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南海北部上层盐度变化观测研究及其机理分析
No full text南海盐度具有显著的年际变化，并且近年来呈现出明显的淡化趋势，本文利用中国科学院南海海洋研究（SCSIO）提供的南海北部开放航次的CTD温盐剖面（2004-2013年，共计595个），探讨南海北部盐度年际变化与淡化趋势以及典型高盐事件的相关影响因子，从而揭示南海北部盐度的变异特征及相关机理。主要发现如下：
南海北部开放航次温盐观测的聚类分析发现南海北部水团的差异主要体现在表层和次表层，且存在明显的年际变化。2004-2006年在吕宋海峡120°E断面和南海18°N断面上层均存在一个明显的高盐值区；2004年、2006年和2011年在吕宋海峡附近的表层等密面和次表层等密面上都出现了南海-黑潮混合水团，且次表层的混合范围更广。这十年间南海北部上层盐度不仅展现出显著的年际差异，在整体上更呈现出淡化趋势，经统计南海北部上层盐度以0.044psu/yr的速率快速淡化。2004-2013年间，南海北部上层盐度主要受到净淡水通量和吕宋海峡盐输运的联合调控。从整体上看，净淡水通量（降雨-蒸发）呈上升趋势，吕宋海峡上层盐输运程下降趋势，增强的淡水输入和减弱的高盐水入侵都有利于南海北部上层盐度的淡化。
除了已被深入探讨过的2012年极端淡化事件，2004-2005年南海北部高盐事件是这十年盐度变化中的另一个重要过程。2004-2005年南海北部盐度相比于气候态均值分别增加了0.10psu和0.14psu，且盐度增大的现象主要发生在150m以浅。2004年净淡水通量仅略低于气候态均值，2005年净淡水通量则明显高于气候态均值，因此净淡水通量不会是导致此高盐事件的有利因素。我们进一步通过块体简化盐度收支方程，定量评估盐度收支方程里中平流输运项（包括跨海盆经吕宋海峡的平流输运项和南海海盆内部南北海盆之间的平流输运项）的贡献。发现在2004年，通过吕宋海峡进入南海北部的盐含量输运显著大于气候态均值，是导致南海北部上层水体盐度迅速增大的主要原因。为探究2005年南海北部盐度持续增强的原因，我们进一步比较2004年和2005年的平流项演变，发现相对于2004年，虽然2005年吕宋海峡盐含量输运略低于气候态均值，但南海内部南海南北海盆间（通过18°N断面进入南海北部）的盐含量输运增强，即在2005年，海盆内部经向平流盐输运的贡献是促使南海北部上层盐度继续增强的关键因素
DIATOM GROWTH RESPONSES TO PHOTOPERIOD AND LIGHT ARE PREDICTABLE FROM DIEL REDUCTANT GENERATION
No full textLight drives phytoplankton productivity, so phytoplankton must exploit variable intensities and durations of light exposure, depending upon season, latitude, and depth. We analyzed the growth, photophysiology and composition of small, Thalassiosira pseudonana, and large, Thalassiosira punctigera, centric diatoms from temperate, coastal marine habitats, responding to a matrix of photoperiods and growth light intensities. T. pseudonana showed fastest growth rates under long photoperiods and low to moderate light intensities, while the larger T. punctigera showed fastest growth rates under short photoperiods and higher light intensities. Photosystem II function and content responded primarily to instantaneous growth light intensities during the photoperiod, while diel carbon fixation and RUBISCO content responded more to photoperiod duration than to instantaneous light intensity. Changing photoperiods caused species-specific changes in the responses of photochemical yield(e(-)/photon) to growth light intensity. These photophysiological variables showed complex responses to photoperiod and to growth light intensity. Growth rate also showed complex responses to photoperiod and growth light intensity. But these complex responses resolved into a close relation between growth rate and the cumulative daily generation of reductant, across the matrix of photoperiods and light intensities
Discovery of Antimycin-Type Depsipeptides from a wbl Gene Mutant Strain of Deepsea-Derived Streptomyces somaliensis SCSIO ZH66 and Their Effects on Pro-inflammatory Cytokine Production
No full textDeepsea microbes are a rich source of novel bioactive compounds, which have developed unique genetic systems as well as biosynthetic pathways compared with those of terrestrial microbes in order to survive in extreme living environment. However, a large variety of deepsea-microbial secondary metabolic pathways remain "cryptic" under the normal laboratory conditions. Manipulation of global regulators is one of the effective approaches for triggering the production of cryptic secondary metabolites. In this study, by combination of various chromatographic purification process, we obtained somalimycin (1), a new antimycin-type depsipeptide, with an unusual substitution of 3-aminosalicylate instead of conserved 3-formamidosalicylate moiety, along with two known (2 and 3) analogs from the 1 wblA(so) mutant strain of deepsea-derived Streptomyces somaliensis SCSIO ZH66. The structures of 1-3 were elucidated on the basis of extensive spectroscopic analyses including LC-MS and NMR. In the evaluation of potent anti-inflammatory activity, compound 2 exhibited strong inhibitory activity on the IL-5 production in ovalbumin-stimulated splenocytes with IC50 value of 0.57 mu M, while 1 and 3 displayed mild effect (> 10 mu M), which might be attributed to their different side-chain substitutions. Moreover, compounds 1-3 showed very weak cytotoxicity against human umbilical vein endothelial cells with LD50 values of 62.6, 34.6, and 192.9 mu M, respectively, which were far over their IL-5 inhibitory activity. These results indicated that these compounds have good potential for further use in anti-inflammatory drug development
