Final answer:
The compound that serves as a fermentable fuel for anoxia-tolerant marine molluscs during short term environmental anoxia stress is methane (CH4) produced by archaea called methanogens
Step-by-step explanation:
The compound that is important as a fermentable fuel for anoxia-tolerant marine molluscs during short term environmental anoxia stress is methane (CH4). Methane is produced by prokaryotes, mostly archaea, called methanogens in the absence of oxygen. These methane-producing bacteria accumulate methane in anaerobic environments and serve as a source of energy for marine molluscs and other organisms.