Final answer:
Chemoautotrophic bacteria and other single-celled organisms utilize chemosynthesis to produce sugars and serve as primary producers in deep-sea ecosystems near hydrothermal vents.
Step-by-step explanation:
Organisms Producing Sugars in Deep Ocean Food Chains
In the deep ocean, particularly near hydrothermal vents, organisms known as chemoautotrophs are the primary producers of sugars, which serve as food and fuel for deep-sea ecosystems. These single-celled organisms synthesize organic molecules using the energy stored in the chemicals spewed out by the vents, in a process distinct from photosynthesis that is known as chemosynthesis. Due to the lack of sunlight in these extreme environments, chemoautotrophy is vital for supporting the diverse and thriving communities surrounding the hydrothermal vents, which include organisms like tube worms, shrimp, and vent mussels. Hydrothermal vents also play a pivotal role in deep-sea ecology and may have been critical in the origins of life on Earth.