Institutional Repository of South China Sea Institute of Oceanology, CAS
Not a member yet
6199 research outputs found
Sort by
One Strain-Many Compounds Method for Production of Polyketide Metabolites Using the Sponge-Derived Fungus Arthrinium arundinis ZSDS1-F3
No full textThielavins W-Z(7), New Antifouling Thielavins from the Marine-Derived Fungus Thielavia sp UST030930-004
No full textEleven new depsides-thielavins W-Z (1-4) and thielavins Z(1)-Z(7) (5-11)-and also four known thielavins-A, H, J, and K (12-15)-were isolated from the ethyl acetate extract of a marine-derived fungal strain Thielavia sp UST030930-004. All of these compounds were evaluated for antifouling activity against cyprids of the barnacle Balanus (=Amphibalanus) amphitrite. The results showed that compounds 1-3 and 6-13 were active, with EC50 values ranging from 2.95 +/- 0.59 to 69.19 +/- 9.51 mu M, respectively. The inhibitive effect of compounds 1-3 and 7 was reversible. This is the first description of the antifouling activity of thielavins against barnacle cyprids
The mitochondrial genome of a sea anemone Bolocera sp exhibits novel genetic structures potentially involved in adaptation to the deep-sea environment
No full textThe deep sea is one of the most extensive ecosystems on earth. Organisms living there survive in an extremely harsh environment, and their mitochondrial energy metabolism might be a result of evolution. As one of the most important organelles, mitochondria generate energy through energy metabolism and play an important role in almost all biological activities. In this study, the mitogenome of a deep-sea sea anemone (Bolocera sp.) was sequenced and characterized. Like other metazoans, it contained 13 energy pathway protein-coding genes and two ribosomal RNAs. However, it also exhibited some unique features: just two transfer RNA genes, two group I introns, two transposon-like noncanonical open reading frames (ORFs), and a control region-like (CR-like) element. All of the mitochondrial genes were coded by the same strand (the H-strand). The genetic order and orientation were identical to those of most sequenced actiniarians. Phylogenetic analyses showed that this species was closely related to Bolocera tuediae. Positive selection analysis showed that three residues (31 L and 42 N in ATP6, 570 S in ND5) of Bolocera sp. were positively selected sites. By comparing these features with those of shallow sea anemone species, we deduced that these novel gene features may influence the activity of mitochondrial genes. This study may provide some clues regarding the adaptation of Bolocera sp. to the deep-sea environment
The regime shift in the 1960s and associated atmospheric change over the southern Indian Ocean
No full textThe change of sea surface temperature (SST) in the southern Indian Ocean (SIO) during the recent six decades has been analyzed based on oceanic reanalysis and model, as well as atmospheric data. The results show that a thermal regime shift in SIO during the 1960s, which is not caught enough attentions, has been of equal magnitude to the linear warming since 1970. Empirical Orthogonal Function (EOF) analyses reveal that a thermal shift is combined with atmospheric changes such as the weakening of westerly during the period of 1960-1967. Inner dynamic connections can be defined that when the westerly winds turn weak, the anticyclonic wind circulation between westerly winds and the trade winds decreases, which further reduces the SST to a negative peak in this period. It is noted that the shifts in the 1960s are also evident for Southern Hemisphere. For example, subtropical high and the entire westerly winds belt at high latitudes both change dramatically in the 1960s. This large-scaled process maybe link to the change of southern annular mode (SAM)
Generation of internal solitary waves over a large sill: From Knight Inlet to Luzon Strait
No full textA fully nonlinear, nonhydrostatic numerical model is utilized to investigate the generation of Internal Solitary Waves (ISWs) upstream of the Knight Inlet sill. While an upstream hydraulic jump initiates the ISW generation and both hydraulic jump and upstream influence contribute to the generation, it is found that upstream influence is dominant and the hydraulic jump is not necessary for the ultimate generation of ISWs. Decreasing the tidal forcing or upstream sill width may render the flow subcritical (i.e., the hydraulic jump disappears) and ISWs can be generated by nonlinear steepening of long wave disturbances induced by upstream influence. Increasing the tidal forcing or upstream sill width may generate a hydraulic jump blocking strong upstream propagating disturbances. The jump subsequently becomes a turbulent bore and later disperses into a train of ISWs as the tide relaxes. Further increase in the tidal forcing may sweep the turbulent bore downstream and a train of ISWs is emitted upstream toward the end of waning tide. By reducing the stratification strength by 1 order of magnitude, the near-sill flow is in the transcritical regime and ISWs are resonantly generated over the lee side slope. Connections to the internal tide release mechanism at Luzon Strait and to the unsteady lee wave model are also discussed. The present work provides some more insights into the ISW generation process at Knight Inlet and the connection between the generation mechanism at Knight Inlet and that at Luzon Strait is identified
