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As the climate changes, animals are adapting along with it. Some land animals are moving towards the planet's poles and higher elevations, and similar changes are going on under the seas. From 30 miles off the North Carolina coast, Jay Price of member station WUNC reports on tropical fish that aren't in the tropics.
JAY PRICE, BYLINE: It's a sunny, late fall morning on the dive boat Midnight Express, anchored 30 miles off the North Carolina coast. In the back of the boat, scientists launch an ice chest-size underwater drone, called a remotely operated vehicle, on a long tether.
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UNIDENTIFIED PERSON #1: Fifty feet out.
UNIDENTIFIED PERSON #2: Fifty feet out.
UNIDENTIFIED PERSON #3: Fifty feet out.
UNIDENTIFIED PERSON #1: Copy that. We're diving. Dive. Dive. Dive.
PRICE: This far offshore, there's nothing to see in any direction except the black-blue sea. Directly under us, though, there's a lot going on. The effects of two major changes for sea life may be at work in one place - a sunken ship. One of these changes is rising sea temperatures from climate change. The other, something called marine urbanization; an ongoing building boom in human-made structures underwater - things like dock pilings, artificial reefs and the submerged parts of oil drilling platforms and offshore wind turbines. These scientists have been finding fish more common farther south, and these seem to prefer shipwrecks to, say, nearby rocky reefs.
AVERY PAXTON: It's really interesting, and we still don't understand fully why they may be enjoying these artificial structures, right?
PRICE: Avery Paxton is a biologist with the National Oceanic and Atmospheric Administration. Inside the boat, scientists concentrate on a screen showing video from the drone they're using to steer it around.
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UNIDENTIFIED PERSON #4: I have visuals of the sea floor. I'm going to stop for a second and orient it.
PRICE: The wreckage is of a tanker, torpedoed in 1942 by a German submarine. It's thick with sea life now - a bustling marine village on an otherwise desert-like sea floor. And some of the fish here now are more typically found on the coral reefs of southern Florida and the Caribbean.
PAXTON: What we do know is that some of them are at the very northern end of their range or some of them are even past what their normally documented ranges are.
PRICE: Paxton has been studying sea life on North Carolina's numerous shipwrecks for years.
PAXTON: And one of the thoughts moving forward is whether or not, if species are to be moving forward, if you could use artificial structures to facilitate - so make these corridors that the species could use if they're moving forward.
PRICE: There have already been some well-documented habitat shifts by some commercially fished species. Black sea bass and summer flounder, for example, that used to be more common off North Carolina have moved north. That's caused problems for fishermen all along the Atlantic coast. Paxton and the other scientists are studying this wreck, though, to learn more about how various species interact, not just those with commercial value.
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PAXTON: All right, we're nearing the full-wrecked structure, about midship. 10:05 survey starts.
PRICE: The drone does a slow sweep down the side of the mangled ship, picking its way through a lot of sharks - big ones - a species called sand tigers. High-definition cameras record video that, later, the scientists will use to identify and tally the fish on the wreck.
PAXTON: One of the main purposes of our mission today is to try to understand how some of the reef fish are responding to the presence of these large predators, like sand tiger sharks.
PRICE: After the first survey is done, the Midnight Express moves a few miles away to another wreck, a German submarine; the U-352. There are lots more sharks and clouds of other fish, too, including one species that grabs their attention.
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PAXTON: That looked like another Spanish hogfish right there.
CHRIS TAYLOR: Yeah, that's right.
PAXTON: Wow, two of them.
TAYLOR: It's pretty cool seeing definitely a few Spanish hogfish.
PRICE: Spanish hogfish are one of the tropical species. Often during surveys, the scientists don't even see the small warm-water fish until they download the recordings from the drone. Finally, the survey is done.
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TAYLOR: ROV's at the surface.
UNIDENTIFIED PERSON #5: Thar she blows.
PRICE: Later, on shore, they'll scrutinize that video. Chris Taylor, another NOAA biologist aboard, says the scientists want to better understand the complex roles artificial reefs play for sea life.
TAYLOR: We're not necessarily promoting broad use of and deployment of artificial structures, but it is a growing call by commercial recreational fishers alike. What we've learned in this study is that the type of structure that you put out there is likely to attract a different community of species.
PRICE: And one implication is whether it's possible to place the right kinds of structures in key places to help different species, whether it's those that fishermen want to target or tropical fish that need stepping stones as they head north in search of cooler water.
For NPR News, I'm Jay Price off the North Carolina coast.
(SOUNDBITE OF THOMAS NEWMAN'S "FIELD TRIP") Transcript provided by NPR, Copyright NPR.