Institutional Repository of South China Sea Institute of Oceanology, CAS
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Teleseismic P-wave traveltime tomography for the Leigiong volcano and Cathaysia block
No full textWe obtained 18968 reliable P wave relative traveltime residuals by adaptive stacking technique based on waveform cross-correlation of 256 distant earthquake records. The teleseismic waveform data were recorded by 94 permanent seismic stations belonging to seismic networks of Guangdong and neighboring provinces. The P wave velocity structure beneath the Leiqiong volcano and Cathaysia block down to 450 km depth was determined by the Fast Marching Teleseismic Tomography (FMTT). The results show an obvious low-velocity anomaly beneath the Leiqiong volcano from 100 km to 450 km depth. This low-velocity anomaly extends to the Cathaysia block with depth increasing. It is suggested that this low-velocity anomaly is caused by the upwelling of thermal materials of the Hainan plume, and the Leigiong volcano is an intraplate hot spot, which is consistent with previous results of body-wave tomography and receiver function studies. It is also inferred that the Hainan plume dips to the northeast and probably extends to 450 km depth from the pattern of the low-velocity anomalies. The low-velocity anomalies beneath the Cathaysia block is likely produced by the northeastward erosion of upwelling hot materials of the Hainan plume. The results may also imply that the lithospheric thickness of the study area tends to be thinner from the land to the sea
IODP349航次地热调查数据分析
No full text海底热流是研究大洋地壳和上地幔岩石圈热状态的重要参数。为了解南海深水区地热特征,利用IODP349航次地热调查资料进行数据处理,得到了4个站位浅层热导率数据和3个钻孔的海底热流数据。结果表明,浅层沉积物样品热导率变化范围为0.8~2.2 W/(m·K),变化范围与沉积物成分有关,热导率随深度的增加有小幅增加的趋势与沉积物压实作用有关;U1431D、U1432C和U1433A三个钻孔热流值分别为24±8mW/m2、105±3mW/m2和89±2mW/m2,后两个钻孔通过与前人实测数据进行对比,与前人结果相当,表明了结果的可靠性;U1431D发生地温梯度倒转和低热流异常可能是与钻孔处于水热循环的下降流附近有关
太空搭载海水钝顶螺旋藻诱变株H_(11)的室外产多糖特性研究
No full text本研究对一株经太空搭载后选育的海水钝顶螺旋藻诱变株H_(11)的室外产多糖能力进行了评估。结果显示,在广州秋季室外平均温度为27°C下,诱变株H_(11)的生物量产率、总糖含量、总多糖含量和水溶性多糖含量分别为19.09±0.03 mg/(L·d)、27.89±1.28%DW、20.95±0.87%DW和19.74±0.93%DW。与野生株WT相比,H_(11)的生物量、总糖、总多糖和水溶性多糖的产率分别提高了15.39%,148.93%,176.50%和187.70%。在冬季室外平均培养温度为17°C条件下,诱变株和野生株生长速率及多糖产率都有所降低,但诱变株在产多糖能力上仍显著高于野生株(P<0.05)。研究表明海水钝顶螺旋藻诱变株H_(11)产多糖能力极高,具有可观的产业应用前景
全球海草的中文命名
No full text海草(seagrass)是地球上唯一一类可以完全生活在海水中的高等被子植物。全球已知海草的种类有70余种,隶属6科13属;中国现有海草22种,隶属4科10属。2014年11月"第十一次国际海草生物学研讨会"(The 11~(th) International Seagrass Biology Workshop)在三亚召开时,国内海草研究专家共同探讨了中国海草的"藻"名更改,并进行了统一命名。然而,国内中文文章在引用非中国海草种类时,同一种海草的中文名称不一致,或者同一属不同的物种以一样的中文名出现,或者用属中文名后接拉丁文方式表达。同时,国外海草的中文名也多以"藻"来命名,容易引起混淆。因此,有必要在中国海草"藻"名更改的基础上,进一步规范全球其他海草的中文命名,以利于国内海草研究
新颖深海微生物酯酶EstC11的酶学性质及其在手性拆分乙酸苏合香酯中的应用
No full text【背景】手性乙酸苏合香酯是重要的手性香料产品,在食品及精细化工等领域都有重要的应用。酶催化不对称合成手性乙酸苏合香酯产品具有极好的工业应用前景。【目的】研究酯酶EstC11的基本酶学性质及其在制备手性乙酸苏合香酯中的应用。【方法】对来自西太平洋深海热液口芽孢杆菌Bacillus sp.CX01中的新颖微生物酯酶基因EstC11进行克隆、表达及酶学性质鉴定。通过对p H、温度、有机溶剂等反应条件的优化提高酯酶手性拆分乙酸苏合香酯的光学纯度。【结果】酯酶EstC11的最适反应p H为8.5,最适温度为25°C,一些金属离子和有机溶剂对酯酶EstC11的水解活性具有不同程度的抑制作用。通过对反应条件的优化,在最适反应条件下(p H 9.0 50 mmol/L Tris-HCl,20°C,50 mmol/L底物浓度)反应3 h后,(R)-乙酸苏合香酯的光学纯度达98%,得率为39%。【结论】通过对酯酶拆分条件的优化,手性拆分乙酸苏合香酯生成(R)-乙酸苏合香酯的光学纯度明显提高,为酯酶EstC11在工业化上的应用奠定了基础
三亚珊瑚礁保护区珊瑚礁生态系统现状及其健康状况评价
