Extracellular hydrolytic enzyme screening of culturable heterotrophic bacteria from deep-sea sediments of the Southern Okinawa Trough

The Southern Okinawa Trough is an area of focused sedimentation due to particulate matter export from the shelf of the East China Sea and the island of Taiwan. In order to understand the geomicrobiological characteristics of this unique sedimentary environment, bacterial cultivations were carried out for an 8.61 m CASQ core sediment sample. A total of 98 heterotrophic bacterial isolates were characterized based on 16S rRNA gene phylogenetic analysis. These isolates can be grouped into four bacterial divisions, including 13 genera and more than 20 species. Bacteria of the gamma-Proteobacteria lineage, especially those from the Halomonas ( 27 isolates) and Psychrobacter ( 20 isolates) groups, dominate in the culturable bacteria assemblage. They also have the broadest distribution along the depth of the sediment. More than 72.4% of the isolates showed extracellular hydrolytic enzyme activities, such as amylases, proteases, lipases and Dnases, and nearly 59.2% were cold-adapted exoenzyme-producers. Several Halomonas strains show almost all the tested hydrolases activities. The wide distribution of exoenzyme activities in the isolates may indicate their important ecological role of element biogeochemical cycling in the studied deep-sea sedimentary environment.

Fine-scale vertical distribution of bacteria in the East Pacific deep-sea sediments determined via 16S rRNA gene T-RFLP and clone library analyses

Although the deep-sea sediments harbor diverse and novel bacteria with important ecological and environmental functions, a comprehensive view of their community characteristics is still lacking, considering the vast area and volume of the deep-sea sedimentary environments. Sediment bacteria vertical distribution and community structure were studied of the E272 site in the East Pacific Ocean with the molecular methods of 16S rRNA gene T-RFLP (terminal restriction fragment length polymorphism) and clone library analyses. Layered distribution of the bacterial assemblages was detected by both methods, indicating that the shallow sediments (40 cm in depth) harbored a diverse and distinct bacterial composition with fine-scale spatial heterogeneity. Substantial bacterial diversity was detected and nine major bacterial lineages were obtained, including Acidobacteria, Actinobacteria, Bacteroidetes, Chloroflexi, Nitrospirae, Planctomycetes, Proteobacteria, and the candidate divisions OP8 and TM6. Three subdivisions of the Proteobacteria presented in our libraries, including the alpha-, gamma- and delta-Proteobacteria. Most of our sequences have low similarity with known bacterial 16S rRNA genes, indicating that these sequences may represent as-yet-uncultivated novel bacteria. Most of our sequences were related to the GenBank nearest neighboring sequences retrieved from marine sediments, especially from deep-sea methane seep, gas hydrate or mud volcano environments. Several sequences were related to the sequences recovered from the deep-sea hydrothermal vent or basalt glasses-bearing sediments, indicating that our deep-sea sampling site might be influenced to certain degree by the nearby hydrothermal field of the East Pacific Rise at 13A degrees N.

Black carbon and polycyclic aromatic hydrocarbons (PAHs) in surface sediments of China's marginal seas

This study investigates the distribution of black carbon (BC) and its correlation with total polycyclic aromatic hydrocarbons (I PAH) pound in the surface sediments of China's marginal seas. BC content ranges from < 0.10 to 2.45 mg/g dw (grams dry weight) in the sediments studied, and varied among the different coastal regions. The Bohai Bay sediments had the highest BC contents (average 2.18 mg/g dw), which comprises a significant fraction (27%-41%) of the total organic carbon (TOC) preserved in the sediments. In comparison, BC in the surface sediments of the North Yellow Sea, Jiaozhou Bay, East China Sea and the South China Sea is less abundant and accounted for an average of 6%, 8%, 14% and 5%, respectively, of the sedimentary organic carbon pool. The concentration of I PAH pound in the surface sediments ranges from 41 to 3 667 ng/g dw and showed large spatial variations among the sampling sites of different costal regions. The Bohai Bay has the highest I PAH pound values, ranging from 79 to 3 667 ng/g dw. This reflects the high anthropogenically contaminated nature of the sediments in the bay. BC is positively correlated to TOC but a strong correlation is not found between BC and I PAH pound in the surface sediments studied, suggesting that BC and PAHs preserved in the sediments are derived from different sources and controlled by different biogeochemical processes. Our study suggests that the abundance of BC preserved in the sediments could represent a significant sink pool of carbon cycling in China's marginal seas.

