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Coral Reef Disease Hits Kāne‘ohe Bay, Hawai‘i
Scientists have discovered an outbreak of coral disease called Montipora white syndrome in Kāne‘ohe Bay, O‘ahu. The affected corals are of the species Montipora capitata, also known as rice coral.
Rice corals provide valuable habitat, shelter, and foraging grounds for a variety of tropical marine fish and invertebrates and provide the fundamental structure of coral reefs. Rice corals are especially important to Hawai‘i’s marine ecosystems because they are one of the more abundant coral reef species in the region. (See related article “Tracking Coral Larvae to Understand Hawai‘i Reef Health,” Sound Waves, August/September 2010.)
Loss of corals can have negative effects on many other reef-associated organisms. In fact, losing a coral reef is similar to losing a rainforest, with many species reliant on that ecosystem for survival.
In addition, coral reefs in Hawai‘i are an important source of tourism and other economic income (fisheries). For example, Kāne‘ohe Bay, where this outbreak is concentrated, is a popular spot frequented by snorkelers, bathers, divers, boaters, and fishermen.
Although this particular disease outbreak seems limited to south Kāne‘ohe Bay, coral diseases have the potential to be widespread, affecting large geographic regions. A prime example is the Western Atlantic and Caribbean, where large tracts of coral reefs have either declined or disappeared owing to diseases.
Science Helping Protect the Reefs
The investigation of this recent outbreak has been led by the University of Hawai‘i’s Hawai‘i Institute of Marine Biology in collaboration with University of Hawai‘i, West O‘ahu, and the U.S. Geological Survey (USGS) National Wildlife Health Center Honolulu Field Station.
Current efforts are focused on determining the extent of the outbreak and collecting samples for laboratory analysis. On a longer-term scale, all three partner organizations are trying to devise better methods to detect coral diseases and determine their causes.
For the most part, the causes of coral diseases are unknown. The current lack of knowledge about precisely what is killing corals has complicated management of coral-reef diseases. Scientists are investigating many possible causes, including host immunity, host physiology, potential infectious agents like bacteria or parasites, and environmental variables such as increased seawater temperatures associated with climate change or land-based sources of pollution.
The USGS is one of the few organizations globally that has applied biomedical tools to investigate animal diseases to coral reefs (yes, corals are animals too). The USGS’ focus in this particular outbreak is to characterize the changes seen in sick corals by looking at the whole coral (what we see with the naked eye) as well as at the cellular level (under the microscope). The USGS is also developing other laboratory tools to help enhance our understanding of coral diseases with the eventual goal of pinpointing the causes of such important diseases.
What Is Montipora White Syndrome?
Corals are basically modified anemones, which are a group of predatory—and often strikingly pretty—marine organisms related to jellyfish. Corals secrete a calcium carbonate skeleton that forms the foundation of coral reefs. The skeleton is covered by a thin layer of tissues. Montipora white syndrome affects the rice coral and involves loss of tissues from the coral until the underlying white skeleton is revealed, hence the name “white syndrome.”
History of Outbreak and Future Risks
On the basis of surveys done since 2006 by the University of Hawai‘i and the USGS, Montipora white syndrome has historically been documented in coral reefs in Kāne‘ohe Bay, albeit at low levels with scattered, isolated colonies affected. Large-scale outbreaks involving multiple coral colonies over a larger geographic area have been documented only in March 2010 and in this recent event.
The reasons for this increase in outbreaks are presently unknown. Tissue-loss diseases like white syndrome are particularly insidious in that they result in immediate loss of coral cover. Often, dead corals are then overgrown by algae, leading to permanent reduction in coral reefs and a change in the ecosystem from a coral-dominated to an algae-dominated reef. Whether this will be the case here remains to be seen.
USGS and partner scientists are actively involved in trying to better understand Montipora white syndrome and other coral diseases. This will allow managers to also determine the environmental drivers of those causes, leading to better intervention and strategies to protect coral reefs.
For more information on this topic and other wildlife health related issues, visit the USGS Honolulu Field Station Web site at http://www.nwhc.usgs.gov/hfs/.
(Reprinted from http://www.usgs.gov/blogs/features/usgs_science_pick/coral-reef-disease-hits-kane%CA%BFohe-bay-hawai%E2%80%98i/; visit this site to view additional USGS Science Features.)
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