Editor's note
On November 1, China's 40th Antarctic Expedition organized by the Ministry of Natural Resources set off from China. From now on, the "China Natural Resources News" will open a special column entitled "Antarctic Chronicle" to publish what the special reporters of this newspaper have seen, heard, thought and felt during their participation in the Antarctic scientific expedition with the "Snow Dragon".
At 3:30 a.m. on January 25, on the amidship deck of the "Snow Dragon", Guo Guijun, the leader of the amidship deck operation team of the Ocean Survey, and Li Kangrong, a member of the team, put the CTD (Thermosalt Depth Profiler) into the sea under the command of experimenter Ding Feng. This is the first site of China's 40th Antarctic Expedition to the waters adjacent to the Antarctic Peninsula. Depending on the mission, each site will have different survey items on the amidships and aft decks, but the CTD survey is a basic project that must be included at each site, and it is also the main means of "physical examination" for the ocean. After the training at the previous drill site, the team members were proficient in operation and tacit cooperation, and the entire CTD casting process was efficient, smooth and stable. The "Snow Dragon" is equipped with a CTD of 24 cylinders with a capacity of 10 liters, and its own sensors measure and transmit data such as water depth, water temperature, salinity, fluorescence, and solubility in real time. Each bottle is numbered and capable of collecting seawater samples at different depths. The CTD is first lowered to the seabed and harvests seawater as it ascends. The water bottle is designed to flow through the water without hindrance, and when it reaches the target water layer, the valves at the upper and lower ends of the water bottle are closed, and the seawater at this depth is sealed inside. Depending on the survey task, the depth distribution of seawater collected by CTD is different at each station or at the same site, and the parameters need to be set in advance each time. However, surface and bottom water are collected at a time, and shallow waters above 200 meters are typically collected at a higher density than deep water. In the control room on the second floor, sailor Chen Yinchu operated a winch to lower the CTD to the depths of the sea, with a total length of more than 8,000 meters of steel cables, and the speed can reach about 70 meters per minute when lowered or recycled at full speed. Guo Guijun commanded on the side, and team member Ma Zekai stared at the computer screen, using the walkie-talkie to report the current depth of the CTD while recording. On the record sheet in front of him, the name of the station, coordinates, weather conditions, and the time of decentralization had been recorded. "CTD depth 100 meters...... 200 m ...... 1500 m ...... 1690 meters, start to slow down", when there were still 100 meters left from the bottom of the sea, Ma Zekai gave an order to slow down the winch. At 4:03, CTD reached the bottom of the sea at a depth of 1,790 meters, and he clicked the button in the computer software, and the No. 1 and No. 2 bottles collected samples of the bottom seawater. The winch starts to recover, the CTD rises, and the water is pumped in time every time the preset depth is reached. 1000m, 500m, 200m, 150m, 100m...... Up to 5 meters, CTD collected a total of 12 layers of seawater samples at different depths.
CTD effluent.
When we examine the body, we usually test a wide variety of blood indicators: blood count, cholesterol, blood sugar, uric acid, ...... The blood samples collected will be assigned to different laboratory instruments according to different needs. At this point, the blood collection for the marine "physical examination" has been completed, and the next step is the laboratory analysis by category. It was nearly 5 a.m. after the CTD was recovered and re-fixed and cleaned in the operation room. According to the pre-arranged sequence and the level and quantity of seawater required, the team collects and processes the seawater samples from the corresponding water bottles. Because the gases in seawater are volatile, the first step is to collect seawater by the team members who do atmospheric analysis. In the atmospheric chemistry laboratory, team member Lu Shengbin is seizing the time to classify and process the freshly collected seawater samples, and the atmospheric components he analyzes mainly include carbon dioxide, methane, dimethyl sulfur, etc. Carbon dioxide and dimethyl sulfur can be detected on-site by on-board instruments. He said that carbon dioxide and methane are both greenhouse gases and are considered to be the main contributors to global warming. Dimethyl sulfur is mainly produced by phytoplankton and bacteria, and is the largest number of biological sulfur-containing compounds emitted into the atmosphere from the ocean, which affects the generation and growth of atmospheric sulfate aerosols after entering the atmosphere, and then affects the radiation characteristics of clouds, which has a natural climate cooling effect and is an important factor in the earth's climate balance.
