Carbon isotopic fractionation in macroalgae from Cádiz Bay (Southern Spain): Comparison with other bio-geographic regions     

Jesús M. Mercado  Carmen B. de los Santos  J. Lucas Pérez-Lloréns  Juan J. Vergara 《Estuarine, Coastal and Shelf Science》2009

The ¹³C signature of forty-five macroalgal species from intertidal zones at Cádiz Bay was analysed in order to research the extension of diffusive vs. non-diffusive utilisation of dissolved inorganic carbon (DIC) and to perform a comparison with data published for other bio-geographic regions. The ∂¹³C values ranged from −6.8‰ to −33‰, although the span of variation was different depending on the taxa. Thus, ∂¹³C for Chlorophyta varied from −7‰ (Codium adhaerens) to −29.6‰ (Flabellia petiolata), while all the Phaeophyceae (excepting Padina pavonica with ∂¹³C higher than −10‰) had values between −10‰, and −20‰. The widest variation range was recorded in Rhodophyta, from values above −10‰ (Liagora viscida) to values lower than −30‰ obtained in three species belonging to the subclass Rhodymeniophycidae. Accordingly, the mean ∂¹³C value calculated for red algae (−20.2‰) was significantly lower than that for brown (−15.9‰) and green algae (−15.6‰). Most of the analysed red algae were species inhabiting crevices and the low intertidal fringe which explains that, on average, the shaded-habitat species had a ∂¹³C value lower than those growing fully exposed to sun (i.e. in rockpools or at the upper intertidal zone). The comparison between the capacity for non-diffusive use of DIC (i.e. active or facilitated transport of HCO₃⁻ and/or CO₂) and the ∂¹³C values reveals that values more negative than −30‰ indicate that photosynthesis is dependent on CO₂ diffusive entry, whereas values above this threshold would not indicate necessary the operation of a non-diffusive DIC transport mechanism. Furthermore, external carbonic anhydrase activity (_extCA) and ∂¹³C values were negatively correlated indicating that the higher the dependence of the photosynthesis on the CO₂ supplied from HCO₃⁻ via _extCA, the lower the ∂¹³C in the algal material. The comparison between the ∂¹³C values obtained for the analysed species and those published for species inhabiting other bio-geographic areas (warm-temperate, cold and polar) suggests that globally (at least for the red and brown algae) the non-diffusive entry of DIC is more widely spread among the species from Cádiz Bay than among those of polar regions. If it is assumed that non-diffusive use of DIC implies saturation of photosynthesis at the present-day CO₂ concentration in seawater, our data indicate that the potential impact of the acidification on photosynthesis in the seaweed communities will be different depending on the latitude.  相似文献   

Photochemical oxidation of benzothiophene in seawater   总被引：3，自引：0，他引：3  

杨桂朋 《中国海洋湖沼学报》2000,18(1):85-91

ＩＮＴＲＯＤＵＣＴＩＯＮｐｈｏｔｏｃｈｅｍｉｃａｌｏｘｉｄａｔｉｏｎｏｆｂｅｎｚｏｔｈｉｏｐｈｅｎｅｉｎｓｅａｗａｔｅｒｉｎｏｒｄｅｒｔｏｌｅａｒｎｍｏｒｅａｂｏｕｔｔｈｅｒｅｍｏｖａｌｐａｔｔｅｒｎｏｆｔｈｉｓｐｏｌｌｕｔａｎｔｉｎｍａｒｉｎｅｅｎｖｉｒｏｎｍｅｎｔｓ.Ｂｅｎｚｏｔｈｉｏｐｈｅｎｅｗａｓｃｈｏｓｅｎｆｏｒｔｈｉｓｓｔｕｄｙｓｉｎｃｅｉｔｉｓｔｈｅｓｉｍｐｌｅｓｔ　　Ｔｈｅｈｉｇｈ -ｐｒｅｓｓｕｒｅｍｅｒｃｕｒｙｌａｍｐｕｓｅｄｉｎｔｈｉｓｓｔｕｄｙｃｏｕｌｄｐｒｏｄｕｃｅｌｉｇ…  相似文献   

