Search

Permanently cold deep-sea sediments (2500-3500 m water depth) with and without indications of thermogenic hydrocarbon seepage were exposed to naphtha to examine the presence and potential of cold-adapted aerobic hydrocarbon-degrading microbial populations. Monitoring these microcosms for volatile hydrocarbons by GC-MS revealed sediments without in situ hydrocarbons responded more rapidly to naphtha amendment than hydrocarbon seep sediments overall, but seep sediments removed aromatic hydrocarbons benzene, toluene, ethylbenzene and xylene (BTEX) more readily. Naphtha-driven aerobic respiration was more evident in surface sediment (0-20 cmbsf) than deeper anoxic layers (>130 cmbsf) that responded less rapidly. In all cases, enrichment of Gammaproteobacteria included lineages of Oleispira, Pseudomonas, and Alteromonas known to be associated with marine oil spills. On the other hand, taxa known to be prevalent in situ and diagnostic for thermogenic hydrocarbon seepage in deep sea sediment, did not respond to naphtha amendment. This suggests a limited role for these prevalent seep-associated populations in the context of aerobic hydrocarbon biodegradation., Competing Interests: Declaration of competing interest Authors declare that they have no known competing financial interests or personal relationships that could influence the work reported in this paper., (Copyright © 2024 The Authors. Published by Elsevier Ltd.. All rights reserved.)

Paleocene deposits of the Subbetic Zone (southern Spain) provide outstanding evidence of the influence of sea mountains on deep marine currents. This part of the Betic Cordillera External Zones corresponds to the distal and deepest area of the original basin, where hemipelagic sedimentation prevailed during most of the Turonian-early Lutetian interval. This sedimentation is recorded by the so-called Capas Rojas and Quipar-Jorquera formations, units up to 250 m and 425 m thick, respectively, predominantly consisting of marls and marl/limestone alternations. These units draped and smoothed an irregular submarine topography of fault-bounded Mesozoic carbonate blocks. Some of these blocks became uplifted and subaerially exposed after a mid-Danian tectonic episode, transforming the Subbetic Zone in an archipelago during the late Danian-early Selandian interval. The emerged blocks were colonized by Microcodium -producing terrestrial plants, Microcodium consisting of aggregates of submilimetric monocrystalline calcite grains. Massive resedimentation of these grains into depressed zones of the archipelago resulted in discrete accumulations up to 100 m thick but of comparatively modest extent (≤150 km2) of calcarenites rich in Microcodium remains. The study of one of these calcarenite units, the Olivares Formation, demonstrates that most of its constituent Microcodium remains were brought to the deep sea by turbidity currents, but were subsequently reworked by oscillatory and unidirectional bottom-currents. The analysis of the Capas Rojas Formation in its type section and surrounding areas, where Microcodium -rich calcarenites are absent, demonstrates that the Danian-Selandian succession is riddled with hiatuses, which resulted in a drastic thickness reduction of the interval. Clearly, the rugged sea floor topography resulting from the mid-Danian tectonic event enhanced the sedimentary transport capacity of bottom-currents that, in addition to piling-up Microcodium -rich calcarenites in restricted zones, disturbed the hemipelagic sedimentation elsewhere in the Subbetic Zone. From late Thanetian times onwards the background hemipelagic sedimentation typical of the Capas Rojas progressively resumed throughout the Subbetic Zone, recording the gradual abatement of the sea floor relief by protracted erosion and/or subsidence. • Change of the bathyal Subbetic to an archipelago recorded by redeposited Microcodium • Pre- and post-archipelago weak deep-sea currents favored hemipelagic deposition. • The archipelago rugged sea-floor topography boosted the strength of deep-sea currents. • Deep-sea currents reworked calciturbidites and created hiatuses in hemipelagites. [ABSTRACT FROM AUTHOR]

The equilibrium partition coefficient of strontium (K Sr eq ) between aqueous solutions and calcite is still poorly known, even though it is a valuable parameter for studies involving the use of calcite trace element geochemistry for reconstructing paleoenvironments and fluid chemistry. In this paper we use pore fluid data from deep sea carbonate sediments to constrain K Sr eq at low temperature (5–17 °C) and show that the derived values are consistent with laboratory calcite precipitation experiments at 25 °C when the latter are corrected for kinetic effects. Using these low-temperature values, and experimental data available at higher temperature based on replacement reactions, we show that all of the data can be accounted for by a single formulation based on the thermodynamics of the relevant components of seawater-like fluids and the SrCO 3 –CaCO 3 solid solution. The value of pore fluid data is that the fluids and carbonate sediment have been in contact for millions of years so local equilibrium is approached, the overall system can be treated with one-dimensional models, and the temperature is constrained. These natural systems provide an opportunity to investigate low-temperature equilibrium in the carbonate system that is difficult to probe in the laboratory because of sluggish exchange kinetics. We estimate values of K Sr eq using measured Sr and Ca concentrations in pore fluid and sediment solid calcite and a numerical model of sediment deposition, reaction and transport. The model is used to fit the Sr, Ca, and sulfate concentrations observed in pore fluids of several calcite-dominated sites that we believe are optimal for understanding Sr partitioning. Combining the pore fluid results with experimental measurements at higher temperature results in the following expression which applies for the temperature range 0–200 °C: K S r eq T = 0.025 exp Δ G r , 0 R 1 298.15 - 1 T where ΔG r,0 is the free energy change associated with the exchange reaction and temperature is in Kelvin. The uncertainty is approximately ±20%. Recently summarized thermodynamic data yield ΔG r,0 = 1.2 kcal/mol (5.0 kJ/mol) which fits well the lower limit of the high temperature data. The corresponding activity coefficient for the SrCO 3 component in the calcite crystal structure is 5.4 for the lower value of ΔG r,0 , and 3.17 for the higher value. The derived low-temperature values of K Sr eq of 0.020 to 0.025 (for 0 °C to 25 °C) have implications for models of marine carbonate diagenesis, and the interpretation of vein carbonate Sr/Ca in oceanic crust. Published data showing much higher K Sr values in Mg-bearing solutions are not representative of equilibrium values for either Mg or Sr. [ABSTRACT FROM AUTHOR]

