Mapping South Texas Banks: DAY TEN (9/26/12)

After recovering the ROV from a dive to the depths, the science party hurries to the back deck to observe all the collections made during the trip. Usually, the collections consist of sediment cores (mud and other ocean bits), sponges, corals, rocks, sea stars, and the like. Today’s ROV dive to Blackfish Ridge resulted in buckets of goodies. The sorting process went something like this: rock, rock, rock, rock, sponge, sea star, soft coral, soft coral….shark tooth!?

Left: Bottle-Brush Bush Black Coral. Image Credit: Maureen Trnka

Right: Piece of rock from Blackfish Ridge. Image Credit: Maureen Trnka

Left: Shark Tooth from Blackfish Ridge. Image Credit: Harriet Nash

Right: Sea Star from Blackfish Ridge. Image Credit: Harriet Nash

That’s right. Sitting in the bottom of one of the sample boxes, among rubble and sand was a shark tooth. Although it was small in size, it interested the scientists at the mere chance of catching such a find on the ocean floor. After some preliminary research, the tooth appears to be from the genus Carcharhinus, but the species couldn’t be identified. The genus of Carcharhinus includes many species of sharks including blacktip sharks, bull sharks and silky sharks. Two silky sharks have been seen so far on the research cruise, so one thought was that perhaps it belongs to that species.

A less successful ROV dive occurred today at Mysterious Bank. The name itself sounds intriguing; as if the bank is crawling with all sorts of unknown and unusual things. In fact, within the first few seconds of the dive, a shark swam right past our camera. This was hoped to be a sign of good things to come. Unfortunately, this was not the case. The majority of the bank was covered with a thick nepheloid layer. The nepheloid layer is a layer in deep water that contains a large amount of suspended sediment and makes for murky water which is difficult to see through. The thickness of the layer can depend on the velocity of ocean currents and the turbulence of the waters. In the case today, the nepheloid layer was so bad that it prevented any samples being taken at Mysterious Bank and only a few observations of the life on the seafloor. It seemed like all was lost at Mysterious Bank; until another shark viewing occurred and even a dolphin came to check out our camera during the ascent of the ROV. The mysteries of Mysterious Bank are saved for another day.

Nepheloid Layer at Mysterious Bank

Image Credit: Schmidt Ocean Institute

Tomorrow brings another ROV dive to the temporarily named “Tom’s Nob.” The safety officer on the ship, Tom Bills, was at the bridge multi-beam mapping the seafloor all throughout the night and happened upon an area of interest.

Safety Officer, Tom Bills aka "Safety Tom"

Image Credit: Mark Schrope

The bank he discovered has never been mapped before, so we are excited to see what interesting features it will have. Each bank we visit is different than the previous one, and each has its own distinct identity. We shall see what is waiting for us at “Tom’s Nob.”