April 5, 2010

In Changing Climate, Math Model Analyzes Coral Surface Bacteria

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Cornell researchers have created mathematical models based on interactions between species in coral reef communities that may provide insight as to why certain bacteria may help cause the reef to become bleached and ultimately destroyed.

The models and their implications for the overall health of coral reefs, was published in the latest issue of Public Library of Science Biology on Mar. 30. In addition to using “educated guesses” of how the models may behave in certain situations, the researchers utilized a study conducted by Kim Richie, a marine microbiologist at Mote Marine Lab and a co-author of the paper.

Prof. Stephen P. Ellner, ecology and evolutionary biology — senior author of the publication — said that the new models would help acquire information about the health of coral reefs by helping researchers understand the devastating repercussions of periods of extended warming on the reefs.

“The main thing we hope to accomplish is focusing people’s attention on the microbial ecosystem surrounding the coral as essential for understanding how corals stay healthy versus getting sick, and for efforts to reduce the impacts of coral disease,” Ellner stated in an e-mail.

The models, divided into two subparts, attempt to elucidate the relationship between beneficial and pathogenic microbes that exist on the mucus layer of coral reefs.

The first model depicts an environment where the beneficial and pathogenic bacteria compete for space, coauthor of the study Prof. Laura E. Jones, ecology and evolutionary biology, stated in an e-mail. Once there is an excessive increase in the water temperature, the beneficial bacteria become “stressed” and allow the pathogenic bacteria to take over the area once occupied by its competitor.

“Once the pathogens become established, conditions must become much cooler than ‘normal’ before the beneficial residents can return,” Jones stated.

The second model –– which was adjusted to allot the bacteria enough space to coexist together –– led to similar results. Pathogenic bacteria again took over the space occupied by stressed beneficial bacteria.

Ultimately, even if the waters return to cooler temperatures, the beneficial bacteria cannot overcome the pathogenic bacteria’s presence in the coral reef and the reef will become bleached and slowly destroyed.

The study was partially funded by a grant provided by the National Science Foundation and the National Institutes of Health joint program on Ecology and Evolution of Infectious Diseases.

According to Ellner, although events such as overfishing, water pollution, ocean acidification and climate change contribute to the decline of coral reefs, it is ultimately the progression of infectuous disease that most damages coral reefs.

Additional research currently being conducted by Prof. Drew Harvell, ecology and evolutionary biology, and Nancy Douglas will attempt to isolate the chemicals in corals that may be the cause these anti-fungal qualities.

Original Author: Hermela Nadew