5 minute read
STUNNING WEATHER ISN’T IT?
Plummeting temperatures hit pretty hard for those of us on dry land, but for sea life in our local waters, it can be much worse.
By Fran Marler
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THE WIND PULLS AND PUSHES, CALLS AND LEADS. Like an arctic maestro unleashing a wintry tune, the elements seem to be at the mercy of its every whim. Rising and falling, a swirling cold front eventually collides with an area of relative warmth over the Gulf Stream, and more often than not, there’s only one outcome.
The cold air wins.
An abrupt temperature drop on the Outer Banks isn’t uncommon during the winter season – and we’re all familiar with how bone chilling an icy tempest can feel when you factor in the wind chill. But as bothersome as those cold snaps may be on land, their offshore effects are many and far reaching.
Especially when it comes to marine life.
“During these strong cold fronts, there can be a quick drop in water temperature,” says Dr. Jim Morley, a biologist with the Coastal Studies Institute (CSI) and East Carolina University whose research focuses on marine ecosystems. “Because fish and other marine life are ectotherms – cold-blooded creatures whose body temperature matches the surrounding water – these cold snaps can take them by surprise, causing them to become stressed and immobilized during these periods.”
The resulting condition is most commonly known as cold stunning, and it’s a hypothermic reaction that can affect an array of sea creatures. While symptoms such as lower heart rates, decreased circulation and lethargy might not seem that dire to the general public, prolonged exposure to dangerously frigid water can lead to secondary health issues that can ultimately be deadly.
Those who are familiar with cold stunning here on the Outer Banks have likely been introduced to the phenomenon through the Sea Turtle Assistance and Rehabilitation (STAR) Center at the North Carolina Aquarium on Roanoke Island – a state-of-the-art facility that provides medical care to sick or injured turtles. In conjunction with volunteers from the Network for Endangered Sea Turtles and National Park Service personnel, local beaches are combed for turtles showing symptoms of a cold stun when temperatures drop dramatically. Once they’re found, the turtles are then carefully transported to the STAR Center where their recovery process can begin.
But while sea turtles seem to suffer the brunt of these brutal cold snaps – and therefore tend to dominate the news surrounding cold stunning – fish can also be deeply affected by abrupt changes in temperature.
“Fish blood contains a specific amount of salt – sodium and chloride – and part of gill function helps regulate this balance,” Jim says. “When metabolism slows due to cold stunning, gill movement and cellular function also begin to slow, and the concentration of salt can increase in their blood – which can be fatal. Their physiology simply isn’t
Cold stunned sea turtles are allowed to warm up slowly at the aquarium’s rehabilitative STAR Center before being given swim tests and an intake examination (inset photo courtesy of the North Carolina Aquarium on Roanoke Island).
engineered to combat these sudden changes in temperature.” With so much at stake in terms of marine life, it only makes sense that one would want to understand the contributing factors involved in local cold stunning events – and geographically speaking, it might seem reasonable to cast a wary eye toward to the glacial flow of the nearby Labrador Current. “It actually doesn’t even play a role,” Jim counters, while pointing out that local cold stunning more typically occurs in the shallow waters of the Pamlico and Albemarle sounds – where there’s not a lot of connectivity with the vast oceanic depths that tend to inhibit such sharp temperature drops on a wide scale. Which isn’t to say that our relatively shallow coastal waterways aren’t teeming with species that can be affected by cold stunning. “We have a diverse range of marine life here,” Jim explains. “And every species has a range of temperatures in which they can be successful and survive.” In addition to the particularly vulnerable tropical species that often get swept up in our estuaries – including everything from Florida-native pink shrimp to stone crabs – common fish such as speckled trout, which has an extreme northern limit that only extends to the Chesapeake Bay, can take a major hit during a cold snap. Other species such as juvenile red drum and green-tail shrimp also fare much better during warmer winters, while brown shrimp and fish such as tautogs tend to be more winter hardy.
“While a large range of marine species can be affected, it can be very hard to say how it will affect entire populations,” Jim says. “In other words, a cold winter or rapid temperature drop can have an impact on local marine species, even when a mass mortality event isn’t observed.”
Unfortunately, there’s also no way to prevent a cold stunning event. During the winter months, coastal weather can be extreme, unpredictable and oftentimes unforgiving – and the water only needs to dip below 50 degrees in order to be a threat. There are, however, agencies in place that are ready to help should you witness a marine animal suffering from cold stunning – including the offices of CSI, the field office for the North Carolina Division of Marine Fisheries in Manteo and the NOAA Fisheries Southeast Marine Mammal Stranding helpline.
“It’s always important to report a stunned turtle or any occurrence where marine life seems to be in distress,” Jim says. “We’re here to learn and help in any way we can.”
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