science

Here are some links to get you started on your research:

Ecosystems, Biomes, and Habitats

http://www.fi.edu/tfi/units/life/habitat/habitat.html

How Barrier Islands Work

http://science.howstuffworks.com/environmental/conservation/issues/barrier-island.htm

How Rainforests Work

http://science.howstuffworks.com/environmental/conservation/issues/rainforest.htm

How Icebergs Work

http://science.howstuffworks.com/environmental/earth/geophysics/iceberg.htm

How Ocean Currents Work

http://science.howstuffworks.com/environmental/earth/oceanography/ocean-current.htm

How Cave Biology Works

http://science.howstuffworks.com/environmental/life/biology-fields/cave-biology.htm

Your question is too vague for us to be able to give you anything other than general answers.

If I took a mountain cat and put it in an deep aquatic ecosystem, like the bottom of an ocean, what would happen?

You're question is way too general but as a start I would recommend looking up the term 'environmental niche'.