Distribution of Biogenic Silica Content in Surface Sediments from the Southern South China Sea and Its Environmental Dignificance

Biogenic silica content was determined in 25 surface sediment samples from the southern South China Sea to study its distribution and its modern oceanic environmental significance, which may provide further scientific evidence for paleoceanography explaination. This study showed that biogenic silica content in surface sediments and its water depth have evidently positive correlation, and the correlation coefficient was up to 0.782. Biogenic silica content was very low in continental shelf shallows and could not reflect the productivity of siliceous micropaleontology in surface waters, which may be affected by sedimentary types and terrigenous matter dilution. Distribution of biogenic silica content in surface sediments from deep water areas showed that it could not only reflect the paleoproductivity of siliceous micropaleontology in surface waters, but also indicate the strong or feeble upwelling. Thus, it was further confirmed that using biogenic silica content in sediments to trace upwelling and its change was effective and reliable. The analyzed result showed that radiolariia and poriferous specula have more contribution for biogenic opal, comparing with diatom in surface sediments from the northern studied area, probably owing to the diatom dissolved easily away and eaten by other organisms with little effort. In the upwelling areas, radiolarian, diatom and poriferous specula all approximately showed high abundance, which was consistent with high biogenic silica content.

Biogenic silica in intertidal marsh plants and associated sediments of the Yangtze Estuary

Biogenic silica （BSi） contents in the marsh plants （Phragmites australis, Scirpus mariqueter and Spartina alterniflora） and associated sediments in Chongming Island eastern intertidal flat of the Yangtze Estuary were determined. The BSi contents in P. australis, S. mariqueter and S. alterniflora varied from 25.78–42.74 mg/g, 5.71–19.53 mg/g and 6.71–8.92 mg/g, respectively. Over the entire growth season, P. australis and S. mariqueter were characterized by linear accumulation patterns of BSi. The aboveground biomass （leaves and culms） of the marsh plants generally contained more BSi than underground biomass （roots）. BSi contents were relatively higher in dead plant tissues than in live tissues which was probably due to the decomposition and the leaching of labile components of plant tissues such as organic carbon and nitrogen. Comparing with the habitats of S. mariqueter and S. alterniflora, the highest BSi content was recorded in sediments inhabited by P. australis, with an annual average of 15.69 mg/g. Overall, the intertidal marshes in the Yangtze Estuary may act as a net sink of BSi via plant uptake and sedimentary burial.

Distribution and accumulation of biogenic silica in the intertidal sediments of the Yangtze Estuary

Sedimentary biogenic silica is known to be an important parameter to understand biogeochemical processes and paleoenviromental records in estuarine and coastal ecosystems. Consequently, it is of great significance to investigate accumulation and distribution of biogenic silica in sediments. The two-step mild acid-mild alkaline extraction procedure was used to leach biogenic silica and its early diagenetic products in intertidal sediments of the Yangtze Estuary. The results showed that total biogenic silica （t-BSi） in the intertidal sediments varied from 237.7-419.4 μmol Si/g, while the mild acid leachable silica （Si-HCl） and the mild alkaline leachable silica （Si- Alk） were in the range of 25.1-72.9 μmol Si/g and 208.1-350.4 μmol Si/g, respectively. Significant correlations were observed for the grain size distributions of sediments and different biogenic silica pools in intertidal sediments. This confirms that grain size distribution can significantly affect biogenic silica contents in sediments. Close relationships of biogenic silica with organic carbon and nitrogen were also found, reflecting that there is a strong coupling between biogenic silica and organic matter biogeochemical cycles in the intertidal system of the Yangtze Estuary. Additionally, the early diagenetic changes of biogenic silica in sediments are discussed in the present study.

Effects of river damming on biogenic silica turnover:implications for biogeochemical carbon and nutrient cycles

Rivers link terrestrial ecosystems and marine ecosystems, and they transport large amounts of substances into oceans each year, including several forms of silicon(Si), carbon(C), and other nutrients. However, river damming affects the water flow and biogeochemical cycles of Si, C, and other nutrients through biogeochemical interacting processes. In this review, we first summarize the current understanding of the effects of river damming on the processes of biogeochemical Si cycle, especially the source, composition, and recycling process of biogenic silica(BSi). Then, we introduce dam impacts on the cycles of C and some other nutrients. Dissolved silicon in rivers is mainly released from phytolith dissolution and silicate weathering. BSi in suspended matter or sediments in most rivers mainly consists of phytoliths and mainly originates from soil erosion. However, diatom growth and deposition in many reservoirs formed by river interception may significantly increase the contribution of diatom Si to total BSi, and thus significantly influence the biogeochemical Si,C, and nutrient cycles. Yet the turnover of phytoliths and diatoms in different rivers formed by river damming is still poorly quantified. Thus, they should be further investigated to enhance our understanding about the effects of river damming on global biogeochemical Si, C and nutrient cycles.

