Proxy reconstructions from marine sediment cores indicate peak temperatures in the first half of the last and current interglacial periods (the thermal maxima of the Holocene epoch, 10,000 to 6,000 ...years ago, and the last interglacial period, 128,000 to 123,000 years ago) that arguably exceed modern warmth
. By contrast, climate models simulate monotonic warming throughout both periods
. This substantial model-data discrepancy undermines confidence in both proxy reconstructions and climate models, and inhibits a mechanistic understanding of recent climate change. Here we show that previous global reconstructions of temperature in the Holocene
and the last interglacial period
reflect the evolution of seasonal, rather than annual, temperatures and we develop a method of transforming them to mean annual temperatures. We further demonstrate that global mean annual sea surface temperatures have been steadily increasing since the start of the Holocene (about 12,000 years ago), first in response to retreating ice sheets (12 to 6.5 thousand years ago), and then as a result of rising greenhouse gas concentrations (0.25 ± 0.21 degrees Celsius over the past 6,500 years or so). However, mean annual temperatures during the last interglacial period were stable and warmer than estimates of temperatures during the Holocene, and we attribute this to the near-constant greenhouse gas levels and the reduced extent of ice sheets. We therefore argue that the climate of the Holocene differed from that of the last interglacial period in two ways: first, larger remnant glacial ice sheets acted to cool the early Holocene, and second, rising greenhouse gas levels in the late Holocene warmed the planet. Furthermore, our reconstructions demonstrate that the modern global temperature has exceeded annual levels over the past 12,000 years and probably approaches the warmth of the last interglacial period (128,000 to 115,000 years ago).
A Gram-stain-negative, rod-shaped, motile and aerobic marine bacterium, designated strain NBU2595
, was isolated from marine sediment sampled on Meishan Island, located in the East China Sea. Strain ...NBU2595
grew at 10-40 °C (optimum, 37 °C), at NaCl concentration of 0-10.0 % (w/v; optimum, 0.5 %) and at pH 6.0-8.0 (optimum, pH 7.0). Catalase and oxidase activities and H
S production were positive. Methyl red reaction and hydrolysis of casein, starch and Tweens 20, 40, 60 and 80 were negative. The major cellular fatty acids were summed feature 8 (C
7
and/or C
6
), C
2-OH and C
3-OH. The sole respiratory quinone was ubiquinone 10. The major polar lipids were phosphatidylglycerol, phosphatidylcholine, phosphatidylethanolamine and phosphatidylmonomethylethanolamine. Comparative analysis of 16S rRNA gene sequences showed highest similarity to
CL-UU02
(97.9%), and low similarities (<92.9 %) to other species. Phylogenetic analyses indicated that strain NBU2595
clustered with the genus
and was closely related to
CL-UU02
. The average nucleotide identity and digital DNA-DNA hybridization values between strain NBU2595
and the related species of the genus
were well below the thresholds for prokaryotic species delineation. The DNA G+C content was 66.5 mol%. Based on its phenotypic, chemotaxonomic and genotypic data, strain NBU2595
should be placed in the genus
as representing a novel species, for which the name
sp. nov. is proposed. The type strain is NBU2595
(=MCCC 1K04773
=KCTC 82223
).
Bacterial and archaeal communities inhabiting the subsurface seabed live under strong energy limitation and have growth rates that are orders of magnitude slower than laboratory-grown cultures. It is ...not understood how subsurface microbial communities are assembled and whether populations undergo adaptive evolution or accumulate mutations as a result of impaired DNA repair under such energy-limited conditions. Here we use amplicon sequencing to explore changes of microbial communities during burial and isolation from the surface to the >5,000-y-old subsurface of marine sediment and identify a small core set of mostly uncultured bacteria and archaea that is present throughout the sediment column. These persisting populations constitute a small fraction of the entire community at the surface but become predominant in the subsurface. We followed patterns of genome diversity with depth in four dominant lineages of the persisting populations by mapping metagenomic sequence reads onto single-cell genomes. Nucleotide sequence diversity was uniformly low and did not change with age and depth of the sediment. Likewise, there was no detectable change in mutation rates and efficacy of selection. Our results indicate that subsurface microbial communities predominantly assemble by selective survival of taxa able to persist under extreme energy limitation.
