Space may be the final frontier, but here on earth the sea is the last vast resource not to be fully explored. As noted on the website Our Amazing Planet in the article “Earth's Final Frontier: Mysteries of the Deep Sea", the sea is 300 times the size of the earth’s inhabitable land. In addition, they note, “Dive beneath the ocean's waves, past the sunlit, teeming waters near the surface, through the oxygen-deficient zones nearly devoid of life, down, down and down some more, to a place where the pressure would crush a human, and you will find the mysterious, alien world of the deep sea,” and that alien world is very much alive, even in the most extreme places.
Trying to explore and figure out exactly what lives in this vastly unexplored part of our planet is made difficult because of extreme conditions. Great pressure as one descends downward can crush metal and break glass. The frigid temperatures can also be highly dangerous.
However, there are also volcanic fissures in the deep Pacific with temperatures up to 752 degrees F (400 C). While nothing living can survive such a temperature, there actually are bacterial organisms living near the vents on these fissures that can survive over 302 F (150 C). This ecosystem is quite unique in that no part of it is dependent upon the sun.
BBC Nature has a video series that includes “The Blue Planet” that documents just a few of these creatures. The hydrogen sulfides, normally poisonous to animal life, are used as food by bacteria nearby. These bacteria are absorbed by tubeworms, which have neither mouth nor anus. The hemoglobin of the tubeworms carries the sulfides to the bacteria in a symbiotic relationship. Other organisms feed upon the bacteria, some directly and some via the tubeworms.
A unique organism in these heated areas is the Pompeii worm, first discovered near hydrothermal vents in the Galapagos Islands. These worms are “perhaps the most heat-tolerant complex organisms on Earth,” according to National Geographic article “Earth's Hottest ‘Bods’ May Belong to Worms.” The temperature at the base of the tubes of these worms may be as high as 176 F (80 C).
Other species nearby some of these vents are various mussels, crabs and lobsters. Many of the breeds of these species are unique to this environment.
The Office of Naval Research also lists in “Habitats: Hydrothermal Vent - Characteristics” assorted fish, shrimp and anemones as species that have been found near these hydrothermal vents.
One would think the remarkable nature of life existing at all in these extremes would only be outdone by the fact that entire ecosystems exist near them. However, even more amazing is that there must be some means of these creatures migrating, since, as the BBC videos point out, these hydrothermal vents tend to last only a few decades. As The Daily Galaxy reports in “Deep-Sea Extremophiles Migrate Hundreds of Miles to New Volcanic Vents -Experts Ask How?”, species can migrate 350 kilometers to newly opened vents. This was surprising and puzzling at the same time, as most reasonable estimates for larvae to travel would have been limited to around 60 km.
As Nature magazine online reported in “Oceanography: Death and rebirth in the deep”, a study was made of various vents, both on the ocean floor and higher up, and they discovered a very complex set of currents created by the interplay of the different speeds of these currents. This was another surprise for them, as it had not previously been considered that surface eddies could have this influence.
This migration means that an explosion at a vent can occur that kills the entire community, but the new ecosystem that eventually emerges is different from the original. The above resources contain references to this phenomenon having been studied at two different vents.
Life is very interesting. This is the only planet where life has been observed. Even life on this planet is very fragile, and an upset in any ecosystem can radically alter the species in it. However, as the life found near the undersea hydrothermal vents demonstrates, life can also not merely exist but thrive in even the most extreme circumstances.