Contribution of phytoliths to total biogenic silica volumes in the tropical rivers of Malaysia and associated implications for the marine biogeochemical cycle

The contribution of phytoliths to total biogenic silica(BSi) volumes in rivers worldwide,and the associated implications for the biogeochemical cycle,require in-depth study.Based on samples from rivers in Peninsular Malaysia,this project investigated the source and characteristics of B Si found in Asian tropical rivers,as well as the process of reverse weathering taking place in these fluvial systems.Results indicated that BSi samples collected in sediments consisted of phytolith,diatom and sponge spicules.Phytoliths,predominantly of the elongate form,comprised 92.8%-98.3% of BSi in the Pahang River.Diatom BSi in this river consisted mainly of pennatae diatoms,but represented a relatively small proportion of the total BSi volume.However,diatom BSi(predominantly of the Centricae form) was more prevalent in the Pontian and Endau Rivers with shares of 68.8% and 79.3% of the total BSi volumes,respectively,than Pahang River.Carbon contents of the BSi particulates ranged from 1.85% to 10.8% with an average of 4.79%.These values are higher than those recorded in other studies to date,and indicate that BSi plays a major role in controlling permanent carbon burial.This study suggests that phytoliths from terrestrial plants are the primary constituents of BSi in the rivers of Peninsular Malaysia,and therefore represent a significant proportion of the coastal silica budget.

The biogenic silica variation and paleoproductivity evolution in the eastern Indian Ocean during the past 20 000 a

The biogenic silica of sediment samples from Core CJ01-185 which is collected from the eastern India Ocean off the Sunda Strait is analyzed to evaluate the impact of the opening of the Sunda Strait on a paleoproductivity evolution. The new results indicate that the biogenic silica mass values of Core CJ01-185 show the lowest 0.86% in the last glacial period, and reach its maxima of 1.89% in the late Holocene. Furthermore, the biogenic silica mass accumulation rate(MARBSi) values also vary with much higher during the late Holocene than during the last glaciation. The input of additional terrigenous materials from the Java Sea has enhanced the paleoproductivity and increased the biogenic silica mass and MARBSi values after the opening of the Sunda Strait. It is suggested that the paleoproductivity in the study area is mainly influenced by the southeast monsoon and upwelling before the opening of the Sunda Strait. However, the paleoproductivity is dominated by the terrigenous materials input other than by the southeast monsoon or upwelling in the Holocene.

Biogenic silica concentration as a marine primary productivity proxy in the Holsteinsborg Dyb, West Greenland, during the last millennium

We analyzed the biogenic silica(BSi)content and produced a diatom-based summer sea-surface temperature(SST)reconstruction for sediment core GC4 from the Holsteinsborg Dyb,West Greenland.Our aim was to reconstruct marine productivity and climatic fluctuations during the last millennium.Increased BSi content and diatom abundance suggest relatively high marine productively during the interval of AD 1000–1400,corresponding in time to the Medieval Warm Period(MWP).The summer SST reconstruction indicates relatively warm conditions during AD 900–1100,followed by cooling after AD 1100.An extended cooling period during AD 1400–1900 is characterized by prolonged low in reconstructed SST and high sea-ice concentration.The BSi values fluctuated during this period,suggesting varying marine productivity during the Little Ice Age(LIA).There is no significant correlation between the BSi content and SST during the last millennium,suggesting that the summer SST has little influence on marine productively in the Holsteinsborg Dyb.A good correspondence between the BSi content and the element Ti counts in core GC4 suggests that silicate-rich meltwater from the Greenland ice sheet was likely responsible for changes in marine productively in the Holsteinsborg Dyb.

Biogenic silica in surficial sediments of Prydz Bay,Antarctica

The content and distribution of biogenic silica were investigated in sediment cores from Prydz Bay, Antarctica, during the CHINARE-18/2L cruise. The results show that the content of biogenic silica（ BSiO2 ） is ranged from 4.89% to 85. 41% , and the average content of biogenic silica is 30.90%, the highest value oc- curred at the IV-10 station. The profile of BSiO2 in sediment is contrast to that of sili- cate in the interstitial water. The content of biogenic silica and organic carbon in the surface sediments in the central area of Prydz Bay gyre were much higher than those in other area, and closely related to the Chla content and primary productivity of phyto- plankton in the surface water column.

