International Journal of Molecular Ecology and Conservation, 2025, Vol.15, No.4, 163-174 http://ecoevopublisher.com/index.php/ijmec 1 64 This study aims to review the main progress in the research of whale fall ecosystems in recent years. It will explore the ecological significance, community succession patterns and driving mechanisms of whale falls, and look forward to future research directions and application prospects. Studying the dynamics of whale fall communities not only holds significant scientific importance, deepening the understanding of life adaptation and evolution in extreme environments, but also helps assess the role of whale falls in the deep-sea carbon cycle and material transport, providing new ideas for deep-sea ecological protection. 2 An overview of the Ecological Significance and Research Progress of Whale Falls 2.1 Definition and discovery history of whale falls The term "whale fall" summarizes the carcass of a whale, its sinking process, and the deep-sea ecosystem formed thereby (Li et al., 2022). In 1987, humans witnessed a whale fall for the first time in the deep sea of the northeastern Pacific Ocean: The USS Alvin manned submersible discovered a blue whale skeleton about 21 meters long off the coast of California. The skeleton was covered with a dense "carpet of life", including a large number of decomporers such as bacterial biofilms and worms (Smith and Baco, 2003; Smith et al., 2015; Georgieva et al., 2023. This is the first recorded natural whale fall ecosystem in science, confirming the existence of a special biological community in the deep ocean that uses whale remains as an energy source. Since then, scientists have successively discovered new whale falls in deep seas such as the Pacific Ocean and the Atlantic Ocean, and found traces of whale fall fossils in the Neogene strata about 30 million years ago in the geological record (Yin et al., 2023). Whale falls are thus regarded as an important "stepping stone" and "relay station" for the evolution of deep-sea organisms (Xie et al., 2023). Whaling records since the 19th century also offer clues that there might have been more whale falls in history than in modern times, providing an important food source for deep-sea creatures. However, large-scale industrial whaling in the 20th century led to a sharp decline in the population of large whales. It is estimated that the frequency of natural whale falls in contemporary times has decreased by at least 50 to 95% compared with that before whaling. Some deep-sea exclusive species that rely on whale falls may thus face the threat of extinction (Smith et al., 2019). In recent years, with the development of technologies such as deep-sea remotely operated vehicles (ROVs), scientists in China and other countries have also begun to actively search for and study whale falls. In 2020, a Chinese scientific research team discovered the remains of a sperm whale about 3 meters long at a depth of approximately 1,500 meters in the South China Sea and conducted in-situ observations. This was the first time that natural whale fall was recorded in China (Figure 1) (Yin et al., 2023). 2.2 The significance of whale falls for deep-sea ecosystems Whale falls bring a large amount of organic matter input to the barren deep-sea environment and are hailed as the "oasis" of deep-sea life (Li et al., 2022; Yin et al., 2023). Under normal circumstances, the deep sea mainly relies on the slow sedimentation of "Marine snow" on the surface to supply nutrients. The amount of organic carbon deposited each year is less than a few grams per square meter. In contrast, the thousands of kilograms of organic carbon carried by a large whale instantly sank into the deep sea after its death, equivalent to the amount of organic carbon that would normally sink over hundreds or even thousands of years. The nutrients rich in whale carcasses quickly gathered various scavengers and microorganisms, forming a vigorous biological hotspot on the originally quiet and desolate seabed (Chen and Wang, 2020). Whale falls provide a rich and continuous source of nutrition. They not only allow large scavengers to feed on soft tissues, but also nourish specialized microorganisms through the high lipid content in bones, and then support subsequent chemical autotrophic communities through microbial products (such as hydrogen sulfide) (Silva et al., 2021; Li et al., 2022). Many new species discovered in whale fall environments have unique adaptations, such as the bone-eating worm Osedax belonging to polychaetes, which feeds exclusively on bones, and mollusks that live in symbiosis with sulfides, etc. (Shimabukuro and Sumida, 2019; Souza et al., 2021). The existence of these species expands our understanding of the extreme adaptability of life. On the other hand, whale falls also connect scattered deep-sea chemogenic habitats by providing "stepping stones". Many invertebrate groups (such as large mussels, tubular worms, etc.) found on whale falls also appeared in hydrothermal vents and cold seeps, supporting the hypothesis that whale falls act as relay stations to promote species diffusion (Pereira et al., 2020; Silva et al., 2021).
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