Moorea: The Coral Reef Community 

From the researcher's perspective...

Perhaps the most visible fishes on coral reef are damselfishes. Small colorful and bold, they will sometimes even come out and nip a snorkeler that gets too close to their patch of algae, or clutch of eggs. The 'Blue-eyed Damselfish' (shown, Plectroglyphidodon johnstonianus) displays these characteristics, and can be seen zipping in and out of the branches of large colonies of Pocillopora corals. Generally yellow with a bright blue eye and a dark bar across the base of the tail, these small fish are active defenders of their home coral from other fish. Coralivores such as butterfly fishes and filefish are quickly chased off, as are wrasses that might dart in to grab a shrimp or crab. This makes the relationship between the damselfish and the coral a mutualism—the coral gains a protector and the fish gains a place to live.

As with many partnerships, everything may look happy on the surface, but underneath a conflict lurks. The fish defends the coral, but is also feeding on it, nipping off polyps and tentacles as its own living larder, while the fish waste fertilizes the algae within the coral, aiding the growth of the coral. One thing is certain: the amount of 'benefit' that each partner receives is under continual negotiation, and both the fish and the coral are looking out for their own best interests. Just a slight change in the circumstances and a mutualism becomes a parasitism, where one partner benefits at the expense of the other. How and why these symbiotic relationships work is the subject of much of the research that is being conducted on coral reefs today.

Chris Meyer, Seabird McKeon, Hannah Stewart, and Matthew Johnson