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World War II shipwrecks off the coast of North Carolina have more to offer than clues about past battles. Diving scientists are excavating the wrecks to learn about the thriving marine life the sunken ships support.

The waters off the North Carolina coast are known as the Graveyard of the Atlantic and Torpedo Junction. Here, dozens of ships — mostly merchant vessels — were sunk by German U-boats. The National Oceanic and Atmospheric Administration (NOAA) estimates that from January to August 1942, more than 50 vessels were lost to the U-boat assault. The remains of those ships, along with several U-boats, rest on the Atlantic Ocean seafloor.

In the nearly 70 years since they first hit the ocean floor, the shipwrecks have transformed into a habitat for an array of species. The nooks and crannies of these wrecks make them perfect artificial reefs.

"In addition to their cultural significance, shipwrecks function as important habitat for a wide variety of fishes, invertebrates and algal species," a NOAA study team wrote in a report on the area.

The wrecks are also uniquely located in an area that is home to both temperate and tropical species of fish and invertebrates, which should allow scientists to examine how the marine communities change as ocean temperatures rise as a result of climate change, according to the NOAA study.

To begin probing the living communities of the sites, last year scientists conducted biological and ecological investigations on four World War II shipwrecks (the Keshena, City of Atlanta, Dixie Arrow and EM Clark), as part of NOAA's Battle of the Atlantic research project.

At each shipwreck site, fish community surveys were conducted to characterize the mobile conspicuous fish, smaller prey fish, and immobile invertebrate and algal communities. The scientists also attached temperature sensors that were placed at all four shipwrecks, as well as at an additional shipwreck, the Manuela.

The data, which establishes a baseline condition to use in future assessments, suggest strong differences in both the fish and bottom-dwelling communities among the surveyed shipwrecks based on ocean depth, according to the study.

The wrecks are located at 75 to 236 feet (23 to 72 meters) deep. The preliminary results suggest that the middle shelf, 82 to 125 feet (25 to 38 m) south of Cape Hatteras, N.C., is more diverse than the outer self (131 to 197 m), which is consistent with past studies.

Scientists found about 40 species of fish, including gray triggerfish, oyster toads, dolphinfish, smooth butterfly rays and slippery dicks.