Pseudo-nitzschia spp. (Bacillariophyceae) and dissolved organic matter (DOM) dynamics in the Ebro Delta (Alfacs Bay, NW Mediterranean Sea)

Samples were collected during one annual cycle (April 2007–March 2008) at Alfacs Bay (NW Mediterranean Sea) central station in order to assess the influence of organic nutrients in the growth of the microalgae assemblage, with special reference to Pseudo-nitzschia spp. This potentially toxic diatom forms natural and recurrent blooms in the study area. To assess further the relationship between Pseudo-nitzschia spp. and nutrients an enrichment experiment with high molecular weight dissolved organic matter (HMWDOM) was performed with field samples obtained during a Pseudo-nitzschia spp. bloom. HMWDOM was extracted from water collected at Alfacs Bay. Five bioassays were prepared: N + P (seawater with addition of nitrate and phosphate), DOM (addition of HMWDOM), (−N + P) + DOM (nitrogen deficient, with addition of phosphate and HMWDOM), (N + P) + DOM (addition of nitrate, phosphate and HMWDOM), seawater control (without added nutrients), and B + DOM (control of bacteria, without microalgae). The experiment was run in batch mode over 4 days. Results from the field study revealed that the concentrations of organic nutrients mostly surpassed the inorganic pool. Pseudo-nitzschia spp. was the most frequent and abundant taxa of the microalgae community. The micro-planktonic assemblage was arranged according to a seasonal factor (ANOSIM and cluster analysis). DON, nitrate and silicate were the most important abiotic parameters contributing to the dissimilarities between seasons (SIMPER analysis) and thereby potentially influencing the seasonal distribution of microalgae in the representative station. In the experimental investigation, Pseudo-nitzschia cells increased by the end of the experiment in the DOM bioassay but no respective increase was observed for chlorophyll a. This could point to an acquisition of nutrients through the DOM fraction that would conjointly reduce the need of chlorophyll a. The data obtained suggest that organic nutrients may exert an important role in the development of microalgae, including Pseudo-nitzschia spp., in the selected location.     

混合培养条件下几种赤潮藻对无机磷源的竞争生长研究

采用批次培养方式,研究混合培养的几种赤潮藻东海原甲藻(PrDrocentrum donghaiense)与中肋骨条藻(Skeletonema costatum)及东海原甲藻与链状亚历山大藻(Alexandrium catenella)对溶解无机磷源的竞争生长响应.结果表明,在富磷及贫磷的培养条件下,中肋骨条藻的比生长率远超过东海原甲藻,而成为培养体系中的绝对优势种.在东海原甲藻与链状亚历山大藻的混合培养体系中,原甲藻大量死亡,可能存在亚历山大藻对原甲藻的他感作用.培养体系中,碱性磷酸酶活性随藻类磷胁迫而显著升高,可能在后期种群利用代谢有机磷源时发挥重要作用,且在不同培养体系中表现出酶活性大小及状态的差异性,该结果可能影响浮游植物对有机磷源的利用效率.     

海洋异养细菌对小球藻生长和无机营养盐吸收的影响研究

从胶州湾海洋异养细菌同小球藻(Chlorella vulgaris)的共存体系中,分离出6株形态特征差异较大的异养细菌,并做变性凝胶梯度电泳(Denature Gel Gradient Electrophoresis,DGGE)分析.其中一株对小球藻的生长有较大的促进作用,而其余菌株则没有明显的效果.6株细菌能在小球藻产生的胞外溶解有机物(Dissolved Organic Mate rials,DOM)溶液中生长良好,共存细菌对提高菌藻体系对无机营养盐的吸收具有较大的贡献.     

