Wrightsville Beach, NC - As spring shakes off the last vestige of winter, a variety of seasonal species are returning to Wrightsville's waters. Anyone who has walked along the water's edge recently has probably noticed all of the washed-up jellyfish.
There are five types of jellyfish commonly found off of the Azalea Coast. The two most likely to wash onto the beach are moon jellyfish, which can be easily identified by the reddish-pink four-leaf clover markings on its back, and the cannonball jellyfish, named for a resemblance to its namesake. It is also known as the cabbage head jellyfish.
"The moon jellies and cannonballs aren't very strong swimmers," said Richard Satterlie, the University of North Carolina Wilmington's Fred Hawkings Distinguished Professor of Biology and Marine Biology who specializes in jellyfish locomotion. "They're influenced by the wind, waves and current direction."
Fortunately, they pose little danger to humans. While moon and cannonball jellyfish use toxins to kill their prey, they are unable to penetrate the skin of humans. Box jellyfish and man-o-wars, which occasionally enter shallower waters and pack a nasty sting, are strong swimmers and typically stick to deeper areas. Sea nettle jellyfish, which show up in clusters toward the middle of the summer, are responsible for most of the minor stings off our coast.
"Any problems we're going to have with jellyfish are going to be related to the fishing industry, rather than stinging people," Satterlie said.
Box jellyfish eat a variety of small fish and crustaceans, which are also prey for many commercial fish.
Jellyfish begin as polyps on the ocean floor. As the water warms, its morphology begins to change, and its tiny disks eventually bud into jellyfish. The jellyfish then reproduce to make more polyps. Moon jelly polyps can produce dozens of jellyfish per reproductive cycle.
Satterlie explained that the warmer waters experienced this winter may cause more jellyfish earlier in the season, but shouldn't have much of an impact on the overall number of jellyfish. The water temperatures are more dependent on the behavior of the Gulf Stream than anything else, and jellyfish populations are dependent on so many more factors than temperature that it would take an extensive longitudinal study to prove any correlation.
"Jellyfish blooms are happening around the world in places we haven't seen before and closing beaches in some places," Satterlie said.
As for the possibility of something like that happening in this region, Satterlie was skeptical.
"It's not going to happen with the species we have here. Maybe if box jellies were coming in numbers, but they stay toward deeper waters. Our area is pretty stable."
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