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.     

Phytoplankton bloom produced by a receding ice edge in the ross sea: spatial coherence with the density field

Measurements of chlorophyll, particulate carbon, and biogenic silica concentrations near a receding ice edge off the coast of Victoria Land, Antarctica, indicated the presence of a dense phytoplankton bloom. The bloom extended 250 kilometers from the ice edge and was restricted to waters where the melting of ice had resulted in reduced salinity. The region involved was one of enhanced vertical stability, which may have favored phytoplankton growth, accumulation, or both. Epontic algae released from melting ice may have served as an inoculum for the bloom. Ratios of organic carbon to chlorophyll and biogenic silica to carbon were unusually high, resulting in high biogenic silica concentrations despite only moderately high chlorophyll levels.     

有机化合物对有害藻类的控制技术研究

随着水体富营养化日益严重,水华、赤潮频繁爆发,藻类问题逐显突出,控藻技术的研究不断深入。从合成有机物和天然有机物2部分综述了有机化合物控藻技术的研究进展,且就有机化合物对有害藻类控制的研究趋势进行了展望,结合我国丰富的陆生植物资源,尤其是中草药资源,开发合理的控藻制剂将是一个很好的出路。     

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.     

Isolation of Virus Capable of Lysing the Brown Tide Microalga, Aureococcus anophagefferens

Viruses have been hypothesized to control blooms of Aureococcus anophagefferens gen. et sp. nov. (Chrysophyceae), a marine phytoplankton that since 1985 has caused devastating summer blooms called "brown tide." By means of ultrafiltration methods, viruses specific to this alga were isolated from both the Great South Bay and Peconic Bay systems of Long Island, New York, during the summer bloom period of 1992. Cell lysis of healthy algal cultures was demonstrated, as well as continuing reinfection with serial transfers of cultures. Electron microscope surveys yielded images of phage-like virus particles with tails that could attach to A. anophagefferens cells within minutes of exposure. The isolation and cultivation of this virus highlights the need for further study of viral infection of eukaryotic algae and the potential for a better understanding of algal bloom control by viral infection.     

Autumn bloom of antarctic pack-ice algae

An autumn bloom of sea-ice algae was observed from February to June of 1992 within the upper 0.4 meter of multiyear ice in the Western Weddell Sea, Antarctica. The bloom was reliant on the freezing of porous areas within the ice that initiated a vertical exchange of nutrient-depleted brine with nutrient-rich seawater. This replenishment of nutrients to the algal community allowed the net production of 1760 milligrams of carbon and 200 milligrams of nitrogen per square meter of ice. The location of this autumn bloom is unlike that of spring blooms previously observed in both polar regions.     

Ecological consequences of a century of warming in Lake Tanganyika

Deep tropical lakes are excellent climate monitors because annual mixing is shallow and flushing rates are low, allowing heat to accumulate during climatic warming. We describe effects of warming on Lake Tanganyika: A sharpened density gradient has slowed vertical mixing and reduced primary production. Increased warming rates during the coming century may continue to slow mixing and further reduce productivity in Lake Tanganyika and other deep tropical lakes.     

Direct coupling of marine invertebrate spawning with phytoplankton blooms

Spawning of green sea urchins and blue mussels may be triggered by a heat-stable metabolite released by various species of phytoplankton. Mussels require a higher phytoplankton density for a maximum response than urchins, perhaps because mussels are exposed to higher concentrations of phytoplankton as a result of their filtering activity. Phytoplankton as a spawning cue appears to integrate numerous physical and biotic factors indicating favorable conditions for larval growth and survival. Evolution of similar direct coupling of the larval phase with phytoplankton blooms may be common among marine invertebrates.     

Phytoplankton and cloudiness in the Southern Ocean

The effect of ocean biological productivity on marine clouds is explored over a large phytoplankton bloom in the Southern Ocean with the use of remotely sensed data. Cloud droplet number concentration over the bloom was twice what it was away from the bloom, and cloud effective radius was reduced by 30%. The resulting change in the short-wave radiative flux at the top of the atmosphere was -15 watts per square meter, comparable to the aerosol indirect effect over highly polluted regions. This observed impact of phytoplankton on clouds is attributed to changes in the size distribution and chemical composition of cloud condensation nuclei. We propose that secondary organic aerosol, formed from the oxidation of phytoplankton-produced isoprene, can affect chemical composition of marine cloud condensation nuclei and influence cloud droplet number. Model simulations support this hypothesis, indicating that 100% of the observed changes in cloud properties can be attributed to the isoprene secondary organic aerosol.     

