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There is enough water on Earth to cover the entire surface
of the planet with a layer 2.7 kilometers thick. Could it have been, say, ten
times more? Water is synthesized in the bowels of the planet as a result of
the decay of radioactive isotopes. Due to volcanoes, its reserves in the oceans
have increased 700 times over 4 billion years. And if volcanic activity were
higher, for example due to the presence of an even more massive natural satellite,
there would be more water.
Now let’s assume that there is enough water to flood the tops of the highest mountains.
And there are waves all around, just waves, and nothing but them – the infinity of water. For you can swim as much as you want, but the sea will not end. Nothing but clouds will appear above the horizon…
Of course, the ocean planets will acquire an oxygen atmosphere. On the Earth, unicellular algae solved this problem long before life came to land. Carbon dioxide, however, can create some problem, since calcium entering the water from rocks eroded by rivers is required to remove it from the atmosphere. But on the other hand, the depths of the ocean are themselves a burial ground of carbon dioxide, which is heavier than water and sinks in accordance with Archimedes’ law.
It is also curious that the water in the ocean will be fresh. After all, it is the rivers that carry salt into the sea. And this is not the only reason why the absence of shores will affect even the life of creatures that are not connected with land in any way.
The flora and fauna of the sea is divided into plankton freely drifting in the water column, “self-propelling” necton and benthos associated with the bottom. Notably, benthos will not be able to play a significant role in the biosphere of the ocean-covered planet, since high pressure and lack of light and oxygen, as it happens in the depths of the Earth’s oceans, will make the bottom practically uninhabitable. On the contrary, a huge role will be played by the pleuston – animals and plants floating on the surface of the water. They are relatively rare in our world, because sooner or later the surf will cast them ashore. Because of it, algae on the one hand acquire air cavities to raise the thallus to the sun, and on the other, cling to the ground.
Floating algae are found in abundance in only one place. This is the Sargasso Sea named after them. By no coincidence, it is also called “the sea without shores”. Only far away in the ocean do the drifting bubbles of siphonophore colonies feel safe. These can be Portuguese man o’ war reaching 50 meters in length, as well as coin-sized by-the-wind sailor Velella.
There will be no obstacles to the development of the pleuston in the water world. The benefits of such a lifestyle are obvious: plants get as close to the Sun as possible, and animals do not need to waste energy to stay at the right depth. The surface of the sea will be covered with tangles of drifting algae. Lots of mollusks and coelenterates, instead of clinging to stones, will prefer to get floats. Attached to each other, shells and hollow skeletons form reliable and unsinkable atolls. After all, each species will be interested in ensuring that the “heritage of the ancestors” serves the descendants, and does not drag them to the bottom.
Floating atolls, like real coral reefs, will attract hordes of fish. And they will also create some conditions for the coming of life “on land”. Probably, lichens, mosses, ferns will appear on floating atolls. Maybe arthropods will also conquer pseudo-land, but only if they appear on such a planet at all. After all, the legs are originally designed to move along the bottom. In the absence of arthropods, mollusks and vertebrates will have to colonize the surface of atolls and islands of entangled algae.
Even the air environment will be populated to some extent. After all, pleistone “takes light away” from phytoplankton, which means that biomass production will be concentrated not in a 200-meter near-surface layer of water, as on the Earth, but directly on the border of water and atmosphere. Accordingly, consumers of plant biomass will mainly concentrate on this border, and not in the water column. In such conditions, it will be more convenient for vertebrates not to swim in the traditional way, but to move in the hydroplaning or even gliding mode, as flying fish do. This is because air has much less resistance to movement than water. Such a lifestyle is likely to contribute to the replacement of gill respiration with a more effective pulmonary one.
Can an intelligent race appear on the ocean planet? Here, most likely, we can not do without an alternative. But since when has the alternative become a problem? There are also even supporters of the alien origin of human… In any case, floating atolls are not a very favorable environment for life.
Even in the Stone Age, it’s kind of depressing without a stone. And there is no such thing even on ordinary coral islands. As also clay, by the way, to make dishes. Moreover, there are no metals there. Shells and nutshells have to be used as containers. Shark teeth are needed to make cutting tools.
The most dangerous thing is that small atolls often rise above the sea by only a meter or two. When a hurricane breaks out, the waves roll across the island. A floating atoll, by the way, may not withstand a storm at all and break apart. It can sink if the disease or the actively breeding predators destroy the polyps, or drift to the pole at the will of the winds and currents.
Translated by Pavel Volkov, 2021
The original Russian article is here