Seismic stratigraphy of the Qiongdongnan deep sea channel system, northwest South China Sea

Based on more than 4000 km 2D seismic data and seismic stratigraphic analysis, we discussed the extent and formation mechanism of the Qiongdongnan deep sea channel. The Qiongdongnan deep sea channel is a large incised channel which extends from the east boundary of the Yinggehai Basin, through the whole Qiongdongnan and the Xisha trough, and terminates in the western part of the northwest subbasin of South China Sea. It is more than 570 km long and 4-8 km wide. The chaotic (or continuous) middle (or high) amplitude, middle (or high) continuity seismic facies of the channel reflect the different lithological distribution of the channel. The channel formed as a complex result of global sea level drop during early Pliocene, large scale of sediment supply to the Yinggehai Basin, inversion event of the Red River strike-slip fault, and tilted direction of the Qiongdongnan Basin. The large scale of sediment supply from Red River caused the shelf break of the Yinggehai Basin to move torwards the S and SE direction and developed large scale of prograding wedge from the Miocene, and the inversion of the Red River strike-slip fault induced the sediment slump which formed the Qiongdongnan deep sea channel.

Diversity of Both the Cultivable Protease-Producing Bacteria and Their Extracellular Proteases in the Sediments of the South China Sea

Protease-producing bacteria are known to play an important role in degrading sedimentary particular organic nitrogen, and yet, their diversity and extracellular proteases remain largely unknown. In this paper, the diversity of the cultivable protease-producing bacteria and their extracellular proteases in the sediments of the South China Sea was investigated. The richness of the cultivable protease-producing bacteria reached 10(6) cells/g in all sediment samples. Analysis of the 16S rRNA gene sequences revealed that the predominant cultivated protease-producing bacteria are Gammaproteobacteria affiliated with the genera Pseudoalteromonas, Alteromonas, Marinobacter, Idiomarina, Halomonas, Vibrio, Shewanella, Pseudomonas, and Rheinheimera, with Alteromonas (34.6%) and Pseudoalteromonas (28.2%) as the predominant groups. Inhibitor analysis showed that nearly all the extracellular proteases from the bacteria are serine proteases or metalloproteases. Moreover, these proteases have different hydrolytic ability to different proteins, reflecting they may belong to different kinds of serine proteases or metalloproteases. To our knowledge, this study represents the first report of the diversity of bacterial proteases in deep-sea sediments.

Mesozoic-Cenozoic tectonic evolution of the Zhuanghai area, Bohai-Bay Basin, east China: the application of balanced cross-sections

The technique of balancing cross-sections, an important method for studying the tectonic history of sedimentary basins, has many applications. It enables one to compile charts for petroleum exploration and development, and growth sections of ancient structures can be restored so that the structural growth history can be studied. In order to study tectonic evolution in the Zhuanghai area of the Bohai-Bay basin, we selected two seismic profiles and compiled two structural growth sections. Based on the two balanced cross-sections, the evolution can be divided into four phases: the Triassic-Middle Jurassic phase, Late Jurassic - Cretaceous phase, Palaeogene extension phase, and Late Palaeogene-to-present phase. The whole area was uplifted during the Triassic-Middle Jurassic phase because of intense extrusion stress related to the Indo-China movement. During the Late Jurassic and Early Cretaceous, intense extension occurred in east China, and the whole area rifted, leading to the deposition of a thick sedimentary sequence. In the Late Cretaceous, the area suffered uplift and compression associated with the sinistral strike slip of the Tanlu fault. In the Palaeogene, a rifting basin developed in the area. Finally, it became stable and was placed in its present position by dextral strike-slip motion. In addition, some problems associated with compiling balanced cross-sections are discussed.

Sporopollen analysis of Core B10 in the southern Yellow Sea and the reflected characteristics of climate changes

Eight sporopollen zones have been divided based on the results of high-resolution sporopollen analysis of Core B10 in the southern Yellow Sea. Based on the results along with C-14 datings and the subbottom profiling data, climatic and environmental changes since the last stage of late Pleistocene are discussed. The main conclusions are drawn as follows: (1) the vegetation evolved in the process of coniferous forest-grassland containing broad-leaved treesconiferous and broad-leaved mixed forest --> coniferous and broad-leaved mixed forest-grassland prevailed by coniferous trees --> coniferous and broad-leaved mixed forest-grassland containing evergreen broad-leaved trees- coniferous and broad-leaved mixed forest-grassland prevailed by broad-leaved trees-deciduous broad-leaved forest-meadow containing evergreen broad-leaved trees- coniferous and broadleaved mixed forest-grassland prevailed by broad-leaved trees- coniferous and broad-leaved mixed forest containing evergreen broad-leaved trees; (2) eight stages of climate changes are identified as the cold and dry stage, the temperate and wet stage, the cold and dry stage, the warm and dry stage, the temperate and wet stage, the hot and dry stage, the temperate and dry stage, then the warm and dry stage in turn; (3) the sedimentary environment developed from land, to littoral zone, to land again, then to shore-neritic zone; and (4) the Yellow Sea Warm Current formed during early-Holocene rather than Atlantic stage.

