Australian Coral Reef Ecology
Ross Cunning, class of 2007 | Majors: Environmental Sciences (B.S.); Biology (B.S.) | Extracurricular: scuba diving, skiing, backpacking, anything outdoors | Home: Indianapolis, IN
In Ross’s Words:
Cleaning symbiosis on coral reefs is one of the most interesting and beautiful natural phenomena I have ever observed. This interspecific interaction is highly specialized, involving the Indo-Pacific cleaner wrasse (Labroides dimidiatus) and many different species of client fish. The client will often approach a "cleaning station" on the reef, which is usually marked by some conspicuous coral formation, and assume a special pose: it will hang in the water, open its mouth, and flare out its fins, allowing the cleaner wrasse to inspect its entire body and remove any tasty parasites it might find.
These interactions are very complex and the way they occur seems to vary spatially with many variables, including density of cleaners and client fish, local abundance of certain fish species and certain trophic guilds, size of available client fish, physical structure of the reef, and many other ecological variables.
At the fringing reefs of Magnetic Island, Queensland, Australia, I studied basic cleaning ecology to lay out a baseline for how these interactions were taking place in an inshore environment, which had not been previously studied. I observed while snorkeling over 500 cleaning interactions, recording data that included client species and size and the duration of cleaning. I also performed visual belt transects across the reef surveying all fish species to quantify relative local abundance. I put all this data together to find out what factors were most important in determining which fish were being cleaned the most.
The results showed that local abundance of a client species was the best predictor of how much it was cleaned, followed by fish size. Size was expected to be a good predictor, as research has shown that larger fish have more parasites on their bodies that the cleaners eat. However, local abundance had not been found to be a significant predictor at the outer reef sites where most of the work on cleaning ecology has been done. This suggests that at this inshore location, where fish species richness and diversity are much lower than at the outer reef, cleaners can not afford to be as selective in choosing clients. Since there are less options available, they must take what they can get. The reason this inshore environment has less fish is because it is only 8 kilometers from the mainland and thus receives a large amount of runoff causing eutrophication, or increased algal growth. Due to deforestation and other human activities, this runoff contains many more nutrients than it naturally would, increasing algal growth even more. This algae is able to outcompete corals, which are the foundation of the coral reef ecosystem. Thus, the effects are transmitted throughout the ecosystem, altering its structure and function. This study was able to help us understand a little better how we are altering the ecology of the world around us.
This research was a life-changing experience for me. Not only did I feel like I made a valuable contribution to science, but I was able to live on a tropical island and spend my days snorkeling over beautiful coral reefs. It was a whole new world I had never seen before, and I was overwhelmed by the richness and complexity of the life that occurs there. I will now pursue coral reef ecology as the focus of my graduate studies.
