Characterization of diatom-derived lipids and chlorophyll within Holocene laminites, Saanich Inlet, British Columbia, using conventional and laser scanning fluorescence microscopy

Conventional fluorescence microscopy and visible light region fluorescence microspectrometry have been combined with laser scanning fluorescence microscopy (LSFM) to examine and characterize soluble sedimentary organic matter (SOM) in Holocene diatomaceous laminites from ODP core 1034, Saanich Inlet, British Columbia, Canada. Microscopic SOM in the laminites is dominated by two components: red-fluorescing chlorophyllinite, and yellow-fluorescing, diatom-derived oils. Both are commonly preserved within the interior of siliceous diatom auxospores and appear as an abundant and intense stain on mineral matter throughout the laminites. The mineral stain is classified as matrix chlorophyllinite and matrix oil, respectively. Accessory insoluble SOM consists of dinoflagellate, prasinophyte and coccoidal alginites, and rare woody huminite, funginite, and sporinite. Visible light region fluorescence microspectrometry of chlorophyllinite reveals a predominance at λ max 670–675 nm, which is consistent with a chlorophyll a source based on comparison with reference samples of chlorophyll a and b. The consistency in λmax and spectral character of chlorophyllinite with increasing depth in Saanich Inlet correlates with a high degree of chlorophyll preservation. Its distribution in the laminites is readily imaged by LSFM using either UV (363 nm) or blue (488 nm) laser excitation and >665 nm emission. Yellow-fluorescing diatom oils have λmax ranging from 485 to 520 nm, suggesting that they may comprise up to 70% saturates. The distribution of entrapped yellow-fluorescing diatom oils as well as matrix oils is also readily imaged with LSFM using a combination of UV laser excitation (363 nm) and 510 ±40 nm emission. Laminae in the Saanich Inlet samples which are highly enriched in both diatom oils and ‘reproductive’ auxospore cells are interpreted as recording intense episodic spring diatom blooms. The observations reported here document microscopically, in situ, possibly pristine preservation of diatom oils (including possible fatty acids) at appreciable depths within Holocene organic-rich laminites. Their recognition in recent and older strata is important, for they serve as potential biomarkers for assessing long term geo-environmental changes such as water temperature. The periodic presence of anomalously high amounts of diatom-derived biological oils in laminae within the recent sediments may mark times of unusually high nutrient levels and paleoproductivity.     

南海晚第四纪的硅藻遗体及其地质意义 Ⅱ.南海北部下大陆坡KL37剖面的硅藻组合

南海下大陆坡KL37剖面共鉴定出硅藻112种和变种，隶属于45属。依据剖面硅藻种类的百分含量变化，自下而上划分两个硅藻带，其中Ⅰ带划分出8个亚带。Ⅰ1、Ⅰ3、Ⅰ5亚带和Ⅱ带的热性种平均含量高于40％；Ⅰ2、Ⅰ4、Ⅰ6、Ⅰ7、Ⅰ8亚带的热性种含量低于40％，反映了该区古温度和古地理条件的变化。并依据结节圆筛藻壳体大小的比值变化，确定出该剖面的地层年代：Ⅱ带属于全新世沉积，Ⅰ带属于晚更新世的沉积。     

从宏观环境质疑“船台说”

从^14C年代、出土古生物和地理环境提出对广州中山四路儿童公园的旁的“秦代船台”遗址提出质疑,认为该处不是海潮可达的江畔,是高地,不适宜造船,是秦汉之交的南越国王宫与宫苑建筑的一部分。     

Disentangling late-Holocene climate and land use impacts on an Austrian alpine lake using seasonal temperature anomalies,ice-cover,sedimentology, and pollen tracers