Prediction of surface ocean pCO2 from observations of salinity, temperature and nitrate: The empirical model perspective

This paper evaluates whether a thermodynamic ocean-carbon model can be used to predict the monthly mean global fields of the surface-water partial pressure of CO₂ (pCO_2SEA) from sea surface salinity (SSS), temperature (SST), and/or nitrate (NO₃) concentration using previously published regional total inorganic carbon (C_T) and total alkalinity (A_T) algorithms. The obtained pCO_2SEA values and their amplitudes of seasonal variability are in good agreement with multi-year observations undertaken at the sites of the Bermuda Atlantic Timeseries Study (BATS) (31°50’N, 60°10’W) and the Hawaiian Ocean Time-series (HOT) (22°45’N, 158°00’W). By contrast, the empirical models predicted C_T less accurately at the Kyodo western North Pacific Ocean Time-series (KNOT) site (44°N, 155°E) than at the BATS and HOT sites, resulting in greater uncertainties in pCO_2SEA predictions. Our analysis indicates that the previously published empirical C_T and A_T models provide reasonable predictions of seasonal variations in surface-water pCO_2SEA within the (sub) tropical oceans based on changes in SSS and SST; however, in high-latitude oceans where ocean biology affects C_T to a significant degree, improved C_T algorithms are required to capture the full biological effect on C_T with greater accuracy and in turn improve the accuracy of predictions of pCO_2SEA.     

条斑紫菜丙酮酸羧化酶基因表达对不同碳源的响应

丙酮酸羧化酶(pyruvatecarboxylase,PYC)在非光合生物中催化丙酮酸羧化生成草酰乙酸(oxaloacetate,OAA),作为糖异生的第一步,在动物维持代谢稳态中具有重要作用。研究发现,PYC在光合生物中也发挥重要作用。为了探究PYC在潮间带大型海藻中的作用,我们从条斑紫菜叶状体中扩增获得PYC基因全长序列(命名为PyPYC),并分析了其序列特征。通过对系统进化树分析表明PyPYC与来自细菌的PYC具有较近亲缘关系。针对条斑紫菜叶状体生长环境所面临的碳源变化,设置了不同类型和不同浓度的无机碳培养条件,采用实时荧光定量(RT-qPCR)检测了该基因对这些无机碳源的响应。结果表明,高浓度的CO₂能显著上调PyPYC基因的表达,而高浓度的HCO₃^-对其影响较小。由此,我们初步认为,当紫菜叶状体暴露在空气中时, PYC在其无机碳利用中发挥一定作用。     

Effects of nutrients on crude oil biodegradation in the upper intertidal zone

To enhance biodegradation, nutrients in the form of slow-release fertilizer (SRF) were applied to oil-contaminated microcosms (3%, v/v) which simulated intertidal environmental systems. Although nutrient concentrations in the interstitial water were not proportional to those in amended SRF, microbial activity, growth of oil-degrading microorganisms, and oil-degradation rate were closely related to the concentration of nutrients in the interstitial water. Adding nutrients at higher dose (microcosm I, 144.4 mg C/kg sand/day, versus microcosm II, 8.5 mg C/kg sand/day) had a positive effect on oil degradation rate, which was especially obvious during the early phase of treatment. Use of pristane, phytane, and nor-hopane as biomarkers enabled the detection of significant treatment differences in hydrocarbon biodegradation, which were not reliable enough when the data were normalized to sand mass.     

西江河口段溶解无机碳稳定同位素组成的时空变化

For researching the spatio-temporal variation of the stable isotopic composition of the riverine dissolved inorganic carbon（DIC）,we had carried out a survey throughout the hydrologic year during which theδ^13CDIC of the surface water and its physicochemical parameter were examined along the Xijiang River Inner Estuarine waterway from September 2006 to June 2007.There was a striking seasonal variation on the averageδ^13CDIC,as the averageδ^13CDIC in summer（-13.91‰）or autumn（-13.09‰）was much less than those in spring（-11.71‰）or winter（-12.26‰）.The riverineδ13C DIC was controlled by decomposed condition of the riverine organic matter linking the seasonal variation of the physicochemical parameter in the surface water according to the correlation analysis which indicated notable relations betweenδ^13CDIC and water temperature（p=0.000;r=-0.569）or betweenδ^13CDIC and oxide-reduction potential（p=0.000;r=0.646）.The striking positive correlation between δ^13CDIC and the sampling distance happened in the summer rainy season,while striking negative correlation happened in the spring dry season,indicating that river-sea interaction influenced water physicochemical parameters and controlled the riverine DIC property in the survey waterway.In view of the riverineδ^13CDIC decreasing for the decomposition of the terrestrial organic matter in the rainy season in summer and increasing for the briny invaded zone extending in the spring dry season along the waterway from the Makou gauging station to the Modaomen outlet,theδ^13CDIC spatio-temporal variation was closely related to the geographical environment of the Xijiang drainage basin.     