No full text为评估三亚珊瑚礁国家级自然保护区珊瑚礁生态系统的健康状况,本文选取东岛、鹿回头、大东海3个站位调查了珊瑚礁群落、珊瑚礁鱼类和大型底栖动物。通过对比分析历史资料、珊瑚礁现场生态调查与监测及组织专家评审,筛选出一、二级指标并设置权重,使用综合指数计算了三亚珊瑚礁保护区珊瑚礁生态系统健康指数。结果显示,三亚珊瑚礁保护区内共有造礁珊瑚10科21属37种,软珊瑚3种,造礁珊瑚覆盖率和软珊瑚覆盖率分别为14.31%和0.19%,其中鹿回头造礁珊瑚覆盖率最高,为21.58%。珊瑚礁鱼类共14科28属36种,其中,雀鲷科的种类数最多,为11种。鹿回头4 m断面珊瑚礁鱼类密度最大,为154尾/300 m~2。砗磲和龙虾极少发现,珊瑚天敌核果螺多见。东岛、鹿回头、大东海珊瑚礁生态系统健康状况均处于"一般"。本文所采用的方法是结合常规珊瑚礁监测可获得的指标进行评价,简便易操作,通过在三亚珊瑚礁保护区的实践,能够很好地反映珊瑚礁生态系统现状及其健康状况,科研和业务化监测部门均可应用
Unusual Rainfall in Southern China in Decaying August during Extreme El Nino 2015/16: Role of the Western Indian Ocean and North Tropical Atlantic SST
No full textPrevious research has suggested that the anomalous western North Pacific anticyclone (WNPAC) can generally persist from an El Nino mature winter to the subsequent summer, influencing southern China precipitation significantly, where southern China includes the Yangtze River valley and South China. Since the late 1970s, three extreme El Nino events have been recorded: 1982/83, 1997/98, and 2015/16. There was a sharp contrast in the change in southern China rainfall and corresponding atmospheric circulations in the decaying August between the 2015/16 extreme El Nino event and the earlier two extreme El Nino events. Enhanced rainfall in the middle and upper reaches of the Yangtze River and suppressed rainfall over South China resulted from basinwide warming in the tropical Indian Ocean induced by the extreme El Nino in August 1983 and 1998, which was consistent with previous studies. However, an anomalous western North Pacific cyclone emerged in August 2016 and then caused positive rainfall anomalies over South China and negative rainfall anomalies from the Yangtze River to the middle and lower reaches of the Yellow River. Without considering the effect of the long-term global warming trend, in August 2016 the negative SST anomalies over the western Indian Ocean and cooling in the north tropical Atlantic contributed to the anomalous western North Pacific cyclone and a rainfall anomaly pattern with opposite anomalies in South China and the Yangtze River region. Numerical experiments with the CAM5 model are conducted to confirm that cooler SST in the western Indian Ocean contributed more than cooler SST in the north tropical Atlantic to the anomalous western North Pacific cyclone and anomalous South China rainfall
On the Simulations of Global Oceanic Latent Heat Flux in the CMIP5 Multimodel Ensemble
No full textSimulations of the global oceanic latent heat flux (LHF) in the CMIP5 multimodel ensemble (MME) were evaluated in comparison with 11 LHF products. The results show that the mean state of LHF in the MME coincides well with that in the observations, except for a slight overestimation in the tropical regions. The reproduction of the seasonal cycle of LHF in the MME is in good agreement with that in the observations. However, biases are relatively obvious in the coastal regions. A prominent upward trend in global-mean LHF is confirmed with all of the LHF products during the period of 1979-2005. Despite the consistent increase of LHF in CMIP5 models, the rates of increase are much weaker than those in the observations, with an average of approximately one-ninth that in the observations. The findings show that the rate of increase of near-surface specific humidity q(a) in MME is nearly 6 times that in the observations, while the rate of increase of the near-surface wind speed U is less than one-half that in the observations. The faster increase of q(a) and the slower increase of U could both suppress evaporation, and thus latent heat released by the ocean, which may be one of the reasons that the upward trend of LHF in the MME is nearly one order of magnitude lower than that in the observations
