Biomarker Evidence of Relatively Stable Community Structure in the Northern South China Sea during the Last Glacial and Holocene

Abstract

High-resolution molecular abundance records for several marine biomarkers during the last glacial and Holocene have been generated for core MD05-2904 (19°27.32'N, 116°15.15'E, 2066 m water depth) from the northern South China Sea. The U K' 37 SST record indicates a 4.4°C cooling during the Last Glacial Maximum for this site, consistent with previous reconstructions. The contents of C 37 alkenones, dinosterol, brassicasterol, and C 30 alkyl diols are used as productivity proxies for haptophytes, dinoflagellates, diatoms, and eustigmatophytes, respectively. These records reveal that both individual phytoplankton group and total productivity increased by several factors during the LGM compared with those for the Holocene, in response to increased nutrient supply. However, the community structure based on biomarker percentages remained relatively stable during the last glacial-Holocene transition, although there were short-term oscillations.

Past dynamics of the East Asian monsoon: No inverse behaviour between the summer and winter monsoon during the Holocene

“…The alkenone SST estimates of core MD05-2904 for the last 25 ka have been published and discussed previously in He et al (2008). Different to our G. ruber s.s. Mg/Ca-based SST record, the alkenone SST record shows an abrupt warming (~2°C) at~14.6 ka and a cooling around 12 ka that is associated with the northern hemisphere Bølling Transition and the YD, respectively (Fig.…”

“…1 for core location) and was supplemented later by AMS-14 C dating (Ge et al, 2010). However, the new age model based on 14 C ages (Ge et al, 2010) would result in a much younger age for the low SSTs around 290 cm core depth that has been interpreted previously to reflect a cooling associated with the North Atlantic Younger Dryas (YD) event (He et al, 2008). Therefore, we rejected one 14 C age at 300,5 cm core depth (He et al, 2008) and correlated the MD05-2904 alkenone SST record to that of the nearby core GIK17940 (using alkenone SST data of Pelejero et al, 1999, and ages of Sarnthein et al, 2007).…”

“…1 for core location). The original age model by He et al (2008) for the upper 10 m of core MD05-2904 was established by correlating the G. ruber δ 18 O record with the G. ruber δ 18 O record of nearby core GIK17940-2 ; see Fig. 1 for core location) and was supplemented later by AMS-14 C dating (Ge et al, 2010).…”

“…yr BP have been assigned to the end of the YD (Alley et al, 1993;Grootes and Stuiver, 1997) and to the onset of the Bølling Transition (Stuiver et al, 1995;Stuiver and Grootes, 2000; see text for details). The assignment of these analogue ages is based on correlating the MD05-2904 alkenone SST record (He et al, 2008) with that of nearby core GIK17940 (using alkenone SST data of Pelejero et al, 1999, and ages of Sarnthein et al, 2007).…”

Introduction to the Special Section “Proxy Records and Mechanistic Studies of the Late Quaternary Paleoceanography of the Western Pacific Marginal Seas Using IMAGES Cores”

“…One group of biomarkers, the alkenones, have been used extensively to estimate SST by the degree of unstauration (the U k 37 ). In this special section, He et al (2008) reported a more innovative approach by using a suite of biomarkers for estimating past changes in productivity and phytoplankton community structure in the northern SCS over the last glacial and Holocene. Their results reveal that productivity was much higher during the glacial for all major phytoplankton groups, and thus for total productivity.…”