Viruses in corals: hidden drivers of coral bleaching and disease?

Marine viruses are the largest, but most poorly explored genetic reservoir on the planet. They occur ubiquitously in the ocean at an average density of 5-15 x 10⁶ viruses per mL of seawater, which represents abundances an order of magnitude higher than those of bacteria. While viruses are known agents of a number of diseases in the marine environment, little is known about their beneficial function to corals. Herein, we briefly introduce the topic of viruses as potential drivers of coral bleaching and disease.