Purpose: There is a growing understanding that methane hydrates (MHs) distributed globally in permafrost and deep sea sediments present an enormous unconventional reservoir of methane (CH4); however, there is also increasing concern about their role in the global climate change. The study focuses on the evaluation of the environmental conditions in the deep Adriatic Sea during the Last Glacial Maximum (LGM, 21.5–18.3 ka BP) and presently with respect to MHs potential occurrence. Materials and methods: The MHs phase stability diagram was calculated in order to evaluate the methane hydrate stability zone (MHSZ) by using the Croatian Legacy Data and the digital bathymetry map of the Adriatic Sea obtained from the Croatian Hydrocarbon Agency (CHA). Environmental data from different surveys published in the scientific literature were used to assess the environmental conditions in the deep Adriatic Sea during the LGM and present. The sea level rise of 100 m since the end of the LGM was taken into consideration. The volume of methane in place (MIP) as an estimation of the amount of CH4 stored in MHs deposits at standard conditions of pressure and temperature (SPT, T0 = 273.15 K, P0 = 0.101325 MPa) was calculated by using combined gas law VSPT = (P×V/T) × (TSPT/PSPT). Results and discussion: Evaluation of the MHs phase stability diagram for the Adriatic Sea in present environmental conditions has revealed that MHs are exactly at the boundary of stability. This has been calculated for the potential temperature of 13 °C, the salinity of 3.87% (data measured at the E2-M3A deep ocean observatory of the Southern Adriatic), and the average geothermal gradient of 17 °C km−1 reported in the literature and verified by the Croatian Legacy Data of CHA. According to the published literature, LGM deep sea temperature was 2–4 ° C lower and seawater was saltier. Consequently, the estimation of MHSZ during the LGM taking into consideration the temperature of 10 °C and salinity of 3.98% revealed a potential deposit of methane in place (MIP) of more than 415 × 109 m3, the majority of which probably dissociated in the sea/atmosphere system in the last 18 ka. Conclusions: The results have shown that MHs reservoir in the deep sea Adriatic basin shows boundary instability for MHs occurrence which might be of importance for studying the role of MHs in climate change. Further research is needed as follows: (1) thermodynamic modeling in order to understand if the MHs dissociation is concluded; and (2) in the case of the transient condition, seismic data analysis in order to reveal the presence of a relic bottom simulating reflection. [ABSTRACT FROM AUTHOR]

δ18O signature of marine deep-sea cherts was previously used to reconstruct past ocean temperature and oceanic bottom water δ18O through the Cenozoic and Mesozoic periods. Oxygen isotopes in deep-sea cherts which were never exposed to meteoric water exhibit a wide range of values indicating that the evolution and maturation of biogenic amorphous opal (opal-A) to opal-CT and microquartz chert is accompanied by isotopic changes. We measured δ18O of diatom opal-A, opal-CT, and microquartz chert in downcore profiles of sediment cores ODP 795 and 799 from the Sea of Japan. Diatom opal-A, opal-CT and microquartz chert were separated and purified from the bulk sediment. This was followed by XRD, SEM/EDS and XPS to identify and quantify the mineral phases, the qualitative elemental concentrations and the amounts of authigenic clays. Diatom opal-A transforms to opal-CT and microquartz chert when it is deposited in sediment originally rich in diatoms relative to other lithologic constituents, such as clay. Diatom opal-A δ18O is in the range of 34–38‰. δ18O of opal-CT is ∼25‰ at the first phase transformation at 330 mbsf in ODP 795 and 420 mbsf in ODP 799. This phase transformation occurs at a temperature of about 40 °C. δ18O of opal-CT remains essentially unchanged until it undergoes the second phase transformation to microquartz chert at 470 mbsf in ODP 795 and at 580 mbsf in ODP 799, at which point its δ18O decreases abruptly to ∼20‰. This phase transformation occurs at a temperature of about 60 °C. The δ18O values of opal-CT and microquartz chert appear to reflect equilibrium formation temperatures of silica corresponding to the geothermal gradient and the local porewater δ18O. The δ18O of opal-CT and microquartz chert are controlled by the geothermal temperatures and compositions of pore waters during polymorphic transformations deep within the sediment, indicating that the δ18O of these phases cannot be used to determine temperature or composition of seawater during diatom growth. [ABSTRACT FROM AUTHOR]

