What do bacteria near hydrothermal vents utilize for chemosynthesis?

Bacteria near hydrothermal vents carry out chemosynthesis primarily by utilizing hydrogen sulfide as a primary energy source. In the extreme environments surrounding these vents, sunlight is not available, making photosynthesis impossible. Instead, these bacteria convert hydrogen sulfide, which is abundant in the mineral-rich water expelled from the vents, into energy through a process called chemosynthesis.

During this process, hydrogen sulfide is oxidized, allowing the bacteria to create organic compounds from carbon dioxide, effectively sustaining themselves in an environment that otherwise lacks the sunlight needed for traditional photosynthetic organisms. This process not only supports the bacterial community but also forms the basis of a unique ecosystem, allowing various other organisms such as tube worms, clams, and other invertebrates to thrive in these extreme conditions.

While oxygen and nitrogen are important elements in marine ecosystems, they do not serve as direct energy sources for chemosynthesis in the context of hydrothermal vents. Thus, hydrogen sulfide's role is crucial, making it the correct choice for this question.