Indian Ocean Dipole Modes Associated with Different Types of ENSO Development
No full textThis study identifies several modes of coevolution of various types of El Nino-Southern Oscillation (ENSO) and Indian Ocean dipole (IOD) by performing rotated season-reliant empirical orthogonal function (S-EOF) analysis with consideration of ENSO asymmetry. The first two modes reveal that early-onset ENSO is associated with subsequent strong IOD development, whereas late-onset ENSO forces an obscure IOD pattern with marginal SST anomalies in the western Indian Ocean. Further studies show that El Nino starting before early summer can more easily force an IOD event than that starting in late summer or fall, even when they are of equivalent magnitudes. This is because the atmospheric responses over the Indian Ocean to the eastern Pacific warming are in sharp contrast between early and late summer. Early-onset (late onset) El Nino can (cannot) cause favorable atmospheric circulation conditions over the Indian Ocean for inducing the western Indian Ocean warming, which facilitates the subsequent IOD development. In addition, the different propagations of ocean dynamic Rossby waves during the early-or late-onset types of ENSO are also accountable for the different IOD development. For the higher-order modes, the rotated S-EOF of "Nino only" cases shows a coevolution between a negative IOD mode and a date line Pacific El Nino, with warm sea surface temperature anomalies originating from the northern Pacific meridional mode
Population dynamics of Randall's threadfin bream Nemipterus randalli from Pakistani waters, Northern Arabian Sea
No full textThe N. randalli fish data consist of 1141 pair of length weight relationship and 24312 length frequencies were measured during 2009 - 2010 survey. The maximum length and weight were 25 cm. and 251 g, respectively. The length weight relationship were a = 0.035, b = 2.744 and R-2 = 0.972. The asymptotic length (L-infinity) and growth coefficient (K) were estimated to 26.25 cm and 0.320 year respectively. The total mortality (Z) was 1.25 year The natural mortality (M) was 0.863, hence the fishing mortality (F) was Z = M = 0.387 year I for N. randalli. The yield per recruit analysis indicated that when t(c) was assumed to be 2, F-max was estimated at 1.3 and F-0.1 at 1.3; while t(c) was assumed to be 1, F-max was estimated at 1.1 and F-0.1 at 0.95. Currently age at first capture is about 1 year and F-current was 0.387, therefore, F-curent was smaller than F-0.1 and F-max. The results during present study indicate that current fishery stock is in sustainable state. However, it is suggested that take some management steps to maintain the stock of N. randalli in Pakistani waters, Northern Arabian Sea
Evaluation of the net CO2 uptake in the Canada Basin in the summer of 2008
No full textThe third Chinese National Arctic Research Expedition (CHINARE) was conducted in the summer of 2008. During the survey, the surface seawater partial pressure of CO2 (pCO(2)) was measured, and sea water samples were collected for CO2 measurement in the Canada Basin. The distribution of pCO(2) in the Canada Basin was determined, the influencing factors were addressed, and the air-sea CO2 flux in the Canada Basin was evaluated. The Canada Basin was divided into three regions: the ice-free zone (south of 77 degrees N), the partially ice-covered zone (77 degrees-80 degrees N), and the heavily ice-covered zone (north of 80 degrees N). In the ice-free zone, pCO(2) was high (320 to 368 mu atm, 1 mu atm=0.101 325 Pa), primarily due to rapid equilibration with atmospheric CO, over a short time. In the partially ice-covered zone, the surface pCO(2) was relatively low (250 to 270 mu atm) due to ice-edge blooms and ice melt water dilution. In the heavily ice-covered zone, the seawater pCO(2) varied between 270 and 300 mu atm due to biological CO2 removal, the transportation of low pCO(2) water northward, and heavy ice cover. The surface seawater pCO(2) during the survey was undersaturated with respect to the atmosphere in the Canada Basin, and it was a net sink for atmospheric CO2. The summertime net CO, uptake of the ice-free zone, the partially ice-covered zone and the heavily ice-covered zone was (4.14 +/- 1.08), (1.79 +/- 0.19), and (0.57 +/- 0.03) Tg/a (calculated by carbon, 1 Tg=10(12) g), respectively. Overall, the net CO2 sink of the Canada Basin in the summer of 2008 was (6.5 +/- 1.3) Tg/a, which accounted for 4%-10% of the Arctic Ocean CO2 sink