Mineral magnetic and geochemical investigations were carried out on a short sediment core collected from the eastern Southwest Indian Ridge (ESWIR) to study the variations in the source components. The magnetic concentration parameter χ arm (representing the concentration of stable single domain (SSD) sized grains), magnetic grain size ratios χ arm /χ lf , χ arm /SIRM, geochemical ratios Fe/Ti, Co/Zn, and Zn/Fe and Ba content serve as hydrothermal indicators, all of which show a distinct top - bottom variability. The magnetomineralogical parameters S-ratio and coercivity (H c) also follow these variations, suggesting an increased contribution of hydrothermal components in the top 15 cm of the core. Significant enrichments of Fe, Mn, and Mg in the samples, along with depletions of detrital elements Al, Si, Rb, Zr, Hf, and Nb in the element/Upper Continental Crust (UCC) values, show that the majority of the detrital component is locally sourced. Thermomagnetic measurements of samples indicate that the major remanence carrier is magnetite in the core, along with minor contributions from titanomagnetite, hematite, and iron sulfides. • First detailed mineral magnetic investigation of metalliferous sediments from SWIR. • Hydrothermal and detrital contributions to the sediments are unmixed. • Results show increased hydrothermal contribution on top section of the core. • Thermomagnetic analysis shows major remanence carrier is magnetite in the core. [ABSTRACT FROM AUTHOR]

ABSTRACT The nucleocytoplasmic large DNA viruses (NCLDV) of eukaryotes (proposed order, “Megavirales”) include the families Poxviridae, Asfarviridae, Iridoviridae, Ascoviridae, Phycodnaviridae, Marseilleviridae, and Mimiviridae, as well as still unclassified pithoviruses, pandoraviruses, molliviruses, and faustoviruses. Several of these virus groups include giant viruses, with genome and particle sizes exceeding those of many bacterial and archaeal cells. We explored the diversity of the NCLDV in deep sea sediments from the Loki’s Castle hydrothermal vent area. Using metagenomics, we reconstructed 23 high-quality genomic bins of novel NCLDV, 15 of which are related to pithoviruses, 5 to marseilleviruses, 1 to iridoviruses, and 2 to klosneuviruses. Some of the identified pithovirus-like and marseillevirus-like genomes belong to deep branches in the phylogenetic tree of core NCLDV genes, substantially expanding the diversity and phylogenetic depth of the respective groups. The discovered viruses, including putative giant members of the family Marseilleviridae, have a broad range of apparent genome sizes, in agreement with the multiple, independent origins of gigantism in different branches of the NCLDV. Phylogenomic analysis reaffirms the monophyly of the pithovirus-iridovirus-marseillevirus branch of the NCLDV. Similarly to other giant viruses, the pithovirus-like viruses from Loki’s Castle encode translation systems components. Phylogenetic analysis of these genes indicates a greater bacterial contribution than had been detected previously. Genome comparison suggests extensive gene exchange between members of the pithovirus-like viruses and Mimiviridae. Further exploration of the genomic diversity of Megavirales in additional sediment samples is expected to yield new insights into the evolution of giant viruses and the composition of the ocean megavirome. IMPORTANCE Genomics and evolution of giant viruses are two of the most vigorously developing areas of virus research. Lately, metagenomics has become the main source of new virus genomes. Here we describe a metagenomic analysis of the genomes of large and giant viruses from deep sea sediments. The assembled new virus genomes substantially expand the known diversity of the nucleocytoplasmic large DNA viruses of eukaryotes. The results support the concept of independent evolution of giant viruses from smaller ancestors in different virus branches.

Cosmic spherules collected from deep sea sediments of the Indian Ocean having different textures such as scoriaceous (4), relict-bearing (16), porphyritic (35) and barred olivine (2) were investigated for petrography, as well as high precision oxygen isotopic studies on olivine grains using secondary ion mass spectrometry (SIMS). The oxide FeO/MgO ratios of large olivines (>20 μm) in cosmic spherules have low values similar to those seen in the olivines of carbonaceous chondrite chondrules, rather than matching the compositions of matrix. The oxygen isotope compositions of olivines in cosmic spherules have a wide range of δ 18 O, δ 17 O and Δ 17 O values as follows: −9 to 40‰, −13 to 22‰ and −11 to 6‰. Our results suggest that the oxygen isotope compositions of the scoriaceous, relict-bearing, porphyritic and barred spherules show provenance related to the carbonaceous (CM, CV, CO and CR) chondrites. The different types of spherules that has experienced varied atmospheric heating during entry has not significantly altered the Δ 17 O values. However, one of the relict-bearing spherules with a large relict grain has Δ 17 O = 5.7‰, suggesting that it is derived from 16 O-poor material that is not recognized in the meteorite record. A majority of the spherules have Δ 17 O ranging from −4 to −2‰, similar to values in chondrules from carbonaceous chondrites, signifying that chondrules of carbonaceous chondrites are the major contributors to the flux of micrometeorites, with an insignificant fraction derived from ordinary chondrites. Furthermore, barred spherule data shows that during atmospheric entry an increase in ∼10‰ of δ 18 O value surges Δ 17 O value by ∼1‰. [ABSTRACT FROM AUTHOR]

The seawater radiogenic neodymium ( 143 Nd/ 144 Nd) isotope signature is an invaluable tool for the reconstruction of past deep water provenance. Sedimentary foraminifera or fish teeth are among the most reliable archives known for Nd isotope based reconstructions of past seawater. As the distribution and preservation of these archives are limited, the extraction of hydrogenetic ferromanganese oxyhydroxides from bulk sediments provide an easily applicable alternative. This method, however, implies the risk of generating artefacts due to the possible release of non-seawater derived Nd during the extraction procedure. Here we revisit and further investigate the reliability of the extraction of seawater derived Nd isotope signatures via leaching of bulk deep sea sediments with two commonly used buffered acetic acid and acid-reductive mix solutions. Repeated application of such stepwise leaching procedures to different non-decarbonated sediments from distinct settings across the deep Atlantic Ocean shows pronounced elemental and Nd isotope trends during the leaching process in the laboratory. Our results show that seawater Nd isotope compositions are extracted together with carbonates and manganese oxides only at the beginning of the leaching series. During chemical extraction, the carbonates effectively work as a buffer preventing acid-induced mobilisation of Fe oxides and volcanogenic material. Once this buffer is consumed, potentially present volcanogenic phases are considerably attacked, leading to shifts in the extracted Nd isotope signal of up to + 12 epsilon units. Such volcanogenic phases are a significant source of contaminant Nd reflected by markedly elevated Al/Nd signatures. We consequently propose a revised weak leaching protocol for carbonate bearing deep sea sediments, which is simple to use, provides excellent agreement with data obtained from uncleaned foraminifera, and can be easily screened for contamination. [ABSTRACT FROM AUTHOR]

