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Current Projects

Genome-Wide Analysis of Coral-Zooxanthellae Symbiosis

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Symbiotic interactions are common and important in a wide variety of plant and animal communities. Among the more complex symbioses is the mutualism between benthic marine invertebrates, especially cnidarians, and photosynthetic dinoflagellate algae (zooxanthellae or Symbiodinium). This type of symbiosis has had a key role in the formation of an important marine ecosystem, the coral reef. In this mutualism, the algae are intracellular symbionts of their cnidarian hosts. The symbiosis between scleractinian corals and their zooxanthellae is highly susceptible to changes in environmental factors such as elevated seawater temperature and/or elevated light levels. Global warming has impacted coral reefs worldwide by causing the disruption of these symbioses (coral bleaching), causing many corals to subsequently die. It is now urgent to gain a better understanding of the molecular and cellular interactions that are critical to the functional integrity of these symbioses.
We are studying coral symbiosis by using microarray expression profiling to identify genes and cellular pathways involved in host-zooxanthellae interactions in theMontastraea faveolata and Acropora palmata mutualistic systems from Caribbean tropical reef areas. This research is an attempt to look at this important mutualistic relationship using a genome wide analysis of gene expression. This project is a large collaborative effort with Alina Szmant (UNC Wilmington) and Mary Alice Coffroth (SUNY Buffalo).

 

Calcification mechanisms in Corals

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Coral-algal symbioses result in high levels of primary productivity as well as rapid deposition of CaCO3 that builds up to form the rock framework of the reef. In order to maintain a positive carbonate budget for the reef structure, it is necessary to sustain elevated coral calcification rates during prolonged periods of time. Climate change could have negative effects on coral calcification. On one hand, elevated sea surface temperatures result in massive coral bleaching and mortality episodes and direct reductions in coral calcification. On the other hand, increases in pCO2 levels will result in decreases in the aragonite saturation state and probably significant reductions in coral calcification as well. Although algal photosynthesis has been implicated in the elevated rates of CaCO3 deposition rates characteristics of reef-building corals, the actual molecular mechanisms responsible for calcification remain largely unknown. In order to evaluate the possible effects of increasing sea surface temperatures and pCO2 levels associated with climate change on coral calcification, it is necessary to understand the molecular mechanisms of coral calcification. We have chosen to focus our efforts on Montastraea faveolata, a brain coral that is one of the major reef builders in the Caribbean.
This work is being carried out at the Instituto de Ciencias del Mar y Limnología (ICML) of Universidad Nacional Autónoma de México (UNAM) in Puerto Morelos Mexico in collaboration with Dr. Roberto Iglesias-Prieto.

 

The Microbial Community and Coral-Pathogen Interactions

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It is now known that a coral colony is a complex ecosystem that encompasses not only the coral and the algal symbionts but also a significant community of other microbial symbionts (i.e. bacterial and protistan). This community is not well characterized and little is known about how it interacts with the coral hosts (i.e. whether they can be the causative agents of disease under stress conditions). Coral disease has been a growing concern worldwide because of increasingly frequent observations of affected colonies in the wild. This prevalence in the past twenty years has been considered a manifestation of a decline in the integrity of tropical benthic marine ecosystems. Both Montastraea faveolata and Acropora palmata are among the most affected species in the Caribbean and therefore require special attention. The ultimate goal of this project is to profile and identify the members of the coral reef microbial community (using 16S microarrays and DNA barcoding) to eventually be able to follow the changes in composition during stress, and identify genes that are involved in the response and recovery processes (using gene expression microarrays).
The microbial sampling is taking place in multiple reef locations (i.e. Hawaii, Florida, Puerto Rico and Panama). This project is a collaborative effort with Gary Andersen at Lawrence Berkeley National Laboratory.