Cold-water corals in a cold seep area on the northern continental slopes of the South China sea and their isotopic characteristics

Cold-water corals (CWCs) were found to occur in association with authigenic carbonates in a cold seep area on the northern continental slopes of the South China Sea (SCS). The taxa identified were: Balanophyllia (Balanophyllia) sp., Balanophyllia (Eupstutunia) sp., Lochmaeotrochus sp., Enallopsammia sp., Crispatotrochus sp.1 and Crispatotrochus sp.2. The delta C-1(3) (-7.36%o to -1.15%o, V-PDB) and Sr-87/Sr-86 ratios (0.709126-0.709184) indicated that CWC aragonite skeletons had been precipitated from seawater without the involvement of seeping fluids. The presence and growth of CWCs on the slopes of the submarine seamounts in the south-western (SW) Dongsha area could be directly linked with the hard substrates provided by exhumed hydrocarbon-imprinted authigenic carbonates and fed by the food particles enhanced by high-velocity internal tides and near-bottom currents. A multi-step process for CWC colonization was proposed that encompassed cold-seepage processes as a driver for hard-substrate generation of CWC, as well as the subsequent settlement and maintenance of CWC larvae under the persistent influence of bottom currents.