmental Change Center of China Research Institute once went to the turbid and seasonal hypoxia Yangtze River estuary to study the relationship between suspended particles and N2O generation. During the research, he found that the main mechanism of N2O generation in this area is nitration. The microorganisms responsible for performing nitration mainly exist on suspended particles greater than 3μm. And through tracking of stable isotopes, it was found that the nitrification activity in water was also concentrated on these particulate matter. That is, the soil and rock particles washed into the seawater will indeed contribute to the generation of N2O in the seawater.
has always believed that the problem of soil and rock erosion caused by over-exploitation is not limited to the soil and rock erosion disasters seen in the news every time heavy rain. These excessive soil and gravel that washes into the sea water continues to silently affect the climate and the ocean in another way. By the time we realize it again, it may be too late.
(This article is reproduced by authorized by low-carbon life; first image source: wikimedia)
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