Final answer:
Anoxia-tolerant marine invertebrates survive by adopting anaerobic metabolism, evolving specialized enzymes for anoxic conditions, and functioning as facultative anaerobes to manage ATP formation and oxidative stress.
Step-by-step explanation:
The marine invertebrates that are anoxia-tolerant exhibit several major metabolic adaptations to survive long periods without oxygen. Firstly, many adopt anaerobic metabolism, which allows them to generate ATP without the need for oxygen, often utilizing pathways like fermentation. Secondly, these organisms might employ the use of specialized enzymes, which have evolved over time to help them adapt to anoxic conditions. Lastly, some organisms function as facultative anaerobes, using different ATP formation pathways depending on the availability of oxygen while simultaneously managing oxidative stress.