Institutional Repository of South China Sea Institute of Oceanology, CAS
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Dimethylsulfide and dimethylsulfoniopropionate production along coastal waters of the northern South China Sea
No full textThe gross biological dimethylsulfoniopropionate (DMSP) and dimethylsulfide (DMS) production in surface and bottom waters along the coasts of the northern South China Sea (SCS) were investigated during summer of July-August 2000. In surface water, the averaged concentrations of particulate DMSP (DMSPp) and DMS were 42.60 +/- 31.94 nM and 2.12 +/- 138 nM, respectively. In bottom water, the mean DMSPp and DMS contents were 26.37 +/- 20.83 nM and 2.09 +/- 1.55, respectively. Both DMSPp and DMS contents significantly varied spatially (P < 0.05, n=40), but not vertically (P> 0.05, n=40). The highest DMSPp concentration (100.62 nM) was recorded on the surface of Shenzhen waters, whereas the lowest (4.33 nM) was on the surface of Zhanjiang waters. DMS fluctuated correspondingly; the highest (6.79 nM) and lowest (0.83 nM) values occurred on the surface of Shenzhen water and bottom water of Nan'ao Island (Shantou), respectively. Correlation analysis further revealed that DMS/DMSPp production was not closely related with salinity and chlorophyll a content (P> 0.05, n=40). However, the bottom DMS increased with increasing temperature when it is lower than 28.2 degrees C (r(2)=0.52, P < 0.01, n=13), whereas it decreased as the temperature further increased (r(2)=0.86, P < 0.01, n=8). Moreover, in surface waters, light intensity showed a significant positive effect on DMSPp production (r2=0.37, P < 0.01, n=20), with elevated DMSP concentration under high irradiance. Overall, the sea-to-air fluxes of DMS across the coastal area of the northern SCS in summer were within the range of 0.24-15.07 mu mol m(-2) d(-1), with a mean flux of 2.12 +/- 3.20 smol m(-2) d(-1). (C) 2016 Elsevier Ltd. All rights reserved
Antiviral Merosesquiterpenoids Produced by the Antarctic Fungus Aspergillus ochraceopetaliformis SCSIO 05702
No full textFive new highly oxygenated alpha-pyrone merosesquiterpenoids, ochraceopones A-E (1-5), together with one new double bond isomer of asteltoxin, isoasteltoxin (6), and two known asteltoxin derivatives, asteltoxin (7) and asteltoxin B (8), were isolated from an Antarctic soil-derived fungus, Aspergillus ochraceopetaliformis SCSIO 05702. Their structures were determined through extensive spectroscopic analysis, CD spectra, quantum mechanical calculations, and X-ray single-crystal diffraction. Ochraceopones A-D (1-4) are the first examples of alpha-pyrone merosesquiterpenoids possessing a linear tetracyclic carbon skeleton, which has not been previously described. All the isolated compounds were tested for their antiviral, cytotoxic, antibacterial, and antitubercular activities. Among these compounds, ochraceopone A (1), isoasteltoxin (6), and asteltoxin (7) exhibited antiviral activities against the H1N1 and H3N2 influenza viruses with IC50 values of >20.0/12.2 +/- 4.10, 0.23 +/- 0.05/0.66 +/- 0.09, and 0.54 +/- 0.06/0.84 +/- 0.02 mu M, respectively. A possible biosynthetic pathway for ochraceopones A-E (1-5) was proposed
The Southwest Indian Ocean thermocline dome in CMIP5 models: Historical simulation and future projection
No full textUsing 20 models of the Coupled Model Intercomparison Project Phase 5 (CMIP5), the simulation of the Southwest Indian Ocean (SWIO) thermocline dome is evaluated and its role in shaping the Indian Ocean Basin (IOB) mode following El NiEeno investigated. In most of the CMIP5 models, due to an easterly wind bias along the equator, the simulated SWIO thermocline is too deep, which could further influence the amplitude of the interannual IOB mode. A model with a shallow (deep) thermocline dome tends to simulate a strong (weak) IOB mode, including key attributes such as the SWIO SST warming, antisymmetric pattern during boreal spring, and second North Indian Ocean warming during boreal summer. Under global warming, the thermocline dome deepens with the easterly wind trend along the equator in most of the models. However, the IOB amplitude does not follow such a change of the SWIO thermocline among the models; rather, it follows future changes in both ENSO forcing and local convection feedback, suggesting a decreasing effect of the deepening SWIO thermocline dome on the change in the IOB mode in the future
