(thunder booms)
- [Narrator] Normally when a hurricane
is barrelling towards us, we tend to 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 middle of the storm, but Isla managed to survive
by swimming towards 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.
(compelling music)
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 cooler, 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 into canals and ponds,
or away from coastal waters altogether
and into the open ocean,
where they can become disoriented and even die.
Hurricanes also bring heavy rains,
so freshwater often floods coastal areas.
And because freshwater is less dense than saltwater,
it sits on top of the saltwater like oil on vinegar,
where it can prevent oxygen
from reaching the salty layer below
and disrupt salinity levels,
which can lead to sores, lesions and ultimately death
in whales, dolphins and porpoises.
Hurricanes can also kick up dirt and sand in shallow seas,
which can kill fish by clogging their gills.
Experts think that 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 sea grass.
In fact, scientists found that coral cover
in the Caribbean decreases on average
by 17% a year after a hurricane strikes.
And that's in addition to the stress
coral already face from human interference
from things like global warming or pollution.
But hurricanes are not always bad news for sea life,
believe it or not.
After Hurricane Katrina damaged or destroyed 90%
of fishing boats in the Mississippi Sound,
scientists observed a huge increase in dolphin births.
Without all the fishing boats around,
dolphins suddenly found themselves
with tons of fish all at their disposal,
and their populations thrived.
And of course, hurricanes impact land animals, too.
Sometimes they change ecosystems altogether.
For instance, the Hawaiian island of Kauai
is now inundated with feral chickens.
Locals say they are the descendants
of domesticated chickens that escaped
when hurricanes blew open coops.
And in North Carolina, torrential rains
from Hurricane Florence overwhelmed
more than 100 hog waste lagoons,
possibly releasing pig waste into the local water supply.
Unfortunately, research indicates
that the intensity of hurricanes will only increase
with climate change.
So if we don't get a handle on it soon,
we'll be in some deep shh pig waste,
we'll be in some deep pig waste.
(compelling music)
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