In part 1 of this topic, I introduced the underwater dome as a setting for science fiction stories. Here, I’ll discuss some of the difficulties of life in an underwater dome, because they can be used to give more detail and flavor to your story.
First, you’ll need to build your dome out of something strong enough to survive the water pressure at depth, and transparent if you want light inside for growing plants or just the happiness of your residents. You’ll need extra strength because the inside of the dome will probably be at surface air pressure; oxygen can be toxic when breathed under pressure, and if you dilute it with helium, that can cause neurological problems (in addition to funny voices). The pressure differential means that if you want to go outside for a swim, you’ll need to spend some time in a pressure chamber.
You shouldn’t just plop your dome down on sand or mud; you’ll either need to set its base on solid rock substrate, or run support pilings down to bedrock. In the second case, I’m thinking your dome will instead need to be a sphere for structural integrity.
The outer surface of the dome will need some coating that prevents anything from growing on or attaching to it (this does not exist in 2014). Otherwise, algae will take advantage of any light coming from inside (street lights, etc.) and quickly cover the dome. You will then need an army of scrubber robots or low-wage workers to wipe off this algae and scrape off tougher organisms like barnacles and tube worms. One possible enhancement would be to build a second framework around the dome, made from materials which encourage corals to grow. Then, your city would be disguised as a coral reef from the outside, and you’d have a coral reef view from everywhere inside, but all of your light would need to be artificial.
Oxygen shouldn’t be a problem; you can raise plants or algae inside the dome, or you can separate the oxygen atoms from water molecules, or perhaps you can invent an artificial gill which collects dissolved oxygen from seawater. Temperature shouldn’t be a problem: If the dome has a tendency to overheat, water is great for carrying heat away. Conversely, if the dome has a problem with cold water, it can have a vacuum layer like a thermos. Seawater can be desalinated for drinking, but food may be a more serious issue.
For some of the scenarios in part 1, the dome can simply have all of its food shipped in. Fishing or harvesting krill seem like natural activities for dome residents, but ocean stocks are depleted, and the dome’s fishermen have to compete with surface trawlers. The kelp farms I saw in my childhood books probably aren’t practical; kelp is mostly water and doesn’t provide much nutrition. Seagrasses are more interesting, but I doubt they’re digestible by terrestrial farm animals. Dome residents can eat manatees or sea turtles which graze the seagrass beds, but they’ll need trained dolphins as herders, and if the dolphins have to spend most of the day herding instead of hunting, they’ll want supplemental fish. Fences aren’t practical as they have to run all the way to the surface, and they quickly become coated with sponges and other organisms, reducing water flow. Clams and oysters are excellent options for staple foods; children spend their days hunting pests like starfish and octopi in the clam and oyster farms.
Is a meat and fish diet acceptable to the dome residents? It seems that most coastal people still rely on a grain like rice or a starch like taro, but I guess a mostly carnivorous diet worked for Eskimos and other extreme northern peoples. To get some greens into their diet, your residents can grow plants inside the dome. Depending on the depth and clarity of the water, plants might need artificial lighting, as the water and dome material may not allow enough light through. Some marine material might be usable as fertilizer, as long as salt can be excluded.
You might be tempted to have your dome residents filter algae from the ocean, and process it into human food or animal feed. I wouldn’t recommend this, however; you never know what you’ll collect along with the algae, such as toxin-producing bacteria or dinoflagellates (unless… is your story about an undiscovered strain of bacteria turning people into zombies?).
If your society is adept at genetic engineering, it could turn shallow ocean environments into breadbaskets by splicing rice genes for grain production into seagrasses, or seagrass genes for salt tolerance into rice. That’s a total game-changer; perhaps your story could revolve around societal disruption as waves of impoverished surface people arrive to try their hand at sea-rice farming. An alternative story line: once the dome cities have their own grain supplies, they decide they don’t need the surface world any more. Perhaps they even turn their genetic engineering skills on themselves, producing offspring who are mermaids/mermen.
Can you think of any additional difficulties in an underwater dome, or additional solutions to the difficulties I’ve listed here? Leave a comment below.