Seasonal variations of sea level anomaly in the subtropical front zone based on satellite-derived data from 2003-2009
No full textWe investigated seasonal variations in the sea level anomaly in the northwestern Pacific subtropical front zone using weekly satellite-derived products and in situ observations from 2003 to 2009. The sea level anomalies had different seasonal cycles in the cold, front and warm zones. In the former two zones, peak values appeared (similar to 15 cm) in July-August and hollow values (similar to-10 cm) in February-March; in the warm zone, sea level anomalies had no apparent seasonal variations. We found that the correlation between sea level anomaly and sea surface temperature reached values of 0.76 in the cold and front zones, but only 0.38 in the warm zone. The steric height anomaly explained 70% variances of sea level anomaly in the former two zones but only 25% in the warm zone. We examined the mechanisms of the different patterns of sea level anomaly variation among the three different zones and concluded that the steric height anomaly induced by air-sea heat exchanges controlled the seasonal variations of sea level anomaly in the former two zones, while the barotropic term accompanied with subtropical countercurrent lead to the obscure seasonal variations in the warm zone. These high frequency variations merit future study
Sources and export of nutrients associated with integrated multi-trophic aquaculture in Sanggou Bay, China
No full textField observations were made from 2012 to 2014 at an integrated multi-trophic aquaculture (IMTA) site in Sanggou Bay (SGB), China, to characterize the nutrients associated with aquaculture activities, and to assess the effects of aquaculture on nutrient cycles in the bay. Dissolved inorganic and organic nutrient levels were measured in rivers, groundwater, and SGB. Seasonal variations in nutrient concentrations were detected in the rivers, particularly enrichment of dissolved inorganic nitrogen (DIN) and silicate (DSi). Nutrient concentrations showed considerable seasonal variation, with higher and significantly different concentrations occurring in autumn than in the other seasons. The composition and distribution of nutrients were also affected by the species being cultured. Dissolved organic nitrogen and phosphorus (DON and DOP) accounted for 27 to 87% of total dissolved nitrogen and 34 to 81% of total dissolved phosphorus, respectively. Phosphorus may be a potentially limiting nutrient for phytoplankton growth in summer. Nutrient budgets were developed based on a simple steady-state box model. These showed that bivalve aquaculture was the major source of PO43-(contributing 64% of total influx) and led to increased riverine fluxes of PO43-. The results indicated that substantial quantities of nitrogen and DSi accumulated in sediments or were transformed into other forms (e.g. phytoplankton cell composition or particles). Large quantities of DIN and PO43- were removed from the bay through harvesting of seaweeds and bivalves, which represented up to 64 and 81% of total outflux, respectively. The results show that aquaculture activities play the most important role in nutrient cycling in SGB
Variations in massive Porites growth rates at Hainan Island, northern South China Sea
