Could modern sharks adapt to live in deep water?
After circumstances make the shallow water in the oceans uninhabitable, great white sharks retreat to the deeper parts of the ocean, about 600 feet down (182 meters) to survive. The sharks can not go more than 450 feet up, as the water up there is uninhabitable. My question is, could sharks adapt to survive in this new environment?
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1 answer
Yes.
There are sharks that live quite deep in the ocean; the goblin shark and frilled shark, for instance, have been known to live over 1,000 meters below sea level (Wikipedia claims great whites have been found at this depth, too). This is off the edge of the continental shelf.
Your depths (~180 meters) puts you only just off the shelf - and still certainly in the photic zone, where there's a good amount of sunlight. This means that your sharks will still be in an ecosystem similar to their old one. They'll still have some of their old food, and they'll be living in temperatures that aren't terribly low.
Deeper into the ocean, you have three issues:
- Food. Sharks are used to a certain lifestyle, with a certain amount and type of prey available. Different organisms frequent the lower areas of the ocean, and so sharks would see less of their favorite fish. Adapting to a new food supply wouldn't be too hard, but having less food overall would.
- Pressure. At depths on the order of a kilometer, pressure becomes an issue, although compounds like TMAO can mitigate it. Deep-sea creatures do have adaptations like TMAO to help them survive. At less than 200 meters, pressure might be a bit of an issue, but not a large one.
- Temperature. Below one kilometer, in the bathyal zone, mean temperatures hover just above freezing - not good for fish, although certainly not inhospitable.
That said . . . I don't see any of these being problems at the depths you give, for the simple reason that your sharks won't be living in deep water at all.
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