“Not so long ago, the oceanic depths were considered a gigantic abyss, filled only with myths, legends and endless unknowns […]. The study of the deep is forcing us to constantly modify our ideas about how life arose on Earth, to redefine the limits of what is possible.” – Helen Scales, 2022, “The Abyss, the hidden life of the oceans […].”
How deep did you dive? This is the dumbest, but most frequently asked question a diver can hear. Recreational divers make efforts to break through the magic 335m barrier, too often losing their lives in the process. Professional divers laid the pipeline at a depth of 534 meters. However, this is still not much against the backdrop of the precipitous depths of Earth’s oceans. Most of the planet’s surface is occupied by abyssal plains, extending to depths of 3-6 thousand. m. In January 1960. Jacques Piccard and Don Walsh descended to the bottom of the hadal Challenger Deep (10,916 meters) aboard the bathyscaphe Trieste. In March 2012. Aboard the Deepsea Challenger, their feat was repeated by James Cameron (10,908 meters), and in April 2019. Aboard the Limiting Factor – Victor L. Vescovo (10,928 m). The surface of the Kallisto ocean may lie as high as 200,000. m under the ice there. Returning to diving, I answer that it doesn’t matter how deep or how long, but what interesting things I saw there. Similarly, in the case of the oceanic depths, the question we ask, whether about Earth or Jupiter’s moons: is there any life there, and if so, what does it look like.
Helen Scales, a real-life marine biologist, takes us on a journey into the oceanic abyss. It describes a world that statistical divers and non-divers are not familiar with. Because who associates the names of the individual ranges of the longest system of mountain ranges on the planet ? Leading through icy abyssal plains and among boiling geothermal chimneys, gushing with a sizable portion of the Periodic Table, it introduces the astonishing inhabitants of the underwater world. It presents a life we can’t imagine – heat-resistant and chemical-eating. There is a scaly snail  with an iron(sic!) shell and scales shining with pyrite. There’s the Vampire of Hell, a grotesque cephalopod that could win a casting call for a sci-fi horror movie, although it only feeds on sea snow . There’s the Pompeian worm, which can tolerate temperatures of 77°C, and yeti crabs, contemplating the chemical composition of water bubbling up from hydrothermal vents or dancing herdily in colonies in the area of cold exudates. Organisms that astrobiologists looking for life on other celestial bodies would not be ashamed to invent. Who, while diving, reading books or watching movies, hasn’t dreamed of someday seeing such creatures and similarly amazing places to visit?
On the pages of the book we also visit, among others. The Lost City – the site of hydrothermal vents where some believe life on Earth may have begun. Hand’s “Extraterrestrial Oceans” also began from this point. In the Lost City, for completely different and surprising reasons, we will also end this article.
Conquerors of the deep
More than 95 percent. The biosphere lives in the deep sea. The first biologist to dive with an aqualung was William Hammer in the 1970s. What do we know about other conquerors of the deep? The leatherback turtle dives to 1,000. m. Spermaceti spermaceti over 2,000. m, and the supply of oxygen in the blood and muscles is sufficient for more than an hour. His lungs collapse at a depth of 300 meters, reversibly, and his heart rate drops to five beats per minute. Another cetacean, the Goosehead Ziphia, dives as high as 2992 meters, and its longest recorded dive lasted 222 minutes .
Unlike recreational divers, cetaceans don’t do it for the records. They hunt octopus and giant squid that live in the bathypelagic zone. As Scales notes, the oxygen minimum zone at depths of a kilometer or more gives apneas a speed advantage over creatures that breathe with gills – a hunting sperm whale reaches a speed of 7 m/s. What amateur divers don’t usually know is that apneic divers can also suffer from DCS, as exemplified by whales .
Depth of life and life in depth. Oceanic wilderness, prairies and ravines
Abyssal plains are the most extensive landforms on Earth. They occupy roughly half of the planet’s surface, and lie between 1.5 and 10 kilometers of silt. These boundless spaces are dotted with thousands of volcanoes, especially near the center of tectonic plates, over hot spots where archipelagos are born. We see the volcanoes, whose peaks protrude above the surface, as islands. Those that didn’t manage to get that high are called gujotas . Another variation of the bottom is subduction zones, where tectonic plates slide under each other, leading to the formation of deep oceanic trenches. The deepest is the Mariana Trench, where the Challenger Deep, mentioned in the introduction, is located. Most subduction zones are part of the Pacific Ring of Fire, which smokes on the surface with its volcanoes. The Andes Mountains in the west of South America are full of them, and every self-respecting island in the vast Malay Archipelago has at least one each.
The fall of the whale
Had it not been for the steady fall of the sea snow, the death of the whale would have been an event to clock the life of an abysmal bottom. It is the cradle of an ecosystem that thrives on many levels to the point of complete decomposition of the remains, the habitat of tens of thousands of species and an island of life in the boundless wilderness of the plains. One of the main collective protagonists of such an event are the 2002 discoveries. Osedax – a genus of bone-eating annelids from the family of tubeworms, deep-sea polychaetes lacking anus, viscera and mouth . Their roots are home to symbiotic bone-degrading bacteria, and inside the female’s tube live dozens of dwarf males. We first admired a study of such an event in an episode of “The Deep,” in BBC Television’s 2017 series of stunning “Blue Planet II “footage.
Deep reefs and coral gardens
Of the approximately 5,000. of known coral species, more than half – as many as 3,300 – live in the ocean depths, even at depths of 8,000. m. They have evolved two types of nutrition: hunting or taxing zooxanthellae – symbiotic organisms whose loss through deterioration is known to divers in tropical waters as reef fading. Deep-sea corals, of course, have no chance to exploit zooxanthellae, so they prefer mountainsides washed by strong and fertile currents. These are mostly octocoral corals (sea feathers, gorgonians, bamboo corals and Venus fans) or black corals with skeletons made of chitin, but there are also hard corals, such as the reef-building but extremely slow-growing Lophelia pertusa .