Nitrogen fate in a subtropical mangrove swamp: Potential association with seawater-groundwater exchange
No full textCoastal mangrove swamps play an important role in nutrient cycling at the land-ocean boundary. However, little is known about the role of periodic seawater-groundwater exchange in the nitrogen cycling processes. Seawatergroundwater exchange rates and inorganic nitrogen concentrations were investigated along a shore-perpendicular intertidal transect in Daya Bay, China. The intertidal transect comprises three hydrologic subzones (tidal creek, mangrove and bare mudflat zones), each with different physicochemical characteristics. Salinity and hydraulic head measurements taken along the transect were used to estimate the exchange rates between seawater and groundwater over a spring-neap tidal cycle. Results showed that the maximum seawater-groundwater exchange occurred within the tidal creek zone, which facilitated high-oxygen seawater infiltration and subsequent nitrification. In contrast, the lowest exchange rate found in the mangrove zone caused over-loading of organic matter and longer groundwater residence times. This created an anoxic environment conducive to nitrogen loss through the anammox and denitrification processes. Potential oxidation rates of ammonia and nitrite were measured by the rapid and high-throughput method and rates of denitrification and anammox were measured by the modified membrane inlet mass spectrometry (MIMS) with isotope pairing, respectively. In the whole transect, denitrification accounted for 90% of the total nitrogen loss, and anammox accounted for the remaining 10%. The average nitrogen removal rate was about 2.07 g per day per cubic meter of mangrove sediments. (C) 2018 Elsevier B.V. All rights reserved
Assessment of fine-scale parameterizations at low latitudes of the North Pacific
No full textFine-scale parameterizations based on shear and stratification are widely used to study the intensity and spatial distribution of turbulent diapycnal mixing in the ocean. Two well-known fine-scale parameterizations, Gregg-Henyey-Polzin (GHP) parameterization and MacKinnon-Gregg (MG) parameterization, are assessed with the full-depth microstructure data obtained in the North Pacific. The GHP parameterization commonly used in the open ocean succeeds in reproducing the dissipation rates over smooth topography but fails to predict the turbulence over rough topography. Failure of GHP parameterization over rough topography is attributed to the deviation of internal wave spectrum from the Garrett-Munk (GM) spectrum. The internal wave field over rough topography is characterized by energetic intermediate-scale and small-scale internal waves that are not described well by the GM model. The MG parameterization that is widely used in coastal environments is found to be successful in reproducing the dissipation rates over both smooth and rough topographies. The efficacy of GHP and MG parameterizations in evaluating the dissipation rates has been assessed. The result indicates that MG parameterization predicts the magnitude and variability of the dissipation rates better than the GHP parameterization