Threats to Reefs

Although natural disturbances are major drivers of coral reef environments and contribute considerably to their dynamic nature, the patterns of natural disturbance observed in the last two decades do not match the rate of degradation of these ecosystems.  Multiple lines of evidence indicate that anthropogenic forcings have had a much stronger impact on the recent rate of coral reef change. The main anthropogenic factors identified as causes of reef degradation are overfishing,  pollution, and impacts of the multitude of environmental changes produced by climate change.

In MSEL we are incorporating the effects of climate change (particularly increases in sea surface temperature and in the frequency an intensity of storms) in spatially realistic models of the coral-macroalgae dynamic in reefs. Much of the information necessary for the parametrisation of such models lies in the relationship between coral vital rates (growth, mortality and recruitment) and temperature for different coral types. Determining if these relationships are linear or non linear and how much difference is found between coral types will help improve the power and accuracy of the models for predicting the likelihood of reef recovery after disturbances under different climate change scenarios.

We are also interested in the symbiotic relationship between corals and dinoflagellates (zooxanthellae), particularly how different holosymbionts react to thermal disturbances. Current lab research explores how the temperature regime in which the holobiont has evolved can affect its response to acute or chronic thermal disturbances.

It is well established that coral reef fish populations are declining globally as a result of overfishing, but the indirect effects of the removal of predators and herbivores from reef communities are still poorly understood, and the development of management strategies in the absence of such knowledge is fraught with guesswork.  Benthic algae are often competitively superior to reef building corals, and the importance of feeding by herbivorous fishes in maintaining reef functionality is now well established in the wider Caribbean although at this point in time it remains less clear in the Indo Pacific.  At MSEL we are teasing apart the roles of key species in structuring communities and controlling algal growth in both the Caribbean and the Indo Pacific, as well as examining how various coral reef management strategies may translate into ecological effects on fish populations and reef resilience in an uncertain future.