Eddy/wind interactions stimulate extraordinary mid-ocean plankton blooms

Episodic eddy-driven upwelling may supply a significant fraction of the nutrients required to sustain primary productivity of the subtropical ocean. New observations in the northwest Atlantic reveal that, although plankton blooms occur in both cyclones and mode-water eddies, the biological responses differ. Mode-water eddies can generate extraordinary diatom biomass and primary production at depth, relative to the time series near Bermuda. These blooms are sustained by eddy/wind interactions, which amplify the eddy-induced upwelling. In contrast, eddy/wind interactions dampen eddy-induced upwelling in cyclones. Carbon export inferred from oxygen anomalies in eddy cores is one to three times as much as annual new production for the region.     

Southwest monsoon of 1979: chemical and biological response of somali coastal waters

In 1979 two areas of upwelling were observed off Somalia, one near 10 degrees N and one near 5 degrees N. The areas of upwelling were characterized by sea surface temperatures between 17 degrees and 22 degrees C, high concentrations of surface nutrients (5 to 20 micromoles of nitrate per liter) and surface chlorophyll a (0.4 to 5.0 milligrams per cubic meter), primary productivity averaging 1.7 grams of carbon per square meter per day, and a phytoplankton assemblage dominated numerically by the diatom Nitzschia delicatissima.     

Climatic warming and the decline of zooplankton in the california current

Since 1951, the biomass of macrozooplankton in waters off southern California has decreased by 80 percent. During the same period, the surface layer warmed-by more than 1.5 degrees C in some places-and the temperature difference across the thermocline increased. Increased stratification resulted in less lifting of the thermocline by wind-driven upwelling. A shallower source of upwelled waters provided less inorganic nutrient for new biological production and hence supported a smaller zooplankton population. Continued warming could lead to further decline of zooplankton.     

上升流和水团对浙江中部近海浮游动物生态类群分布的影响

依据2010年4月、7月和11月对浙江中部近海上升流海域进行的海洋调查资料,运用定量、定性方法,探讨了上升流对该海域浮游动物生态类群分布的影响.结果表明:3个季节共鉴定浮游动物64种,桡足类占主要优势,包括5个生态类群,分别是暖温带近海种、暖温带外海种、亚热带近海种、亚热带外海种和热带大洋种.在种类数组成上,春季以暖温带近海种为主,夏季则是亚热带近海种和亚热带外海种居多,秋季也是亚热带种居多,其中夏季暖温带种种类数要高于春季和秋季,这一现象与同时期东黄海沿海有所不同,主要是由于上升流将一些在海洋底部度夏的暖温种带至海洋表面造成的.此外,3个季节生态类群都是以近海种为主,表明沿岸流是影响这一海域的最主要的水团.在丰度组成上,4月暖温带近海种占总丰度的98.79％,7月暖温带近海种也是组成丰度的重要部分,10月则是亚热带近海种丰度最高.丰度组成所反映的规律与种类数组成规律一致.上升流的存在导致夏季近海暖温带种大量出现,是影响这一海域浮游动物生态类群组成的重要因素;受长江径流和椒江径流的影响,近海种成为主要生态类群,是这一海域浮游动物的一个重要的生态特征.     

Massive phytoplankton blooms under Arctic sea ice

Phytoplankton blooms over Arctic Ocean continental shelves are thought to be restricted to waters free of sea ice. Here, we document a massive phytoplankton bloom beneath fully consolidated pack ice far from the ice edge in the Chukchi Sea, where light transmission has increased in recent decades because of thinning ice cover and proliferation of melt ponds. The bloom was characterized by high diatom biomass and rates of growth and primary production. Evidence suggests that under-ice phytoplankton blooms may be more widespread over nutrient-rich Arctic continental shelves and that satellite-based estimates of annual primary production in these waters may be underestimated by up to 10-fold.     