Wolfgang Schott is the pioneer in paleoceanography and has established this research field within marine geology. His papers from the first half of the twentieth century are all published in German; therefore, the most inspiring results are given here as original quotes in English, since they paved the ground for all scientific discussions on climate stratigraphy, past ocean currents, and glacial interglacial cycles. [ABSTRACT FROM AUTHOR]

In order to determine the sediment provenance and potential iron (Fe) source in abyssal environment, deep sea surface sediments from a transect of the equatorial Pacific Ocean (0–10°N along ~131°W) were investigated for clay mineral assemblages, the elemental composition of smectite, and biogeochemical characteristics, including total organic carbon (TOC), total nitrogen (TN), and adenosine triphosphate (ATP), all of which are closely related to the specific sediment source and cellular process. Not only the relative composition of clay minerals but also two types of smectite (Fe-rich and Al-rich) were detected along the latitudinal transect. The composition of smectite collected close to the equator (0–6°N) was more Fe-rich compared to that of smectite collected at 7–10°N, which was Al-rich. These two distinct compositional groups indicate the existence of at least two sources of smectite at the study sites: (1) Fe-rich smectite supplied from South America and (2) Al-rich smectite derived from Asia and North America. These results suggest that the elemental composition of smectite can be used alongside other conventional proxies to differentiate the provenances of abyssal sediments in the central Pacific Ocean based on the southernmost latitude with Asian and North American sources (7°N) as the present-day mean Intertropical Convergence Zone (ITCZ) position. Moreover, an increase in the Fe content of smectite (N0: 22.1 wt%, N6: 19.3 wt%, and N10: 16.5 wt%) is positively correlated with the latitudinal distribution of ATP concentrations in surface sediments. Therefore, Fe-rich smectite may be important as a Fe source associated with microbial activity in deep sea environments with potential consequences for microbe–mineral interactions. • Elemental composition of smectite in deep sea sediments. • Contributions of Fe-rich smectite as a bioavailable iron to the Equatorial Pacific Ocean. • Microbial activity along the transect of equatorial Pacific Ocean. • Clay mineral provenance of sediments along the transect of equatorial Pacific Ocean. [ABSTRACT FROM AUTHOR]

Marine bacteria colonising deep-sea sediments beneath the Arctic ocean, a rapidly changing ecosystem, have been shown to exhibit significant biogeographic patterns along transects spanning tens of kilometres and across water depths reaching several thousands of metres (Jacob et al., 2013). Jacob et al. adopted what has become a classical view of microbial diversity based on operational taxonomic units clustered at the 97% sequence identity level of the 16S rRNA gene and observed a very large microbial community replacement at the Hausgarten Long-Term Ecological Research station (Eastern Fram Strait). Here, we revisited these data using the oligotyping approach with the aims of obtaining new insights into ecological and biogeographic patterns associated with bacterial microdiversity in marine sediments and of assessing the level of concordance of these insights with previously obtained results. Variation in oligotype dispersal range, relative abundance, co-occurrence, and taxonomic identity were related to environmental parameters such as water depth, biomass, and sedimentary pigment concentration. This study assesses ecological implications of the new microdiversity-based technique using a well-characterised dataset of high relevance for global change biology.

Reconstructing past modes of ocean circulation is an essential task in paleoclimatology and paleoceanography. To this end, we combine two sedimentary proxies, Nd isotopes ( ε Nd ) and the 231 Pa/ 230 Th ratio, both of which are not directly involved in the global carbon cycle, but allow the reconstruction of water mass provenance and provide information about the past strength of overturning circulation, respectively. In this study, combined 231 Pa/ 230 Th and ε Nd down-core profiles from six Atlantic Ocean sediment cores are presented. The data set is complemented by the two available combined data sets from the literature. From this we derive a comprehensive picture of spatial and temporal patterns and the dynamic changes of the Atlantic Meridional Overturning Circulation over the past ∼25 ka. Our results provide evidence for a consistent pattern of glacial/stadial advances of Southern Sourced Water along with a northward circulation mode for all cores in the deeper (>3000 m) Atlantic. Results from shallower core sites support an active overturning cell of shoaled Northern Sourced Water during the LGM and the subsequent deglaciation. Furthermore, we report evidence for a short-lived period of intensified AMOC in the early Holocene. [ABSTRACT FROM AUTHOR]