Quantification of methane fluxes from hydrocarbon seeps to the ocean and atmosphere: Development of an in situ and online gas flux measuring system
No full textNatural hydrocarbon seeps in the marine environment are important contributors to greenhouse gases in the atmosphere. Such gases include methane, which plays a significant role in global carbon cycling and climate change. To accurately quantify the methane flux from hydrocarbon seeps on the seafloor, a specialized in situ and online gas flux measuring (GFM) device was designed to obtain high-resolution time course gas fluxes using the process of equal volume exchange. The device consists of a 1.0-m diameter, 0.9-m tall, inverted conical tent and a GFM instrument that contains a solenoid valve, level transducer, and gas collection chamber. Rising gas bubbles from seeps were measured by laboratory-calibrated GFM instruments attached to the top of the tent. According to the experimental data, the optimal anti-shake time interval was 5 s. The measurement range of the device was 0-15 L min(-1), and the relative error was +/- 1.0%. The device was initially deployed at an active seep site in the Lingtou Promontory seep field in South China Sea. The amount of gas released from a single gas vent was 30.5 m(3) during the measurement period, and the gas flow rate ranged from 22 to 72 L h(-1), depending on tidal period, and was strongly negatively correlated with water depth. The measurement results strongly suggest that oceanic tides and swells had a significant forcing effect on gas flux. Low flow rates were associated with high tides and vice versa. The changes in gas volume escaping from the seafloor seeps could be attributed to the hydrostatic pressure induced by water depth. Our findings suggest that in the marine environment, especially in the shallow shelf area, sea level variation may play an important role in controlling methane release into the ocean. Such releases probably also affect atmospheric methane levels
Bottom water hydrodynamic provinces and transport patterns of the northern South China Sea: Evidence from grain size of the terrigenous sediments
No full textSediment transport in the source-to-sink systems of the northern South China Sea (SCS) has been of increasing interest during the past few decades. However, the mechanisms for sediment redistribution remain unclear. Sources and transport patterns in the northern SCS were investigated in this study based on grain size analyses of 205 surface sediment samples. Detailed characterizations of hydrodynamic conditions and sediment transport have been made using the log-ratio method to partition grain size components of surface sediments in the northern SCS. Results reveal that sediment dispersal patterns in the region generally contain traction, saltation, graded and uniform suspension modes. Based on the spatial distribution characteristics, the study area can be classified into three hydrodynamic provinces. Province A contains high traction concentrations that are exposed to the longshore current and topographic features, which are distributed in the Taiwan Shoal, Dongsha Islands and extends from the Pearl River estuary to the southeast of Hainan Island. Province B is characterized by higher values of saltation and graded suspension, which are widespread along the northern slope of the SCS, and its formation is interpreted as the result of interactions between down- and along-slope processes. Province C reaches its greatest concentration in the abyssal areas, particularly in the vicinity of Luzon Island, which settles only under calm conditions. Combined with previous data concerning magnetic susceptibility distributions of surface sediments from the northern SCS, the sediment transport route near the mainland is traced. Furthermore, based on distribution pattern of sortable silts and hydrodynamic provenance of the terrigenous sediments, the sediment transport route in the deep water region of the northern SCS is outlined. It flows along marginal channels which cut across the continental slope along isobaths. Taken together, the combination of grain-size components and sortable silts of surface sediment used here is a promising tool to better assess the modern variability of hydrodynamic conditions and transport processes in marine environments