Biofouling on deep-sea submersible buoy systems off Xisha and Dongsha Islands in the northern South China Sea

• No marine fouling has been reported in waters off the Xisha Islands and east of the Dongsha Islands, the South China Sea.
• The dominant fouling organisms were the Lepas species in waters east of the Dongsha Islands.
• No macrofouling organisms were believed to occur between the mixing layer and near the seabed, but Obelia sp. was found.

To understand the deep-sea characteristics of marine fouling communities off Xisha and Dongsha Islands in the northern South China Sea, an investigation was conducted. A submersible buoy system was moored for 12 months at northwest of Xisha Islands at a depth profile of 1667 m (Station B6). Another was deployed in waters east of Dongsha Islands and exposed for 2 months at a depth profile of 1223 m (Station B9). The fouling samples were collected from the sediment trap (about 410 m below sea water surface), float and the kevlar rope. At Station B6, only the hydroid, Obelia sp., was found at 410 m. As for station B9, the pedunculate barnacles Lepas anatifera Linnaeus, 1758 and Conchoderma hunteri (Owen, 1830) were collected and identified. The former mainly occurred at 15–30 m, the latter at 35–50 m. Moreover, factors affecting the distributions of fouling organisms are discussed.