Whitney Bernstein, Marine Chemistry & Geochemistry


Sensitivity of Coral Reef Calcification to Environmental Conditions: Florida

Coral reefs are tremendously valuable ecosystems.  Personally, it is their natural beauty and the surprising creatures, from the crocodile fish to the cleaner wrasse to the Christmas tree worm, that I appreciate most. However, for many other people, coral reefs provide their primary food and medicinal resources, or reefs serve as the foundation of their tourism-based economy.  For the global oceans, coral reefs play an important role as the most diverse ecosystems, of which only about 10% of the species are currently known.

For these reasons, I have become interested in how sensitive the complex ecosystems are to the environment. It is clear that destructive fishing practices, over-fishing, coastal development and pollution can destroy coral reefs.  Some of these stresses can be addressed with careful management and conservation projects. However, there is also evidence that climate change and ocean acidification will cause stress to these ecosystems. That is, rising temperatures due to increased CO2 in the atmosphere can result in more frequent thermal stress episodes and lead to bleaching and coral death. The increased atmospheric CO2 also makes the ocean more acidic, thus making it harder for corals to grow their carbonate skeletons. These global impacts can be more pervasive and addressing these impacts may be more complicated than addressing point source stresses such as fishing and pollution. Therefore, it is important to really understand just how the coral reefs respond to the temperature and chemistry of the reef waters.

For my thesis, I am exploring how temperature and carbonate chemistry of reef waters impact the growth rates (calcification rates) of corals and coral reef communities in the Red Sea, Puerto Rico, and the Florida Keys.  With my adviser, Konrad Hughen, I am using x-ray imagery to examine the annual growth bands (like tree rings) of the skeletons of many coral colonies from the Red Sea. I am comparing these long records of growth to proxy temperature records that are constructed by taking advantage of the fact that the ratio of strontium to calcium in the carbonate skeleton depends on temperature. This study will show how the temperature sensitivity of Red Sea corals compares to the temperature sensitivity of corals from other regions of the globe.

I am also examining net community calcification rates – that is how much carbonate is accumulated by the entire community: corals, sand, calcifying algae, mollusks, etc.  Because calcification causes a direct impact on the carbonate chemistry of the water, I can measure the rate of calcification by measuring how the chemistry of the water changes as the water moves across the reef. WHOI scientists, Dan McCorkle and Steve Lentz, have helped me do this work in the Red Sea.  I am also collaborating with Chris Langdon at the University of Miami to measure community calcification rates in Puerto Rico and the Florida Keys. Ultimately, these studies will set baseline rates against which to compare future measurements in order to quantify the impacts of environmental changes. Additionally, these studies will add to our knowledge of how reef composition and reef environmental character result in different community calcification rates around the globe.

The COI Student Research Award was instrumental in facilitating my field work in Puerto Rico in August 2011 and in Florida in February 2012. The OLI Student Research Fellowship has enabled me to continue pursuing my research interests beyond the primary focus of my adviser’s research and to take full advantage of collaborative research opportunities that have profoundly shaped the outcome of my thesis.