Response of coastal marine eco-environment to river fluxes into the sea: a case study of the Huanghe (Yellow) River mouth and adjacent waters   总被引：3，自引：0，他引：3  

Fan H  Huang H 《Marine environmental research》2008,65(5):378-387

The impact of the Huanghe (Yellow) River outflows on its estuary was investigated with river gauging and shipboard hydrographic observations. The river flux has been decreasing dramatically; the discharges of water and sediment in the 1990s dropped to 27.4% and 31.9% of those in the 1950s, respectively, resulting in frequent and lengthy events of downstream channel dry-up since the 1970s. There were accumulatively 897 zero-flow days during the 1990s in the river course below the Lijin Hydrological Station, 100 km upstream from the river mouth, which is 82.4% of that in 1972. As freshwater input decreases, river-borne nutrients to the estuarine increased significantly. Concentration of dissolved inorganic nitrogen (DIN) in the 1990s was four times of that in 1950s. Changes in amount and content of the riverine inputs have greatly affected the estuarine ecosystem. Over the past several decades, sea surface temperature and salinity in the estuary and its adjacent waters increased and their distribution pattern altered in response to the reduction of freshwater inflow. The distribution of and seasonal succession in nutrient concentrations in the surface layer have also changed with a shift of river outlet and the decrease in riverine nutrient loads. Furthermore, deterioration of estuarine ecosystem by less river input has decreased primary productivity in the deltaic region waters, and in turn depressed the fishery.  相似文献   

The carbon dioxide system and net community production within a cyclonic eddy in the lee of Hawaii   总被引：1，自引：0，他引：1  

Feizhou Chen  Wei-Jun Cai  Yongchen Wang  Yoshimi M. Rii  Robert R. Bidigare  Claudia R. Benitez-Nelson 《Deep Sea Research Part II: Topical Studies in Oceanography》2008,55(10-13):1412

The dynamics of dissolved inorganic carbon (DIC) and processes controlling net community production (NCP) were investigated within a mature cyclonic eddy, Cyclone Opal, which formed in the lee of the main Hawaiian Islands in the subtropical North Pacific Gyre. Within the eddy core, physical and biogeochemical properties suggested that nutrient- and DIC-rich deep waters were uplifted by 80 m relative to surrounding waters, enhancing biological production. A salt budget indicates that the eddy core was a mixture of deep water (68%) and surface water (32%). NCP was estimated from mass balances of DIC, nitrate+nitrite, total organic carbon, and dissolved organic nitrogen, making rational inferences about the unobserved initial conditions at the time of eddy formation. Results consistently suggest that NCP in the center of the eddy was substantially enhanced relative to the surrounding waters, ranging from 14.1±10.6 (0–110 m: within the euphotic zone) to 14.2±9.2 (0–50 m: within the mixed layer) to 18.5±10.7 (0–75 m: within the deep chlorophyll-maximum layer) mmol C m⁻² d⁻¹ depending on the depth of integration. NCP in the ambient waters outside the eddy averaged about 2.37±4.24 mmol C m⁻² d⁻¹ in the mixed layer (0–95 m). Most of the enhanced NCP inside the eddy appears to have accumulated as dissolved organic carbon (DOC) rather than exported as particulate organic carbon (POC) to the mesopelagic. Our results also suggest that the upper euphotic zone (0–75 m) above the deep chlorophyll maximum is characterized by positive NCP, while NCP in the lower layer (>75 m) is close to zero or negative.  相似文献   

First-principles study of Ga₇As₇ ionic cluster and influence of multi-charge on its structure     

杨建宋  李宝兴 《海洋学报(英文版)》2010,29(9)

