Institutional Repository of South China Sea Institute of Oceanology, CAS
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Biases of five latent heat flux products and their impacts on mixed-layer temperature estimates in the South China Sea
No full textFive latent heat flux (LHF) products are evaluated based on in situ observations in the South China Sea (SCS), including the ECWMF ERA-Interim (ERA-I), the NCEP2, the Objectively Analyzed air-sea Fluxes (OAFlux), the Japanese 55 year Reanalysis (JRA55), and the TropFlux data sets. The results show that there are good correlations between the LHF products and observations, ranging from 0.68 to 0.74. However, mean biases of 28 to 40Wm(-2) exist in the LHF products with respect to the observations. For root-mean-square errors, the OAFlux data set is the closest to the observations, followed by ERA-I and TropFlux, while the NCEP2 data set shows significant overestimation. It is found that the biases in the near-surface-specific humidity are most correlated with the biases in the LHF products, followed by the biases in the near-surface wind speed, air temperature, and sea surface temperature. The biases in the LHF products have a prominent seasonal variation that is 25 W m(-2) higher in boreal winter than in summer. Using the thermal equation, it is shown that the tendency errors of the mixed-layer temperature estimated by the biases in the LHF products vary from 22.0 to 3.5 degrees C/month in the SCS. When all of the products are averaged, the errors are reduced to a range of 20.7 to 1.5 degrees C/month. It is noteworthy that the errors in summer are more obvious than those in winter, since a thinner mixed layer in the summer can amplify the effect of even a small bias in the LHF
Thermocline Fluctuations in the Equatorial Pacific Related to the Two Types of El Nino Events
No full textThe interannual fluctuations of the equatorial thermocline are usually associated with El Nino activity, but the linkage between the thermocline modes and El Nino is still under debate. In the present study, a mode function decomposition method is applied to the equatorial Pacific thermocline, and the results show that the first two dominant modes (M1 andM2) identify two distinct characteristics of the equatorial Pacific thermocline. The M1 reflects a basinwide zonally tilted thermocline related to the eastern Pacific (EP) El Nino, with shoaling (deepening) in the western (eastern) equatorial Pacific. The M2 represents the central Pacific (CP) El Nino, characterized by a V-shaped equatorial Pacific thermocline (i.e., deep in the central equatorial Pacific and shallow on both the western and eastern boundaries). Furthermore, both modes are stable and significant on the interannual time scale, and manifest as the major feature of the thermocline fluctuations associated with the two types of El Nino events. As good proxies of EP and CP El Nino events, thermocline-based indices clearly reveal the inherent characteristics of subsurface ocean responses during the evolution of El Nino events, which are characterized by the remarkable zonal eastward propagation of equatorial subsurface ocean temperature anomalies, particularly during the CP El Nino. Further analysis of the mixed layer heat budget suggests that the air-sea interactions determine the establishment and development stages of the CP El Nino, while the thermocline feedback is vital for its further development. These results highlight the key influence of equatorial Pacific thermocline fluctuations in conjunction with the air-sea interactions, on the CP El Nino
Petrogenesis of Huangbanjigou high magensiun andesite in Early Cretaceous Yixian Formation, western Liaoning
