Different controls on sedimentary organic carbon in the Bohai Sea: River mouth relocation, turbidity and eutrophication

Xu, Yunping; Zhou, Shangzhe; Hu, Limin; Wang, Y.; Xiao, Wenjie

doi:10.1016/j.jmarsys.2017.12.004

Cited by 15 publications

(7 citation statements)

References 45 publications

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“…The reasonable explanation is that there might be some deposition hiatus between 3000 BP and 1855 CE of core CJ06-435. The calculated CSR in the upper layer (since 1855 CE, as calculated to 0.17-0.48 cm yr −1 ) and the lower layer (3000-8500 BP, as calculated to 0.016-0.057 cm yr −1 ) of core CJ06-435 are comparable to the nearby records by He et al (2019) and Xu et al (2018). Therefore, we only focused on the vegetation successions and climate change between 8500 and 3000 BP, and only gave a cautious discussion for the chronology uncertain interval in this study.…”

Section: Paleovegetation Reconstruction and Its Climate Significancesupporting

confidence: 80%

“…1; He et al, 2019), 0.04-0.06 cm yr −1 between 2000 BP to 1855 CE (in cores ZK228, HB-1 and GYDY, Fig. 1; He et al, 2019), and 0.35-1.38 cm yr −1 since 1855 CE (Wu et al, 2015;Qiao et al, 2017;Xu et al, 2018). Although core CJ06-435 is offshore compared to the other cores (e.g., H9601, H9602, ZK228, HB-1, ZK1 and GYDY), and it should have a lower CSR compared to those cores.…”

Section: Paleovegetation Reconstruction and Its Climate Significancementioning

confidence: 97%

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Holocene vegetation dynamics in response to climate change and hydrological processes in the Bohai region

et al. 2020

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Abstract. Coastal vegetation both mitigates the damage inflicted by marine disasters on coastal areas and plays an important role in the global carbon cycle (i.e., blue carbon). Nevertheless, detailed records of changes in coastal vegetation composition and diversity in the Holocene, coupled with climate change and river evolution, remain unclear. To explore vegetation dynamics and their influencing factors on the coastal area of the Bohai Sea (BS) during the Holocene, we present high-resolution pollen and sediment grain size data obtained from a sediment core of the BS. The results reveal that two rapid and abrupt changes in salt marsh vegetation are linked with the river system changes. Within each event, a recurring pattern – starting with a decline in Cyperaceae, followed by an increase in Artemisia and Chenopodiaceae – suggests a successional process that is determined by the close relationship between Yellow River (YR) channel shifts and the wetland community dynamics. The phreatophyte Cyperaceae at the base of each sequence indicate lower saline conditions. Unchannelized river flow characterized the onset of the YR channel shift, caused a huge river-derived sediment accumulation in the floodplain and destroyed the sedges in the coastal depression. Along with the formation of a new channel, lateral migration of the lower channel stopped, and a new intertidal mudflat was formed. Pioneer species (Chenopodiaceae, Artemisia) were the first to colonize the bare zones of the lower and middle marsh areas. In addition, the pollen results revealed that the vegetation of the BS land area was dominated by broadleaved forests during the Early Holocene (8500–6500 BP) and by conifer and broadleaved forests in the Middle Holocene (6500–3500 BP), which was followed by an expansion of broadleaved trees (after 3500 BP). The pollen record indicated that a warmer Early and Late Holocene and colder Middle Holocene were consistent with previously reported temperature records for East Asia. The main driving factors of temperature variation in this region are insolation, the El Niño–Southern Oscillation and greenhouse gases forcing.

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Section: Paleovegetation Reconstruction and Its Climate Significancesupporting

confidence: 80%

Section: Paleovegetation Reconstruction and Its Climate Significancementioning

confidence: 97%

Holocene vegetation dynamics in response to climate change and hydrological processes in the Bohai region

et al. 2020

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“…The detailed instrumental capabilities were described by Xu et al. (2018). Biomarkers were identiﬁed based on interpretation of mass spectra and comparison with the NIST library.…”

Section: Methodsmentioning

confidence: 99%

Distribution, Source, and Burial of Sedimentary Organic Carbon in Kermadec and Atacama Trenches