台湾海峡西北部海坛岛东南沿岸上升流对表层沉积硅藻的影响

[目的]探讨台湾海峡西北部海坛岛东南沿岸上升流对表层沉积硅藻的影响。[方法]以台湾海峡西北部海坛岛东南沿岸的表层沉积硅藻为材料,对其进行筛选、制片、观察,研究其属种分布特征和上升流对其的影响。[结果]按照表层沉积硅藻的丰度分布特征,将其分为三个研究区,以柱状小环藻、具槽直链藻和波状辐裥藻为主要的优势种群。结合温度、盐度的资料,可以得出海坛岛东南沿岸海域存在上升流。[结论]该研究为进一步探讨海坛岛东南沿岸海域表层沉积硅藻与上升流的关系提供了科学依据。     

Coherent high- and low-latitude climate variability during the holocene warm period

A faunal record of sea-surface temperature (SST) variations off West Africa documents a series of abrupt, millennial-scale cooling events, which punctuated the Holocene warm period. These events evidently resulted from increased southward advection of cooler temperate or subpolar waters to this subtropical location or from enhanced regional upwelling. The most recent of these events was the Little Ice Age, which occurred between 1300 to 1850 A.D., when subtropical SSTs were reduced by 3 degrees to 4 degrees C. These events were synchronous with Holocene changes in subpolar North Atlantic SSTs, documenting a strong, in-phase link between millennial-scale variations in high- and low-latitude climate during the Holocene.     

岩滩水电开发对库区水环境的影响

【目的】研究岩滩水电开发对库区水环境的影响,为今后河流梯级开发库区水环境的保护以及水利生态调控提供理论依据。【方法】分别在枯水期和丰水期对红水河岩滩水电站库区水生态进行调查,结合库区建坝后藻类生态学研究数据,分析库区水质理化因子和藻类生物量变化特征。【结果】岩滩库区建坝后,而藻类生物量在枯水期和丰水期中有明显差异,丰水期高于枯水期;和建坝初期比较,藻类组成中喜静水的绿藻种类增加,硅藻种类下降,但藻类总密度增加明显;藻类密度和主要营养盐无明显的相关性,主要生源要素氮、磷浓度较建库前有较明显变化,特别库区可溶性硝酸盐增加显著,但磷酸盐浓度则下降。【结论】岩滩水电站库区水体营养状况呈现富营养化趋势,若有外源性磷进入库区,则极易引发严重的藻类“水华”。     

西江下游浮游植物群落周年变化模式

西江肇庆段是珠江干流汇入珠三角河网水域的咽喉通道,对2009年该江段的浮游植物群落组成及变化进行系统阐析。调查期间共发现浮游植物7门,245种(包括变种、变型),其中硅藻和绿藻是浮游植物群落组成的最主要类群,分别占总种数的42.44%和34.69%,其次是裸藻和蓝藻。PCA分析结果显示,浮游植物各类群的种类丰富度和生物量的周年变化趋势主要受水温和径流量的影响。浮游植物种类丰富度的周年变化呈现明显的高温季节高,低温季节低的特征,除因大多数藻类物种直接喜好高温之外,径流量的增大有助于真浮游绿藻种类的外源注入及半浮游和偶然性浮游硅藻种类的增加。浮游植物生物量的周年变化呈现明显的双峰型,峰值分别出现在8月和11月。然而8月份第1个高峰出现之前,生物量波动不大,尽管水温的升高有助于生物量的增加,但是径流量增大所带来的稀释作用掩盖了水温上升对浮游植物生长的促进作用。真浮游植物生物量的变化趋势和数值与总浮游植物极其接近,主要得益于真浮游硅藻物种颗粒直链藻在总种群中的绝对优势地位。综上,水温升高对浮游植物种类丰富度和生物量的增长均有促进,径流量的增大虽然有助于种类丰富度的增加,但不利于生物量的增加。     

围隔中不同密度鲢对浮游植物的影响

试验采用2.5 m×2.5 m围隔,共设置4个试验鱼密度:0、116、176、和316 g/m2,研究了不同密度的鲢对浮游植物的影响。结果表明,仅在无鱼围隔中有大量个体较大的透明溞(Daphnia galeata)产生,并且在无鱼围隔中,浮游植物生物量最低,透明度显著的高于其他的围隔。与其它类似的围隔试验所不同的是:在无鱼围隔中没有蓝藻水华的发生。在有鱼围隔中,浮游甲壳动物始终由个体较小的微型裸腹溞占优势。并且浮游植物的生物量随着鲢密度的升高而降低。浮游植物的种类组成在不同鲢密度的围隔中比较相似,与无鱼围隔相比,绿藻和裸藻生物量所占的比率较低,蓝藻生物量所占的比率较高。     