No full textOlivine-hosted melt inclusions and their hosts, together with the bulk rocks were used to investigate the petrogenesis of the Huangbanjigou volcanic rocks in the Early Cretaceous Yixian Formation, western Liaoning Province. The Huangbanjigou volcanic rocks show the features of high magnesium andesite, such as SiO2 = 53. 41% similar to 53.74%, MgO = 8. 15%similar to 8.23%, Mg-# = 70 (Mg-# = mol Mg/(Mg + Fe2+)). They are sub-alkaline series, plating in the field of basaltic andesite in the TAS diagram. They also exhibit the characteristics of the mantle attributions, such as moderately high Ni (119 x 10(-6) similar to 125 x 10(-6)) and high Cr (467 x 10(-6) similar to 521 x 10(-6)). The Huangbanjigou high magnesium andesites have 920 x 10(-6) similar to 930 x 10(-6) Sr, 16. 1 x 10(-6) similar to 16. 4 x 10(-6) Y and 57 similar to 58 Sr/Y. In the mantle primitive-normalized spider diagram, the Huangbanjigou high magnesium andesites show fractionation from light to heavy rare earth elements, significant and slight negative anomalies of Nb-Ta-Ti and Zr-Hf,, respectively, and positive anomalies of BaSr-Pb; all these features resemble that of the continental lower crust. The olivine-hosted melt inclusions have 6. 5% similar to 9. 7% MgO and 51% 53% SiO2, unlike those of the typical high magnesium andesite. They are alkaline series, falling in the field of basaltic trachyandesite in the TAS plot. There are significant or slight negative relationships between MgO and other major element oxides, pointing to the olivine-controlled fractionation. Olivine crystals of the Huangbanjigou high magnesium andesites have Fo = 75 similar to 91, CaO = 0. 10%similar to 0. 18%, NiO = 0. 05%similar to 0. 41%, Fe/Mn = 60 similar to 80. There are large compositional discrepancies between the bulk rocks and the melt inclusions of the Huangbanjigou high magnesium andesites, such as the melt inclusions with higher Al2O3 and lower SiO2. Together with their similar trace element features to those of the continental lower crust, we suggest that the Huangbanjigou high magnesium andesites is the product of the crust-mantle interaction; they must assimilate an acid silicate melt from the lower crust during their magma evolution in the crust depth. We suggest that the mantle-derived melts of the Huangbanjigou andesites are the partial melts of the orthopyroxene-rich pyroxenite, on the basis of (1) relatively low Ni but high Me of the bulk rocks; (2) low CaO of the melt inclusions; (3) melt inclusion plotting in the SiO2-enriched side of the thermal divide boundary in the phase diagram of the CATS Olivine -Quartz; and (4) the olivine crystals with low Ca and steeper relationship between Fo and Ni. We argue that the widespread high magnesium andesites in the Early Cretaceous Yixian Formation, western Liaoning Province, likely underwent crust-mantle interaction; hence, they can not be considered as an important evidence of the delamination process resulting in the large scale thinning of the lithosphere
Geochemical record of methane seepage in authigenic carbonates and surrounding host sediments: A case study from the South China Sea
No full textSediments at marine methane seep sites provide potential archives of past fluid flow that serve to explore seepage activities over time. Three gravity cores (D-8, D-F, and D-7) were collected from seep sites on the northern slope of the South China Sea where gas hydrates were drilled in the subsurface. Various carbon and sulfur contents, delta C-13 values of total inorganic carbon (delta C-13(TIC)), delta S-34 values of chromium reducible sulfur (delta S-34(CRS)), trace element contents, grain size, and AMS C-14 dating of planktonic Foraminifera in the sediments were determined to explore the availability of related proxies at seeps and to trace past methane seepage activities. Evidence for the presence of methane seepage and consequently anaerobic oxidation of methane comes from the occurrence of C-13-depleted authigenic carbonate nodules (delta C-13 values as low as -49 parts per thousand) discovered at an interval of 150-200 cm in core D-7. This finding is supported by high S/C ratios and molybdenum enrichment in the same interval. However, low contents of CRS and negative delta S-34(CRS) values are present. It is suggested to reflect a transient methane seepage event, which continued for about 1 ka based on the C-14 ages. Cores D-8 and D-F have delta C-13(TIC) values close to zero, low S/C ratios and CRS contents, negative delta S-34(CRS) values, and no trace element enrichment, suggesting a negligible impact of methane-seepage on the sediments. The negative delta S-34(CRS) values of the studied seep impacted and background sediments suggest that the application of delta S-34(CRS) alone as a proxy to identify AOM-related process may be insufficient. Sediment carbon-sulfur-trace element systematics and 14C ages used here have the potential to be a promising tool to recognize transient methane seepages and constrain their timescales. (C) 2017 Elsevier Ltd. All rights reserved
