- Deep ecosystems formed by mollusks discovered in the most inhospitable marine trenches on the planet.
- Bivalve mollusks and gastropods stand out for their extreme adaptation to environments without light and rich in chemical compounds.
- The blue dragon and the sea sheep, two unique species, attract attention due to their biology and potential risks.
Marine life continues to surprise the scientific community. Thanks to recent discoveries that challenge what was thought known about the limits within which certain animals can live. Mollusks, a group that includes everything from bivalves to sea slugs, have been the focus of several recent investigations conducted at extreme depths in the North Pacific oceans.
During scientific campaigns in the Kuril-Kamchatka and Aleutian TrenchesAt depths of up to nearly 10.000 meters, an international team documented invertebrate communities thriving in light-deprived environments subject to low temperatures and a lack of oxygen. In this inhospitable environment, mollusks and tubeworms have been observed forming ecosystems based on chemosynthesis, a process by which organisms obtain energy from chemical reactions rather than sunlight.
Mollusks in the hadal zone: survival in extreme conditions
The so-called hadal zones constitute some of the most unknown and extreme environments on the planet.. From 6.000 meters deep, in large oceanic trenches resulting from the meeting of tectonic plates, scientists have recorded the presence of various mollusks, specifically mussel-like bivalves and gastropods adapted to the cold, darkness, and crushing pressure. In addition, some of these mollusks, such as gastropods, have also been documented in explorations in different areas of the deep ocean, including areas of interest such as the aquatic dinosaurs.
The Fendouzhe submersible has been key in these explorations, allowing for sampling and direct observations on previously unexplored seabeds. Experts have scanned more than 2.500 kilometers of seafloor, identifying colonies of mollusks and worms in symbiosis with microbes that allow them to harness compounds such as hydrogen sulfide and methane.
The study, published in the journal Nature, suggests that chemosynthetic life is more widespread than previously thought, and these animals have developed unique mechanisms to survive where light never reaches. The existence of these ecosystems also challenges previous theories about the carbon cycle and the primary energy source in the deep. Microbial activity creates methane and sulfide from sedimentary organic matter, serving as the basis for these surprising communities.
Singular species: blue dragon and sea sheep
Among the most striking mollusks discovered or sighted recently is the so-called blue dragon (Glaucus atlanticus)., a small, brightly colored nudibranch that occasionally appears in Spanish waters, especially after storms and changes in currents. This sea slug floats upside down and is capable of storing toxins from its prey, which can pose a risk to bathers. Direct contact can cause symptoms such as pain, vomiting, or skin irritation, which is why authorities generally recommend avoiding handling it if found on the beach.
The so-called sea sheep (Costasiella kuroshimae) This is another fascinating example of the diversity of mollusks. This tiny animal, famous for its adorable appearance, lives primarily on seaweed-covered seabeds in parts of the Pacific. The most striking aspect of its biology is its ability to retain chloroplasts from the algae it consumes, allowing it to carry out photosynthesis and produce its own food, a phenomenon known as kleptoplasty. This adaptation, in addition to providing it with nutrients, offers camouflage and some protection from predators.
Both species, although not formally considered threatened, see their survival conditioned by factors such as pollution, habitat deterioration, and climate change, which affect both water quality and food availability.
Research promotion and future challenges
Technological advances in submersible vehicles have allowed us to expand our knowledge about life in the deepest parts of the ocean.Missions like those carried out by the Fendouzhe have opened a window to the direct exploration of previously inaccessible seabeds, pointing to the possible existence of corridors of chemosynthetic life spread across different tectonic trenches on a global scale.
Furthermore, these discoveries provide fundamental information for better understanding the global carbon cycle and ecosystem dynamics under extreme conditions. Scientists believe that, if the extent of these communities is confirmed, it could have significant implications for carbon sequestration and the formation of methane deposits in the seafloor.
These discoveries not only expand the catalog of known species, but also highlight the enormous adaptive capacity of mollusks and other marine invertebrates. Thanks to this work, our knowledge of life on the ocean floor continues to advance, revealing unknown ecosystems and surprising life forms that will be key in the coming years.
