a. algae
b. corals
c.mangover
d. small fish
Amongst the given choices above the correct answer is letter a. algae.
In the coral reef ecosystem, the algae, specifically the blue green algae are the primary producers, they are the ones eaten by fishes and other aquatic organisms. But actually the corals themselves are also producers and a consumer as well. Other primary producers are phytoplankton, brown algae and seagrass.
#BrainliestBunch