October 18, 2018 — Hurricanes can be just as deadly for marine life, sometimes stranding them on land or far out at sea. But sometimes marine life benefits or even thrives after these extreme weather events.
Normally when a hurricane is headed for us, we run the other way. But not Isla. She’s a leatherback turtle who was meandering off the coast of Virginia when she accidentally swam straight into Hurricane Florence. Scientists were worried she’d get caught up in the worst of the storm but Isla managed to survive by swimming toward deeper waters.
Turns out, there’s a part of hurricanes we don’t often think about: What happens under the surface. And Isla is just one example.
Far out at sea, fish that live near the surface might feel some turbulence as a storm passes. But most sea creatures — including dolphins, whales, and sharks — avoid the rough surface water and swim to calmer seas. But it’s a different story near shore.
Changes in water temperature and salinity can be catastrophic for marine life. Hurricanes can generate massive waves. Which mix warm surface water with colder, saltier water below generating currents that extend up to 91 meters below the surface. These currents are so strong that they can sweep manatees inland to canals and ponds or away from the coastal waters they prefer, and out into the open ocean. Where they can become disorientated, and even die.
Hurricanes also bring heavy rain, so freshwater often floods coastal regions. And because freshwater is less dense than salt water, it sits on top of the sea water like oil on vinegar. Where it can prevent oxygen from reaching the salty layer below. And disrupt the salinity levels, which can lead to sores, lesions, and ultimately death in whales, dolphins, and porpoises.
Hurricanes also kick up dirt and sand in shallow seas. Which can kill fish by clogging their gills. Experts think this is probably one of the factors that killed an estimated 9.4 million saltwater fish in 1992, during Hurricane Andrew. The dirty, murky water also blocks sunlight from reaching corals and seagrass. In fact, scientists found that coral cover in the Caribbean decreases by 17% in just one year after a hurricane strikes. And that’s in addition to the stress coral already face from human interference.
But it’s not always so bad for sea life. After Hurricane Katrina damaged or destroyed almost 90% of fishing boats in the Mississippi Sound scientists observed a huge increase in dolphin births. Without the fishing boats, dolphins suddenly found themselves with more available prey which helped their populations thrive.