The discovery of deep sea coral forests in the spring of 2018 filled a significant gap in the benthos research and even in carbon cycling in the South China Sea. Previously, the researches of deep-sea benthos were restricted to the sediment-covered soft bottom due to the technical limitations, and the rocky hard bottom was believed to be barren of life. Using submersible technique in the mid-1990s, deep-water coral reefs were first discovered in the Atlantic Ocean, which opened a new research direction in marine sciences. Two groups of deep sea corals have been recognized: scleractinian hexacorals and gorgonian octocorals. The aragonite skeleton of the former group build up deep sea coral reefs, while the latter make up deep sea coral forests with high-Mg calcite skeleton in many gorgonian corals. All kinds of carbonate coral skeletons can record environment changes of the deep sea and provide excellent material for high-resolution paleoceanography. Although the development of deep sea coral reefs in the Pacific Ocean is hampered by its extremely shallow aragonite compensation depth, deep sea coral forests are ubiquitous in the ocean. Up to now, most parts of the Pacific have not yet explored in this respect, and deep sea corals remain outside the research scope. The present paper is a literature review and calls for attention to the deep sea forests. It starts with the composition and distribution of deep sea coral reefs and forests, followed by discussions on the significance of deep sea coral forests in marine ecology and in paleoceanographic reconstructions.

Keywords： Deep sea ; Coral ; South China Sea ; Benthos ; Paleoceanography.