Ivan Kobrinsky wrote:
Cereus-validus:


Yes. Only as deep as the light reaches.


In the context it is important to consider that sunlight
only can penetrate about 100 to 200 meters deeply into the
sea. In deeper levels (like in more about 2 400 meters sea
depth) photosynthesis is also manufactured. There are living
bacteria, that - like plants - the light for power production
use completely without daylight.

SNIP
It is my understanding that these bacteria are using chemosynthesis and
not photosynthesis.