Question

Coral bleaching, which causes high coral mortality, has been occurring widely in coral reefs. Coral bleaching actually refers to the death of symbiotic dinoflagellates living within the corals. Why does coral bleaching cause the corals to die?
a. Dinoflagellates protect the corals from pathogenic bacteria.

b. Dinoflagellates provide nutrients from the products of photosynthesis which are essential for zooxanthellae survival.

c. Dinoflagellates secrete the calcium carbonate that forms the "exoskeleton" of coral animals.

d. Dinoflagellates attract zooplankton and other prey that the corals eat.

e. Dinoflagellates protect the corals from UV radiation.

Answer 1

Answer:

b. Dinoflagellates provide nutrients from the products of photosynthesis which are essential for zooxanthellae survival.

Explanation:

The endosymbiotic dinoflagellates are found in the bodies of corals. These endosymbiotic dinoflagellates are called zooxanthellae and are immobile. Being autotrophic, zooxanthellae carry out photosynthesis to produce the organic food required for corals. Death of endosymbiotic dinoflagellates deprives the coral of organic nutrients leading to their death. This is why the endosymbiotic dinoflagellates are required for survival and productivity of coral reefs.