Significant outbreaks of viruses may be associated with coral reef bleaching events, especially as a result of multiple environmental stresses including rising ocean temperatures and ocean acidification.
A recent study at Oregon State University has documented a virus outbreak, including a herpes-like virus during a bleaching event on the Australian Great Barrier Reef. The finding are published in Frontiers in Microbiology, and are especially important as we are currently experiencing coral bleaching on a global scale.
When corals are exposed to warmer water, pollution, or other stressful environmental conditions, the coral can expel symbiotic zooxanthellae algae that live in their tissues, resulting in coral bleaching. When the algae is expelled the coral loses it’s main food source and becomes more susceptible to disease.
“People all over the world are concerned about long-term coral survival,” said Rebecca Vega-Thurber, an assistant professor of microbiology in the OSU College of Science and corresponding author on the study. “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.”
To come to these findings an area of coral off Heron Island was exposed to high levels of ultraviolet light at low tides during a period of heavy rain and high temperatures. They found that during this period, viral loads exploded to levels 2-4 times higher than ever recorded in corals, followed by a significant bleaching event over just three days.
The study found that a diverse group of viruses are present in acroporid coral, the viruses included a new megavirus, a somewhat atypical herpes-like virus, and a gamma-retrovirus. Viruses are abundant residents of stony coral colonies however they become a serious threat when their numbers reach extreme levels due to stressful conditions.
The findings, Vega-Thurber said, suggest that a range of stresses may have made the corals susceptible to viral attack, particularly high water temperatures such as those that can be caused by an El Nino event and global warming. [Science Daily]