Major and trace elements, minerals and grain-size were analysed from a sediment core covering the last 4,000 years of an Austrian Alpine lake (Oberer Landschitzsee, ObLAN, 2,076 m a.s.l.). These analyses were combined with autumn and spring temperature anomalies and ice-cover estimated from a diatom and chrysophyte cyst, thermistor-based regional calibration dataset and selected pollen markers published previously. Diatom-inferred pH (Di-pH) and DOC (Di-DOC) completed the multi-proxy approach, which, together with ordination techniques (PCA and RDA), helped (1) to confirm proposed climatic patterns and hypotheses, and (2) to disentangle the complex interactions between climatic and anthropogenic impacts. Shifts in chemical and physical weathering, erosion, production, lake stratification, redox potentials and air pollution were the major processes that have affected Oberer Landschitzsee in relation to climate, lake/catchment interactions, and human impact. Geochemistry supported the finding that the four waves of high-altitude land use (Early to Middle Bronze, ca. 1,800–1,300 B.C.; Late Bronze to Hallstatt, ca. 1,000–500 B.C.; Celtic to Roman, ca. 300 B.C.–400 A.D.; and Medieval, ca. 1,000–1,600 A.D.) were coupled mainly with warm periods. Increased production, onset of lake stratification, and the deterioration of hypolimnetic oxygen conditions were the major changes governing in-lake processes during climate warming. They resulted in specific element assemblages associated with organic matter accumulation (Br), oxygen depletion (As, Ga, Cu, S), and changes in redox (Fe/Mn). The Se/Di-DOC ratio was introduced to track shifts between in-lake production and allochthonous sources. Nutrient loading from pastures, coupled with climate warming, could explain that in-lake production was highest during Roman and Medieval land use. Lithogenic elements mainly originated from chemical weathering of silicate bedrock and they increased when intense land-use was coupled with climate deterioration and/or increased humidity. These perturbations were highest during a High Medieval climate fluctuation around 1,000 A.D. The association of sand with LOI and C/N and the decoupling of sand from quartz and feldspar separates erosion from physical weathering. Di-DOC, S, and C/N showed hybrid characters in relation to climate and human impact. The mineral proportions indicated gradients in relation to weathering, snow-cover and running waters, as well as vegetation. Air pollution by metallurgic industries, starting during the High Medieval and culminating during the Late Medieval, caused lead accumulation and could have contributed to As and S enrichment. Corresponding features in the distribution of selected elements and pollen tracers, as well as changes in mineral proportions, supported the hypotheses of shifts in seasonal climate and an overall trend towards more continental climate conditions since Medieval times.     

The use of soft X-ray spectromicroscopy to investigate the distribution and composition of organic matter in a diatom frustule and a biomimetic analog

Diatoms play a significant role in the global carbon cycle through their role in biogenic silica production and the transport of organic matter to the seafloor. Recent work has shown that silicified diatom frustules contain a significant amount of organic matter, and that the proportion of diatom-bound organic matter increases with depth in the water column and sediments. Here, we investigate the association between organic matter and the mineral phase. We used a combination of scanning transmission X-ray microscopy (STXM) and carbon X-ray absorption near-edge structure (XANES) spectroscopy to characterize the distribution and composition of organic matter in frustules of the diatom Cylindrotheca closterium and a biomimetic silica gel. To our knowledge, this study represents the first successful attempt to simultaneously image and obtain chemical information about the organic matter within a diatom frustule using X-ray spectromicroscopy near the carbon edge. Organic carbon, most likely protein, was distributed throughout the frustules and was not removed by harsh chemical treatment. The physical structure of the frustules appeared to be related to the chemical composition of this organic matter, with aromatic or unsaturated carbon being concentrated in the most intricately patterned regions of the frustule. A similar physical and chemical structure was observed in a biomimetic silica gel precipitated spontaneously with polylysine. These results are consistent with the theory that organic constituents of diatom frustules direct silica precipitation and become incorporated within the silica matrix as it forms. The relationship between organic matter composition and silica morphology, the failure of harsh chemical treatments to remove this organic matter, and the spontaneous nature of the co-precipitation of silica and organic matter indicate some chemical interaction between the siliceous and organic components of diatom frustules. Frustule-bound organic matter should therefore be protected from decomposition in the water column or diagenetic alteration in sediments unless the frustule dissolves.     

一种淡水水华硅藻——链状弯壳藻(Achnanthidium catenatum)

作为区域重要饮用水源的浙江绍兴汤浦水库于2010年5月期间暴发以硅藻和蓝藻为主的藻类水华.对库尾、库中和坝前3处浮游植物样品进行采集和分析,结果表明,汤浦水库浮游植物密度在1.13×108～1.56×108cells/L之间,水华优势种之一为我国大陆地区首次报道的羽纹纲硅藻———链状弯壳藻(Achnanthidium catenatum),另一种为丝状蓝藻———湖泊假鱼腥藻(Pseudanabaena limnetica),两者的平均相对丰度分别为65.6%和28.2%;链状弯壳藻是弯壳藻属中唯一适应浮游生长的种类,具有独特的带面观,能以壳面相连形成2～3个细胞的短链状群体;对国内外3次链状弯壳藻为优势种的水华案例进行分析,发现该藻为广温性种类,适应低光强和低磷浓度生长;水华生消机理则需进一步研究.     