Preliminary analysis of grain-size populations with environmentally sensitive terrigenous components in marginal sea setting

Terrigenous components were separated from the bulk sediment of Core A7 from the Okinawa Trough and Core A37 from the Ryukru Trench and grain-size distributions of these sub-samples were analyzed. Based upon an analysis of the grain-size data of the two sedimentary sequences, grain-size populations are identified to be sensitive to sedimentary environmental changes. The modal values and size ranges of the two main grain-size populations in Core A7 are evidently different from those of Core A37, indicating the spatial variability of sediment sources and transport processes between the two places. The downcore variations in the content of the environmentally sensitive grain-size populations reveal that during the accumulation of sedimentary material the environment remained relatively stable at the site where Core A7 was collected, except for the apparent events for the formation of two turbidite layers and a volcanic ash layer. However, the sedimentary sequence of Core A37 shows six sedimentary cycles, indicating a highly variable sedimentary environment at this location.

A comprehensive investigation of an offshore active fault in the Western Sagami Bay, central Japan

Offshore active faults, especially those in the deep sea, are very difficult to study because of the water and sedimentary cover. To characterize the nature and geometry of offshore active faults, a combination of methods must be employed. Generally, seismic profiling is used to map these faults, but often only fault-related folds rather than fracture planes are imaged. Multi-beam swath bathymetry provides information on the structure and growth history of a fault because movements of an active fault are reflected in the bottom morphology. Submersible and deep-tow surveys allow direct observations of deformations on the seafloor (including fracture zones and microstructures). In the deep sea, linearly aligned cold seep communities provide indirect evidence for active faults and the spatial migration of their activities. The Western Sagami Bay fault (WSBF) in the western Sagami Bay off central Japan is an active fault that has been studied in detail using the above methods. The bottom morphology, fractured breccias directly observed and photographed, seismic profiles, as well as distribution and migration of cold seep communities provide evidence for the nature and geometry of the fault. Focal mechanism solutions of selected earthquakes in the western Sagami Bay during the period from 1900 to 1995 show that the maximum compression trends NW-SE and the minimum stress axis strikes NE-SW, a stress pattern indicating a left-lateral strike-slip fault.

Modification to the Hardisty equation, regarding the relationship between sediment transport rate and particle size

Bagnold-type bed-load equations are widely used for the determination of sediment transport rate in marine environments. The accuracy of these equations depends upon the definition of the coefficient k(1) in the equations, which is a function of particle size. Hardisty (1983) has attempted to establish the relationship between k(1) and particle size, but there is an error in his analytical result. Our reanalysis of the original flume data results in new formulae for the coefficient. Furthermore, we found that the k(1) values should be derived using u(1) and u(1cr) data; the use of the vertical mean velocity in flumes to replace u(1) will lead to considerably higher k(1) values and overestimation of sediment transport rates.

Origin, development and evolutionary model of shelf desertization environment in late stage of Upper Pleistocene

Based on the study of palaeo-environmental evolution in the shelves of the Eastern China Seas, the concept of ''shelf desertization'' in the late stage of Upper Pleistocene is defined; the environmental background and evolutionary process of shelf desertization are analysed. Study on the records of subbottom profiling and the data of core samples from shelf areas revealed that during low sea-level stages, the sedimentary environment in the exposed shelf plains was dominated by aeolian depositional process under cold and dry climatic conditions, i.e. under the action of strong winter-monsoon winds. Parts of the exposed marine strata were disintegrated, and aeolian sand dunes were formed on the disintegrated marine deposits, from which the finer sediment grains were blown away by wind and deposited in the downwind areas to form the derivative loess deposits. Thus a desertization environmental system was formed in the exposed shelf plains of the Eastern China Seas.

Manganese abnormity in holocene Sediments of the Bohai Sea

Manganese abnormity has been observed in the Holocene sediments of the mud area of Bohai Sea. On the basis of grain size, chemical composition, heavy mineral content and accelerator mass spectrometry (AMS) C-14 dating of foraminifer, relationships between manganese abnormity and sedimentation rates, material source, hydrodynamic conditions are probed. Manganese abnormity occurred during the Middle Holocene when sea level and sedimentation rates were higher than those at present. Sedimentary hiatus was not observed when material sources and hydrodynamic conditions were quite similar. Compared with the former period, the latter period showed a decrease in reduction environment and an inclination toward oxidation environment with high manganese content, whereas provenance and hydrodynamic conditions showed only a slight change. From the above observations, it can be concluded that correlation among manganese abnormity, material source, and hydrodynamic conditions is not obvious. Redox environment seems to be the key factor for manganese enrichment, which is mainly related to marine authigenic process.

