Much is unknown about the diseases that affect coral reef ecosystems. Prof. C. Drew Harvell, ecology and evolutionary biology, is part of a newly created international Coral Reef Targeted Research and Capacity Building Project that seeks to better understand the mechanisms of disease spread among coral reefs. The project also seeks to determine ways to prevent the further destruction of these reefs, and is the largest international assessment of ocean disease ever.
The international project is funded by the Global Environment Fund and the World Bank, with $28.8 million in funding already in place for the first five years of a fifteen year period of research and assessment. Harvell is currently the chair of one of six working groups within the project, which altogether is comprised of over 70 scientists from around the world.
Harvell’s group focuses on understanding the cause of death and the spread of diseases among coral reefs in four sites of interest located around the world. These sites include Mexico, where the Mesoamerican Barrier Reef system is located; the Philippines, which is close to the center of coral reef biodiversity; and the coast off East Africa, where warm climate changes have had an adverse affect on the reefs located there.
According to Harvell, current research shows climate changes have a negative impact on coral reefs. In fact, the idea for Harvell’s group stemmed from the aftermath of the ’97-’98 El Nino, which resulted in ninety percent coral reef mortality in the Indian Ocean. The reason behind this, Harvell explained, is that the symbiotic algae that live in coral reef tissue and provide the reef with carbon have sensitive thermal tolerance. They are also responsible for the reef’s color.
When temperatures become too warm, the algae leave their host, and “bleaching” of the reef occurs.
Human practices can also lead to coral reef death, including global warming induced by excess carbon dioxide build-up in the atmosphere due to human activity. Poor land-use practices can also account for reef deaths, especially when silt or septic system run-off enters the reef ecosystem. Run-off can lead to the addition of excess nutrients that can have a detrimental impact on coral reefs.
In addition, Harvell mentioned that certain bacteria, protozoa and parasites are also responsible for reef decay and death.
Despite these observations, Harvell noted that there is much that is unknown about disease among coral reefs. In a recently published paper co-Authored by Harvell in “Frontiers in Ecology and the Environment”, studies show that while reports of disease in marine organisms are on the rise, microbiological, theoretical and molecular tools for managing disease are underdeveloped. Recent research has shown that the rate of transmission of disease is higher under water than on land, although “we don’t know much about [specific diseases] and don’t know where they come from,” Harvell said. The current hypothesis, according to Harvell, is that a majority of these diseases are due to land based micro-organisms that somehow manage to enter the reef ecosystem, perhaps through agricultural run-off.
The control of pathogens is especially difficult, Harvell explained, because land-based practices of quarantining, culling or vaccinating are not effective for under water organisms.
Better understanding of the diseases affecting coral reefs is important because of the benefits they provide for tropical and developing nations. Among these are the roles coral reefs play in the tourism economy of many nations.
“The World Bank recognizes this,” Harvell said, noting that “people [initially] didn’t realize the importance of this issue.”
Jessica Ward, a graduate student in Harvell’s lab and a leader of the working group’s site in Mexico, hopes that the group can address some pressing issues. “It’s great to work in a group made up of people at the top of their fields,” she said, noting that “people with diverse backgrounds” can provide answers to some of the questions being addressed “by coming at it from different angles.”
Ward hopes that the Group can “get a handle on how much disease is out there [among the reefs] as well as identify what the pathogens are.”
Ward noted that it is difficult to persuade people to change their agricultural practices if “we don’t know what the pathogens are … people don’t listen.” Harvell hopes that within the next few years, the research that the Working Group conducts will result in diagnostic tools and molecular probes to better understand the diseases plaguing the coral reef ecosystem. The long term goals, Harvell emphasized, are to “promote sustainability of coral reefs through capacity building and targeted research.”
Archived article by Samira Chandwani
Sun Staff Writer