Mesopelagic refers to the oceanic zone that lies between 200 and 1000 meters below the surface of the ocean. This zone is also sometimes referred to as the twilight or middle pelagic zone. This is an important habitat for a variety of marine life, including many species of fish, squid, and crustaceans. The mesopelagic zone is characterized by low light levels and high pressure, making it difficult for most organisms to survive in this environment.