ABSTRACTThe South China Sea (SCS) is the largest marginal sea of the western Pacific Ocean, yet little is known about archaeal distributions and TEX86-based temperatures in this unique oceanic setting. Here we report findings of abundances in both core lipids (CL) and intact polar lipids (IPL) ofArchaeafrom surface water (CL only) and core-top sediments from different regions of the SCS. TEX86-derived temperatures were also calculated for these samples. The surface water had extremely low abundances of CL (average of 0.05 ± 0.13 ng/liter;n= 75), with higher values present in regions where upwelling is known to occur. The core-top sediments had CL values of 0.1 to 0.9 μg/g, which are on the low end of CL concentrations reported for other marine sediments and may reflect the oligotrophic nature of the open SCS. The IPL ofArchaeaaccounted for 6 to 36.4% of total lipids (CL plus IPL), indicating that the majority of archaeal lipids in core-top sediments were derived from nonliving cells. The TEX86-based temperatures of surface water were overall lower than satellite-based sea surface temperatures or CTD-measuredin situtemperatures. The core-top sediment samples, however, had TEX86temperatures very close to the mean annual sea surface temperatures, except for samples with water depths of less than 100 m. Our results demonstrated low and heterogeneous distributions of archaeal lipids in surface water and core-top sediments of the SCS, which may reflect local or regional differences in productivity ofArchaea. While TEX86-based temperatures for core-top marine sediments at deep water depths (>100 m) generally reflected mean annual sea surface temperatures, TEX86temperatures in surface water varied basin wide and underestimated sea surface temperatures in most locations for the season when surface water samples were collected.
Sea-surface temperatures for the last 7200 years from the eastern Sunda Shelf, South China Sea: Climatic inferences from planktonic foraminiferal Mg/Ca ratios