•A historically polluted marine sediment from the National Interest Site of Bagnoli-Coroglio (Naples) was used for the study.•Chemical characterization of the sediment revealed the presence of 16 ...different PAHs with a concentration range between 19.4 µg g−1 and 636 µg g−1.•Several batch tests were performed to simulate a sediment-washing operation and evaluate the ability of selected surfactants to mobilize in aqueous PAHs.•Surfactant solutions resulted 30 times more efficient than water.•PAHs mobilization can be increased with a series of multiple sediment washing.
The persistent presence of Polycyclic Aromatic Hydrocarbons (PAHs) in soils and sediments due to their chemical properties requires new methods to mobilize and make them more available for remediation purposes. In this work, the evaluation of the abilities of eight different non-ionic sugar-based and totally biodegradable surfactants, such as synthetic alkyl polyglycosides (APGs), biological sophorolipids (SLs) and biological rhamnolipids (RLs), was conducted in order to provide a preliminary guideline for the selection of the surfactant and the technical approach for PAHs extraction from the sediment. The reference sample was a marine sediment collected from Bagnoli (Naples, Italy) that was characterized to evaluate the level of PAHs contamination, which resulted equal to 3.51 g Kg−1 of total PAHs in the sediment. By using surfactants solutions with a surfactant concentration five times greater than critical micelle concentration (Cs = 5x CMC), a preliminary washing test in batch configuration was conducted, then followed by multiple consecutive washes (MCW) of the sediment to assess the solubilization of PAHs from the sediment by the action of selected surfactants. The results show an evident advantage given by the employment of each studied surfactant in mobilizing PAHs, compared to distilled water as benchmark. In detail, the synthetic alkyl polyglycosides APG2 led to a 3.4 % of total PAHs mobilization in the preliminary washing test with a maximum peak of 9.8 % for a single compound. The MCW test demonstrates that more consecutive washes can increase the amount of total PAHs removed, with a similar contribution from each wash, and that biosurfactants can be more attractive after several washes thanks to the increased capacity of PAHs mobilization. Interestingly, the high efficiency of surfactant to mobilize PAHs makes the soil washing a more attractive technology for removing PAHs from the marine sediments.
This study investigates the presence of microplastics (MPs) in seawater, sediments, and organisms along the coastal areas of Da Nang, Vietnam. The results obtained revealed MP concentrations ranging ...from 111 to 304 MPs/L in seawater and 2267 to 4600 MPs/kg in sediment. In organisms such as oysters, mussels, crabs, snails, and fish, MP levels ranged from 1.8 to 17.3 MPs/g (wet weight). Fiber MPs were found to be predominant across seawater, sediment, and organisms. The study identified eight, ten, and eleven types of MPs in seawater, sediment, and organisms, respectively, with Nylon, Polytetrafluoroethylene (PTFE), and Ethylene vinyl alcohol (EVOH) being the most prevalent. Notably, MP concentrations were significantly higher in benthic organisms such as oysters, mussels, and crabs compared to fish (t-test, p < 0.05), suggesting habitat dependency. Similar concentrations, shapes, and types of MPs in seawater, sediments, and organisms demonstrate a tendency for MP accumulation in aquatic organisms within the marine environment.
•First comprehensive study of microplastics in coastal areas of Da Nang, Vietnam•Dominant microplastic types in seawater, sediments, and organisms were identified.•Dominance of fiber microplastics across seawater, sediments, and organisms•Identification of Nylon, PTFE, and EVOH as predominant microplastic types•Habitat-dependent microplastic contamination in benthic organisms
Antibiotic resistance genes (ARGs) have been steadily increasing due to the extensive overuse of antibiotics in the marine environment. Currently, the research considering ARGs distribution in marine ...ecosystems gains more interest. As the coastal sea has been regarded as one of the most polluted areas by antibiotic contaminants in China. However, no comprehensive review of the spatial distribution of ARGs in marine environment surrounding China. The main objective of this review is to investigate the level, characteristic, and spatial distribution of ARGs in the marine environment (seawater and sediments) surrounding China. Key sea areas, such as Bohai Sea, Yellow Sea, East China Sea, and South China Sea were selected in this review. The marine environment was the reservoir of ARGs, and ARGs in seawater were generally 1 to 2 orders of magnitude higher than that in sediments. Total ARGs were more abundant in the Yellow Sea, followed by the Bohai Sea, the East China Sea, and the South China Sea. This study raises questions regarding the spread and distribution for antibiotic resistance in marine environments.
