Huh, I wrote this message 12 hours ago, guess it didn't send:
Shallow ocean is good, as are all the icons. I'm not quite sure I like the slab of meat for protein. It's not a bad icon, I just don't think its very intuitive. We're in the cell stage and meat is more of a multicellular formation. I liked the polypeptide chain you had before more. For the hydrothermal vent I'd suggest making it less "puzzle-y". If the bottom right part was one whole piece, I think it would look a lot better.
Also, should we start voting on icons yet? The second one for ammonia and third one for oxygen are just perfect in my opinion.
Here are the colors:
Glucose: 150, 170, 180
Oxygen: 60, 160, 180
CO2: 20, 50, 100
Ammonia: 255, 220, 50
Amino acids: 255, 150, 200