The primary producers of the deep hydrothermal vent ecosystem are: Green algae, Blue-green algae, Coral reefs, Chemosynthetic bacteria

Deep hydrothermal vents are anaerobic sites and lack oxygen. Blue-green algae, coral reefs and green algae are aerobic photoautotrophs and can not survive without Sunlight and oxygen. Chemotrophs are the organisms that use either organic or inorganic compounds as the source of energy (not Sunlight) and hence can survive under deep hydrothermal vents that are devoid of Sunlight. Since, chemotrophs use the organic or inorganic source, not water, as electron donor, oxygen is not produced and the surroundings are anaerobic. Therefore, the correct answer is option D.