I found this interesting: “If viruses are causing disease or bleaching of colonies, it’s also unknown whether this is happening now more than in the past.” Sort of like ocean acidification, they don’t have any long term data.
UPDATE: Commenter “Climate Weenie” says it best in comments to this story:
Remember ‘Global Warming is killing the frogs?’ – turned out to be fungus spread by biologists.
‘Global Warming is killing the bees!’ – parasites
‘Global Warming is killing the bats!’ – fungus
Now, ‘Global Warming is killing the coral!’ – virus.
From Oregon State University:
Viruses linked to algae that control coral health
CORVALLIS, Ore. – Scientists have discovered two viruses that appear to infect the single-celled microalgae that reside in corals and are important for coral growth and health, and they say the viruses could play a role in the serious decline of coral ecosystems around the world.
These viruses, including an RNA virus never before isolated from a coral, have been shown for the first time to clearly be associated with these microalgae called Symbiodinium. If it’s proven that they are infecting those algae and causing disease, it will be another step toward understanding the multiple threats that coral reefs are facing.
The research was published today in the ISME Journal, in work supported by the National Science Foundation.
“We’re way behind in our knowledge of how viral disease may affect coral health,” said Adrienne Correa, a researcher with the Department of Microbiology at Oregon State University. “If viral infection is causing some bleaching, it could be important in the death of corals and contribute to reef decline. This potential threat from viruses is just starting to be recognized.”
Corals co-exist with these algae in a symbiotic relationship, scientists say, in which the algae provide energy to the coral, and contribute to the construction of reefs. The coral in turn offers a place for the algae to live and provides nutrients for it.
Corals and viruses have evolved along with their resident algae for millions of years. They have persisted through previous climate oscillations, and the presence of viruses within corals or their algae doesn’t necessarily indicate they are affecting coral colony health. If viruses are causing disease or bleaching of colonies, it’s also unknown whether this is happening now more than in the past.
“Corals are known to face various environmental threats, such a warming temperatures, competition and pollution,” Correa said. “Some of the environmental changes of the past were likely more gradual and allowed the coral and its associates more time to adapt.
“The stresses challenging coral reefs now are more intense and frequent,” she said. “This may mean viruses cause more problems for corals and their algae now than they did historically.”
In continued research at OSU, scientists will inoculate Symbiodinium with the viruses and try to prove they are causing actual disease. If the viruses are killing the algae, scientists said, it could have significant implications for coral reef health and survival. There are almost two dozen known diseases that are affecting coral, and scientists still do not know the cause of most of them.
Coral abundance has declined about 80 percent in the Caribbean Sea in the past 30-40 years, and about one-third of all corals around the world are threatened with extinction.
Here’s the abstract:
Unique nucleocytoplasmic dsDNA and +ssRNA viruses are associated with the dinoflagellate endosymbionts of corals
Adrienne M S Correa, Rory M Welsh and Rebecca L Vega Thurber
The residence of dinoflagellate algae (genus: Symbiodinium) within scleractinian corals is critical to the construction and persistence of tropical reefs. In recent decades, however, acute and chronic environmental stressors have frequently destabilized this symbiosis, ultimately leading to coral mortality and reef decline. Viral infection has been suggested as a trigger of coral–Symbiodinium dissociation; knowledge of the diversity and hosts of coral-associated viruses is critical to evaluating this hypothesis.
Here, we present the first genomic evidence of viruses associated with Symbiodinium, based on the presence of transcribed +ss (single-stranded) RNA and ds (double-stranded) DNA virus-like genes in complementary DNA viromes of the coral Montastraea cavernosa and expressed sequence tag (EST) libraries generated from Symbiodinium cultures. The M. cavernosa viromes contained divergent viral sequences similar to the major capsid protein of the dinoflagellate-infecting +ssRNA Heterocapsa circularisquama virus, suggesting a highly novel dinornavirus could infect Symbiodinium.
Further, similarities to dsDNA viruses dominated (~69%) eukaryotic viral similarities in the M. cavernosa viromes. Transcripts highly similar to eukaryotic algae-infecting phycodnaviruses were identified in the viromes, and homologs to these sequences were found in two independently generated Symbiodinium EST libraries. Phylogenetic reconstructions substantiate that these transcripts are undescribed and distinct members of the nucleocytoplasmic large DNA virus (NCLDVs) group.
Based on a preponderance of evidence, we infer that the novel NCLDVs and RNA virus described here are associated with the algal endosymbionts of corals. If such viruses disrupt Symbiodinium, they are likely to impact the flexibility and/or stability of coral–algal symbioses, and thus long-term reef health and resilience.