Biological-Water-Salt System in Modern Salt Lake

The relationship between modern salt lake biological community and inorganic environment (including salt and water) is harmonious and unified, thus forming a biological-water-salt system. This system is the basis of salt production.

First of all, the simple food chain of salt lake creatures

Figure 1- 1 Biological food chain in biological-water-salt system

In the biological-water-salt system of salt lake, biological communities can be divided into producers, consumers and decomposers according to their properties and functions. Algae are producers, brine shrimp, brine flies (larvae and pupae) and protozoa are consumers, and halophilic bacteria are decomposers. The above three forms a simple food chain, namely algae-bacteria-protozoa-brine shrimp, brine fly and so on. (figure 1- 1).

1. Producer-algae

Algae in salt lakes (see Chapter 2, Section 1 for details) are producers. Some scholars call it a productive organism. Chlorophyll-containing green algae can use solar energy for photosynthesis, release O2 and promote environmental oxidation. At the same time, it also absorbs some minerals from the water to nourish its own cells and maintain and reproduce life. Algae is the main food target of consumers. The influence of algae on water environment and its role in salt formation are as follows (Liu Zhili, 1998):

1) Algae can absorb K+, Mg2+, Ca2+, Fe, P, etc. In the water environment, and change the ion content in the water environment;

2) The metabolism of algae changes the microenvironment, which makes the pH value increase and the Eh value decrease. Many metal and nonmetal ions are oxidized into salts and gradually precipitate, thus changing the ion concentration in water;

3) A large number of organic substances, such as organic acids, protein, polysaccharides, etc. It is produced during the growth of algae and after the death of algae, and it is easy to form salts and complexes with metal ions in water;

4) Various organic substances on the surface of algae cells can mechanically capture mineral salt particles and generate adsorption. In this way, the chemical reaction of cation+anion → salt is pushed to the right. The result of this action is that the ion balance system of the solution is changed, and some ions constantly form salts;

5) Algae and mineral particles combine to form a dense layer, which has anti-seepage effect and is beneficial to the formation of salt. Algae mats composed of algae bodies are rich in various active groups and have strong binding force to metal ions. The combination of complexation and seepage control plays a role in enriching and integrating minerals.

2. Consumers-brine shrimp, brine fly, protozoa, etc.

Salt lake brine shrimp, brine fly, protozoa, etc. (See Chapters 2, 3 and 4 for details) Consumers, whose main foods are bacteria and algae. Artemia is a filter-feeding organism, which feeds on biological debris and mineral debris in addition to algae and bacteria. Therefore, brine shrimp and brine fly, as consumers, have played a role in purifying brine. Without their life activities, brine bodies such as salt lakes will become stagnant water, not to mention precipitated salts. Therefore, it is precisely because of the life activities of the salt lake that this brine can deposit clean and high-quality salt.

The influence of consumers in brine on the water environment of salt lake and their contribution to salt formation are enormous. They can not only aggregate into minerals, change the pH value and Eh value of brine, but also form single minerals or aggregate into minerals in the body, thus promoting the deposition of salts.

3. decomposer-bacteria

In the biological-water-salt system, bacteria are decomposers or decomposing organisms. For details about salt lake bacteria, see the second section of Chapter 2 of this book. The bodies of producers and consumers in salt lakes are decomposed into chemical elements and simple compounds by bacteria. These chemical elements and simple compounds become the nutrient sources of phytoplankton. When bacteria decompose other substances, they will consume oxygen in salt water, which is produced by algae under photosynthesis. Protozoa, brine shrimp and brine flies eat phytoplankton again, so they start a new cycle to keep the whole biological-water-salt system in a relatively balanced state. The interdependence and harmonious coexistence of organisms in the biological-water-salt system is an important pillar to maintain ecological balance.

The role of halophilic bacteria in the process of salt formation is absolute and enormous. At the same time, halophilic bacteria are also the main components of salt minerals, but halophilic bacteria have been replaced by salt minerals, but they still retain their morphology. In a sense, halophilic bacteria and salt minerals are twin brothers. According to the available data, there is no natural salt mineral that is not composed of halophilic bacteria. It should be said that halophilic bacteria constructed salt minerals.

Second, salt lake biology and temperature.

On the earth, salt lakes are widely distributed in tropical desert arid climate zone, tropical desert zone, temperate desert arid climate zone, temperate desert zone and desert grassland zone. Of course, salt lakes of different origins can also be found in temperate and polar regions. Salt lakes are distributed in these areas because of dry weather, little rainfall and easy evaporation.

Under the condition of strong sunshine, due to physical and biological factors, high salinity brine is heated very quickly. For example, the temperature of the Mediterranean salt flats can reach 45℃. The optimum survival temperature of halophilic bacteria is between 40℃ and 55℃ (Juez, 1988), and the highest temperature is close to 85℃. This led to the formation of some thermophilic salt minerals. It's hard to understand until we know that biological action affects the warming of salt water.

Three. Salt Lake Biology and Pressure

According to the known data, most salt lakes are shallow, so there is no great pressure at the bottom. However, there are deeper examples in salt lakes. For example, the deepest part of the Dead Sea is 320m, where a large number of anaerobic bacteria live and need to bear considerable pressure (Nissenbaum, 1975). For another example, the geothermal brine in the Red Sea is a special case of deep ultra-salty brine, where the pressure of halophilic bacteria is also great.

Four, salt lake biology and nutrition

As mentioned earlier, there is a simple food chain in the salt lake. With the gradual increase of salinity, the individuals of brine shrimp and brine fly become smaller, and their carcasses are delicious food for halophilic bacteria to survive. However, with the rapid increase of salinity, due to a large number of previous deaths, the number of brine shrimp and brine fly decreased, and the number of deaths also decreased significantly, making the food source of halophilic bacteria a problem. In recent years, American microbiologist Ed Delong believes that halophilic bacteria use a new method to convert solar energy to produce nutrients, which is another way for organisms to adapt to the environment. Scientists first discovered bacteriorhodopsin in bacteria. Bacteriorhodopsin can convert light into mobile electrons, which can be used as energy to promote the formation and metabolism of bacteria, thus forming a unique photosynthetic mechanism in halophilic bacteria, which can also solve the problem that halophilic bacteria can survive and reproduce for a long time without food sources in super-salt environment (Xiaofeng, 2002).

Five, the biological function of solarization salt field

In recent 30 years, halophilic organisms have been paid more and more attention by salt-making and scientific research departments at home and abroad in improving the yield and quality of sun-dried salt. In salt field brine, in fact, in all biological-water-salt systems, a large number of halophilic organisms (including algae, salted shrimp, brine flies, bacteria, etc. ) plays an important role in the process of drying salt (forming salt), which can be summarized as follows: ① the function of gathering salt substances; ② the function of purifying salt water; ③ Promoting the evaporation and concentration of brine; ④ The function of biological anti-seepage, that is, organisms and their excreta combine organic and inorganic debris to form an anti-seepage layer, and controlling brine leakage in the salt field is the key to ensure the successful operation of the salt field; ⑤ The corpse of halophilic bacteria accumulates salt minerals, forming bacterial structure; ⑥ Larvae and molting of brine shrimp at different growth stages and larvae and molting of brine fly are extremely important components of evaporite.

The biological function of solarization salt field provides an important example for us to study the biogenesis of evaporite.