Wrecks as Artificial Deep Reefs
There are many known cases of Lophelia pertusa colonizing man-made structures, such as shipwrecks and oil rigs here and in the eastern North Atlantic Ocean. Artificial structures such as rigs and wrecks can contribute valuable real estate because they provide hard substrate for coral larvae to settle on, which is often a limited commodity in the deep sea. Such structures also allow the corals to be higher in the water column, where stronger currents occur, providing increased chances for food delivery and clearing of sediments.
Although we suspected that we might find Lophelia on the GulfOil ship wreck because of its age (approximately 70 years) and water depth (600m), we were astonished to see the spectacular coverage of Lophelia on this wreck. As we approached, the wreck looked as if it were wearing a white fur shawl, with huge expanses of dense Lophelia along the structures on the deck. This wreck may be the most spectacular deep reef in the Gulf!
Artificial Deep Reef Effect
One of the goals of the Lophelia II project is to assess whether man-made structures that reach the sea floor at depths where Lophelia and other deep corals thrive serve as artificial reefs. In shallow waters, artificial reefs are known to attract and concentrate fishes and invertebrates, and therefore function like natural reefs in that biodiversity is enhanced. We were interested to see whether the fishes and invertebrates that we observe on natural deep reefs also occur near the Lophelia growing on the GulfOil.
Although it will take a while to quantify the numbers of animals we saw on the GulfOil, many of the ‘usual suspects’ were observed at the wreck, including conger eels, Hoplostethus fishes (see video from Oct. 20), black belly rose fishes, and squat lobsters such as Eumunida picta and Munidopsis species. In fact, one Hoplostethus took such a liking to Jason that it interfered with our mosaic imaging by sitting under the ROV where the camera is, blocking our photos! From the Lophelia samples taken by Jason during this dive, we will be able to use genetic analyses to determine which natural reefs may have provided the coral larvae that have grown into the spectacular deep reef that now exists here. This will help us understand the relationship between natural and artificial deep reefs in the Gulf, and ultimately, help the BOEMRE to set up proper protection for these sensitive biological areas.
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