泰山PM10及其中化学成分变化特征

为研究华北平原区域背景气溶胶成分及其变化特征,2010年6月至2011年7月在泰山顶采集了64个PM10滤膜样品,分析了样品的PM10及其中无机盐离子和有机碳（OC）、元素碳（EC）的质量浓度,并对各成分相关性等进行了分析。泰山PM10年均质量浓度约为68.4 mg/m³,其中无机盐离子约占总质量的64.8%,碳气溶胶约占17.4%。无机盐离子的质量浓度从春季逐渐增大,夏季达到峰值,秋季下降,冬季最小;OC质量浓度从春季至秋季逐渐增高,冬季最低,EC变化类似,但夏秋两季差别不大。二次有机碳（SOC）与OC的比值四季均在50%以上,年均值约为58.5%。通过后向轨迹聚类分析发现,在经过城市的较短轨迹以及南方较短混合轨迹的影响下,泰山PM10质量浓度较高,而西北长距离传输气团PM10浓度均较低。     

西南典型地下河系统无机-有机指标特征及健康风险评价

岩溶地下水为全球约25%的人口提供饮用水源,地下河作为主要岩溶地下水类型,是中国西南岩溶区重要供水水源,掌握其水质污染状况及人体健康风险,对岩溶区水资源保护与安全用水具有重要意义。本文以广西桂林会仙狮子岩地下河系统为例,采集地下河水样品22组(无机和有机样品各11组),采用电感耦合等离子体质谱、离子色谱、气相色谱-质谱等方法测定11项无机离子、10项金属元素及41项有机指标的质量浓度,运用单指标污染标准指数法、健康风险评价模型揭示了研究区无机与有机指标分布、污染及健康风险。结果表明：(1)狮子岩地下河水中无机超标指标有NH~+₄(1.33倍)、Fe(1.2倍)、Al(1.5倍)和Mn(1.01倍),超标点多位于地下河排泄区;检出18项有机物,其中挥发性有机物(VOCs)、半挥发性有机物(SVOCs)和有机氯农药(OCPs)检出率分别为18.75%、30.77%和91.67%,研究区存在普遍的农药残留(49.14～109.83ng/L)。(2)与地下水对照值相比,研究区受到10项无机指标的轻度～中度污染、14项有机指标的轻度污染,个别采样点受到NO~-_3<...     

新疆艾比湖湿地自然保护区不同土壤类型无机碳分布特征

土壤无机碳（SIC）是干旱区土壤碳库的重要组成部分,分析其特征和储量是开展干旱区荒漠生态系统碳循环研究的必要基础。基于新疆艾比湖湿地自然保护区土壤剖面的实测数据,分析了不同土壤类型SIC分布特征及其差异性,估算了研究区SIC储量,并探讨SIC含量与分布、储量特点以及与土壤有机碳（SOC）和理化因子间关系。结果表明：各类型平均SIC含量为53.06～79.90 g·kg–1;类型间SIC含量有显著差异（p<0.05）,50 cm以上各层SIC含量顺序为灰棕漠土>盐碱土>水成土>荒漠风沙土,50 cm以下则盐碱土和水成土逐渐占优势。SIC含量的垂直分布总体表现为低-高-低的特征（10 cm单位土壤深度）,除灰棕漠土外,SIC含量在剖面上的变化较均匀。研究区无机碳密度平均为9.37 kg·m-2,SIC库储量为234.50 Tg。SIC含量与SOC及含水量呈显著的正相关,并随土壤深度增加有增加趋势;与土壤容重和表层pH值负相关,相关性较弱。