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Climate Change Relevant Stressors on Coral Reef Fish Physiology

ARC Centre of Excellence for Coral Reef Studies, James Cook University (Australia)
Involved Scientist: Jodie L. Rummer, Ph.D.

In our lab, we use oxygen consumption rates of fishes as a proxy for aerobic metabolism. When a fish is at rest, it is consuming oxygen at a certain rate, which is approximately the minimum energy required for basic maintenance of the animal. Conversely, when a fish is swimming at a maximum sustainable speed or recovering from being chased, it may be consuming oxygen at a maximal rate. The Firesting contactless spot O2 monitoring system is great for these measurements for many reasons. Firstly, I can adhere the spot to the inside of small chambers for tiny reef fish species like damselfishes, and it doesn’t displace volume or impede the fish’s movement like a traditional oxygen probe. But, I can also still use the same system in large chambers for highly prized fisheries species like coral trout and rock cod or even small reef sharks! Having this flexibility is important to me in setting up a new lab, as I don’t need to have multiple systems for the different types of animals I study. Secondly, for our applications, it is also crucial to be able to monitor, in real time, as a fish approaches and then recovers from swimming maximally or being chased and the time scale over which recovery back to a resting state occurs. The software allows us to monitor this while we are running the experiments.

Individually, resting and maximum measurements are interesting and important and can tell us a lot about how a fish is responding to a stressor. But we do know it is important to investigate both, as stressors may impact one more than the other, depending on the species we study. If fish performance decreases under environmental conditions associated with climate change, such as elevated temperature (global warming) or elevated CO2 (ocean acidification), it essentially becomes more expensive for a fish to be alive. The fish may not be able to chase prey or evade a predator as effectively or allocate enough energy for important life history process like growth and reproduction, all of which are crucial for the future structure of marine communities.