连续T构箱梁桥竖向的升温模式

以黑龙江省三股线高架桥的实测温度数据为依据,对竖向温度梯度的变化规律进行了研究,得出了该桥的竖向升温模式;并对该升温模式、铁路桥规和公路桥规规定的竖向升温模式产生的温度自应力及外约束应力进行了计算与对比分析.结果表明,箱梁竖向最大升温温差发生在每天14时左右,1a中9月份的竖向升温温差相对较大;运用本地区竖向升温模式计算的混凝土拉应力略大于现行公路规范计算值,小于现行铁路规范计算值.     

Short-period climatic fluctuations: effects on diatom biomass

An analysis of the weekly averages of diatom biomass measured near the coast of Southern California (32 degrees 50'N, 117 degrees 10'W) during the period from 1928 through 1939 indicates that three major blooms account for 85 percent of each year's diatom biomass. The average duration of a single bloom is 5.5 weeks. The diatom blooms coincide with upwelling, but their individual characteristics depend on the detailed features of the circulation patterns of the water masses. That is, if upwelling takes place after a large influx of subtropical or even tropical water because of the slackening California Current, the resulting diatom blooms are smaller by several orders of magnitude than those observed when the flow of the current is strong. This influx of subtropical water into the region is reflected in positive anomalies of temperature, salinity, and sea level.     

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。     

Warming of the Eurasian landmass is making the Arabian Sea more productive

The recent trend of declining winter and spring snow cover over Eurasia is causing a land-ocean thermal gradient that is particularly favorable to stronger southwest (summer) monsoon winds. Since 1997, sea surface winds have been strengthening over the western Arabian Sea. This escalation in the intensity of summer monsoon winds, accompanied by enhanced upwelling and an increase of more than 350% in average summertime phytoplankton biomass along the coast and over 300% offshore, raises the possibility that the current warming trend of the Eurasian landmass is making the Arabian Sea more productive.     

Climate impact on plankton ecosystems in the Northeast Atlantic

It is now widely accepted that global warming is occurring, yet its effects on the world's largest ecosystem, the marine pelagic realm, are largely unknown. We show that sea surface warming in the Northeast Atlantic is accompanied by increasing phytoplankton abundance in cooler regions and decreasing phytoplankton abundance in warmer regions. This impact propagates up the food web (bottom-up control) through copepod herbivores to zooplankton carnivores because of tight trophic coupling. Future warming is therefore likely to alter the spatial distribution of primary and secondary pelagic production, affecting ecosystem services and placing additional stress on already-depleted fish and mammal populations.     

Phytoplankton community structure and the drawdown of nutrients and CO2 in the southern ocean

Data from recent oceanographic cruises show that phytoplankton community structure in the Ross Sea is related to mixed layer depth. Diatoms dominate in highly stratified waters, whereas Phaeocystis antarctica assemblages dominate where waters are more deeply mixed. The drawdown of both carbon dioxide (CO2) and nitrate per mole of phosphate and the rate of new production by diatoms are much lower than that measured for P. antarctica. Consequently, the capacity of the biological community to draw down atmospheric CO2 and transport it to the deep ocean could diminish dramatically if predicted increases in upper ocean stratification due to climate warming should occur.     

Runoff of deicing salt: effect on irondequoit bay, Rochester, new york

Salt used for deicing the streets near Rochester, New York, has increased the chloride concentration in Irondequoit Bay at least fivefold during the past two decades. During the winter of 1969-70 the quantity and salinity of the dense runoff that accumulated on the bottom of the bay was sufficient to prevent complete vertical mixing of the bay during the spring. Comparison with 1939 conditions indicates that the period of summer stratification has been prolonged a month by the density gradient imposed by the salt runoff.     