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•QnrA was the predominant ARG in the marine areas surrounding China.•The relative abundances of ARGs in seawater were higher than that in sediments.•The Yellow Sea held the highest relative abundance of ARGs.•Human activities have impacts on the abundance of ARGs in the marine environment.
Vanadium (V) is a redox-sensitive trace metal that typically exists in one of three oxidation states (+3, +4 and +5) in natural waters; a feature increasingly used in paleoredox studies of ancient ...marine sediments. However, our knowledge of V geochemistry in low-oxygen marine environments is still limited, especially regarding interactions of V with reduced iron minerals such as green rust. Carbonate green rusts (GRCO3) are mixed FeII/FeIII-phases found in some modern ferruginous settings, such as Lake Matano (Indonesia), and were likely abundant in ancient ferruginous marine systems where they may have played an essential role in authigenic V enrichments in sediments. Here, we present an abiotic pathway of V removal from seawater via reduction and adsorption onto amorphous GRCO3. Suspensions of the freshly precipitated GRCO3 (1 g L−1) were added to vanadate (1 mg VV L−1 initial concentration) in anoxic synthetic seawater solutions. Vanadium removal by GRCO3 was rapid and efficient, with 92 – 99% of V removed in under 20 seconds. Synchrotron-based X-ray absorption near edge structure (XANES) spectroscopy showed that VV adsorbed by GRCO3 was partially reduced to a mixture of VV and VIV, with the average oxidation state of adsorbed V increasing (+4.3 to +4.7) with increasing solution pH (7.5 to 8.5). Upon subsequent exposure to aerated seawater, V-bearing GRCO3 oxidized to lepidocrocite γ–FeO(OH) within 24 h, with concomitant reduction of all solid-phase VV to VIV. During oxidation, V was not released back into solution; rather, extended X-ray absorption fine structure (EXAFS) modeling revealed that VIV was structurally incorporated into lepidocrocite as octahedral vanadyl (VO2+). Our work further constrains the aqueous geochemistry of V, which has implications for understanding V cycling and removal mechanisms in both modern and ancient marine systems.
Vanadium (V) is a promising paleoredox tracer in ancient marine sediments due its range of possible oxidation states (+3 to +5) and its unique redox-sensitivity. However, the interactions between V ...and the sulfide minerals common under ancient depositional conditions remain poorly studied. Iron monosulfide (FeS) is the first sulfide phase to form in anoxic-sulfidic waters and sediments, and an important precursor for sedimentary pyrite. Here we investigate the adsorption of dissolved VV by freshly precipitated FeS under conditions relevant to marine waters. We report near complete removal of aqueous V (94–98%; ∼2 × 10−5 M) by FeS (1 g L−1) in anoxic seawater within 24 h. Synchrotron-based X-ray absorption spectroscopy (XAS) at the V and Fe K-edges shows that aqueous VV was rapidly (<60 s) reduced to solid-phase VIII during reductive sorption by FeS. Iron K-edge and X-ray diffraction data show that the products of the subsequent oxidation of VIII-bearing FeS were elemental sulfur and lepidocrocite. Solid-phase V was oxidized within 24 h from +2.97 to +4.0, with no loss of V to solution. EXAFS analysis suggests, based on the predominance of V┄Fe backscatters at ∼3.0 Å, that octahedral VIV may have been incorporated in the structure of lepidocrocite during its formation. These results provide valuable insight into the relationship of V and FeS in marine environments, including the adsorption mechanism and V speciation relevant to the fate of V during early diagenesis in marine sediments.
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•FeS rapidly adsorbs and reduces vanadate (VV) to VIII in anoxic seawater.•Upon oxidation, V co-precipitates with lepidocrocite and structurally incorporates.•Results suggest a new one-way path for V sequestration in euxinic environments.
