An outbreak of viruses including one that resembles herpes is being liked to a series of coral bleaching in Australia's Great Barrier Reef, a new study says.

Researchers from the Oregon State University (OSU) discovered that a number of environmental factors have been placing significant stress on the ecology of the Great Barrier Reef. One of these is the spread of three groups of viruses that likely caused the corals in the area of the ocean to bleach.

With oceans of the world facing another large-scale coral bleaching event, experts at the National Oceanic and Atmospheric Administration (NOAA) believe that the findings of the recent study could have far-reaching implications on the environment.

Corals typically experience bleaching when they are exposed to various environmental stresses, such as pollution, overfishing, or a sudden warming of ocean water. These conditions cause the organisms to lose their color and release the symbiotic algae that live within their tissues.

The event proves to be very harmful for the corals because it causes them to lose their primary source of food and makes them more vulnerable to contracting diseases. Organisms that are exposed to prolonged or severe cases of bleaching are also more susceptible to death.

"People all over the world are concerned about long-term coral survival," Prof. Rebecca Vega-Thurber of OSU's College of Science and one of the authors of the study, said.

"This research suggests that viral infection could be an important part of the problem that until now has been undocumented, and has received very little attention."

Viral Explosion In The Great Barrier Reef

The viral outbreak in the Great Barrier Reef was traced to a period when the corals were exposed to high levels of ultraviolet (UV) light during low tides. The researchers believe that this was caused by a combination of high temperatures and heavy rain, both of which are known to be sources of significant stress for corals.

During this period, the population of viruses in the corals reached levels that were two to four times higher compared to those previously recorded in the marine organisms. There was also a widespread bleaching event that occurred in the area for about three days.

Some of the viral cultures detected in water included megaviruses and retroviruses, as well as some type of the herpes virus, which was abundant in that area of the ocean.

Herpes viruses have been in existence since ancient times, and can be found living inside a number of larger organisms, such as mammals, oysters, marine invertebrates and corals.

Vega-Thurber explained that in their study, they found that various stresses may have caused the corals to become highly vulnerable to attacks from viruses. One source of stress in particular is the significant increase in water temperatures as a result of global warming and El Nino. 

She said that the coral bleaching event is bad news for the environment since it occurred fairly rapidly on a pristine system such as the Great Barrier Reef.

While the reef system can still recover from the bleaching, Vega-Thurber said that such events are occurring more widely in different parts of the world.

In 2015, the NOAA revealed that the world was undergoing another widespread coral bleaching, which is the third one to occur following the events in 1998 and 2010.

The bleaching started in northern portions of the Pacific Ocean in 2014, and had moved south throughout 2015. It is now likely to spread even further this year, according to NOAA officials.

Experts from the environment agency said that by the end of 2015, close to 95 percent of coral reefs in the United States were exposed to conditions that can trigger bleaching.

Areas where corals have died become more susceptible to the destructive effects of storms. There are also fewer natural habitats for fish and other aquatic animals if corals were to succumb to bleaching.

The findings of the Oregon State University study are featured in the journal Frontiers in Microbiology.

Photo: U.S. Geological Survey | Flickr