象山港滨海电厂温排水对浮游生物的生态影响

应用海洋数值模式ECOM-si耦合一个可用于实时计算的太阳辐射强度和海面热通量计算模块,采用N2P2ZD型生态模型,研究评估了象山港海域的浮游生物量受港内两大滨海电厂(国华电厂和乌沙山电厂)温排水的影响程度。数值模式的模拟结果表明,温排水及其卷载和余氯杀伤效应对海域的浮游生物量有显著影响,一定程度上改变了象山港浮游生物量的季节变化规律和空间分布特征。在春季和初夏等增温季节,温排水的存在可使藻华的发生期提前;夏季高温期,水温超过最佳生长温度,则使浮游植物生物量下降,且可降低赤潮发生的风险;在秋季降温期和冬季低温期,水温低于最佳生长温度,温排水有助于缓解水温的下降,有助于提高该时期海域的初级生产力。除了季节变化上有增有减外,浮游植物和浮游动物量年均水平由于温排水的温升和杀伤效应而降低,碎屑量随之上升,总体上弥补了海域水体总有机体含量的损失,但海域的年均总有机体变化量仍为负值。国华电厂温排水的影响大于乌沙山电厂。无论从温升范围和浮游生物量变化幅度上,国华电厂对铁港的影响都大于黄墩港。     

南江水库蓝藻水华应急处置前后浮游植物群落结构及环境因子变化

为了解实验室研发的应急处置对南江水库蓝藻水华的治理效果和在治理过程中的水质变动情况,分别对南江水库在修复前、中和后的水质和浮游植物群落结构的变化开展研究。结果表明：修复后TN、TP质量浓度显著下降,优势种从修复前的唯一优势种水华束丝藻(Aphanizomenon flos-aquae)变化为修复后的鞘丝藻(Lyngbya)、水华束丝藻、巨颤藻(Oscillatoria princeps)、隐球藻(Aphanocapsa)以及尖针杆藻(Synedra acus);浮游植物生物密度从修复前(39.20±0.52)×10⁷ cells/L下降为修复后的(5.50±0.13)×10⁷ cells/L;生物量从修复前(24.64±3.25)mg/L下降为修复后的(7.97±1.56)mg/L。Shannon-Wiener多样性指数、Pielou均匀度指数和Margalef丰富度指数在修复前期显著低于修复中期(P<0.05)。冗余分析(RDA)表明水温(WT)、总磷(TP)是影响浮游植物的主要环境因子,其中总磷(TP)是蓝藻水华暴发的关键性因子。上...     

The North Atlantic spring phytoplankton bloom and Sverdrup's critical depth hypothesis

More than 50 years ago, Harald Sverdrup developed a simple model for the necessary conditions leading to the spring bloom of phytoplankton. Although this model has been used extensively across a variety of aquatic ecosystems, its application requires knowledge of community compensation irradiance (IC), the light level where photosynthetic and ecosystem community loss processes balance. However, reported IC values have varied by an order of magnitude. Here, IC estimates are determined using satellite and hydrographic data sets consistent with the assumptions in Sverdrup's 1953 critical depth hypothesis. Retrieved values of IC are approximately uniform throughout much of the North Atlantic with a mean value of 1.3 mol photons meter-2 day-1. These community-based IC determinations are roughly twice typical values found for phytoplankton alone indicating that phytoplankton account for approximately one-half of community ecosystem losses. This work also suggests that important aspects of heterotrophic community dynamics can be assessed using satellite observations.     

Phytoplankton blooming off the u.s. East coast: a satellite description

A "bloom" of near-surface phytoplankton occurs in the Atlantic Slope region of the western Atlantic Ocean off the U.S. East Coast in the spring. Satellite time series of sea-surface temperature and phytoplankton pigment concentration, derived from measurements of the National Oceanic and Atmospheric Administration NOAA-7 Advanced Very-High-Resolution Radiometer and the National Aeronautics and Space Administration Nimbus-7 Coastal Zone Color Scanner, respectively, give information on the spatial extent and temporal development of such a bloom for a 28-day period in April through May 1982. The phytoplankton concentration of the slope area is comparable to that of the Atlantic Shelf. Total primary productivity of the slope during this period is equivalent to that of the shelf. The primary productivity within a warm-core ring and in the Gulf Stream system is less by a factor of 2.