Save seawater samples.
In the chemistry lab, team member Zhang Leilei began to process seawater samples to analyze the dissolved oxygen in them. She said that since the mid-20th century, the global ocean dissolved oxygen content has decreased significantly, especially the area of hypoxia in the bottom seawater. Oxygen reduction is one of the serious side effects of ocean warming, affecting the community structure, productivity and habitat of marine organisms. Team member Yang Disong collected samples of seawater from all 12 layers, partially loaded them into a filter, filtered the chlorophyll in the seawater onto a fiberglass filter the size of a one-yuan coin, and then wrapped them in tin foil, frozen them, and brought them back to China for analysis. He said that thanks to chlorophyll, phytoplankton can convert carbon dioxide from seawater into carbohydrates through photosynthesis. Chlorophyll is an important indicator to evaluate the number of marine phytoplankton, which can reflect the productivity of the sea area. At the same time, Yang Disong also used instruments to test the pH of each layer of seawater on site. In recent years, ocean acidification has also been a major challenge for marine ecology. Team member Yang Zhedong uses freshly collected seawater to filter particulate organic carbon in the chemistry laboratory and preserve the filtered samples. Seawater particulate organic carbon not only reflects the biological activities in seawater, but also has an important significance for the ocean carbon cycle and the regulation of global climate change under the influence of carbon dioxide. In the biological laboratory, Xian Haochen, a member of the team, filtered the microplankton samples with seawater and put them into test tubes for cryopreservation, so as to return to the domestic laboratory for molecular biology analysis, and at the same time processed the large-volume metagenomic samples in the bottom layer of the ocean surface. He said that metagenomics, as an emerging discipline to study the ecological distribution, population genetic characteristics and gene interactions of microbial populations, is a powerful tool for studying marine microbial communities. Team member Zhang Xinran used directly collected seawater to filter virus samples, and about 300 liters of seawater from each station were filtered in stages, and finally concentrated into 50 milliliters, at which time all other organisms in the seawater except the virus were filtered out. She said there are about 1×1,031 virus particles in the ocean, 15 times the total number of all other ocean dwellers. Viruses act like a water pump to facilitate the circulation of elements in the ecosystem, and by cracking the host (marine bacteria and algae), the virus indirectly causes the amount of carbon dioxide in the atmosphere to decrease by about 3 gigatons of carbon per year, curbing the process of global warming. In the analytical chemistry laboratory, team member Zhou Bin is processing and analyzing nutrient samples in seawater, mainly including ammonia, phosphate, silicate, nitrate and nitrite. He said that the marine ecosystem around the Antarctic continent is affected by many factors, among which nutrient cycling is a crucial link. Nutrients in seawater mainly refer to nitrogen, phosphorus, silicon, these nutrients, they are the essential components for the growth and reproduction of marine phytoplankton, Antarctic phytoplankton convert the nutrients in seawater into organic matter, become the basis of the food chain. Atmospheric precipitation and glacial meltwater are the main sources of nitrogen in the Antarctic seas, while phosphorus and silicon mainly come from sediments and glacial meltwater on the seafloor. "Due to the movement of ocean currents, these nutrients are not evenly distributed in the Antarctic seas. Our operational work is to understand how nutrients change in the Antarctic seas on both spatial and temporal scales. Zhou Bin said. The last team member finished processing and analyzing the seawater sample, and it was already more than 8 o'clock in the morning. The various precious samples and analysis data of the polar seawater obtained from the survey will provide support for the study of marine ecology. At this time, the "Snow Dragon" was getting closer and closer to the second investigation site. At about 10 o'clock, CTD went into the water again, and the team members who "checked" for the ocean began to be busy again.
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Source: China Natural Resources News
Chief Reporter: Wang Shaoyong
Text Editor: Dai Lu
New Media Editor: Qu Bingjie (Trainee)
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