从藻类化石的垂直分布探讨杭州西湖的演变历程

于１９９４年春在杭州西湖东北面,西面及湖中心小瀛洲３个钻孔共取了７０号岩芯样,经浮选,筛选,以显微镜检鉴定化石藻种,并分析其垂直分布,从而探讨西湖的形成历史,西湖自晚更新世以来的６个化石藻带由下而上依次为：轮藻带,微藻带,微红金颗藻－近缘针杆藻－条纹小环藻带,圆筛藻带,圆筛藻－近缘针杆藻－微红金颗藻桥穹藻－异极藻－短缝藻带和水花束丝藻带,从而反映了西湖的６个发育时期,淡水古湖沼期,淡咸水过渡期,海     

Assessment of geochemical and sedimentological characteristics of atmospheric dust in Shiraz,southwest Iran

Geogenic dust is commonly believed to be one of the most important environmental problems in the Middle East.The present study investigated the geochemical characteristics of atmospheric dust particles in Shiraz City(south of Iran).Atmospheric dust samples were collected through a dry collector method by using glass trays at 10 location sites in May 2018.Elemental composition was analysed through inductively coupled plasma optical emission spectrometry.Meteorological data showed that the dustiest days were usually in spring and summer,particularly in April.X-ray diffraction analysis of atmospheric dust samples indicated that the mineralogical composition of atmospheric dust was calcite+dolomite(24%)palygorskite(18%)quartz(14%)muscovite(13%)albite(11%)kaolinite(7%)gypsum(7%)zircon=anatase(3%).The high occurrence of palygorskite(16%-23%) could serve as a tracer of the source areas of dust storms from the desert of Iraq and Saudi Arabia to the South of Iran.Scanning electron microscopy indicated that the sizes of the collected dust varied from 50 μm to0.8 μm,but 10 μm was the predominant size.The atmospheric dust collected had prismatic trigonal-rhombohedral crystals and semi-rounded irregular shapes.Moreover,diatoms were detected in several samples,suggesting that emissions from dry-bed lakes,such as Hoor Al-Azim Wetland(located in the southwest of Iran),also contributed to the dust load.Backward trajectory simulations were performed at the date of sampling by using the NOAA HYSPLIT model.Results showed that the sources of atmospheric dust in the study area were the eastern area of Iraq,eastern desert of Saudi Arabia,Kuwait and Khuzestan Province.The Ca/Al ratio of the collected samples(1.14) was different from the upper continental crust(UCC) value(UCC=0.37),whereas Mg/A1(0.29),K/Al(0.22) and Ti/Al(0.07) ratios were close to the UCC value(0.04).This condition favours desert calcisols as the main mineral dust sources.Analysis of the crustal enrichment factor(EF_(crustal)) revealed geogenic sources for V,Mo,Pb,Sr,Cu and Zn(2),whereas anthropogenic sources affected As,Cd,Cr and Ni.     

Allelopathy at the land/sea interface: microalgae and Brazilian pepper

Microalgae are significant contributors to biodiversity and primary production in shallow coastal habitats. The invasive Brazilian pepper (Schinusterebinthifolius) can occupy former mangrove habitats in disturbed areas, and its allelopathic capability can affect growth rates of microalgae. The four microalgae tested against dilution extracts of Schinus fruits varied in their growth response, suggesting variable but unpredictable impacts on microalgal biodiversity, primary production, and community structure.     

Marine diatom uptake of iron bound with natural colloids of different origins

Natural colloids are abundant in seawater and are an intermediary in the fate, transport and bioavailability of many trace elements. Knowledge of the pathways and mechanisms of the biological uptake of colloidal Fe and other Fe species is of paramount importance in understanding Fe limitation on marine phytoplankton and thus carbon sequestration in the ocean. Whether the natural colloids serve as a source for the biological Fe requirements of marine phytoplankton, or just as a sink for particle-reactive metals in the oceans remains largely unknown. This study examined the bioavailability of Fe bound with colloids from different regions to a coastal diatom (Thalassiosira pseudonana). Natural colloids were isolated by cross-flow ultrafiltration and radiolabeled with ⁵⁹Fe before being exposed to phytoplankton. Control experiments were conducted to ensure that ⁵⁹Fe radiolabeled onto the colloids remained mostly in the colloidal phase. Both the natural oceanic and coastal colloidal organic matter complexed Fe (1 nm–0.2 μm) can be biologically available to the marine diatom even though its uptake was lower than the low molecular weight counterparts. By comparing the measured Fe internalization fluxes and the calculated maximum diffusive uptake fluxes, it is evident that ligand exchange kinetics on the cell surface may control the internalization of macromolecular Fe. The calculated concentration factors under dark and light conditions were generally comparable. Colloidal Fe, as an important intermediary phase, can be actively involved in the planktonic food web transfer through biological uptake and regeneration processes. The bioavailable fraction of Fe may be substantially underestimated by only considering the truly dissolved Fe or overestimated when using the external fluxes, such as aerosol Fe, as the bioavailable fraction.