Institutional Repository of South China Sea Institute of Oceanology, CAS
Not a member yet
6199 research outputs found
Sort by
Arctic Micromonas uses protein pools and non-photochemical quenching to cope with temperature restrictions on Photosystem II protein turnover
No full textMicromonas strains of small prasinophyte green algae are found throughout the world's oceans, exploiting widely different niches. We grew arctic and temperate strains of Micromonas and compared their susceptibilities to photoinactivation of Photosystem II, their counteracting Photosystem II repair capacities, their Photosystem II content, and their induction and relaxation of non-photochemical quenching. In the arctic strain Micromonas NCMA 2099, the cellular content of active Photosystem II represents only about 50 % of total Photosystem II protein, as a slow rate constant for clearance of PsbA protein limits instantaneous repair. In contrast, the temperate strain NCMA 1646 shows a faster clearance of PsbA protein which allows it to maintain active Photosystem II content equivalent to total Photosystem II protein. Under growth at 2 A degrees C, the arctic Micromonas maintains a constitutive induction of xanthophyll deepoxidation, shown by second-derivative whole-cell spectra, which supports strong induction of non-photochemical quenching under low to moderate light, even if xanthophyll cycling is blocked. This non-photochemical quenching, however, relaxes during subsequent darkness with kinetics nearly comparable to the temperate Micromonas NCMA 1646, thereby limiting the opportunity cost of sustained downregulation of PSII function after a decrease in light
The complete mitochondrial genome of Pseudorhombus dupliocellatus (Pleuronectiformes: Paralichthyidae)
No full textThe Pseudorhombus dupliocellatus belongs to family Paralichthyidae of Pleuronectiformes. In this study, the complete mitochondrial genome of P. dupliocellatus is determined and described. The mitogenome is 16 621 bp in length and consists of 13 protein-coding genes, 22 tRNAs, 2 rRNAs, a control region, and a L-strand replication origin. The arrangement of the mitogenome is identical to that of the typical teleost. The overall base composition is 26.9%, 25.3%, 31.0%, and 16.8% for A, T, C, and G, respectively, with a slight bias on A+T content (52.2%). The phylogenetic tree of 13 species all in Pleuronectiformes demonstrated that P. dupliocellatus, as well as the other Paralichthyidae fishes containing Paralichthys olivaceus and Pseudorhombus cinnamoneus, clustered in a Glade and had a closer relationship with Pleuronectidae species than Bothidae ones. This study is expected to contributing to the systematic evolution of Paralichthyidae and further Pleuronectiformes
Survival and growth of reciprocal crosses between two stocks of the Hong Kong oyster Crassostrea hongkongensis (Lam & Morton, 2003) in southern China
No full textThe Hong Kong oyster, Crassostrea hongkongensis, is one of the most economically important and well-known oyster species in southern China. To explore the possibility of improving the performance of the Hong Kong oyster, complete diallel crosses between two oyster stocks, the Zhuhai stock (Z: fast growth line F4) and the Maowei Sea stock (M: resistant line F3), were conducted using pooled gametes. Three replicates, each consisting of two pure stocks (ZZ and MM) and two reciprocal crosses (ZM and MZ), were successfully generated. High fertilization rate and hatching level were observed among all the experimental groups, suggesting that there was no sperm-egg recognition barrier between geographic populations. Reciprocal crosses had higher survival rate compared to the pure stock crosses and the rate of survival increased with progeny growth. Growth heterosis became obvious both in larval and adult stages, and was primarily influenced by the egg origin and mating strategy at the larval stage. Also, the phenotypic traits of all progeny differed amongst the culture sites, suggesting a significant environmental effect. The Zhuhai site was more suitable for oyster aquaculture than the Maowei Sea site. Thus, our results demonstrated that crossbreeding between Zhuhai and Maowei Sea stocks of Hong Kong oyster to produce superior heterosis represents a promising means to improve the fishery yield of this species in southern China
Distribution of picoplankton in the northeastern South China Sea with special reference to the effects of the Kuroshio intrusion and the associated mesoscale eddies
