Biological control of short-term variations in the concentration of DMSP and DMS during a Phaeocystis spring bloom

In the spring of 1995, short-term variations in the concentration of particulate and dissolved dimethylsulfoniopropionate (DMSP) and dimethylsulfide (DMS) were monitored in the western Wadden Sea, a shallow coastal region in open connection with the North Sea. Significant correlations were found between abundance of Phaeocystis globosa and particulate DMSP; concentrations increased rapidly from 100 to 1650 nM in the middle of April. Highest DMS concentrations were found during the initial phase of the exponential growth of the bloom. DMS production and loss rates of DMSP and DMS were estimated experimentally during various phases of the bloom. DMS production and consumption were roughly in balance, with production only slightly exceeding consumption at the start of the bloom. Rates of production and consumption were highest during the exponential growth phase of Phaeocystis and declined in the course of the bloom (from 300–375 to less than 5 nmol dm⁻³ d⁻¹). Demethylation of DMSP increased during the bloom (from 11 to 1300 nmol dm⁻³ d⁻¹); it accounted for up to 100% of the DMSP loss at the end of the bloom. The shift from DMSP cleavage to demethylation in the course of a Phaeocystis bloom implies that DMS concentrations are not necessarily highest at the peak or towards the end of blooms.     

Behavior of Cu, Ni and Cd during nutrient depletion in a spring bloom in Funka Bay

The concentrations of Cu, Ni and Cd were determined in Funka Bay during a spring phytoplankton bloom, consisting of diatoms. Just after the bloom, both dissolved Cd and nutrients were removed in the euphotic zone. However, the removal ratio of Cd to phosphate was very different from that in seawater. The removal of Cd took place at a Cd/phosphate ratio of 0.07×10⁻³, which was lower than in seawater before the bloom (0.25×10⁻³), leading to an increase in this ratio in seawater exceeding 0.7×10⁻³ at the end of the bloom. Elevated concentrations of Cd and phosphate were observed in the deeper layer after the bloom due to the decomposition of detrital materials produced in the bloom. The ratio of Cd/phosphate in the regeneration step was 0.24×10⁻³ which was different from the removal ratio of 0.07×10⁻³. These observations suggest that the high Cd/phosphate ratio in the regeneration would reflect a relatively high regeneration rate of Cd than that of phosphate. No significant decrease in Cu and Ni concentrations was observed during the development of the bloom, suggesting that biological removal of these metals was not so significant during the spring bloom. The concentrations of Cd, Cu and silicate in surface waters increased after the bloom with decreasing salinity due to the influence of a spring thaw.     

A Preliminary Study on the Polar Climate Predictability

Studies have revealed that predictability of the atmospheric general circulation is generally high in the tropics throughout the year and that there is some predictability in the Northern extra-tropical winter at-mospheric circulation through some patterns of tele connection. Predictability of the general circulation at the polar regions has still remained as a ‘cold’ topic and little has been known about this question. Based on a preliminary study on the predictability by using the Institute of Atmospheric Physics (IAP) general circulation model, it is found that the SST-related predictability of the Southern winter lower atmospheric circulation in Antarctica is reasonably high and that there is some predictability in the 500 hPa and 200 hPa geopotential height fields over Europe and the Okhotsk Sea region during the Northern winter. It is sug-gested that more researches on this issue based on data analysis and model simulations are needed to obtain better understanding.     

初春南黄海水文特征及环流状况的分析

根据1996年初春中韩黄海水循环动力学合作调查所获资料,分析了南黄海水文特征及其环流状况,并获得了以下几点主要认识:(1)初春南黄海的温、盐分布特征及环流基本形态,与以往所揭示的冬季状况基本相似.然而,本次调查发现,在30m以浅,黄海中部暖水舌轴线比冬季的明显偏东;且出现一范围较小的孤立的相对高温高盐区.在垂向,一种中层冷水和表层逆温跃层现象出现在黄海局部区域.(2)直接测流的结果,不仅部分地印证了由温、盐场所显示的环流基本形态,而且较好地揭示了流场中发生的一些新现象,其中尤其是绕济州岛的流动.(3)黄海暖流水是对马暖流水和陆架水混合而成.而且,它主要是在济州岛西侧水域,从锋带中衍生出来的.     