Luo

et al. 2021

JGR Biogeosciences

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Knowledge of sedimentary organic carbon (OC) in hadal trenches, the deepest ocean realm, is rudimentary. Here, we conducted a comprehensive analysis of total OC (TOC), stable and radio-carbon isotopes (δ 13 C and Δ 14 C), and biomarkers (e.g., n-alkanes, n-alkanols and n-fatty acids) in 12 sediment cores collected from hadal (trench axis) and non-hadal (abyssal plains and slopes) settings of the Kermadec Trench (Southwestern Pacific) and Atacama Trench (Southeastern Pacific) regions. Our results show that the TOC in the Atacama Trench region (0.86% ± 0.69%) is significantly higher than that of the Kermadec Trench region (0.29% ± 0.08%), likely related to different surface primary productivity. In both trench regions, the hadal sites are generally characterized by more negative δ 13 C, higher TOC/TN ratio, and similar or higher abundance ratio of terrigenous/marine biomarkers as compared to the non-hadal sites, suggesting the selective preservation of terrigenous biogenic/fossil OC at the hadal trench axis. The linear increase in 14 C age with sediment depth in non-hadal cores reflects steady depositional conditions, whereas seven out of eight hadal sediment cores show 14 C age reversals presumably due to occasional mass-transport deposits. Our results suggest (1) a strong heterogeneity in sedimentary OC characteristics between trenches and within each trench and (2) relatively high accumulation rates of terrigenous OC in both the Kermadec Trench (0.35 ± 0.04 g m −2 yr −1 ) and the Atacama Trench (1.4 ± 0.5 g m −2 yr −1 ). Thus, hadal trenches appear to represent an important environment for terrigenous carbon deposition in the deep ocean. Plain Language SummaryThe hadal zone mainly composed of trenches is the deepest ocean realm with water depth over 6,000 m. Due to the challenge of observation and sampling at the extreme depth, the hadal zone is one of the least explored ecosystems on Earth. Limited studies have suggested that hadal trenches have higher benthic biomass and microbial activity compared to surrounding abyssal plains, which has overturned a traditional view that the hadal zone is a "biological desert." Here, we conducted comprehensive geochemical analysis of sedimentary organic carbon in Kermadec Trench (Southwestern Pacific) and Atacama Trench (Southeastern Pacific). Our goal is to understand source, distribution, and burial of organic carbon that is an important food and energy source for benthic organisms in hadal trenches. We have obtained three key findings. (1) While extensive heterogeneity in sedimentary organic carbon in trench interior and between two trenches, the trench bottoms generally have higher fractional abundance of terrigenous organic carbon compared to surrounding abyssal/bathyal sites. (2) Mass-transport deposits induced by episodic events (like earthquakes) profoundly influence organic carbon content and compositions in hadal trenches. (3) The hadal zone is an important but previously overlooked sink for terrigenous organic carbon in the deep ocean. XU ET AL.

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“…The detailed procedures for geochemical analyses have been described elsewhere (Xu et al, 2017; Yao et al, 2015). These geochemical parameters include organic carbon (OC) content, nitrogen (N) content, atomic OC/N ratio, stable carbon isotope ratio (δ 13 C), mineral surface area (SA), and grain size.…”

Section: Methodsmentioning

confidence: 99%

Intact Ether Lipids in Trench Sediments Related to Archaeal Community and Environmental Conditions in the Deepest Ocean

Wu²,

Xiao

et al. 2020

JGR Biogeosciences

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Archaea play an important role in marine biogeochemical cycle; however, their phylogenetic distribution and lipid composition in the hadal zone (6–11 km water depth) are poorly known. Here, we analyzed archaeal membrane lipids and 16S rRNA gene sequences in sediments from Mariana Trench (MT), Massau Trench (MS), and New Britain Trench (NBT), varying from 1,560 to 10,840 m depth. Forty‐two intact polar lipids (IPLs) were identified, including glycerol dialkyl glycerol tetraethers (GDGTs), OH‐GDGTs, glycerol dialkyl diethers (GDDs), and archaeol (AR) with polar headgroups of monohexose (1G), dihexose (2G), trihexose (3G), and hexose‐phosphohexose (HPH). Compositional and spatial distribution patterns of archaeal lipids suggest benthic Thaumarchaeota as a major source for IPLs, consistent with the predominance of Thaumarchaeota genes (>80%). The redundancy analysis (RDA) based on lipid and 16S rRNA data separates samples into three groups: extremely deep water (MT), significant terrestrial influence (NBT 1, 4, and 6), and predominant marine influence (MS, NBT 2, 3, 7, and 10). 1G‐GDDs and 1G‐AR positively correlate with water depth, likely reflecting the adaptation of benthic archaea to elevated hydrostatic pressure or variation of archaeal community in trench sediments. Bathyarchaeota are more abundant in sediments receiving terrestrial input; this pattern was attributed to their capability of utilizing terrestrial organic matter as an energy source. Our study highlights important environmental influences (e.g., pressure and organic matter quality and quantity) on benthic archaeal community and archaeal IPL compositions, which should be considered when IPLs and core lipids are applied as chemotaxonomic markers and paleo‐proxies.

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Different controls on sedimentary organic carbon in the Bohai Sea: River mouth relocation, turbidity and eutrophication

Cited by 15 publications

References 45 publications

Holocene vegetation dynamics in response to climate change and hydrological processes in the Bohai region

Holocene vegetation dynamics in response to climate change and hydrological processes in the Bohai region

Distribution, Source, and Burial of Sedimentary Organic Carbon in Kermadec and Atacama Trenches

Intact Ether Lipids in Trench Sediments Related to Archaeal Community and Environmental Conditions in the Deepest Ocean

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