Performance evaluation of reciprocal hybrids derived from the two brackish oysters, Crassostrea hongkongensis and Crassostrea sikamea in southern China
No full textInterspecific hybridization has been used as an important tool for genetic manipulation in oyster culture with the aim to produce a new strains having desired traits from both the parental species. A two by two factorial cross between sympatric oyster species, Hong Kong oyster (Crassostrea hongkongensis) and Kumamoto oyster (Crassostrea sikamea), yielded hybrids that were fast growing (a characteristic of Hong Kong oyster) and had superior meat quality (characteristic to Kumamoto oyster). Reciprocal hybrids were obtained by the acceptable level of fertilization and hatching rate compared to these of two parental species. The survival rate of the hybrids was similar to that of the parental species. The hybrids exhibited fully developed gonads and gametes when sex-uallymature. Relative to C. sikamea, the hybrids also showed significant growth advantages as in shell height and wet weight. The shell morphology of the hybrid was dictated by maternal inheritance. Our results revealed that reciprocal hybrids exhibited larger growth heterosis and survival advantage (in terms of C. sikamea), as well as a higher meat weight, showing great potential for application in the oyster aquaculture industry in southern China. Statement of relevance: We firstly conducted the interspecific hybridization between the largest (Crassostrea hongkongensis) and smallest oysters (C. sikamea) in Crassostea genus, and then obtained reciprocal hybrids with obvious the heterosis (in terms of C. sikamea). These hybrids are very useful as a new stock for the oyster aquaculture industry. (C) 2017 Elsevier B.V. All rights reserved
Isobenzofuranones and Isochromenones from the Deep-Sea Derived Fungus Leptosphaeria sp SCSIO 41005
No full textFour new isobenzofuranones, leptosphaerins J-M (1-4), including an unusual naturally-occurring centrosymmetric dimer skeleton (1), and two new isochromenones, clearanols I-J (9-10), were obtained from a culture of a deep-sea sediment-derived fungus Leptosphaeria sp. SCSIO 41005, together with four known isobenzofuranones (5-8) and six known isochromenones (11-16). These structures were elucidated by extensive spectroscopic analyses, and absolute configurations were assigned on the basis of electronic circular dichroism and optical rotations data comparison. Additionally, the absolute configurations of the new compounds 1 and 9, together with the known one 7 with stereochemistry undetermined, were further confirmed by single crystal X-ray diffraction experiments. A plausible biosynthetic pathway of these isobenzofuranones and isochromenones was also proposed
Organophosphorus flame retardants in. mangrove sediments from the Pearl River Estuary, South China
No full textForty-eight surface sediments were collected from three mangrove wetlands in the Pearl River Estuary (PRE) of South China to investigate the distribution of organophosphorus flame retardants (OPFRs) and the relationship between OPFRs and microbial community structure determined by phospholipid fatty acid. Concentrations of Sigma OPFRs in mangrove sediments of the PRE ranged from 13.2 to 377.1 ng g(-1) dry weight. Levels of OPFRs in mangrove sediments from Shenzhen and Guangzhou were significantly higher than those from Zhuhai, indicating that OPFRs were linked to industrialization and urbanization. Tris(chloropropyl)phosphate was the predominant profile of OPFRs in mangrove sediments from Shenzhen (38.9%) and Guangzhou (35.0%), while the composition profile of OPFRs in mangrove sediments from Zhuhai was dominated by tris(2-chloroethyl) phosphate (25.5%). The mass inventories of OPFRs in the mangrove sediments of Guangzhou, Zhuhai and Shenzhen were 439.5, 133.5 and 6623 ng cm(-2), respectively. Redundancy analysis revealed that OPFRs induced a shift in the structure of mangrove sediment microbial community and the variations were significantly correlated with tris(1,3-dichloro-2-propyl)phosphate and tris(2-butoxyethyl) phosphate. (C) 2017 Elsevier Ltd. All rights reserved
Observations of the turbulent kinetic energy dissipation rate in the upper central South China Sea