一个天然水体硅藻区系的演替

本文报导了山西省太谷县一个天然水体硅藻区系的演替。标本自1979年11月到1981年1月逐月定点采集,初步鉴定的结果,共10科25属104个分类单位。从逐月硅藻种类的消长情况,看出该水体硅藻区系的演替,其中一些种常年出现,如:库津小环藻叔曼变种Cyclotella kuetzingiana var。Schumannii Grun,变异直链藻Melosira varians Ag。新月形桥弯藻Cymbella cymbiformis(Ag？Kuetz)V.H.另一些种从4月或6月到次年1月出现,前者如:弯羽纹藻Pinnularia gibba Ehr,后者如:短角美壁藻Caloneis silicula(Ehr.)Cl,有些种在一年中仅出现1——2次,如:大美壁藻Caloneis permagna(Bailey.)Cleve.,彩虹长篦藻Neidium iridis(Ehr.)Cl.,作者认为常年出现的种对温度反应极为迟钝。而一年中仅出现1——2次的种则对温度反应极为敏感。如果在某一个时期一些种大量出现,可以看作这种温度为最适温度,如;弯羽纹藻P.gibba Ehr。10月气温16℃,水温14℃。这样就提供了培养硅藻的温度范围。同时,也可以作为鉴定化石硅藻时推测当时(古气候)的参考。     

Blue-green algal inhibition of diatom growth: transition from mesotrophic to eutrophic community structure

Cell-free filtrates of axenic or bacterized cultures of the dominant blue-green algae from a freshwater lake inhibited the growth of diatoms isolated from the same lake. Lake waters, collected during blue-green algal blooms, also inhibited diatom growth. In situ observations over a 5-year period indicate that diatom bloom populations vary inversely with the levels of the preceding blue-green algal populations. Blue-green algal dominance of eutrophic lakes is attributed to this allelopathy, and dilution is proposed as one cause for the limited occurrence of blue-green alga dominance in marine waters.     

Oceanic Rossby waves acting as a "hay rake" for ecosystem floating by-products

Recent satellite observations of Rossby waves and chlorophyll anomalies propagating in subtropical gyres have suggested that wave-induced upwelling could stimulate photosynthesis. Instead, we show that chlorophyll maxima are located in abnormally warm water, in Rossby wave-induced convergences. This excludes inputs of nutrients from deeper water. We argue that the sea color anomalies are not caused by chlorophyll but by floating particles evolved from the ecosystem and accumulated by Rossby waves, acting as "marine hay rakes," in convergence zones. Such processes may be determinant for the distribution of living organisms in oligotrophic areas.     

Stable isotopes in a mollusk shell: detection of upwelling events

The California mussel Mytilus californianus records with high fidelity annual temperature variations of nearshore waters in the oxygen isotope composition of its shell. The onset and termination of upwelling events (and metabolic activity) are recorded in the associated carbon isotope signal, and the magnitude and timing of upwelling can be estimated. The method has implications for studying the history of upwelling and the life history of living and fossil mollusks and for analyzing shell midden deposits.     

Global climate change and intensification of coastal ocean upwelling

A mechanism exists whereby global greenhouse warning could, by intensifying the alongshore wind stress on the ocean surface, lead to acceleration of coastal upwelling. Evidence from several different regions suggests that the major coastal upwelling systems of the world have been growing in upwelling intensity as greenhouse gases have accumulated in the earth's atmosphere. Thus the cool foggy summer conditions that typify the coastlands of northern California and other similar upwelling regions might, under global warming, become even more pronounced. Effects of enhanced upwelling on the marine ecosystem are uncertain but potentially dramatic.     

底泥营养物质释放对围隔水生生态系统的影响

采用围隔研究了底泥对湖泊生态系统的影响.试验用的8个围隔设置于武汉东湖,其中E1～E4围隔采用富营养的东湖Ⅰ站底泥,E5～E8围隔采用相对贫营养东湖Ⅲ站底泥;E1、E2及E5、E6围隔中注入湖水,其余围隔注入自来水.试验持续2个半月.研究结果表明,加入I站底泥的围隔中pH、总氮(TN)、总磷(TP)平均值显著高于加入Ⅲ站底泥的围隔.E1～E4围隔中自8月初形成持续的微囊藻水华,其生物量显著高于没有微囊藻水华的E7、E8围隔,E5、E6围隔则形成短期微囊藻水华.E1～E4围隔浮游植物多样性指数远低于没有微囊藻水华的E7、E8围隔.上述结果表明,在浅水水体中,底泥对水质的影响要远远大于湖水,围隔中蓝藻水华发生的磷域值介于E5、E6和E7、E8围隔中磷含量之间,为0.06～0.10 mg/L.     

