International Journal of Marine Science, 2024, Vol.14, No.2, 111-119 http://www.aquapublisher.com/index.php/ijms 113 Figure 1 Distribution of new species in global oceans In 2006, scientists discovered a new species of worm called Pyrodesmia flamea in the hydrothermal vent system of the South Pacific Ocean. This type of worm can survive in high temperature environments exceeding 350 ℃, and its body is covered with special structures that can resist extreme heat (Zhang et al., 2021). In addition to the discovery of a single species, deep-sea exploration has also revealed complex biological communities. In the cold water coral reefs of the North Atlantic, scientists have discovered dozens of previously unrecorded marine organisms that collectively build a complex ecosystem. 2.2 Iconic discovery cases: giant creatures and microorganisms in the deep sea At the beginning of the 21st century, an international scientific research team used deep-sea submersibles to explore a remote area of the Pacific Ocean. When the submersible descended to a depth of about 2000 meters, scientists successfully discovered a new deep-sea giant fish-Megamouth. Megamouth fish live in the dark, high-pressure environment of the deep sea and are usually solitary, only gathering during the breeding season. Megamouth fish feed on other deep-sea creatures such as fish, crustaceans, and invertebrates. In addition to hunting, megamouth fish spend most of their time swimming, possibly in search of food or to avoid predators. As apex predators, they help control the populations of other organisms and prevent certain species from overpopulating and disrupting the ecological balance. Deep-sea microorganisms may be more overlooked than giant creatures, but they are one of the most fundamental and important components of deep-sea ecosystems. In the deep-sea exploration of the 21st century, scientists have discovered a large number of deep-sea microorganisms that exist in environments such as seafloor sediments, hydrothermal vents, and cold-water corals (Shen, 2023). Deep-sea microorganisms live in extreme environments of high pressure, low temperature, low light, and lack of nutrients (Reysenbach and Shock, 2002). In order to survive in such conditions, they must possess special physiological and metabolic mechanisms (Figure 2). Some deep-sea microorganisms can use chemical substances (such as hydrogen sulfide, methane, etc.) released from hydrothermal vents on the seafloor as energy and nutrients through chemical synthesis to grow autotrophically. Other microorganisms rely on the remains or excreta of other organisms for heterotrophic growth. Because nutrients are limited in deep-sea environments, microorganisms must reproduce quickly to maintain populations. At the same time, they adapt to changing environmental conditions through continuous mutation and evolution. This high degree of adaptability and reproductive ability allows deep-sea microorganisms to maintain strong vitality in extreme environments.
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