Question

deep in the ocean sunlight can hardly reach yet there are plants such as Brown and red algae found here how do you think they are able to synthesise their food

Answer 1

Every organism evolves in order to survive under changing environment. I may NOT BE 100% SURE, but I think they feast on the dead organisms that are settled down at the sea bed, converting them into simpler substances by breaking them down.

Hope This Helps.....