湖泊蓝藻水华发生机理研究进展

蓝藻水华是富营养化湖泊常见的生态灾害,通过产生毒素、死亡分解时使水体缺氧和破坏正常的食物网威胁到饮用水安全、公众健康和景观,会造成严重的经济损失和社会问题,揭示其发生机理是进行防治的基础.综述了蓝藻水华发生机理的主要假说和证据,主要分为环境因子(营养盐、氮磷比、温度、微量元素、浮游动物牧食、水文和气象条件等)和生理生态特性(伪空泡、胶质鞘、CO2浓缩机制、适应低光强、贮藏营养物质、防晒、产毒素和固氮等)两个方面;评述了主要新理论,展望了今后的研究.到目前为止的研究表明寻找一两个关键因子并不能阐明蓝藻水华的发生机理.现存的理论或假说尽管已经在蓝藻水华的防治实践中产生重要作用,但仍然未能清楚地阐释其发生的客观规律.认为蓝藻水华是在各种环境因子(外因)的耦合驱动下,水华蓝藻由于其独特的生理生态特性(内因),产生巨大的生物量而在浮游植物群落中占绝对优势,在合适的水文气象条件下集聚于水表而形成.因此水华机理的研究应同时关注水华蓝藻的生理生态学规律和蓝藻水华发生的各种环境条件.不同环境因子协同影响水华蓝藻的不同生理生态特性的表达,从而影响水华的发生过程,将可能是以后研究的重点.蓝藻水华机理的研究在微观方面正趋向于应用分子生物学手段分析蓝藻生理过程,宏观方面则将广泛应用遥感遥测技术观测全湖蓝藻的变化规律.今后加强对水华蓝藻生理生态特性的基因表达与调控和环境多因子耦合作用于蓝藻水华过程的研究将有重要意义.蓝藻水华的机理研究包括现象、过程和原因3个层次的问题,通过大量的现象和过程的研究,不断揭示其发生过程中水华蓝藻的群落演替、种群发展、细胞活性和分子机理等变化规律,才能找到其发生的真正原因,为其防治提供理论依据和更好的治理措施.在蓝藻水华防治方面,控制营养盐和生态修复可能将是今后很长时间内最根本最有效和最具操作性的方法.     

Emergence of anoxia in the California current large marine ecosystem

Eastern boundary current systems are among the world's most productive large marine ecosystems. Because upwelling currents transport nutrient-rich but oxygen-depleted water onto shallow seas, large expanses of productive continental shelves can be vulnerable to the risk of extreme low-oxygen events. Here, we report the novel rise of water-column shelf anoxia in the northern California Current system, a large marine ecosystem with no previous record of such extreme oxygen deficits. The expansion of anoxia highlights the potential for rapid and discontinuous ecosystem change in productive coastal systems that sustain a major portion of the world's fisheries.     

Late Miocene Origin of the Benguela Upswelling System off Northern Namibia

Deep Sea Drilling Project cores collected at site 362/362A suggest the time of initiation of the Benguela upwelling system off northern Namibia. Studies of sediment accumulation rates, diatom abundances, microfossil temperature preferences (for planktic foraminifers, calcareous nannoplankton, and silicoflagellates), productivity (expressed as the organic carbon content), and phosphorus incorporation in calcareous skeletons all suggest that major, sustained upwelling began in the early late Miocene. Upwelling brought cold, nutrient-rich waters to the surface, and the modern Benguela system dates from this time (about 10 million years before the present).     

Upwelling intensification as part of the Pliocene-Pleistocene climate transition

A deep-sea sediment core underlying the Benguela upwelling system off southwest Africa provides a continuous time series of sea surface temperature (SST) for the past 4.5 million years. Our results indicate that temperatures in the region have declined by about 10 degrees C since 3.2 million years ago. Records of paleoproductivity suggest that this cooling was associated with an increase in wind-driven upwelling tied to a shift from relatively stable global warmth during the mid-Pliocene to the high-amplitude glacial-interglacial cycles of the late Quaternary. These observations imply that Atlantic Ocean surface water circulation was radically different during the mid-Pliocene.