Hurricanes Typhoons and Cyclones
Meteorology and Weather
Oceans and Seas

Do hurricanes impact sea life?

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Todd L Ross
09/20/2019

Yes, hurricanes can have a dramatic effect on sea life.

Hurricanes form when a low-pressure area moves across tropical waters, picking up moisture. Warm air rises, forming another low-pressure area, which causes more air to rush in. That air rises, forming clouds and thunderstorms. The storm is officially categorized as a hurricane when wind speeds reach 74 mph.

A hurricane can create waves as high as 18.3 meters (60 feet), and its raging winds can create half as much energy as the electrical generating capacity of the entire world. Any organisms caught in those waves will certainly experience some disruption. Here are a few of the ways that a hurricane might affect fish, mammals, and other creatures:

  • Salinity Changes - As the storm moves over land, it will also cause runoff from the land to enter the ocean; because freshwater is less dense than saltwater, it sits on top of the ocean and prevents oxygen from reaching the deeper, saltier layers.
    This can affect some organisms significantly, particularly coral, which can take years to recover from severe storms. The freshwater layer can also cause lesions in whales, dolphins, and other animals that surface regularly. Dolphins can suffer the effects of salinity changes within about 72 hours of exposure.
  • Temperature Changes - Hurricanes can also rapidly change water temperature, which changes the water’s ability to hold dissolved oxygen. Again, this affects coral—and coral is a critical component of many ocean ecosystems.
  • Rough Undercurrents - Any animals caught in the rough undercurrents of a hurricane will move with the water, and if they survive the trip, they’ll be disoriented. Undercurrents can be powerful at 91 meters (roughly 300 feet) below the surface, so most fish and mammals can’t simply avoid the storm by diving deeper.
  • Changing Water Levels - In September 2019, two manatees—a mother and her calf—found their way past a marina barrier near Daytona Beach, Florida. The Florida Fish and Wildlife Conservation Commission were able to rescue the sea cows.

The animals had passed through the barrier when Hurricane Dorian raised the Halifax River’s water levels. That’s not an unusual occurrence in a hurricane; more water means less effective natural and artificial barriers, and animals end up where they’re not supposed to be.

We should note that some organisms know how to stay out of the path of hurricanes. Some larger animals—including sharks, dolphins, and whales—can sense and avoid the storms, sticking to calmer waters. However, slow-moving and immobile organisms aren’t able to move out of the way. The results can be disastrous for ocean ecosystems.

"When Hurricane Andrew hit Louisiana the government estimated that more than 9 million fish were killed offshore,” the National Wildlife Federation wrote in 2011. “Similarly an assessment of the effect of that same storm on the Everglades Basin in Florida showed that 182 million fish were killed. Hurricane Katrina also had a huge effect on dolphin species. Many dolphins were hurt during the storm and were rescued and underwest rehabilitation.”

Ocean life can take years to recover from major hurricanes. As climate change increases the intensity and frequency of tropical storms, some ecosystems will experience profound losses.