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Cold-water coral (CWC) habitats are considered important centers of biodiversity in the deep sea, acting as spawning grounds and feeding area for many fish and invertebrates. Given their occurrence in remote parts of the planet, research on CWC habitats has largely been derived from remotely-sensed marine spatial data. However, with ever-developing marine data acquisition and processing methods and non-ubiquitous nature of infrastructure, many studies are completed in isolation resulting in large inconsistencies. Here, we present a concise review of marine remotely-sensed spatial raster data acquisition and processing methods in CWC habitats to highlight trends and knowledge gaps. Sixty-three studies that acquire and process marine spatial raster data since the year 2000 were reviewed, noting regional geographic location, data types ('acquired data') and how the data were analyzed ('processing methods'). Results show that global efforts are not uniform with most studies concentrating in the NE Atlantic. Although side scan sonar was a popular mapping method between 2002 and 2012, since then, research has focused on the use of multibeam echosounder and photogrammetric methods. Despite advances in terrestrial mapping with machine learning, it is clear that manual processing methods are largely favored in marine mapping. On a broader scale, with large-scale mapping programs (INFOMAR, Mareano, Seabed2030), results from this review can help identify where more urgent research efforts can be concentrated for CWC habitats and other vulnerable marine ecosystems. [ABSTRACT FROM AUTHOR]

Cold-water corals (CWCs) are frequently found at cold seep areas. However, the relationship between fluid seepage and CWC development is not clear. Here, for the first time, we report the occurrences, species identification, mineralogy, carbon and oxygen isotopes, as well as elemental compositions of fossil CWC skeletons from gas-hydrate-bearing sediment in drilling cores from the South China Sea (SCS). Three sites (GMGS-08, GMGS-09B, and GMGS-16) were investigated but CWCs were only found at one site (GMGS-09B). Interestingly, the CWCs were found in three horizons and they were all embedded with authigenic carbonates. Three genera of fossil CWCs (Crispatotrochus sp., Solenosmilia sp. and Enallopsammia sp.) were identified. The CWC fragments are predominantly aragonite. The CWCs exhibit δ13C values between −8.4‰ and −0.6‰ that are significantly higher than δ13C values of the associated seep carbonates (δ13C values with an average of −55.6‰, n = 19), which indicates a carbon source other than methane for the CWCs. It appears that authigenic carbonates provide a substratum for coral colonization. Bathymetric high points, appropriate water temperature and stronger bottom-water currents at site GMGS-09B might be crucial to keep conditions favorable for the growth of CWCs in the studied area. In addition, high trace-element concentrations of Cr, Ni, Pb, U, Ba, Th, and Sr suggest that the CWCs are influenced by strong fluid seepage that can reach the water-sediment interface, and associated microbial activity. Hence, it also becomes evident that CWCs in hydrocarbon-rich seepage areas not only provide a critical constraint on the impact of fluid emission on the bottom water chemistry, but also are likely to be very precise recorders of the end time of cold seep activity. [ABSTRACT FROM AUTHOR]