What Happens to Marine Wildlife During Hurricanes?

Hurricanes stir up trouble both above and below the ocean surface. Ryan Janssens/Shutterstock

Hurricanes are incredibly powerful storms that wreak havoc on marine and coastal ecosystems as they work their way from deeper water toward land. The force of the storm churns up water, mixing warmer water at the surface with cooler water from farther down the water column. In all this churning, what happens to the wildlife living in the storm-tossed waters?

While some species can sense the approaching danger and head to safer areas, those that cannot escape the path of the hurricane are displaced or don't survive.

"When Hurricane Andrew hit Louisiana the government estimated that more than 9 million fish were killed offshore. 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," wrote the National Wildlife Federation.

Meanwhile, those species that survive may find their ecosystem dramatically altered, with new threats to livability ranging from increased silt to decreased salinity.

Who can escape, and who can't

Some underwater life can escape when they sense a hurricane's approach. Sharks, for instance, are known to detect barometric changes that cue them to head for safer water.

"Terra Ceia Bay in Florida, 14 tagged blacktip sharks swam into deeper waters just prior to Tropical Storm Gabrielle’s landfall in 2001," Marti Welch of the National Science Teachers Associated noted in 2006.

In one study published in Journal of Fish Biology, the authors looked at the movement of the blacktip sharks alongside meteorological data and found that they left when the storm was approaching, and came back after it passed, showing it is an innate behavior to sense the approaching of a hurricane.

This wasn't an isolated incident. "When Hurricane Charley approached in 2004, six out of eight radio-tagged sharks being tracked by underwater hydrophones moved to open water. The other two disappeared from the sensing equipment’s range. The timing of the departure appeared to coincide with the decreasing air and water pressure."

A small pod of dolphins swimming underwater
Dolphins seem to be aware when a storm is about to hit, and they make their way to safer waters. Sergey Novikov/Shutterstock

Marine mammals such as dolphins also may sense changes and head out of the area. It could be barometric pressure or sudden salinity changes from the driving rains that trigger dolphins to seek safety.

"Just three days prior to Hurricane Jeanne, researchers conducted a survey of the Indian River Lagoon dolphin population in Florida," Welch wrote. "They were unable to locate any dolphins. Scientists suspect that dolphins react to drastic salinity changes and decreased food associated with hurricane rainfall. Salinity changes may cause a dolphin’s health to decline after about 72 hours of fresh water exposure."

It isn't always the case that dolphins and other cetaceans sense danger and get out of the way, though. Some dolphins have been pushed by the strong waters of hurricanes into shallow lagoons or even into drainage channels where they need to be rescued, rehabilitated and released back into the ocean.

Sharks and cetaceans are larger and more mobile than many other species, which don't have the option of leaving. Many fish species, sea turtles, crabs and other less mobile sea life are at the mercy of the raging water. And the danger doesn't end when the hurricane hits land and moves away from the water.

A hurricane's aftermath

Coral reefs are extremely susceptible to a chemical found in the most common sunscreens. (Photo: Jolanta Wojcicka/Shutterstock)

Huge waves and turbid waters can shift massive amounts of sand that smother sea sponges and sea whips and break apart coral reefs. If they survive the initial storm, corals still may undergo life-threatening stress from cooled water temperatures or murky water that blocks out the sunlight needed for photosynthesis.

"An assessment of Elkhorn coral conducted in Puerto Rico indicated that hurricanes and white-band disease reduced the coral by over 80 percent during the 1970s and 1980s. Consequently, Elkhorn coral was added to the Endangered Species Act candidate species–list," Welch pointed out.

It may take years or even decades for corals to recover from a hurricane, which in turn means entire reef ecosystems take that long to come back from the damage.

While we often focus on the damage hurricanes inflict on land, their power alters the sea over which they travel as well. And as it may take years for land-based habitats to recover, so too does it take underwater habitats and populations of wildlife species time to bounce back.