Live benthic foraminifera in the Yellow Sea and the East China Sea: vertical distribution, nitrate storage, and potential denitrification
No full textBenthic foraminifera were investigated to determine their vertical distribution, nitrate storage, and potential denitrification in the Yellow Sea (YS) and the East China Sea (ECS). The phytodetritus content and freshness as well as sediment redox conditions were key factors determining the vertical distribution of foraminifera in sediments of the YS and the ECS. The intracellular nitrate (ICNO3) concentrations of Nonionella stella, Hanzawaia nipponica, Bolivina robusta, Cancris auriculus, and Globobulimina pacifica ranged from 3 to 114 mM, which in some cases was several hundred-fold more than the pore water nitrate (PWNO3) concentrations. The genus Hanzawaia was for the first time reported to store ICNO3 (316 +/- 73 pmol ind.(-1); 11 +/- 3 mM). The significant correlation between the ICNO3 concentration and foraminiferal abundance (Pearson correlation: r = 0.401, p < 0.01, n = 60) suggested that foraminifera may have an important role in nitrate storage in the sediments. The foraminiferal intracellular nitrate (FINO3) pool ranged from 9 to 74% of the ICNO3 pool in sediments, indicating that nitrate may be stored by other sediment organisms (e.g. diatoms). The chlorophyll a concentration, chloroplastic pigment equivalents (CPE), and chlorophyll a:phaeopigment ratio were all significantly positively correlated with the ICNO3 concentration (Pearson correlation: r = 0.563, 0.603, and 0.457, respectively; p < 0.01; n = 60), indicating that phytodetritus (e.g. diatoms) might also contribute to sedimentary ICNO3. Potential foraminiferal denitrification rates ranged from 9 to 92 mu mol m(-2) d(-1) in the YS and the ECS, indicating that benthic foraminifera might play a role in sedimentary denitrification
Hydrous orthopyroxene-rich pyroxenite source of the Xinkailing high magnesium andesites, Western Liaoning: Implications for the subduction-modified lithospheric mantle and the destruction mechanism of the North China Craton
No full textMetasomatism of the lithospheric mantle by subduction-related fluids/melts is recorded in the Early Cretaceous Xinkailing high magnesium andesites (HMAs) from Western Liaoning. Olivine -hosted melt inclusions within the Xinkailing HMAs are alkaline and record a much lower SiO2 content and higher Al2O3 and CaO contents than the sub-alkaline bulk rock compositions. These observed compositional differences between bulk rocks and melt inclusions suggest that a crustally derived, high-SiO2 melt was incorporated in the Xinkailing HMAs within the pre-eruptive magma chamber. The process of this incorporation accounts for the compositional differences between upper (HMAs) and lower (high magnesium basalts) successions of the Yixian Formation. Olivine phenocrysts also record unusually high Ni and Ni/MgO contents with high Fo values. Based on the fact that bulk rocks record low Ni contents, whereas olivine crystals record a steep correlation between Fo and Ni and low CaO and CaO/FeO contents, in addition to the likely considerable depression of the olivine liquidus temperature, we argue that a hydrous (2-6% H2O) orthopyroxene-rich pyroxenite source was formed by the reaction between subducted slab-released SiO2-rich fluids and overlying mantle peridotite. We further propose that during a series of Phanerozoic successive subduction events around the Eastern NCC, a significant amount of water may have been transported to the lithospheric mantle, thus lowering its viscosity and ultimately destabilizing the cratonic lithosphere. (C) 2017 Elsevier B.V. All rights reserved
Interseasonal and interspecies diversities of Symbiodinium density and effective photochemical efficiency in five dominant reef coral species from Luhuitou fringing reef, northern South China Sea
