The plants, algae and chemosynthetic autotrophic bacteria occupy the first trophic level of the food web that surrounds oceanic hydrothermal vents.
Step-by-step explanation:
A hydrothermal vent is a place where the magma meets the ocean water. It is a highly chemical rich area which has abundant supply of iron oxide, calcium and the magnesium deposits.
When the hot smoke that comes out mixed with the freezing water and gets cooled down it forms rocks that are rich is chemical deposits. They also as any other ecosystem have organisms that can photosynthesize as their first trophic level.