A preliminary study on thermoluminescence characteristics of sediments from the North Pacific

Thirty-eight surficial deposit samples were collected from the equatorial North Pacific, and the natural thermoluminescence (TL) characteristics of both bulk and clay fraction samples ( < 2 mu m fractions) were studied by the FJ427 - Al automatic TL Dosimeter for the first time. With the measurements of clay mineral composition, element composition by XRD and ICP, the correlations between TL intensity and sedimentary environment proxies were analyzed, such as water depth, ratio of FeO to Fe2O3 contents, LOI, and major clay mineral concentration, and it was found the bulk sample's TL signal was stronger than the clay ones. Usually, increase in the clay components may result in the decrease of TL intensity. From the shape of TL curves, the pelagic sediments can be divided into two groups: the majority group has two glow peaks, in general, the first peak is broad and flat, but the second narrow and sharp; the minority group only has a single peak because the first is absent. The peak centers of TL curves are almost fixed, falling in the temperature sections 230 similar to 260 and 390 similar to 405 degrees C respectively. Lorentz model packed in the Origin 7.5 was chosen to deal with the TL curves. From the processing results, three parameters ( H, C and A), corresponding to the height, center, and kurtosis of TL curve, were obtained to describe the curve characteristics. The correlations between TL curve parameters and sedimentary environment proxies were also calculated. On the basis of the above work, the relationship between TL characteristics and sediment type, mineral composition, sedimentary environment of surface sediments was discussed in the study area, and a conclusion is: sediments from the environment of shallower water, higher organic contents and weaker reductivity have stronger TL signals.

Development of the East Asian monsoon: Mineralogical and sedimentologic records in the northern South China Sea since 20 Ma

We here reconstruct the past change of the East Asian monsoon since 20 Ma using samples from Ocean Drilling Program (ODP) Site 1146 in the northern South China Sea based On a multi-proxy approach including a monomineralic quartz isolation procedure, identification of clay minerals by X-ray Diffraction (XRD) and grain-size analysis of isolated terrigenous materials. Terrigenous supply to ODP Site 1146 was dominated by changes in the strength of multiple sources and transport processes. Grain-size data modeled by an end-member modeling algorithm indicate that eolian dust from the and Asian inland and fluvial input have contributed on average 20% and 80% of total terrigenous material to ODP Site 1146, respectively. Specifically, about 40-53% of the total (quartz+feldspar) and only 6-11% of the total clay is related to eolian supply at the study site. Detailed analysis of the sedimentary environment, and clay minerals combined with previous studies shows that smectite originates mainly from Luzon, kaolinite from the Pearl River and illite and chlorite from the Pearl River, Taiwan and/or the Yangtze River. The proportion and mass accumulation rate (MAR) of the coarsest end-member EM1 (interpreted as eolian dust), ratios of (illite+chlorite)/smectite, (quartz+feldspar)% and mean grain-size of terrigenous materials at ODP Site 1146 were adopted as proxies for East Asian monsoon evolution. The consistent variation of these independent proxies since 20 Ma shows three profound shifts in the intensity of East Asian winter monsoon relative to summer monsoon, as well as aridity of the Asian continent, occurred at similar to 15 Ma, similar to 8 Ma and the youngest at about 3 Ma. In comparison, the summer monsoon intensified contemporaneously with the winter monsoon at 3 Ma. The phased uplift of the Himalaya-Tibetan plateau may have played a significant role in strengthening the Asian monsoon at similar to 15 Ma, 8 Ma and 3 Ma. (C) 2007 Elsevier B.V. All rights reserved.

Preservation of black carbon in the shelf sediments of the East China Sea

Concentrations and carbon isotopic (C-14, C-13) compositions of black carbon (BC) were measured for three sediment cores collected from the Changjiang River estuary and the shelf of the East China Sea. BC concentrations ranged from 0.02 to 0.14 mg/g (dry weight), and accounted for 5% to 26% of the sedimentary total organic carbon (TOC) pool. Among the three sediment cores collected at each site, sediment from the Changjiang River estuary had relatively high BC contents compared with the sediments from the East China Sea shelf, suggesting that the Changjiang River discharge played an important role in the delivery of BC to the coastal region. Radiocarbon measurements indicate that the ages of BC are in the range of 6910 to 12250 years old B. P. (before present), that is in general, 3700 to 9000 years older than the C-14 ages of TOC in the sediments. These variable radiocarbon ages suggest that the BC preserved in the sediments was derived from the products of both biomass fire and fossil fuel combustion, as well as from ancient rock weathering. Based on an isotopic mass balance model, we calculated that fossil fuel combustion contributed most (60%. 80%) of the BC preserved in these sediments and varied with depth and locations. The deposition and burial of this "slow-cycling" BC in the sediments of the East China Sea shelf represent a significant pool of carbon sink and could greatly influence carbon cycling in the region.