The diversity of microorganisms inhabiting the deep sea surface sediments was investigated in 9 stations (700-1900 m depth) in the Levantine basin by 454 massive tag sequencing of the 16S rDNA V4 region using universal primers. In total, 108,811 reads (an average of 10,088 per sample) were assigned to 5014 bacterial and 966 archaeal operational taxonomic units (OTUs; at 97% cut off). The 55% of the reads were of archaea, indicating dominance of archaea over bacteria at eight of the stations. The diversity and estimated richness values were high (e.g., H' ranged from 5.66 to 7.41 for bacteria). The compositions of the microorganisms at all stations were remarkably similar, with Bray-Curtis similarities of 0.53-0.91 and 0.74-0.99 for bacterial and archaeal orders respectively. At two stations, very high abundances of only a few genera (Marinobacterium, Bacillus, Vibrio, Photobacterium) were accountable for the dissimilarities documented compared to the other deep sea stations. Half of the bacterial reads (51%) belonged to the phylum Proteobacteria, comprising mainly Gammaproteobacteria (41-72% of the proteobacterial reads per sample), Deltaproteobacteria (12-29%), Alphaproteobacteria (7-18%) and Betaproteobacteria (3-14%). The most abundant bacterial family was Sinobacteraceae (order Xanthomonadales) with 5-10% of total bacterial reads per sample. Most abundant reads (15.4% of all microbial reads) were affiliated with Marine Group 1 archaea, putatively capable of ammonia oxidation (213 OTUs), and bacteria involved in nitrification were found in all samples. The data point to the significant role that chemolithotrophic carbon assimilation and nitrification fill in the oligotrophic deep sea Levant sediments. [ABSTRACT FROM AUTHOR]

In the present study, the ecological distribution of marine Actinobacteria isolated from seamount and non-seamount stations in the Tyrrhenian Sea was investigated. A collection of 110 isolates was analyzed by Automated Ribosomal Intergenic Spacer Analysis (ARISA) and 16S rRNA gene sequencing of representatives for each ARISA haplotype (n = 49). Phylogenetic analysis of 16S rRNA sequences showed a wide diversity of marine isolates and clustered the strains into 11 different genera, Janibacter , Rhodococcus , Arthrobacter , Kocuria , Dietzia , Curtobacterium , Micrococcus , Citricoccus , Brevibacterium , Brachybacterium and Nocardioides . Interestingly, Janibacter limosus was the most encountered species particularly in seamounts stations, suggesting that it represents an endemic species of this particular ecosystem. The application of BOX-PCR fingerprinting on J. limosus sub-collection (n = 22), allowed their separation into seven distinct BOX-genotypes suggesting a high intraspecific microdiversity among the collection. Furthermore, by screening the biotechnological potential of selected actinobacterial strains, J. limosus was shown to exhibit the most important biosurfactant activity. Our overall data indicates that Janibacter is a major and active component of seamounts in the Tyrrhenian Sea adapted to low nutrient ecological niche. [ABSTRACT FROM AUTHOR]

Metal speciation study in combination with major element chemistry of deep sea sediments provided possible metal enrichment pathways in sediments collected from environmentally different locations of Central Indian Ocean Basin (CIB). Metal speciation study suggests that Fe–Mn oxyhydroxide phase was the major binding phase for Ni, Cu and Pb in the sediments. The second highest concentrations of all these metals were present within the structure of the sediments. Easily reducible oxide phase (within the Fe–Mn oxyhydroxide binding phases) was the major host for all the three metals in the studied sediments. Major element chemistry of these sediments revealed that there was an increased tendency of Cu and Ni to get incorporated into the deep sea sediment via the non-terrigenous Mn-oxyhydroxide fraction, whereas, Pb gets incorporated mostly via amorphous Fe-hydroxides into the sediment from the CIB. This is the first attempt to provide an insight into the mechanism of metal enrichment in sediment that host vast manganese nodule. [ABSTRACT FROM AUTHOR]

A paleoceanographic reconstruction of the southern Panama Basin for the last 23.000 years, based on the benthic foraminiferal analysis from the deep sea core ME0005A-24JC (0.01°N, 86.28°W, water depth 2941) is presented. Cluster and SHEBI (SHE Analysis for Biozone Identification) analyses performed on the benthic foraminiferal assemblages, evidence a faunal turnover in the early Holocene at 14 ky BP. Between 23 and 14 ky BP, Fursenkoina rotundata , Hoeglundina elegans , Globobulimina affinis , Globobulimina pacifica , Cibicidoides wuellerstorfi and Uvigerina hispidocostata were common. Conversely, from 14 ky to the present, the assemblage is represented by Chilostomella oolina , Laticarinina pauperata , and Uvigerina proboscidea . This faunal turnover suggests significant fluctuations in oxygen content at the sea floor and the organic matter (OM) influx, which could reflect: (1) fluctuations in the surface productivity related to the equatorial divergence and, (2) OM advection caused by the dynamic of the deep sea currents. Paleoproductivity estimates and benthic foraminiferal rates depict a general trend towards lower values since the Last Glacial Maximum (LGM) with a conspicuous change at 14 ky BP. Therefore, the paleoceanographic reconstructions of the ME0005A-24JC core suggest a transition from La Niña-like conditions during the LGM to El Niño-like conditions in the recent, as previously proposed for the Eastern Equatorial Pacific. Estimates of the paleo-intensity of deep sea currents based on the relative percentage abundance of the epifaunal foraminifera Cibicidoides wuellerstorfi suggest stronger deep sea currents on the Carnegie Ridge before 14 ky BP. [ABSTRACT FROM AUTHOR]

Marine bacteria colonizing deep-sea sediments beneath the Arctic ocean, a rapidly changing ecosystem, have been shown to exhibit significant biogeographic patterns along transects spanning tens of kilometers and across water depths of several thousand meters (Jacob et al., 2013). Jacob et al. (2013) adopted what has become a classical view of microbial diversity -- based on operational taxonomic units clustered at the 97% sequence identity level of the 16S rRNA gene -- and observed a very large microbial community replacement at the HAUSGARTEN Long Term Ecological Research station (Eastern Fram Strait). Here, we revisited these data using the oligotyping approach and aimed to obtain new insight into ecological and biogeographic patterns associated with bacterial microdiversity in marine sediments. We also assessed the level of concordance of these insights with previously obtained results. Variation in oligotype dispersal range, relative abundance, co-occurrence, and taxonomic identity were related to environmental parameters such as water depth, biomass, and sedimentary pigment concentration. This study assesses ecological implications of the new microdiversity-based technique using a well-characterized dataset of high relevance for global change biology. [ABSTRACT FROM AUTHOR]

