Deep Sea Phenomenon

Read the section titled 'Gigantism'

(Read the above link first)

I wonder if the oceans in Felarya work the same way? If so, one could only imagine how big a creature would get when the normal size is at least 50 ft... *Thinks about what would happen if a Leviathian Mermaid were to live in a zone like that *

Setting aside the magical, unexplainable aspects of Felarya, if there were bodies of water that extended that far downward (provided that gravity is the same or is almost similar to Earth's), not only would some source of light and/or heat need to exist (hydrothermal vents), but also a source of food (chemosynthetic bacteria).

So let's say that all that is in play and that there are hydrothermal vent communities thriving in the abyssopelagic zones of Felaryan seas; could something (a mermaid) venture downward towards this high pressure, dark, and very harsh environment and become larger? Unfortunately, I'd say no — given that Earth-like characteristics are in play. If anything, they'd get smaller — a lot smaller. If a creature was so incredibly adaptive that they could either:

a) Quickly travel to the abyssal zone of a body of water and withstand ridiculous increases in pressure and rapid decrease in temperature, or—
b) Gradually travel downward to negate sudden environmental changes likely to cause death, and slowly adapt to the changes regardless of how extreme they are,

Then sure, a creature could travel to that kind of area from the surface of the ocean. But like I said earlier, even if this were possible — and I wouldn't even assume that it isn't in Felarya — then the increase in pressure would actually add tremendous amounts of weight on each molecule of the said creature, essentially forcing it to shrink.

As for going the other way (from abyssopelagic/hadalpelagic to epipelagic), then the creature would have to be able to sustain similar but still extreme alterations in environment as mentioned above (rapid decrease in temperature from leaving heat source, decrease in pressure). If they could avoid the painful and life-threatening effects of caisson disease naturally, then maybe they'd actually grow. Although, physics play a role in the shrinking/growing aspects of each method, so I'd not count on much of a change in appearance.

*high-fives marine biology teacher*

Sephimink|Kyle wrote:

A bunch of sciencey stuff

...I hate reality!

Sephimink|Kyle wrote:

If a creature was so incredibly adaptive that they could either:

a) Quickly travel to the abyssal zone of a body of water and withstand ridiculous increases in pressure and rapid decrease in temperature, or

...

Then sure, a creature could travel to that kind of area from the surface of the ocean. But like I said earlier, even if this were possible — and I wouldn't even assume that it isn't in Felarya — then the increase in pressure would actually add tremendous amounts of weight on each molecule of the said creature, essentially forcing it to shrink.

...

If they could avoid the painful and life-threatening effects of caisson disease naturally, then maybe they'd actually grow.

Going down from the surface to a great depth isn't particularly hard or dangerous for some creatures, like the sperm whale. Sperm whales can dive to depths that allow them to access most of the abyssal plains (the ocean floor), and since they are mostly water, just like us, going to great depths doesn't cause a dangerous pressure gradiant to build up between their bodies and the outside water (although their ribcage is designed to collapse as their air filled lungs do).

They do suffer somewhat from decompression sickness (cassion disease) but not nearly as much as they would if they breathed in oxygen from the surrounding water while at great depth.

I think that gigantism would be more common in creatures that dwelled in the depths permanely, especially in crabs and other scavengers. All the dead plankton, dead fish, dead everything eventually sinks to the bottom, so a viable food source doesn't seem to be a problem.