No full textAnnual density banding in massive coral skeletons provides a means to retrospectively monitor coral growth rates. In this study, we present new records of annual skeletal density, linear extension and calcification rates for 16 Porites spp. coral cores from northeastern Hainan Island, northern South China Sea. Based on average growth characteristics from 1948 to 2001, P. lobata had significantly higher linear extension and calcification rates and lower density than P. lutea. We also found evidence of an age-related effect on growth, whereby skeletal density de creased and linear extension rate increased through time. This did not affect calcification rates. The average calcification rate for northeastern Hainan Island Porites matches that expected for Indo-Pacific Porites based on average sea surface temperatures (SST) from 1961 to 1990. After removal of the ontogenetic trends, average 16-core calcification rates from 1923 to 2002 showed an initial increase, matching observed SST warming. After 1982, however, calcification significantly decreased, although SST did not continue to warm. We suggest that the lower calcification rates from 1983 to 2002 may be a response to eutrophication of coastal waters as a result of extensive coastal aquaculture development. In summary, our new growth records from Hainan Island show that, despite species differences, calcification rates were typical of Indo-Pacific Porites but that in the latter half of the 20th Century, calcification rates have likely responded to both globally and locally induced changes in the marine climate experienced by the corals
Seasonal variations of seawater pCO(2) and sea-air CO2 fluxes in a fringing coral reef, northern South China Sea
No full textEvidence based on four field surveys conducted between July 2009 and April 2011 indicates that both sea surface partial pressures of CO2 (pCO(2)) and sea-air CO2 fluxes at Luhuitou fringing reef in Sanya, Hainan Island, northern South China Sea (SCS) are subject to significant seasonal variations. The diurnal variation of seawater pCO(2) ranges from 264 to 579 mu atm in summer, which is much larger than that in autumn (152-335 mu atm), in winter (84-260 mu atm), and in spring (114-228 mu atm). The sea-air CO2 flux in summer (similar to 9.6 mmol CO2 m(-2) d(-1)) is also larger than that in other seasons (i.e.,similar to 3 mmol CO2 m(-2) d(-1) in spring, similar to 3.5 mmol CO2 m(-2) d(-1) in autumn, and similar to 2.7 mmol CO2 m(-2) d(-1) in winter). The atmospheric pCO(2) in this reef shows small diurnal and seasonal variations. The integration of the time-series pCO(2) data shows that the reef area is a weak source of atmospheric CO2 at similar to 0.54 mol CO2 m(-2) yr(-1). Further analyses indicate that the seasonal variations of the surface seawater pCO(2) in Luhuitou fringing reef are mainly affected by seasonally-dependent biological metabolic processes (organic processe and inorganic process), and that the organic process play a more important role than the inorganic process. Seasonal sea surface temperature (SST) variations and hydrodynamic processes may also have some influence on seawater pCO(2) variation
Remote sensing of spatial-temporal distribution characters of suspended sediment concentration in Hangzhou Bay, China
No full text近岸海域悬浮泥沙对海洋环境有重要影响。杭州湾悬浮泥沙分布规律是多种环境因素共同作用的结果。随着大量近岸跨海工程的建立，使杭州湾海域影响悬浮泥沙分布的原因变得更为复杂。本文就以下科学问题做了研究：1）杭州湾悬浮泥沙浓度时空分布规律；2）跨海工程对杭州湾悬浮泥沙浓度时空分布的影响；3）潮流对杭州湾悬浮泥沙浓度时空分布的影响；4）地形对杭州湾悬浮泥沙浓度时空分布的影响
The applicability analysis of the island rule theory and its application to the inter-ocean circulation in the China adjacent seas
No full text岛屿环流理论是一种可用于解释域际环流形成动力机制和估算域际环流流量的动力学理论。本文首先系统回顾了该理论的发展历程和数学推导过程，并设计了一系列矩形海域的理想情景，应用MITgcm模式模拟了不同情况下岛屿周边的海水流动。以这些数值实验为基础，结合理论分析的方法，分析了各种情况下岛屿环流理论的适用性。本研究给出了一种考虑了摩擦作用的多岛屿环流的解析表达形式，并将该解析解与数值模拟结果进行了对比验证。在分析了在岛屿西侧存在海槛时岛屿环流理论计算解与数值实验结果的差异之后，发现在海槛足够高时，经典岛屿环流理论已经不再适用，并且当海槛南北范围较长时，岛屿西侧风应力对该区域海水通量的影响显著加强。数值实验结果还表明，即便存在海水垂向层化和风应力强迫场随时间变化，经典理论在某些情况下仍然可以良好再现岛屿周边海水流动特点，而在另外一些情况下，考虑了压强梯度修正项以后所得的结果与数值模拟结果更加符合
Characterization and New parameterization of Double Diffusive Convection in the Ocean
No full text海洋混合是海洋中普遍且重要的动力过程，其本质是驱使海水各种特性逐渐趋向均匀。对于层结的海洋环境，混合对海洋中物质、动量、能量及热量的交换和输运以及海洋环流系统的驱动与维持起着不可或缺的作用。在海洋中，虽然存在多种驱动混合的机制，但最终都体现在小尺度或微尺度结构的湍流混合和弱对流混合形式。在弱对流混合中，双扩散是非机械驱动的最主要混合形式。在海洋中，只要温度或盐度两者之一具有“不稳定”的垂直分布（即温度随深度增加而升高，或盐度随深度增加而减少），由于分子热扩散系数远大于盐扩散系数（κT ≈ 100κS），便可能引起双扩散对流。双扩散又分为“盐指（SF）”和“扩散对流（DC）”两种基本类型