No full textAlthough it is well established that different coral species have different susceptibilities to thermal stress, the reasons behind this variation are still unclear. In this study, 384 samples across five dominant coral species were collected seasonally between September 2013 and August 2014 at Luhuitou fringing reef in Sanya, Hainan Island, northern South China Sea, and their algal symbiont density and effective photochemical efficiency (I broken vertical bar (PSII)) were measured. The results indicated that both the Symbiodinium density and I broken vertical bar (PSII) of corals were subject to significant interspecies and seasonal variations. Stress-tolerant coral species, including massive Porites lutea and plating Pavona decussata, had higher symbiont densities but lower I broken vertical bar (PSII) compared to the vulnerable branching species of Acropora over the course of all four seasons. Seasonally, coral symbiont densities were the lowest during winter, while during the same period, I broken vertical bar (PSII) of corals was at the highest point. Further analysis suggested that dissolved inorganic nutrients and upwelling in the reef area were probably responsible for the observed seasonal variations in symbiont density. The fact that Porites lutea has the lowest I broken vertical bar (PSII) during all four seasons is likely related to their symbionts' lower capacity to provide required photosynthates for calcification. These results suggest that a coral's thermal tolerance is primarily and positively dependent on its symbiont density and is less related to its effective photochemical efficiency
Relationship between nutrients and plankton biomass in the turbidity maximum zone of the Pearl River Estuary
No full textNutrients, dissolved and particulate organic carbon and plankton (bacterio-, phyto- and zoo-) were compared in the turbidity maximum zone (TMZ) and adjacent areas (non-TMZ) in the Pearl River estuary. Our results showed that high levels of suspended substances had marked effect on dynamics of nutrients and plankton in the TMZ. Based on the cluster analysis of total suspended solids (TSS) concentrations, all stations were divided into two groups, TMZ with average TSS of 171 mg/L and non-TMZ of 45 mg/L. Suspended substances adsorbed POI43- and dissolved organic carbon, resulting in higher particulate phosphorus and organic carbon (POC) and lower PO43- and DOC in the TMZ, compared to the non-TMZ. However, suspended substances had limited effect on nitrogenous nutrients. Phytoplankton growth was light -limited due to high concentrations of suspended substances in the TMZ and a peak of phytoplankton abundance appeared in the non-TMZ. In contrast, the highest bacterial abundance occurred in the TMZ, which was likely partly responsible for low DOC levels. Two peaks of zooplankton abundance observed in the TMZ and non-TMZ in the Pearl River estuary were primarily supported by bacteria and phytoplankton, respectively. Our finding implied that high levels of suspended solids in the TMZ affect the trophic balance. (C) 2016 The Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences. Published by Elsevier B.V
夏季大亚湾大型底栖动物群落结构
No full text利用2013年8月在大亚湾海域进行的海洋生态调查所采集的底栖动物样品及环境参数,研究了夏季大亚湾海域底栖动物种类组成、数量分布、群落结构及其环境影响因子。结果表明,调查共采集到大型底栖动物153种,其中环节动物81种、软体动物37种、甲壳动物25种、棘皮动物6种、其他类动物4种;环节动物种数占总种数的52.94%,是构成大亚湾大型底栖动物的主要类群。优势种类为短吻铲荚螠和波纹巴菲蛤。底栖动物平均丰度和平均生物量分别为410ind·m~(–2)和84.83g·m~(–2)。等级聚类分析(CLUSTER)将大亚湾的底栖动物分为5个群落。相关性分析表明,影响夏季大亚湾底栖动物群落结构的主要环境因子为沉积物石油类。BIOENV分析表明,底栖动物种类丰度与有机质和重金属的铅、铜和镉等环境因素密切相关
广州市南沙水产养殖区抗生素的残留特性
No full text水产养殖业迅猛发展带来的抗生素残留问题已经受到社会各界的高度关注,抗生素在水产品中的残留会直接影响水生生态系统安全以及人类健康。应用固相萃取-高效液相色谱-串联质谱法(solid-phase extraction-rapid resolution liquid chromatography–tandem mass spectrometry,SPE-RRLC-MS/MS)检测了35种抗生素(14种磺胺类,10种氟喹诺酮类,6种大环内酯类,2种四环类和3种其他类)在广州市南沙水产养殖区各环境介质和鱼体不同组织中的残留水平,研究结果表明,在养殖区的水体、颗粒物、沉积物和饲料中共检出12种抗生素,浓度最大值分别为60.76ng·L~(–1)(脱水红霉素)、1691ng·g~(–1)(莫能菌素)、2.41ng·g~(–1)(恩诺沙星)和74.96ng·g~(–1)(恩诺沙星);鱼体血液、肝脏和肌肉中共检出11种抗生素,浓度最大值分别为33.52μg·L~(–1)(脱水红霉素)、199ng·g~(–1)(诺氟沙星)和22.30ng·g~(–1)(诺氟沙星)。鱼体血液、肝脏和肌肉对抗生素的生物富集系数均值范围分别为147~336、7~8891和8~16。表明不同组织对不同抗生素具有不同富集能力。基于风险熵评价鱼肉中抗生素的残留风险,表明食用这些鱼类不会给人体健康带来风险。本研究结果可以为保障广州市水产品的食用安全,确保水产养殖业可持续健康发展及提升各级环保部门对抗生素环境残留的综合监管能力提供参考