How do sulfur-converting microbes enable hydrothermal vent ecosystems to function in the absence of sunlight?

At hydrothermal vents, sunlight is unavailable, so the food web relies on chemical energy rather than photosynthesis. Sulfur-converting microbes use energy released by processing sulfur compounds to make organic food, which supports other organisms in the ecosystem. This makes choice A correct; they do not capture heat itself and turn it into sugars.

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