Literally every answer was wrong so the answer on apex (as all the other answers werent even an option for me) is decaying plant matter
minerals and salts (apex)
Decaying Plant Matter: APEX
A.
c. Decomposing animal matter
buffer
Antitoxin
Decaying Plant Matter: APEX
A.
c. Decomposing animal matter
buffer
There are several, including decomposing animal matter, and various minerals and salts.
Buffer
You didn't say which meaning you want to use for this word. A buffer can be a barrier which lessens or absorbs a shock. The airbag acts as a buffer in case of an accident. She was the buffer between them, and kept the argument from getting out of hand. Buffer can also mean a chemical substance which minimizes the acidity of a substance. I need a bottle of buffered aspirin; the buffer keeps it from upsetting your stomach. Buffer can also be a verb meaning to do either of the above. The neutral zone between the two countries buffered their rivalry. That substance buffers the chemicals.
water acts as a buffer, so it moderates the temperature
Water
bicarbonate buffer is instant, followed by respiratory, renal, and phosphate.
water
There are many seashores that have a moderate temperature. This is because the water acts as a buffer and stabilizes temperature.