| Photographic transects were taken in 2009 and 2010 on the VK826, VK906 and GB535 lease blocks to quantify the amount of the seafloor covered by living or dead colonies of the deep-sea coral L. pertusa, as well as species composition of associated fauna. Carbonate coral skeletons were collected from the same reefs and were analyzed for delta13 C, delta18O and Delta14C. The photographic evidence shows the VK826 reef had a total coral cover area of 1289 m2 with 33+/-19.2% live coral cover in areas that had coral in 2009. In 2010 the total coral coverage was 280 m2 with 31+/-13.5% live coral cover. VK906 had 53 m2 of total coral coverage area showing 22+/-26.0% live coral cover in areas containing coral in 2010, while GB535 showed no corals in the photographic evidence in 2010. The carbonate substrates at these sites have formed due to natural hydrocarbon seepage, which is ongoing in localized areas. The dissolved methane water samples show small amounts of CH4 in the water above the reefs. The values of delta 13C (-6.5‰-0.5‰) and delta18O (0.8‰-3.7‰) measured in the coral skeletons were consistent with the previously reported values for L. pertusa from the Gulf of Mexico. The delta 13C skeleton values show evidence of an environmental gradient among these coral communities. Delta14C showed growth rates (Linear extension rates) of 4 to 15mm yr-1 and ages of 90 to 440 ybp. |