No full textMeasurements of the turbulent kinetic energy dissipation rate (epsilon), velocity, temperature, and salinity were obtained for the upper ocean of the central South China Sea (14.5A degrees N, 117.0A degrees E) during an experimental campaign from May 11 to 13, 2010. Dissipation in the diurnal mixed layer showed a diurnal variability that was strongly affected by the surface buoyancy flux. Dissipation was enhanced (epsilon similar to 10(-7) W kg(-1)) at night due to the convective mixing and was weakened (epsilon similar to 10(-9) W kg(-1)) in daytime due to the stratification. Dissipation in the thermocline varied with time under the influence of internal waves. Shear from high-frequency internal waves (period similar to 8 h) played an important role in enhancing the turbulent mixing in the thermocline. In the period of strong high-frequency internal waves, the shear from high-frequency internal waves became strong and the depth-averaged epsilon in the thermocline was elevated by almost one order of magnitude. Compared with the dissipation in the thermocline, dissipation below was weaker (the time-averaged epsilon similar to 10(-10) W kg(-1)). The observation indicates that the dissipation rates during the measurements can be parameterized by the MacKinnon-Gregg model that is widely used in the continental shelf but are not in agreement with the Gregg-Henyey model used for the open ocean
Storm-induced changes in pCO(2) at the sea surface over the northern South China Sea during Typhoon Wutip
No full textIn situ oceanographic measurements were made before and after the passage of Typhoon Wutip in September 2013 over the northern South China Sea. The surface geostrophic circulation over this region inferred from satellite altimetry data features a large-size anticyclonic eddy, a small-size cyclonic eddy, and smaller-size eddies during this period. Significant typhoon-induced changes occurred in the partial pressure of CO2 at the sea surface (pCO(2sea)) during Wutip. Before the passage of Wutip, pCO(2sea) was about 392.92 +/- 1.83, 390.31 +/- 0.50, and 393.04 +/- 4.31 mu atm over the cyclonic eddy water, the anticyclonic eddy water, and areas outside two eddies, respectively. The entire study region showed a carbon source (1.31 +/- 0.46 mmol CO2 m(-2) d(-1)) before Wutip. In the cyclonic eddy water after Wutip, high sea surface salinity (SSS), low sea surface temperature (SST), and high pCO(2sea) (413.05 +/- 7.56 mu atm) made this area to be a carbon source (3.30 +/- 0.75 mmol CO2 m(-2) d(-1)). In the anticyclonic eddy water after Wutip, both the SSS and SST were lower, pCO(2sea) was also lower (383.03 +/- 3.72 mu atm), and this area became a carbon sink (-0.11 +/- 0.55 mmol CO2 m(-2) d(-1)), in comparison with the pretyphoon conditions. The typhoon-induced air-sea CO2 flux reached about 0.03 mmol CO2 m(-2) d(-1). Noticeable spatial variations in pCO(2sea) were affected mainly by the typhoon-induced mixing/upwelling and vertical stratifications. This study suggests that the local air-sea CO2 flux in the study region was affected significantly by oceanographic conditions during the typhoon
Geophysical implications for the formation of the Tamu Massif-the Earth's largest single volcano-within the Shatsky Rise in the northwest Pacific Ocean
No full textRecent geophysical research programs survey the Tamu Massif within the Shatsky Rise oceanic plateau in the northwest Pacific Ocean to understand the formation of this immense volcano and to test the formation hypotheses of large igneous province volcanism. Massive sheet basalt flows are cored from the Tamu Massif, implying voluminous eruptions with high effusion rates. Seismic reflection data show that the Tamu Massif is the largest single volcano on Earth, characterized by a central volcanic shield with low-gradient flank slopes, implying lava flows emanating from its center and spreading massive area on the seafloor. Velocity model calculated from seismic refraction data shows that crustal thickness has a negative correlation with average velocity, implying a chemically anomalous origin of the Tamu Massif. Seismic refraction and reflection data reveal a complete crustal structure across the entire volcano, featured by a deep crust root with a maximum thickness of similar to 30 km, and Moho geometry is consistent with the Airy Isostasy. These recent findings provide evidence for the two end-member formation models: the mantle plume and the plate boundary. Both are supported by some results, but both are not fit with some either. Consequently, plume-ridge interaction could be a resolution that awaits future investigations. (C) 2016 Production Science China Press. Published by Elsevier B.V. and Science China Press