河西绿洲区春小麦蒸腾蒸散的变化研究

在甘肃张掖绿洲区利用浮力称重式蒸散仪对春小麦蒸散量进行了测定,对蒸散量的日变化和季节变化特征进行了论述。研究结果表明:小麦田的日蒸散量在白天12:00~16:00达到最大,夜间20:00~08:00最小甚至呈负值。灌溉前后蒸腾强度出现峰值的时间有所变化。但灌溉以后,蒸腾与蒸散量均呈增大趋势。日蒸散量随着净辐射的增加而加大。在小麦不同的生育阶段,蒸散量有所不同,小麦拔节以前较小,拔节以后开始增大,灌浆期达到最大,接近成熟时逐渐降低。     

三峡水库香溪河库湾春季水华期间浮游植物昼夜垂直分布与迁移

三峡水库蓄水后,香溪河库湾每年春季均会暴发硅、甲藻水华.为了揭示香溪河库湾水华的暴发规律,于2008年春季对水华期间优势浮游植物的昼夜垂直分布格局及其影响因子进行了研究.利用时间深度等值图模拟浮游植物在水柱中的昼夜垂直分布格局,并用Morisita指数对其进行定量检验,采用修正的K-S test来检验浮游植物是否存在昼...     

浅议龙门石窟风景区旅游资源的开发利用及保护

龙门石窟是我国重点文物保护单位 ,以雕像众多、龛窟雕饰细腻逼真闻名于世。石窟风景区内赋存有地下热水、温泉群等其他旅游资源。文章论述了石窟雕像载体的岩体特征 ,评价了温热水、温泉群的水质特性 ,分析了风景区旅游资源的利用现状 ,就进一步开发旅游资源和保护好风景区环境 ,提出了建议。     

泉水信息在研究水文地质条件中的应用

根据仁村东泉、西泉流量变化特征与降水之间的有关信息 ,分析了泉域相应的水文地质条件 ,其与实际情况相吻合。用这种方法分析泉域水文地质条件 ,不仅可以加深对泉域水文地质条件的认识 ,而且对查明泉域水文地质条件 ,并合理投入工程量有着一定的指导意义。     

连云港洪门古沙堤沉积特征及其意义

通过钻孔、年代地层、沉积物粒度和有孔虫组合综合分析,并配合探地雷达,对洪门古沙堤的成因类型以及古海岸环境进行了探讨。洪门古沙堤沉积物和海州湾现代沙滩、苏北平原贝壳堤相比较,颗粒集中在粗砂—极粗砂范围,分选性偏差,极有可能形成于靠近河口或受河口影响的环境。探地雷达揭示洪门古沙堤曾有过向海方向的进积和生长,指示当时沙源丰富。洪门古沙堤的浅钻地层反映了洪门地区在6400 aBP左右为滨海沼泽环境,此时期与青莲岗文化期的年代相吻合;湖沼沉积结束后,洪门地区迎来了中全新世的最大海侵,受周围地形的制约,洪门地区可能形成了河口浅海湾环境,普遍沉积了2 m左右的青灰色淤泥沉积,有孔虫组合反映当时的环境并非完全开敞,而是受到一定程度限制的近岸浅水环境,反映了洪门地区为浅海湾环境;6000 aBP左右,随着砂砾质沉积物供应的丰富以及相对海平面下降,洪门古沙堤开始发育,直到5000 aBP苏北和连云港地区普遍发生海退,古沙堤发育结束。     

中国水产品出口影响因素研究

渔业经济对于促进我国农业经济乃至国民经济的增长具有显著的作用,近年来国际水产品市场格局的剧烈变化为中国水产出口贸易带来考验。为改善现况,研究采用层次分析-决策实验与评价实验室-结构解释模型(AHP-DEMATEL-ISM)结合的方法,从贸易准备、企业生产、贸易磋商、市场流通4个阶段出发,挖掘影响中国水产品出口的根本因素及各因素之间的内在联系。结果表明,贸易磋商环境影响最大,企业生产环境、市场流通环境以及贸易准备环境次之;冷链物流、政策扶持、技术壁垒以及关税壁垒是影响中国水产品出口的根本因素。