Description: Membrane lipids of marine planktonic archaea have provided unique insights into archaeal ecology and paleoceanography. However, past studies of archaeal lipids in suspended particulate matter (SPM) and sediments mainly focused on a small class of fully saturated glycerol dibiphytanyl glycerol tetraether (GDGT) homologues identified decades ago. The apparent low structural diversity of GDGTs is in strong contrast to the high diversity of metabolism and taxonomy among planktonic archaea. Furthermore, adaptation of archaeal lipids in the deep ocean remains poorly constrained. We report the archaeal lipidome in SPM from diverse oceanic regimes. We extend the known inventory of planktonic archaeal lipids to include numerous unsaturated archaeal ether lipids (uns-AELs). We further reveal (i) different thermal regulations and polar headgroup compositions of membrane lipids between the epipelagic (≤ 100 m) and deep (〉100 m) populations of archaea, (ii) stratification of unsaturated GDGTs with varying redox conditions, and (iii) enrichment of tetratetraunsaturated archaeol and fully saturated GDGTs in epipelagic and deep oxygenated waters, respectively. Such str atified lipid patterns are consistent with the typical distribution of archaeal phylotypes in marine environments. We, thus, provide an ecological context for GDGT-based paleoclimatology and bring about the potential use of uns-AELs as biomarkers for planktonic Euryarchaeota.

Description: We reconstruct the environmental evolution of the East China Sea in the past 14 kyr based on glycerol dialkyl glycerol tetraethers (GDGTs) in a sediment core from the subaqueous Yangtze River Delta. Two primary phases are recognized. Phase I (13.8–8 cal kyr BP) reflects a predominantly continental influence, showing distinctly higher concentrations of branched GDGTs (averaged 143 ng/g dry sediment weight, dsw) than isoprenoid GDGTs (averaged 36 ng/g dsw), high BIT index (branched vs. isoprenoid tetraethers) values (〉0.78) and a fluctuating GDGT-0/crenarchaeol ratio (R 0/5, varied from 0.52 to 3.81). Within this interval, temporal increases of terrestrial and marine influence are attributed to Younger Dryas (YD) (ca. 12.9–12.2 cal kyr BP) cold event and melt-water pulse (MWP) -1B (11.5–11.1 cal kyr BP), respectively. The prominent transition from 8 to 7.9 cal kyr BP shows a sharp decrease in BIT index value (〈0.4) and increase in crenarchaeol, which marks the beginning of phase II. Afterwards, the proxies remain relatively constant, which indicates that phase II (7.9 cal kyr BP-present) is a shelf sedimentary environment with high stand of sea level. Overall, the BIT index in our record serves as a good marker for terrestrial influence at the site, and likely reflects the flooding history of the region. The TEX86 (TetraEther Index of tetraethers consisting of 86 carbons) proxy is not applicable in phase I because of an excess terrestrial influence; but it seems to be valid for revealing the annual SST in phase II (21.6±0.9°C, n=49). In contrast, the MBT'/CBT (Methylation of Branched Tetraethers and Cyclization of Branched Tetraethers) proxy appears to faithfully record the annual mean air temperature (MAT) (14.3±0.63°C, n=68) and presents an integrated signal over the middle and lower Yangtze River drainage basin.

Description: We establish the cyst-theca relationship of the cyst species Trinovantedinium pallidifulvum Matsuoka 1987 based on germination experiments of specimens isolated from the Gulf of Mexico. We show that the motile stage is a new species, designated as Protoperidinium louisianensis. We also determine its phylogenetic position based on single-cell PCR of a single cell germinated from the Gulf of Mexico cysts. To further refine the phylogeny, we determined the LSU sequence through single-cell PCR of the cyst Selenopemphix undulata isolated from Brentwood Bay (Saanich Inlet, BC, Canada). The phylogeny shows that P. louisianensis is closest to P. shanghaiense, the motile stage of T. applanatum, and is consistent with the monophyly of the genus Trinovantedinium. Selenopemphix undulata belongs to a different clade than Selenopemphix quanta (alleged cyst of P. conicum), suggesting that the genus Selenopemphix is polyphyletic.

Description: From a large number of case studies on terrestrial deposits we know that Late Holocene climate fluctuations have an important impact on the terrestrial environments. However, it is hitherto not clear how the marine sediments can be used to shed light on the environment and climate change of the catchment. To provide such insight, we used the major element, trace element and rare earth element (REE) compositions in the southern Yellow Sea (SYS) sediments to reconstruct the changes in weathering and erosion of their source regions. The sediments originate predominantly from the upper crust of East China and are transported into the basin especially by the Yellow River (Huanghe) and to a lesser extent by the Yangtze River (Changjiang). The chemical index of alteration (CIA; 53.7–59.7) suggests low chemical weathering of the source rocks since the Middle Holocene. This is consistent with the relatively cool and arid climate in North China after the Holocene Megathermal. Comparison of element ratios, including Al/Ca, K/Ca, Al/Na, K/Na, Rb/Sr, Li/Ba and the CIA shows that we can use the latter as a robust proxy for climate change. The CIA-based mean annual precipitation and mean annual temperature show a series of climate fluctuations in the catchment. A relatively warm and humid Period I (5.3–2.9 cal. ka BP), a relatively cool and dry Period II (2.9–0.9 cal. ka BP) and an increasingly cool and dry Period III (0.9–0.3 cal. ka BP). These periods can be linked to climate intervals recognized elsewhere.

Description: Proxies based on long-chain alkane-1, mid-chain diols (diol for short) are obtaining increasing interest to reconstruct past upper ocean temperature and productivity. Here we evaluate performance of the sea surface temperature proxies (long-chain diol index (LDI), diol saturation index (DSI), and diol chain length index (DCI)), productivity and upwelling intensity proxies (two diol indices DIR and DIW and the combined diol index (CDI)), and the nutrient diol index (NDI) as a proxy for phosphate and nitrate levels. This evaluation is based on comparison of the diols in sediment trap samples from the upwelling region off NW Africa collected at 1.28 km water depth with daily satellite derived sea surface temperatures (SSTs), subsurface temperatures, productivity, the plankton composition from the trap location, monthly phosphate and nitrate concentrations, wind speed, and wind direction from the nearby Nouadhibou airport. The diol-based SST reconstructions are also compared the long-chain-alkenone-based SST reconstructions. The alkenone SSTs correlate best with satellite SST (r2 D0.60). Amplitude and absolute values agree very well as do the flux-corrected time series averages. For the diol proxies the situation is more complicated. Diol proxies including 1,14 diols lag trade wind speed by 30 d. Since wind is nearly always from the NNE to NNW and induces the upwelling, we relate the variability in these proxies to upwelling-induced processes. Correlation with the abundance of upwelling species and wind speed is best for.