This paper investigates the structures and stabilities of neutral Ga₇As₇ cluster and its ions in detail by using first-principles density functional theory. Many low energy structures of Ga₇As₇ cluster are found. It confirms that the ground state structure of neutral Ga₇As₇ cluster is a pentagonal prism with four face atoms like a basket structure, as reported by previous works. The ground state structures of positive Ga₇As₇ cluster ions are different from that of the neutral cluster. These investigations suggest that Ga atoms occupy the capping positions more easily than As atoms. Mulliken population analyses also show that Ga atoms can lose or obtain charge more easily than As atoms. It finds that the neutral Ga₇As₇ cluster can become more stable by gaining one or two additional electrons but further more electrons would cause the decrease of binding energy. The ionisation energy increases with the increase of the number of the removed electrons. These calculated results indicate that the net magnetic moment of the neutral Ga₇As₇ cluster is zero because all electrons are paired together in their respective molecular orbits. But for the ionic Ga₇As₇ cluster with odd number of electrons, the net magnetic moment is 1.0 μ_B due to an unpaired electron.  相似文献   

Measurement of the secular motion frequency and the space charge density in the linear ion trap     

周飞  谢艺  徐酉阳  黄学人  冯芒 《海洋学报(英文版)》2010,29(11)

This paper reports that a cloud of laser-cooled ⁴⁰Ca⁺ is successfully trapped and manipulated in the home-built linear ion trap constructed for quantum information processing (QIP). The frequency of the secular motion and the space charge density of the ion cloud are measured, which help knowing the characteristic of the trapping potential and are the prerequisite of QIP with the trapped ions.  相似文献   

浅析广西北海市偏酸性地下水的形成原因   总被引：4，自引：0，他引：4  

周训 张华 赵亮沈晔  严霞欧业成  黄喜新 《地质学报》2007,81(6):850-856

广西北海市滨海平原松散沉积物中分布有潜水含水层和承压含水层,地下水的pH值普遍偏低,一般4.0～6.0者居多。第四系松散沉积物的矿物成分石英占50%～80%,含少量粘土矿物,化学成分中SiO2占绝大多数。以难溶成分为主的沉积物和长期的淋滤作用使地下水具有低矿化度。天然状态下偏酸性地下水的H 来源于碳酸的离解、粘土层中的H2O 以及雨水中的酸度。碳酸则是由CO2溶解于水而形成。其中CO2主要来源于生物成因。地下含水系统中缺少可以中和酸的碱性物质,有利于H 集聚,使地下水pH值偏低。  相似文献   

TOPEX/POSEIDON高度计资料用于中国近海M₂分潮的同化反演     

丘仲锋  何宜军 《海洋与湖沼》2005,36(4):376-384

以整个中国海为研究区域,把开边界取在TOPEX/POSEIDON(T/P)高度计资料数据点,利用趋近插值法将高度计资料同化到二维非线性潮汐数值模式中,反演了中国近海M2分潮的分布.计算结果与60个验潮站资料比较,符合良好振幅平均绝对偏差为6.7cm,相角偏差为5.5°,均方根偏差为12.6cm.根据计算结果给出东中国海和南海M2分潮的同潮图,与相关文献比较,符合良好.研究结果表明,以本方法利用T/P资料来反演中国海潮汐是可行的.  相似文献   

跨海地铁盾构管片混凝土耐久性及寿命预测分析          下载免费PDF全文

王金龙  刘伟宝  杨虎  陆采荣 《海洋工程》2022,40(5):139-146

根据某跨海地铁2号线的工况，确定跨海区间盾构管片的环境类别和作用等级，由各原材料氯离子含量计算推荐配合比混凝土氯离子含量，并对推荐配合比混凝土开展氯离子扩散系数试验和抗压强度试验。分别使用《海港工程高性能混凝土质量控制标准》(JTS 257-2—2012)、《混凝土结构耐久性评定标准》(CECS 220：2007)中的评定方法及多因素耦合评价(MFC)方法，基于钢筋开始锈蚀阶段t_i、混凝土保护层锈胀开裂阶段t_c、混凝土功能明显退化阶段t_d对混凝土结构使用年限t_e进行预测。结果表明，以上3种耐久性预测模型预测跨海地铁2号线推荐配合比使用年限的计算结果均大于100年，能够满足使用100年的要求。  相似文献