Final answer:
Alvin discovered hydrothermal vents in the abyssal zone, which support life through chemosynthetic bacteria using energy from chemicals rather than sunlight.
Step-by-step explanation:
The research submersible Alvin is renowned for its significant contributions to deep-sea exploration. One of Alvin's notable discoveries was the identification of hydrothermal vents and the unique ecosystems surrounding them in the abyssal zone of the ocean. This zone, characterized by very high pressure, low nutrient content, and the absence of sunlight, is home to diverse life forms, including a variety of invertebrates and fishes. Hydrothermal vents support unique communities of organisms that rely on chemosynthetic bacteria which use chemicals like hydrogen sulfide to produce energy, forming the base of a food chain independent of sunlight.