No full textWe investigated picoplankton distribution patterns and environmental variables along an east-to-west transect in the northeastern South China Sea (SCS) during late winter 2016, giving us the opportunity to examine the impacts of the Kuroshio intrusion and the associated eddies. The results indicated that the subsurface (50-75 m) phytoplankton biomass chlorophyll (Chl a) maximum (SCM) disappeared and was replaced by higher Chl a in the middle part of the transect due to the impacts of the Kuroshio intrusion and mesoscale eddies. Both flow cytometry and pyrosequencing data revealed that picoplankton abundance and community structure were significantly influenced by perturbations in complex physical processes. Picoeukaryotes represented most of the total phytoplankton biomass, and their maximum abundance (>10(4) cells mL(-1)) occurred within cyclonic eddy-affected regions (Stations 11 and 12), whereas the abundance of Prochlorococcus was the lowest in these regions. Prochlorococcus showed a higher abundance in the Kuroshio-affected area, while Synechococcus was mostly distributed at the upper well-lit depths, with its maximum abundance observed in surface waters (0-30 m) adjacent to the cyclonic eddy center. Heterotrophic bacteria (HBA) displayed high abundance along the transect, consistent with the total phytoplankton biomass. Phylogenetic analysis revealed 26 bacterial phyla, with major components belonging to Proteobacteria, Cyanobacteria, Actinobacteria, and Bacteroidetes, as well as SAR406. Notably, relatively more Rhodobacterates, Flavobacteriales, Alteromonadales, and Vibrionales that were distributed in surface waters of the cyclonic eddy center were specifically associated with the phytoplankton (mainly picoeukaryotes) bloom. Our study highlights the impacts of the Kuroshio intrusion in regulating the microbial ecology of the northeastern SCS and the potential coupling between phytoplankton and bacteria. (C) 2017 Elsevier B.V. All rights reserved
Deposition of duststorm particles during 2000-2012 in the South Yellow Sea, China based on satellite data
No full textIn this study, about 220 satellite images between 2000 and 2012 were obtained from FY -series, MODIS, CBERS, HJ-1A and HJ-1B to estimate the impact of duststorms on the South Yellow Sea (SYS), which serve as an important source of particles there. The analyzing results from the images support a total occurrence of 88 duststorms (including the locally -generated dusty weather) that affected the SYS during 2000-2012. The annual occurrence was about 4-10 times (10 times in 2000 and 2004; four times in 2009 and 2012), predominantly in March (29%), April (33%) and May (22%). By mapping the distribution of their frequency, the duststorms influencing the SYS were found primarily moving from the northwest (39 times, 44.3%) and west (37 times, 42%) to the study region with only 11 duststorms (12.5%) coming from the north and 1 duststorm (1%) from the southwest. We estimated that an annual amount of 0.5-3.5 million tons of sediment particles was brought to the SYS by the duststorms during 2000-2012
Windward and leeward margins of an Upper Ordovician carbonate platform in the Central Tarim Uplift, Xinjiang, northwestern China
No full textIn the Central Uplift of the Tarim Basin, northwestern China, the Katian (Upper Ordovician) limestones of the Lianglitag Formation extend from outcrops in the Bachu area to the subsurface in the Tazhong Oil Field (TZOF) area. Reefs and inner platform deposits are the dominant facies throughout the formation. The reef composition illustrates a palaeoecologic gradient from microbial-dominated buildups on the northwestern margin to metazoan-dominated reefs on the eastern and southern margins of the platform. Between these areas no outcrops are present. In the present study, data including litho- and biofacies logs and correlations from eight wells are presented, six of them of the region between Bachu and Tazhong, and two wells along the former platform margin from the TZOF. Calcimicrobial carbonates are common in core from the inner platform part. Benthic biota documented here resembles that of the microbial mounds and bioclastic limestones in the Bachu outcrop area, and thus is considered as the eastward extension of this realm. However, metazoan-dominated boundstones formed by corals, stromatoporoids, sponges together with calcareous algae are abundant along the southern platform margin, and are similar in composition to the reefs of TZOF in the easternmost part of the platform. The palaeoecologic differentiation between microbial- and metazoan-dominated reefs suggests a strong environmental gradient from a well-oxygenated windward eastern and southern side of the platform, which favoured the open ocean and which was dominated by metazoan reefs, and the inner platform as well as the northwestern, leeward margin of the platform with warmer, less-oxygenated water, which favoured the growth of microbial carbonates. Assuming the trade winds as cause for the contrasting facies on both sides of the platform a palaeo-position of Tarim south of the ITCZ seems probable because a position north of it would require a post Ordovician clockwise rotation of Tarim of about 90 which is possible but less probable. Crown Copyright (C) 2017 Published by Elsevier B.V. All rights reserved
A numerical study of rotation effect on the propagation of nonlinear internal solitary waves in the northern South China Sea