Archaearepresent a significant portion of biomass in the marine sediments and may play an important role in global carbon cycle. However, the identity and composition of deep sea sedimentArchaeaare unclear. Here, we used the archaeal 16S rRNA gene primers to determine the diversity and community structure ofArchaeafrom shallow water (<100 m) and deep water (>1500 m) sediments in the South China Sea. Phylogenetically the archaeal community is separated between the shallow- and deep sea sediments, with the former being dominated by theThaumarchaeotaand the latter by the Marine Benthic Group B, E and the South African GoldMine Euryarchaeotal Group as well asThaumarchaeota. Sand content showed significant correlation withThaumarchaeota, suggesting that the porous media may create an oxic environment that allowed these aerobic organisms to thrive in the surface sediments. The carbon isotope composition of total organic carbon was significantly correlated to the distribution of archaeal groups, suggesting thatArchaeaoverall may be constrained by the availability or sources of organic carbon in the sediments of the South China Sea. [ABSTRACT FROM AUTHOR]

Abstract: We carried out several experiments with carbonate-rich and clay-rich sediments that were redeposited in plastic cubes or in 1-meter-long cylindrical tubes with the aim of investigating the sensitivity of the depositional remanent magnetization (DRM) to various environmental and physical parameters. In contrast to previous studies, we did not observe any difference in the DRM acquired with or without saline water for either kind of sediment. Taking advantage of a gelatin that fixes the position of particles in suspension, we were able to measure the magnetization of suspended sediments within water-filled columns and thus to test the degree of alignment of magnetic grains. The magnetization of clay-rich sediments was not far from saturation but the magnetization was considerably reduced after deflocculation because the large flocs that favored alignment of magnetic grains were destroyed by the deflocculant. Similarly, the large flocs found at the bottom of the deposition tubes also reveal an efficient magnetic alignment. In contrast, the weak magnetization of the carbonate-rich sediments with small flocs yielded accurate and well-grouped magnetization directions that were not sensitive to deflocculation. Only a fraction of magnetic grains was mechanically oriented by the field in this case because of the weak net magnetic moments of the grains embedded within small flocs. The DRM was constrained by redeposition in plastic cubes performed without gelatin and with different field intensities. The DRM intensity of the carbonate-rich sediments is linearly related to field strength, which attests to their suitability for studies of relative paleointensity. Tests performed with mud from several stratigraphic levels in different marine sediment cores failed to reveal a significant influence of carbonate content on DRM, which suggests a relatively minor role of lithological changes on records of relative paleointensity. [Copyright &y& Elsevier]

The aim of this study was to determine the existence of cosmic spherules in oceanic sediments. Two cores recovered from the Clarion-Clipperton fault zone (northeastern Pacific Basin) contain magnetic spherules of extraterrestrial origin. Their chemical compositions and morphological features show the degree of heterogeneity of cosmic material reaching the earth's surface. The diverse origins of spherules from the Pacific Ocean explains their diverse composition and does not allow for the classification of the material into a single group. In addition, the time interval over which sediments accumulated extends for an estimated period of approximately 200 000 years to the present. [ABSTRACT FROM AUTHOR]

Bacteria and fungi were recovered from deep-sea sediments of the Middle Pacific, West Pacific, and East Pacific by using different isolation media. More than 150 strains were isolated, 90 of which were selected for initial identification and cytotoxic activity tests. The strains were identified by 16S rRNA gene sequencing and grouped into 19 different genera, including Acinetobacter, Arthrobacter, Bacillus, Burkholderia, Halomonas, Hyphomicrobium, Kocuria, Marinobacter, Microbacterium, Micrococcus, Nocardiopsis, Phialocephala, Planomicrobium, Planococcus, Leifsonia, Pseudoalteromonas, Pseudomonas, Psychrobacter, Shewanella, and Streptomyces. The cytotoxicities of the strains toward the mouse temperature-sensitive p34cdc2 mutant tsFT210, murine lymphoma P388 and human leukemia K562 cell lines were determined preliminarily by the sulforhodamine-B (SRB) or methyl thiazolyl tetrazolium (MTT) bioassay method. The metabolites from three bacteria ( Bacillus sp. EP39, Pseudomonas sp. WP133, and Pseudomonas sp. WP168) and one fungus ( Phialocephala sp. FL30r) had strong cytotoxic activities (Inhibition rate > 50%). Nine cytotoxic compounds belonging to phenazine, indole, polyether, and ester were isolated from them through bioassay-guided chromatography and identified by spectral methods. [ABSTRACT FROM AUTHOR]