Lovers of the deep are the coral-related stilbopods, also known as lacewing corals because they also produce calcareous skeletons, like the well-known Red Sea fire coral(Millepora). They evolved in the depths 65 million years ago and are colored with colors invisible at greater depths, such as red, pink, brown and even purple and blue. Up to more than 9,000. m we meet lilacs, equipped with five grasping feathery arms . The deepest vertebrate, however, is the snail fish(Liparidae), which has been seen at a depth of 8,000. m. It has a transparent skull and produces antifreeze. Despite having eyes, it hunts by touch, sensing with its mouth the ripples aroused by moving amphibians. Several deep-sea shrimps have developed eye-like organs that respond to blackbody radiation emitted by hydrothermal vents . This allows them to live close to, but at a safe distance from, the holes that emit the hot water jet.
Submerged in low temperatures, the life of the ocean depths goes on very slowly, much slower than on the surface or in shallow seas warmed by the sun’s rays. This makes it extremely sensitive to any interference. Bamboo corals can live 35-200 years. Individual sea lilies live to be 340 years old. Golden corals can live 2,700 years. Black corals as old as 4,200 years. Therefore, the destroyed ecosystem will not recover in our lifetime. Unfortunately, the depths are threatened by the international appetite for deposits of metals needed for tablets and smartphones, but especially electric car batteries! There is a disturbing Polish accent in all of this, about which the second part…
Przemysław Trześniowski – a computer scientist by education, Mayan archaeologist, NACD and IANTD cave diver, technical diving instructor, one high-mountain underwater archaeologist and the only Polish cave archaeologist underwater, sidemount and precursor diver in Poland fascinated by archaeoastronomy, astrobiology, cosmology, marine biology, Mayan history and archaeology. As an independent researcher, he collaborates with several scientific centers in Poland and Mexico, and has participated in scientific projects in Mexico, El Salvador, Guatemala, Peru, Ukraine and at Ostrów Lednicki, the cradle of the Piast dynasty. He shares his passion, popularizing science in the form of lectures and presentations. He publishes in media outlets such as “Archaeowieści” and “Live Archaeology.” He leads, as a guide, cave dives in the Yucatan. For the past few years, he has also been organizing tours of Mesoamerica, treks and field workshops with the idea of popularizing Mayan history and architecture in Mexico, Guatemala, Belize and Honduras. He is a resident of Mexico.
In the article, I used, among other things. From the works:
 This is the mid-ocean ridge (MOR), which flourishes at the junction of seven major tectonic plates. It has a length of about 65,000. km, and including all side strips 80 thousand. km. The longest range is the Mid-Atlantic Ridge, stretching from Greenland to Antarctica.
 The shell of scaly-footed snails (Crysomallon squamiferum) is made of three layers. Only the middle one is equivalent to the stratum corneum (periocastrum) of brachiopods and shellfish. The outer one is made of iron sulfides like pyrite, the inner one is made of aragonite.
 Precipitation of organic and inorganic particles from the subsurface zone of the ocean into its deeper regions. Food source of numerous organisms of the mesopelagic and bathypelagic zones, such as Vampyroteuthis infernalis. Sea snow primarily removes gigantic amounts of carbon from the atmosphere. It is stimulated by phytoplankton blooms caused by sperm whale feces (carbon pump). One-third of theCO2 produced by humans enters the ocean.
 On diving mammal records: Nicola J. Quick et al. (2020) Extreme diving in mammals: first estimates of behavioral aerobic dive limits in Cuvier’s beaked whales. “Journal of Experimental Biology” 223 (18): https://doi.org/10.1242/jeb.222109.
 DCS (Decompression Sickness) – decompression sickness syndrome. The case of the seawall (Balaenoptera borealis); L. Norina et al. (2020) Decompression Sickness (DCS) in a Sei Whale (Balaenoptera Borealis) Stranded In Batu Pahat, Johore, Peninsular Malaysia. “Archives of Veterinary and Animal Sciences” 2(1).
 Some of the guiotas are popular dive sites, such as. Monad Shoal in the Philippines, where cosogon sharks can be found at depths accessible to recreational divers, living at the edge of the photic zone (about 180-200 m). Cosogons benefit on Monad from the so-called. cleaning stations (no Polish name) – places where selected fish species can clean their skin of parasites.
 Although discovered more recently and living in places that are difficult for researchers to access, at least 26 species are already known; Yoshihiro Fujiwara et al. (2019) New species of bone-eating worm Osedax from the abyssal South Atlantic Ocean (Annelida, Siboglinidae). “Zookeys” 8(814):53-69. https://doi.org/10.3897/zookeys.814.28869.
 In 2018. A formation made of lophelia, which is 130 km long and 0.1 km wide, has been discovered off the coast of South Carolina. There are known sites in the Mediterranean Sea, on the Mid-Atlantic Ridge and off the northwest coast of Africa, where colonies of hard corals have grown continuously for 50,000 years. years.
 Probably Bathycrinus volubilis to a depth of 9102 m in the Izu-Ogasawara Trench; Tatsuo Oji (2009) Discovery of Dense Aggregations of Stalked Crinoids in Izu-Ogasawara Trench, Japan. “Zoological Science” 26(6):406-408. https://doi.org/10.2108/zsj.26.406.
 Zbinden and Cambon-Bonavita (2020) Rimicaris exoculata: biology and ecology of a shrimp from deep-sea hydrothermal vents associated with ectosymbiotic bacteria. “Marine Ecology Progress Series” 652:187-222.