No full textIn the paper, the rotation effect on the propagation of internal solitary waves (ISWs) in the northern South China Sea (SCS) is studied by applying non-dimensional analysis and a modified two-dimensional regularized long wave equation model. First, the contribution of each term in the model equation with rotation effect is estimated. It is shown that, the rotation effect is important once the scale of the propagating ISWs is larger than 100 km. Then, the model equation is differentiated and set up for the numerical simulation of ISWs in the northern SCS. Several numerical experiments are designed, and it is found that, the rotation effect mainly affects the symmetry of the ISW crestline, the amplitudes of the leading ISW and the north/south-ward extension crestline. With the rotation effect, the ISW crestline is not symmetrical, and the ISW amplitude decreases faster. For an incident depression internal soliton with an amplitude larger than 60 m, after the leading ISW propagates a distance of 330 km, the length of ISW crestline gets larger than 150 km, the contribution of rotation effect on the variation of leading ISW amplitude can reach more than 8%; the rotation effect and the bottom topographic effect on the variation of ISW amplitudes are opposite. The contribution of rotation effect on the variation of leading ISW amplitude decreases with an increase in amplitude of incident soliton, but it increases with the extension distance from the center of ISW crestline for the northern southern crestlines of propagating ISWs. (C) 2017 Elsevier Inc. All rights reserved
Types, Characteristics and Significances of Migrating Pathways of Gas-bearing Fluids in the Shenhu Area, Northern Continental Slope of the South China Sea
No full textThe first marine gas hydrate expedition in China has been conducted by Guangzhou Marine Geological Survey in the Shenhu Area, northern continental slope of the South China Sea. Previous study has analyzed the P-T conditions, geophysical anomalies and saturation calculations of these gas hydrates, but has not documented in detail the migration of gas-bearing fluids in the study area. Based on the interpretations of 2D/3D seismic data, this work identified two types of migration pathways for gas-bearing fluids in the Shenhu area, i.e., vertical and lateral pathways. The vertical pathways (large-scale faults, gas chimneys and mud diapirs) presented as steep seismic reflection anomalies, which could be traced downward to the Eocene source rocks and may penetrate into the Late Miocene strata. The deeper gases/fluids might be allowed migrating into the shallower strata through these vertical conduits. However, the distributions showed distinct differences between these pathways. Large-scale faults developed only in the north and northeast of the Shenhu area, while in the drilling area gas chimneys were the sole vertical migration pathways. Since the Pliocene, normal faults, detachment faults and favorable sediments have constituted the lateral pathways in the Shenhu gas hydrate drilling area. Although these lateral pathways were connected with gas chimneys, they exerted different effects on hydrate formation and accumulation. Gas-bearing fluids migrated upward along gas chimneys might further migrate laterally because of the normal faults, thereby enlarging the range of the chimneys. Linking gas chimneys with the seafloor, the detachment faults might act as conduits for escaping gases/fluids. Re-deposited sediments developed at the early stage of the Quaternary were located within the gas hydrate stability zone, so hydrates would be enriched in these favorable sediments. Compared with the migration pathways (large-scale faults and mud diapirs) in the LW3-1 deep-sea oil/gas field, the migration efficiency of the vertical pathways (composed of gas chimneys) in the gas hydrate drilling area might be relatively low. Description and qualitative discrimination of migration pathways in the Shenhu gas hydrate drilling area are helpful to further understand the relationship between good-quality deep source rocks and shallow, mainly biogenically-produced, hydrates. As the main source rocks of the Baiyun sag, lacustrine mudstones in the Wenchang and Enping Formations may provide thermogenic methane. Gas chimneys with relatively low migration efficiency created the vertical pathways. Caused by the Dongsha tectonic movement, the release of overpressured fluids might reduce the vertical migration rates of the thermogenic methane. The thick bathyal/abyssal fine-grained sediments since the Late Miocene provided migration media with low permeability. These preconditions may cause carbon isotopic fractionation of thermogenic methane during long-distance vertical migrations. Therefore, although geochemical analyses indicate that the methane forming gas hydrate in the Shenhu area was mainly produced biogenically, or was mixed methane primarily of microbial origin, thermogenic methane still contribute significantly