The detection of periodic fluctuations is important in the quest for a deeper understanding of the drivers of past climates in the interests of being better able to understand the climate changes which are likely in the decades to come. Paleoclimatological information derived from natural archives is typically accompanied by chronological uncertainty and variable temporal resolution, both of which complicate the analysis of their time series and both are often ignored. This has, however, changed in recent years with the development of statistical tools supporting, e.g. spectral analysis tasks, which aim to take these problems into account. In cases where the original data is no longer available, it may not be possible to assess the reliability of published reports of periods detected. In this study we aim to test/model whether or not a signal for a given period can be robustly detected from a sedimentary proxy record considering its mean sampling resolution and degree of chronological uncertainty. To achieve this aim, annually sampled time series free of gaps and timescale error were modeled with white or red noise, resampled in a controlled way to simulate different time resolutions with timescale uncertainty, ultimately mimicking a real-life sedimentary record. In fact, an ensemble of potential timescales was retrieved, and their spectral characteristics explored. It was found that: (i) although sampling frequency (i.e. temporal spacing) is limiting from the side of the smallest-period, (ii) at higher mean sampling resolutions, it can ameliorate the detectability of periodic signals even in the presence of timescale error; furthermore, (iii) the increase in mean sampling resolution is less influential in an autocorrelated time series, since more information is retained due to the phenomenon of persistence. An online tool called CUSP was also developed, which gives a suggestion whether a given period can be considered to be present in a robust way utilizing our test results. [Display omitted] • Pseudoproxy time series modeled with chronological uncertainty and variable temporal spacing. • Time series derived from white noise and red noise periodic signals separately. • Each chronological uncertainty and mean sampling resolution pair considered. • Threshold determined above which periodic signals cannot be robustly detected. • Developed tool helps testing the robustness of periodic signals in sedimentary records. [ABSTRACT FROM AUTHOR]

Recent studies of the sedimentary record of the Japan Trench indicate unique earthquake-induced depositional characteristics. To correlate such deposits to historical earthquakes, we studied the stratigraphy of two sedimentary cores obtained from basins of the Japan Trench at 7400 m and 7600 m water depth using paleomagnetic secular variation (PSV). Because of their high sedimentation rates, results show that excellent geomagnetic records are preserved in the sediments in spite of the great water depth. Paleomagnetic secular variation, especially declination during the past 3000 years revealing a distinctive feature of large oscillation, offers an opportunity to make precise stratigraphic correlations. Identification of boundaries between thick fine turbidite intervals and hemipelagite intervals was made based on rock magnetic properties. Successful applications of extraction of paleomagnetic data solely from the hemipelagic interval demonstrate that stratigraphic positions of turbidite in paleomagnetic secular variation record are mutually well correlated in PSV variations. Even over long distances between sites, the turbidites induced by earthquakes can be correlated exactly. The turbidite ages were determined by referring to the PSV master curve. Especially, the ages of turbidite units regarded as induced by the Jogan earthquake can be inferred from two cores that closely approximate its documented age. • Rockmagnetic properties can distinguish fine grain turbidite from hemipelagite. • Paleomagnetic secular variation chronology is available even for deep sea deposits. • Synchronicity of earthquake induced turbidite was confirmed. [ABSTRACT FROM AUTHOR]

Abstract: An investigation of the distribution, speciation and methylation of the mercury in deep-sea sediments of the Mediterranean Sea was performed. The samples were collected at different locations in the Western and Eastern Basins of the Mediterranean during the cruise of the Italian research vessel Urania in summer 2003 as part of MERCYMS project. Total mercury (HgT) and methylmercury (MeHg) in pore water and sediments was determined down the sediment profile and coupled with other biogeochemical parameters. The diffusive fluxes of HgT and MeHg were calculated to estimate the importance of sediment–water exchange as potential sources of HgT and MeHg. In addition, isotopically enriched 199Hg was used to determine the methylation potentials. The concentrations of HgT in sediments ranged between 0.06 and 2.23 nmol g−1 and vary irregularly with depth, which may reflect changes or redistribution during diagenetic processes. No correlation between HgT and organic carbon content was found, but a relatively high proportion of MeHg to HgT of approx. 2.0% was observed. The integrated flux of HgT was estimated to be 109 kmol year−1 and agrees well with the mass balance calculation preformed for total underwater emissions of HgT in the Mediterranean Sea of 80 kmol year−1 by Rajar et al. [Rajar, R., Četina, M., Horvat, M., Žagar, D., 2007-this issue. Mass balance of mercury in the Mediterranean Sea. Mar. Chem. doi:10.1016/j.marchem.2006.10.001]. The emissions of MeHg were estimated to be 14 kmol year−1 and indicate that deep-sea sediments could be an important source of the MeHg content in marine biota. It was found that accumulation of MeHg in surficial sediments of the Mediterranean is not directly related to the potential rates of bacterial Hg methylation. Much of the MeHg produced in the sediments are lost to the overlying water. Our results suggest that MeHg production depends on partitioning of Hg(II) influenced by the organic carbon content in the sediment. Reduction of organic carbon in sediment could increase pore water Hg(II) and enhance bacterial production of MeHg. [Copyright &y& Elsevier]

A new probe for autonomous high precision temperature measurements in deep sea sediments has been developed by Fa. Antares and the University of Bremen and extensively tested during several expeditions. The miniaturized temperature data loggers (MTLs) were constructed to be extremely robust, small (16 cm long) and easy to operate in waterdepths up to 6000 m. The temperature range extends from −5 to +60°C with an absolute accuracy of ±0.1 K. Higher absolute accuracy requires calibration with a high precision thermometer. The resolution of the A/D converter is 16 bit which leads to a temperature resolution of 0.001 K. The logging duration and sampling rate can be chosen independently. Up to 18 h of measurement are possible with the highest sample rate of 1 s. Data are stored in the non-volatile memory which holds up to 64 800 measurements. The probe is configured and data downloaded without opening the pressure case by using specialized software and interface hardware. The MTLs offer a wide variety of marine science applications wherever a high precision temperature measurement is of interest. Our main application is the investigation of temperature gradients in deep sea sediments where measurements of gradients over a large depth interval are required by fixing loggers on either different kinds of core barrels or on long lances. During four expeditions, we used the loggers to measure sediment temperature gradients in several geological settings. The design of the attachments to the different carriers was varied to optimize the results for different needs. These tests were highly successful and the data of high quality. Therefore the loggers can be recommended for regular use in marine applications. [Copyright &y& Elsevier]

