Why is it said that “when a whale dies, all things come to life” is the gentleness from the sea?

The term "whale fall" first appeared in 1991, when Allison et al. used it for the first time to analyze the formation principle of whale fossils. Literally, the "fall" of whale fall refers to the process of whale carcasses sinking from the sea surface to the bottom of the sea. Whales are huge in size, and most whales die naturally due to malnutrition or disease during long-distance migration. After death, negative buoyancy is generated, and the carcasses initially sink to the bottom of the sea. During the fall, there are few scavengers in the middle waters that gather on the carcasses. Under the action of water pressure, the lungs contract and the carcasses sink rapidly, and the carcasses reach the bottom of the sea relatively intact.

Whale falls are the largest organic debris currently formed in the ocean and the most nutritious of all organic debris, rich in lipids and proteins. The animal communities of large whale falls can go through four succession stages:

During the mobile scavenger phase, 7-45 days after the whale falls reach the seabed, scavenging fish and invertebrates will quickly gather near the whale falls to remove soft tissues. 38 species have been identified and characterized from this phase, most of which are general scavengers, including hagfish and sleeper sharks. Other important scavengers include crustaceans. Most of the soft tissues of whale falls are directly eaten by scavengers, and this phase lasts about 3.6 to 18 months.

The first phase of the opportunist phase is a period of rough scavenging activity that disperses the remains of the whale into the surrounding sediments, triggering a microbial response. For a 5-35 ton whale carcass, this phase lasts approximately 2-4.5 years.

In the chemoautotrophic stage, after the soft tissue is stripped off, the lipid-rich whale bones are exposed, which can provide the most durable energy source. The degradation and utilization of whale bones are mainly completed by anaerobic bacteria. A large number of heterotrophic and chemoautotrophic bacteria grow on the bone surface, bone sutures and bone density, and tens of thousands of mussels hide in the bone seams. This stage is extremely species-rich, with an average of 185 species per skeleton. In this stage, large whale skeletons can support biological communities for 40-80 years.

In the reef stage, after the organic matter of the whale fall is exhausted, it eventually becomes a reef suitable for biological settlement. In 1971, sea anemones were found to settle on whale bones at a depth of 4,800 m in the Clarion Clipperton Zone, suggesting that the whale fall was more than 10,000 years old.

Biodiversity plays an important role in regulating marine ecosystems. 407 species of organisms were found in whale falls in the Gulf of California, which is not much different from the 469 species richness of hydrothermal springs, which have been studied more intensively, and far exceeds the approximately 230 species of cold springs. The high number of some species indicates that they have adapted well to the habitat of whale falls. The geographical distribution characteristics of whale falls also determine that they play an irreplaceable role in the maintenance and evolution of deep-sea biodiversity. Whale falls, cold springs and hydrothermal vents are all deep-sea reducing habitats. In particular, whale falls in the chemoautotrophic stage have the same food web as cold springs and hydrothermal vents, which starts with chemosynthetic bacteria. The three have certain similarities in community structure and energy flow.

Whales use their bodies to repay the sea that carries them. Every time a whale falls, a complete ecosystem is generated, which operates in the desolate deep sea for decades or even hundreds of years. In the deep sea of ​​the North Pacific, at least 43 species and about 12,000 organisms rely on whale falls for survival. In view of the sharp decline in the number of whales and the rarity of whale falls, it is particularly important to protect the existing whale populations. The lifespan of each whale and the final whale fall can have a profound impact on the marine ecosystem, reflecting the role of large biomass in maintaining the global ecological balance. In short, whale falls are not only a spectacular farewell ceremony for life, but also an indispensable part of the deep-sea ecosystem. It reveals the nature of the cycle of life and death in nature, and also calls on humans to cherish and protect marine resources more to ensure the integrity and stability of this ecological chain.

References

[1] Wang Baobao. Ecological overview of whale falls[J]. Biology Teaching, 2021, 46(06): 62-63.

[2] Lin Mingli, Li Songhai. Progress and prospects of whale fall ecology research[J]. Journal of Tropical Biology, 2023, 14(01): 32-41.

[3] Qu Youfang. When a whale falls, all things come to life: a tribute to the tenderness of the sea[J]. New Education, 2020, (30): 23-24.

[4] Ma Ruiqi. After the whale dies...Once the whale dies, all things are reborn[J]. Popular Science (Primary School Edition), 2021, (12): 20-22.