The loss of color observed in coral when the ph of their environment is lowered is due to loss of bacteria attack by bacteria loss of algae attack by algal species

loss of algae

Explanation:

The colonies of the coral polyp forms the coral reef which develops a mutualistic association with the photosynthetic algae called as Zooxanthellae in sea water. This mutalistic relationship provides algae with shelter, the coral reefs receives a color as being covered by the algal colonies, and supplies both of the organisms with nutrition. But certain conditions like high temperature and low pH affects this mutualistic relationship. The lower pH suggests that the water is acidic. These conditions causes algal colony to swell and removes the algae from the surface of the coral reef. The removal of the algal colony from the coral reef is called as coral bleaching as the white calcium carbonate walls of the reef gets exposed.

correct answer is a. and d.