Spatial and temporal distribution of C37 alkenones in suspended materials in the northern East China Sea

• Published in: Palaeogeography, palaeoclimatology, palaeoecology palaeoclimatology, palaeoecology, 2018-03, Vol.493, p.102-110
• Main Authors: Ko, Tae Wook, Lee, Kyung Eun, Bae, Si Woong, Lee, Sunghye
• Format: Article
• Language: English
• Subjects: Emiliania huxleyi; Paleothermometer; Particulate organic matter; Productivity; Sea surface temperature
• ISSN: 0031-0182; 1872-616X
• DOI: 10.1016/j.palaeo.2018.01.004

The temporal and spatial distributions of long-chain (C37) alkenones in suspended materials in the northern East China Sea (ECS) were investigated to examine the applicability of alkenone unsaturation index as a proxy for sea surface temperature (SST) and that of total C37 alkenone concentration as a proxy for marine primary productivity. Surface and subsurface seawater samples were collected at three-month intervals (February, May, August, and November) during 2007–2010. The results showed that alkenones were synthesized throughout the year, with peaks in May. Alkenone temperatures corresponded to in situ temperatures. The vertical distribution of alkenone concentration indicated that alkenone production depth is the surface mixed layer (0–20m). These results indicate that alkenone temperatures from marine sediments on the continental shelf most likely reflect the annual average SST. No clear inferences could be made on the influence of nutrients and salinity on the alkenone temperature in this area. Seasonal changes in alkenone concentration were compared with those in chlorophyll-a concentration to investigate the suitability of using total C37 alkenone concentration as a proxy for productivity. Where the chlorophyll-a concentration was high, the alkenone concentration was low, and vice versa, because the main primary producer was not the coccolithophores. Therefore, it is not appropriate to use alkenone concentration as a primary productivity proxy in the ECS. However, comparisons to coccolithophore abundance show that total C37 alkenone concentration can be used as a haptophyte productivity proxy in this area. •Alkenones were synthesized throughout the year in the northern East China Sea.•Alkenone production depth was surface mixed layer.•Alkenone unsaturation index can be used as a proxy for annual mean SST.•Alkenone content can be used as a proxy for haptophyte productivity.