Dissolved organic matter (DOM) in marine sediment pore waters derives largely from decomposition of particulate organic matter and its composition is influenced by various biogeochemical and ...oceanographic processes in yet undetermined ways. Here, we determine the molecular inventory of pore water DOM in marine sediments of contrasting depositional regimes with ultrahigh-resolution mass spectrometry and complementary bulk chemical analyses in order to elucidate the factors that shape DOM composition. Our sample sets from the Mediterranean, Marmara and Black Seas covered different sediment depths, ages and a range of marine environments with different (i) organic matter sources, (ii) balances of organic matter production and preservation, and (iii) geochemical conditions in sediment and water column including anoxic, sulfidic and hypersaline conditions. Pore water DOM had a higher molecular formula richness than overlying water with up to 11,295 vs. 2114 different molecular formulas in the mass range of 299–600Da and covered a broader range of element ratios (H/C=0.35–2.19, O/C=0.03–1.19 vs. H/C=0.56–2.13, O/C=0.15–1.14). Formula richness was independent of concentrations of DOC and TOC. Near-surface pore water DOM was more similar to water column DOM than to deep pore water DOM from the same core with respect to formula richness and the molecular composition, suggesting exchange at the sediment–water interface. The DOM composition in the deeper sediments was controlled by organic matter source, selective decomposition of specific DOM fractions and early diagenetic molecule transformations. Compounds in pelagic sediment pore waters were predominantly highly unsaturated and N-bearing formulas, whereas oxygen-rich CHO-formulas and aromatic compounds were more abundant in pore water DOM from terrigenous sediments. The increase of S-bearing molecular formulas in the water column and pore waters of the Black Sea and the Mediterranean Discovery Basin was consistent with elevated HS- concentrations reflecting the incorporation of sulfur into biomolecules during early diagenesis. Sulfurization resulted in an increased average molecular mass of DOM and higher formula richness (up to 5899 formulas per sample). In sediments from the methanogenic zone in the Black Sea, the DOM pool was distinctly more reduced than overlying sediments from the sulfate-reducing zone. Bottom and pore water DOM from the Discovery Basin contained the highest abundances of aliphatic compounds in the entire dataset; a large fraction of abundant N-bearing formulas possibly represented peptide and nucleotide formulas suggesting preservation of these molecules in the life inhibiting environment of the Discovery Basin. Our unique data set provides the basis for a comprehensive understanding of the molecular signatures in pore water DOM and the turnover of sedimentary organic matter in marine sediments.
Microbial transformation of arsenic (As) plays a key role in As biogeochemical cycling and affects the mobility, bioavailability, and toxicity of As. This study aims to investigate the accumulation ...of As in marine sediments at different water depths in the East China Sea and reveal the abundance and diversity of the aioA, arrA, arsC, and arsM genes through quantitative real-time polymerase chain reaction (qPCR) and high-throughput sequencing. Results showed that the As content in sediments ranged from 5.53 mg kg−1 to 17.70 mg kg−1, which decreased with water depth. Abundant As biotransformation genes with low diversity were identified in these sediments, of which arsM and arrA were the most abundant. Significant positive correlation exists between the arsM and arrA gene abundance and between arsC and aioA, indicating the co-occurrence of the As biotransformation genes in microbes in marine sediments. Metagenomics analysis revealed that arsM gene was mainly distributed in Alphaproteobacteria, Solibacteres, Deltaproteobacteria, Clostridia, and Bacilli in these sediments. Among the sediment properties, total N, total S, C/N, and TOC were important factors that shaped the abundance profile of the genes involved in As transformation. This study provides a picture of As biotransformation genes in marine sediments from the East China Sea, which may affect As transformation and the ultimate fate of As in a marine environment.
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•As content in marine sediments from the East China Sea decreased with water depth.•As biotransformation genes were analyzed by metagenomics in marine sediments.•arsM and arrA were abundant and co-existed in marine sediments.•α-, δ-Proteobacteria, Solibacteres, Clostridia, were main microbes carrying arsM.•Total N, S, C/N and TOC were important factors shaping the diversity of these genes.
This study depicts the As distribution and its biotransformation genes in marine sediments from the East China Sea.
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