When a storm churns across the ocean, the warm surface waters provide additional moisture and can fuel the storm into a hurricane. As the hurricane grows larger and more potent, it can generate waves as high as 18.3 meters (60 feet), tossing and mixing warmer surface waters with the colder, saltier water below. The resulting currents can extend as far as 91.5 meters (300 feet) below the surface, wreaking deadly havoc on marine life.
If the wild currents fail to break up coral reefs in their path, the rain-infused water they bring reduces salt levels and otherwise stresses corals. As the hurricane moves toward shore, the underwater tumult can cause shifting sands and muddy shallow waters, blocking the essential sunlight on which corals and other sea creatures rely.
Slow-moving fish and turtles and shellfish beds are often decimated by the rough undercurrents and rapid changes in water temperature and salinity wrought by a hurricane. Sharks, whales, and other large animals swiftly move to calmer waters, however, and, generally speaking, are not overly affected by hurricanes.
Delicate branching corals, like staghorn and elkhorn species, are among the most vulnerable to breakage and can be reduced to rubble during hurricanes or even less severe storms. Sometimes, though, the breaking of coral into pieces may actually help a coral colony reproduce through a process called fragmentation. If conditions are favorable and the coral fragments come to rest where they can reattach to the seafloor, fragmentation can result in colonies flourishing in new locations. In other instances, corals that reproduce through broadcast spawning may get a little extra help from late summer storms, which help the coral larvae disburse to uncolonized areas.