Because the seahorses are in danger, people are trying to conserve coral reefs. This means that other organisms in the coral reef are being protected as well as the reef itself. So, seahorse protection on the reef means protection for the entire reef.
There is a symbiotic relationship between zooxanthellae and coral. The zooxanthellae is a type of algae which accelerates coral skeleton growth, gives coral its beautiful colors, removes coral waste and provides nutrients for the coral. In return the coral gives it a home.