Skeletonema cf.costatum Biogenic Silica Production Rate Determinated by PDMPO Method

Diatoms are the only ecological phytoplankton that require silicic acid for growth.They are also the dominant contributor of ocean's total primary productivity.Generation and circulation with silica walls,which the siliceous organisms form,is an important component of the marine biological pump.It is crucial to the study of the operational mechanisms of biological pump with different sea areas.Moreover,it is the key link to the study of global silicon cycle.This paper introduces the basic mechanism of the formation of diatom silica walls and a new way of researching silicic acid metabolism,namely the 2-(4-pyridyl)-5-((4-(2-dimethylaminoethylaminocarbamoyl)-methoxy)phenyl)oxazole(PDMPO) dyeing method.Under a fluorescence microscope after excitation with bright green fluorescence,it can combine with silicic acid to form a complex into the Si deposition within diatom cells.The advantage of this method is that it can monitor the metabolism of silicate after adding PDMPO.For experimentation and sample collection in each of the specified time points,samples were determinated through the unutilized silicic acid,silica dissoluble intracellular and Si deposition within diatom cells,not only using hot alkaline digestions method but also PDMPO dyeing method.Results showed a good linear relationship between PDMPO fluorescent value and biogenic silica concentration.It was also indicated that PDMPO had no deleterious impact on Skeletonema cf.costatum growth for 34 h and was useful for tracking newly-deposited biogenic silica in diatoms' frustules.

Biogenic Silica Change and Its Environment Response in Shallow Borehole in the Coastal Water at Zhoushan,Zhejiang Province,China

Using a biogenic silica(Bio-Si)alkali extraction method,Bio-Si contents of 100 sedimentary covers from Cx21 borehole in the coastal water of Zhoushan, Zhejiang Province,China are analyzed.Combining with the data materials such as(210)~Pb sedimentation rate,sediment particle size,annual average sea surface temperature near the borehole from 1890 to the present,runoff discharge of Hankou station in

Spatial-temporal dynamics of biogenic silica in the southern Yellow Sea

Concentrations of biogenic silica(BSi) in the southern Yellow Sea were determined during four cruises(spring:April–May 2014;autumn: November 2014;summer: August–September 2015;winter: January 2016). Samples of BSi were measured using the double extraction method. Seasonal and spatial variations of BSi and the potential correlation between chlorophyll a(Chl a) content and BSi in four seasons were measured in this study. Significant spatial variability was observed in seawater BSi concentrations. The average concentration of BSi was highest in winter and lowest in spring. Furthermore, the relationships between concentrations of BSi and hydrological parameters were also discussed. There was a significant positive correlation between Chl a and BSi. The concentrations of BSi showed significant relationships with temperature and the concentrations of silicates, total inorganic nitrogen and total inorganic phosphorus, indicating that distribution of BSi was affected by temperature and nutrient level.

The distribution and concentration of particulate biogenic silica in surface waters of Prydz Bay, Antarctica, during the austral summer of 2011

The concentrations and distributions of particulate biogenic silica （PBSi） in the upper surface waters of Prydz Bay, Antarctica, were investigated during the 27th Chinese National Antarctic Research Expedition cruises of January 2011. We aimed to characterize the correlations between PBSi and plankton, nutrients and particulate organic carbon. The results showed that the concentrations of biogenic silica ranged from 0.76--19.72 ktmol-dm3 and the average concentration of biogenic silica was 6.06 mol.dm3. The distribution of surface PBSi had significant regional characteristics： The concentrations were higher south of 67S than to the north. The distribution of PBSi, chlorophyll a and particulate organic carbon showed similar patterns, and PBSi distribution had a negative correlation with that of silicate. In the vertical direction, the mole ratio of PBSi and POC （Si/Co） decreased with increasing depth. This trend indicated a higher rate of PBSi dissolution, or a lower rate of organic matter reminer- alization rate, in the upper 200 m.