Geochemistry and Hf-Nd isotope characteristics and forming processes of the Yuntoujie granites associated with W-Mo deposit, Guangxi, South China
No full textThe Yuntoujie W-Mo deposit is so far the only Indosinian granite-related deposit with an element association of W-Mo in the Nanling ore belt, South China. The granites in the Yuntoujie ore field consist of the Yuntoujie batholith and late-stage granites. The W-Mo mineralization is associated closely with the late-stage granites. Here we report major and trace element, Sr-Nd isotope and zircon Hf isotope compositions of the Yuntoujie batholith and the late-stage granites. The Yuntoujie batholith and the late-stage granites have high SiO2 (70.77-74.86 wt.%) and alkaline (K2O + Na2O = 6.27-8.27 wt.%) concentrations and are characterized as peraluminous (A/CNK > 1.1, A/NK = 1.30-1.43). The Yuntoujie batholith and late-stage granites feature negative correlation between Th, Y and Rb, no positive correlation between P2O5 and SiO2 and high A/CNK values > 1.1, suggesting that they could be classified as S-type granites. The Yuntoujie batholith and the late-stage granites might be sourced from the partial melting of Proterozoic crust without contribution from juvenile crust, as evidenced from the low Nd-143/Nd-144 values of 0.511942-0.512477, the epsilon(Nd)(t) values of -8.52 to -11.76 (falling in the field of Nd isotope evolution for the Proterozoic crust), and the zircon epsilon(Hf)(t) values of -7.19 to -14.89 with the T-DM2 ranging from 1713 Ma to 2187 Ma. The major and trace element compositions of the Yuntoujie batholith and late-stage granites, especially the low CaO/Na2O and CaO/(MgO + FeOT) ratios and the high Rb/Ba and Rb/Sr ratios, further indicate that their sources are predominantly argillaceous sedimentary. The trace element characteristics, such as the positive correlation between La/Yb and La and between Ba and Sr and negative correlation between Ba and Rb, suggest that the late-stage granites are the product of highly fractionated melts of the Yuntoujie magma chamber. Moreover, 1) the tetrad effect observed in the REE patterns for the late-stage tourmaline muscovite monzogranite porphyry and 2) the abundant fluid inclusions in their quartz phenocrysts imply that the processes of the volatile phase exsolution and the fluid-melt reaction had taken place in the evolved water-saturated magma. These geochemical features, together with the fact that the Yuntoujie magma chamber had survived for > 10 Myr, suggest that the peraluminous magma experienced a prolonged period of crystallization differentiation, which plays a key role in the formation of W-Mo mineralization associated with granites. From the observations that the granites in the Yuntoujie district were formed about 20-10 Ma later than the peak age of the Indosinian collisions and that they all fall in the post-CEG area in the tectonomagmatic discrimination diagrams, we proposed that the Yuntoujie granites were formed in the post-collisional environment (C) 2016 Elsevier B.V. All rights reserved
Pleistocene iceberg dynamics on the west Svalbard margin: Evidence from bathymetric and sub-bottom profiler data
No full textLarge icebergs leave evidence of their drift via ploughing of the seabed, thereby providing a geological record of episodes of calving from thick ice sheets. We interpret large-scale curvilinear depressions on the western Svalbard margin as ploughmarks produced by the keels of icebergs that grounded on the seafloor as they drifted through this area. Iceberg ploughmarks were identified at modern water depths between 300 m and 1000 m and in two distinct stratigraphic units. Combining data from sediment cores with seismic stratigraphy from sub-bottom profiler data suggests that the ploughmarks developed in two phases: (1) during Marine Isotope Stage (MIS) 6; and (2) during MIS 2, indicating the presence of large drifting icebergs on the western Svalbard margin during both the Late Saalian and Late Weichselian glaciations. Sediment-core data along the western Svalbard margin indicate a sharp increase in mass transported sediments dated at 23.7 +/- 0.2 ka, consistent with the MIS 2 age of the younger iceberg ploughed surface. The ploughmarks are oriented in two main directions: SW-NE and S-N. S-N oriented ploughmarks, which shallow to the north, indicate iceberg drift from the south with a SW NE component marking the zone of splitting of the West Spitsbergen Current (WSC) into the Yermak Slope Current (YSC) and North Spitsbergen Current (NSC). Large MIS 6 and MIS 2 icebergs most likely had an Arctic Ocean source. We suggest that these icebergs probably left the Arctic Ocean southward through Fram Strait and circulated within the Norwegian-Greenland Sea before being transported northwards along the Svalbard margin by the WSC. An additional likely source of icebergs to the western Svalbard margin during MIS 2 was the ice-sheet terminating in the western Barents Sea, from which icebergs drifted northward.(C) 2017 Elsevier Ltd. All rights reserved