Rock magnetic parameters of sediments reflect palaeoenvironmental and palaeoclimatic conditions during deposition in the marine and in the continental realm. The processes which lead to enhancement or degradation of the magnetic properties are well known – though not completely understood. They include variable terrigenous material influx, organic and inorganic in situ formation of ferromagnetic minerals and diagenetic destruction of these minerals. Cyclical changes in the magnetic mineral assemblages occurring at the orbital periodicities involved in standard Milankovitch theory have been observed in numerous sedimentary records, at least during the last seven million years. This confirms the relationship between rock magnetism and past global change. Quantitative interpretation of the magnetic signals, however, is still in its infancy and is hampered by the complex interplay of the signal formation processes. [ABSTRACT FROM AUTHOR]

Environmental controls affecting the composition and distribution of deep sea benthic foraminifera were analyzed in the Panama Basin (Eastern Equatorial Pacific). For this study, results of the analysis of a new set of 33 core-top samples from the upper-lower slope (714–3819 mbsf) were integrated with previous data from this area. The composition of the foraminiferal assemblages resembles a typical deep sea association, illustrating a close relationship with dissolved oxygen at the seafloor and indirectly with surface productivity. Low oxygen content and organic matter influx, as inferred in the eastern Panama Basin, are connected to terrigenous supply and seasonal upwelling on the Panama Bight and southern Costa Rica. Buliminids, bolivinids, and Epistominella spp. are common elements of the continental slope. In addition, physiographic aspects such as the type of substrate, turbidity fluxes, and bottom currents also exert control over some of the described taxa and defined morphogroups. A broad exploration of the infaunal/epifaunal relationships in the basin does not suggest a clear relationship with dissolved oxygen content. However, there are fluctuations in the proportion of some of the defined epifaunal morphogroups and selected taxa (e.g. Cibicidoides wuellerstorfi , Chilostomella oolina , and Hoeglundina elegans, among others) along the Carnegie Ridge. These changes are explained by the variable physiographic features (surface upwelling, strong bottom currents) that coalesce in this part of the Panama Basin. Furthermore, re-evaluation of the foraminiferal morphogroups in two deep sea cores that comprised the last 25 ky, indicate that some taxa of the recent samples (Cassidulina spp. and Siphouvigerina peregrina, among others) reacted to paleoproductivity and bottom current fluctuations at the end of the Last Glacial Maximum and the Younger Dryas. Despite the lack of ecological data in the foraminiferal assemblages for a large proportion of the Panama Basin, the application of selected taxa or morphogroups as proxies for paleoceanographic conditions is promising. • Detailed integration of the deep sea foraminiferal data for the Panama Basin, Eastern Equatorial Pacific. • The foraminiferal assemblages are related to both the dissolved oxygen content in sediments and the surface productivity. • Selected foraminiferal morphogroups have regional distributions along the basin. • Some of the analyzed foraminiferal morphogroups responded to paleoceanographic fluctuations since the Last Glaciation. [ABSTRACT FROM AUTHOR]

The nucleocytoplasmic large DNA viruses (NCLDV) of eukaryotes (proposed order, "Megavirales") include the families Poxviridae , Asfarviridae , Iridoviridae , Ascoviridae , Phycodnaviridae , Marseilleviridae , and Mimiviridae , as well as still unclassified pithoviruses, pandoraviruses, molliviruses, and faustoviruses. Several of these virus groups include giant viruses, with genome and particle sizes exceeding those of many bacterial and archaeal cells. We explored the diversity of the NCLDV in deep sea sediments from the Loki's Castle hydrothermal vent area. Using metagenomics, we reconstructed 23 high-quality genomic bins of novel NCLDV, 15 of which are related to pithoviruses, 5 to marseilleviruses, 1 to iridoviruses, and 2 to klosneuviruses. Some of the identified pithovirus-like and marseillevirus-like genomes belong to deep branches in the phylogenetic tree of core NCLDV genes, substantially expanding the diversity and phylogenetic depth of the respective groups. The discovered viruses, including putative giant members of the family Marseilleviridae , have a broad range of apparent genome sizes, in agreement with the multiple, independent origins of gigantism in different branches of the NCLDV. Phylogenomic analysis reaffirms the monophyly of the pithovirus-iridovirus-marseillevirus branch of the NCLDV. Similarly to other giant viruses, the pithovirus-like viruses from Loki's Castle encode translation systems components. Phylogenetic analysis of these genes indicates a greater bacterial contribution than had been detected previously. Genome comparison suggests extensive gene exchange between members of the pithovirus-like viruses and Mimiviridae Further exploration of the genomic diversity of Megavirales in additional sediment samples is expected to yield new insights into the evolution of giant viruses and the composition of the ocean megavirome. IMPORTANCE Genomics and evolution of giant viruses are two of the most vigorously developing areas of virus research. Lately, metagenomics has become the main source of new virus genomes. Here we describe a metagenomic analysis of the genomes of large and giant viruses from deep sea sediments. The assembled new virus genomes substantially expand the known diversity of the nucleocytoplasmic large DNA viruses of eukaryotes. The results support the concept of independent evolution of giant viruses from smaller ancestors in different virus branches., (Copyright © 2019 Bäckström et al.)