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Blog: June 22, 2011

By Paula Whitfield
Marine Biologist
NOAA NCCOS

Scuba diver on the Kassandra Louloudis. This image is a good example of how a high-quality camera can sometimes make the conditions look better than they actually were. While the visibility looks good in this photograph, in reality it was slightly murky and green. (UNC CSI)

Sometimes scuba diving does not seem like work, and then again, sometimes it really does. Normally, diving off the coast of North Carolina can be some of the most beautiful and exciting diving in the world, but diving near the shoals off North Carolina is another matter entirely. The shoals off of North Carolina (there are three) are incredibly dynamic areas, oceanographically speaking. The shallow sandy shoals act as barriers to water movement, so the northerly flowing gulf stream gets squeezed as it flows around the shoals providing some pretty 'dynamic conditions' underwater. This means high currents, low visibility, or both. In other words, you never really know what you are going to get when you jump in the water on a shipwreck near the shoals.

Brian Degan, one of the biologists working on the BOTA project, reels in his meter tape after conducting a fish survey along a transect line. During the survey, he identified the species, abundance, and size of the fish within a certain distance of the transect line. (NOAA)

On this mission our goal is to conduct biological surveys on several shipwrecks near Diamond Shoals, off Cape Hatteras, NC. Cape Hatteras just happens to be a zoogeographic transition zone, which means there are two opposing water masses that converge right in this area - the warm tropical Gulf Stream current to the south of Cape Hatteras and a temperate, cold water current to the north. As marine biologists, my colleagues Christine Buckel, Brian Degan and I are interested in comparing the different communities found on these shipwrecks on the north and the south side of Diamond Shoals. Shipwrecks are not only culturally important, but due to their high relief and structural complexity they provide excellent habitat for a large diversity of fishes, invertebrates and algae species.

On this trip, we have five days of ship time to conduct fish and habitat surveys on as many shipwrecks as we can, but sometimes the underwater conditions don't always work out. On our first dive on the shipwreck Keshena we had beautiful conditions and underwater visibility of at least 40 feet. There were lots of schooling scad (Decapterus species) and large Amberjack (Seriola dumerili). The next dive took us closer to Diamond Shoals and the shipwreck Kassandra Louloudis and you could see the water getting greener and cloudier - this is not a good sign. Under these circumstances we just hoped that conditions would be good enough for us to get the work done. The Kassandra Louloudis turned out to be one of those 'hard' dives, with lots of current and low visibility (about 15 -20 ft).

A school of Atlantic spadefish swim around the scuba divers as they make their way back to the surface. (UNC CSI)

On the second day of diving, we did not even get in the water due to extremely high current on the U-701 (possibly 1 knot or more) and then because of extremely low visibility (~ 2ft) on the City of Atlanta. Then today, our third day, we did a dive on the shipwreck, Dixie Arrow, which happens to be well south of the shoals. The conditions and the marine life on this shipwreck can only be described as spectacular!! The water was crystal blue and clear, and visibility must have been 100 feet or better; it was the best conditions I have seen in ten years! There were sand tiger sharks (Carcharias Taurus), rainbow runners (Elagatis bipinnulata), barracuda (Sphyraena barracuda), amberjack (Seriola dumerili), lots of schooling scad (Decapterus species) and atlantic spadefish (Chaetodipterus faber). This was definitely one of those dives that did not seem like work.