硅的生物地球化学过程及其在养殖碳汇形成过程中的作用和影响

硅(Si)是地球上丰度仅次于氧的第二大元素,其生物地球化学过程与大气CO_(2)变化、海洋生物泵以及海岸带富营养化等过程密切相关,因此,硅循环也成为全球环境变化研究关注的核心问题之一。本文在总结已有研究的基础上,论述了硅生物地球化学过程及其对碳循环的调节及影响,进一步聚焦近海规模化贝类养殖活动,分析了贝类养殖生态系统硅循环与碳循环的耦合作用及机理,展望了未来值得关注的关键科学问题。研究表明,地质尺度上,硅酸盐矿物风化是地表所有次生硅的来源,风化过程也是一个重要的碳汇过程。陆地生态系统中,植硅体较难降解,在其形成过程中会包裹有机碳而形成稳定的有机碳库,因而植硅体碳具有重大的碳汇潜力,很有可能成为全球碳汇的重要组成部分。海洋生态系统中,作为初级生产主要贡献者的硅藻(Bacillariophyta)吸收硅酸盐合成有机碳并将其打包在生源硅颗粒中向深层海洋输送并埋藏,埋藏量可占海洋碳埋藏总量的40%,生物硅泵驱动了生物碳泵;在近海贝类养殖区,通过硅藻作为滤食性贝类的饵料来源,硅酸盐成为渔业碳汇重要的物质支撑。因此,研究硅生物地球化学循环过程中,综合考虑各过程及其耦合作用是非常必要的,对深入了解其在贝类养殖碳汇中的作用及探究潜在养殖增汇途径具有重要意义。

生物成因微晶石英特征及其对海相页岩储层孔隙发育的影响

【目的】石英是海相页岩中最重要的矿物之一,以多种形式存在,并具有多种的硅质来源和成因,而不同类型的石英对于岩石力学性能和孔隙演化的贡献是不同的,且相关研究目前仍较薄弱,制约了对页岩储层特征的深入认识。【方法】简述了近年来海相页岩石英分类的最新进展,并在此基础上,在前期研究较为薄弱的下扬子地区,利用鼓地1井上奥陶统五峰组—下志留统高家边组海相页岩样品,综合运用薄片分析、X射线衍射分析、地球化学分析、场发射扫描电镜、核磁共振、能谱分析和阴极发光等多种方法手段,探究海相页岩石英类型和硅质来源,并进一步讨论生物成因微晶石英对页岩力学性质和孔隙发育等储层性质的影响。【结果】下扬子地区鼓地1井五峰组—高家边组页岩石英类型主要为碎屑石英、微晶石英和生物骨架石英,其中碎屑石英为陆源输入,而微晶石英则为自生来源。硅质生物骨架镜下证据、生物硅含量、主微量元素特征等指标综合分析表明硅质生物可为微晶石英提供重要的硅质来源。【结论】海相页岩中的生物成因微晶石英增强了页岩的脆性,并且相互连接,形成刚性的硅质基质框架,很大程度上提高了页岩的力学性能。此外,这一刚性框架能够有效地保护微晶石英内部的有机质孔隙和粒间孔隙不被压实,有利于孔隙的保存。

九寨沟箭竹海沉积物中BSi含量及其环境指示意义

通过对九寨沟箭竹海沉积物样品中生物硅(BSi)含量的分析,讨论箭竹海沉积物中BSi含量与总有机碳(TOC)及粒度的关系,进而探讨BSi含量反映自然和人类因素对湖泊水体和沉积物的影响。箭竹海沉积物中BSi含量介于5.5～15.8 mg/g之间,BSi含量与TOC呈显著正相关关系。BSi含量还较显著地受到粒度影响,较细颗粒沉积物对BSi有较强的吸附作用。箭竹海沉积物中BSi含量变化与气温波动关系不密切,主要反映了森林砍伐和旅游开发等人类活动对湖泊水体和沉积物的影响。

大亚湾大鹏澳海域C、N、BSi的沉积记录研究

研究了大亚湾大鹏澳海域鱼类养殖区、贝类养殖区以及核电站附近3个站位50～78cm的柱状沉积物中生物硅（BSi）、总有机碳（TOC）、总氮（TN）等生源要素的垂直变化，以揭示人类活动对海洋环境影响的沉积记录。位于近岸海水养殖区的两个沉积柱中，近年来TOC含量呈明显上升趋势，而核电站附近海域略有下降。从TOC／TN比值判断（三个沉积柱平均分别为9．54、7．42、7．9），该海域TOC是陆源和水生两种来源的混合物。此外，养殖区上表层沉积物中水生有机碳（TOCa）含量呈明显下降趋势，而TOC／TN比值则上升，说明养殖区水生初级生产力及其对总初级生产力的贡献下降；相反，陆源污染所造成的陆源有机碳（TOCl）含量明显增加。在核电站附近海域，TOCa含量明显上升，TOC／TN和TOCtl力的贡献逐年上升，而核电站海域硅藻的贡献则下降。

Source of silica and its implications for organic matter enrichment in the Upper Ordovician-Lower Silurian black shale in western Hubei Province,China:Insights from geochemical and petrological analysis

