Symbiotic Relationships

First things first, there are three types of symbiotic relationships: mutualism, commensalism, and parasitism, all of which are found within a coral reef. Mutualism is when two organisms both benefit from their relationship, such as zooxanthellae and coral polyps. Zooxanthellae provide the coral polyps with an energy source through photosynthesis to build coral structures, while the coral provides the zooxanthellae with shelter. 

Commensalism, which is when one species benefits from their relationship while the other is unaffected, can be found in the relationship between a pearl fish and a sea cucumber. The pearl fish uses the sea cucumber's anus as a hiding spot from predators; the sea cucumber is oddly unaffected by this action.

Lastly, parasitism is when one species uses another as shelter or for a food source and is harmed in the process, such as when a trematode hosts on a snail and uses it for reproduction. So, instead of the snail producing more snails, it produces more trematodes. This means that the snail’s reproduction is harmed for life.