How do deep underwater plants survive without photosynthesis?

Question

How do deep underwater plants survive without photosynthesis?

Answer 1

If light does not penetrate, then plants will not exist there.  (The news story the other answerer provided mentions nothing about plants living without sunlight.)  In fact, in the ocean, there are very few plants anyway.  Only seagrasses are plants and they live in very shallow areas.  Algae (which are protists, not plants) live deeper, but still require light for photosynthesis.  Red algae (Rhodophyta) are some of the deepest species because they have a pigment called phycoerythrin that absorbs blue light, which is the wavelength that can penetrate the deepest.

Answer 2

There are indeed deep underwater plants where the sunlight does not reach, but they get their energy from underwater volcanic vents.

Answer 3

All underwater plants use photosynthesis from sunlight that makes its way through the water. In areas where the water is too deep for sunlight, there are no plants.