To improve the understanding of the relationship between silica source and organic matter accumulation,the origin of silica and its implications for organic matter enrichment in the Upper OrdovicianLower Silurian(O_(3)w-S_(1)l)black shale in western Hubei Province in the middle Yangtze area,were investigated through geochemical and petrological analyses.The results show that the O_(3)w-S_(1)l black shale is mainly composed of five lithofacies with varying graptolite abundance,total organic carbon(TOC),and silica contents.Biogenic silica and terrigenous siliciclastic input constitute the main silica sources in O_(3)w-S_(1)l black shale and they exhibit an upward inverse variation trend interpreted to be related to sea-level changes.Moreover,with the increase in biogenic silica content or decrease in terrigenous siliciclastic input,TOC values in black shale initially rise and then fall,which is different from originally expected simple linear relationship.We infer that organic matter enrichment and the distribution of silica from different origins are controlled by sea-level changes and variations in terrigenous input in a continental shelf with little hydrothermal influence.An environment with appropriate sea level and terrigenous input should be most favorable for organic matter accumulation,rather than one with excessive high sea level and less terrigenous input.

Effects of Rice Straw Silicification and Characters of Extraction Biogenic Silicon on the Degradation of Fibrous Components in Rice Straw

Straw of seven rice varieties with early-, middle- and late maturity was collected from Huazhong Agricultural University in Hubei. A study was carried out for rice straw in the aspects of the characters of straw silicification and extraction biogenic silica (EBSi), the relationship between characters of EBSi and kinetic characteristics of degradation of fibrous components in fistulated cows, as well as the effect of urea treatment on rice straw desilicification. Although total silica content (ADISi) in rice straw was similar, the efficiency of extraction biogenic silica (EEBSi) and cellulose in early varieties were significantly higher than those in middle (18.9% and 9.1 %) and late ones (26.1% and 11.2%). The degradability of EBSi and cellulose of early varieties were higher than those of middle by 70.0% and 17.5%, and of late varieties by 47.8% and 23.7% , respectively. The in sacco degradability and in vitro VFA production of early varieties were also higher than those of middle by 14.5% and 19.0%, and late by 12.9% and 14.8%. Comparing the morphological fractions of the rice straws, EEBSi, cellulose content, and in vitro VFA production were different with the order of blade < sheath < stem. A significant correlation was found between the contents of EBSi and cellulose (r= 0.86), and the two contents were remarkably correlated with the potential straw degradability (a + b) by r = 0.90 and 0.84 respectively. Therefore, EBSi in rice straw was a main factor affecting the potential degradability of rice straw, rather than the ADISi of straw. Urea treatment improved rice straw degradability, degradation rate and potential degradability by 10.8% , 27.9% , and 10.1% respectively, compared to untreated straws.

基于FTIR对水库沉积物中TOC,TN和BSi含量的快速测定

利用傅里叶变换红外光谱(Fourier transform infrared spectroscopy,FTIR)分析了中国西南喀斯特地区岩滩(Yantan,YT)水库中的沉积物,探讨了基于FTIR的沉积物总有机碳(total organic carbon,TOC)、总氮(total nitrogen,TN)和生物硅(biogenic silica,BSi)含量的快速分析方法.采用偏最小二乘回归(partial least squares regression,PLSR)方法,分别建立了TOC/TN/BSi含量的FTIR预测模型,并根据实测数据对这一预测模型的预测精度进行了验证.结果表明:该方法可有效提取水库沉积物中的地球化学信息,应用于高分辨率古环境变化的研究;需要样品量少,预处理过程简单,并因其快速和经济的特点,在测定大量沉积物样品时具有极大的优势.

Revisiting the dissolution of biogenic Si in marine sediments： a key term in the ocean Si budget

Of the ~240*10^(12)mol year^(-1)of biogenic silica(bSi)produced by diatoms and other silicifying organisms,only roughly 3%–4%escapes dissolution to be permanently buried.At the global scale,how,where and why b Si is preserved in sediment is not well understood.To help address this,I compile 6245 porewater dissolved Si concentrations from 453 sediment cores,to derive the concentration gradient at the sediment–water interface and thus diffusive fluxes out of the sediment.These range from\0.002 to 3.4 mol m^(-2)year^(-1),and are independent of temperature,depth and latitude.When classified by sediment lithology,predominantly siliceous sediments unsurprisingly have higher mean diffusive fluxes than predominantly calcareous or clay-rich sediment.Combined with the areal extent of these lithologies,the‘best-guess’global sedimentary b Si recycling flux is69 9 10^(12)mol year^(-1).