Characteristics of seasonal and spatial variations of primary production over the southeastern Bering Sea shelf   总被引：3，自引：1，他引：3  

TaeKeun Rho  Terry E. Whitledge 《Continental Shelf Research》2007,27(20):2556-2569

In situ primary production data collected during 1978–1981 period and 1997–2000 period were combined to improve understanding of seasonal and spatial distribution of primary production in the southeastern Bering Sea. Mean daily primary production rates showed an apparent seasonal cycle with high rates in May and low rates in summer over the entire shelf of the southeastern Bering Sea except for oceanic region due to lack of data. There was also an increasing trend of primary production rates in the fall over the inner shelf and the middle shelf. There was a decreasing trend of primary production rates between late April and mid-May over the inner shelf while there was an abrupt increase between late April and mid-May over the middle shelf and the outer shelf. In the shelf break region, there was an increasing pattern in late May. These suggest that there was a gradual progression of the development of the spring phytoplankton bloom from the inner shelf toward the shelf break region. There was also a latitudinal variability of primary production rate over the middle shelf, probably due to either spatial variations of the seasonal advance and retreat of sea ice or horizontal advection of saline water in the bottom layer. Annual rates of primary production across the southeastern Bering Sea shelf were 121, 150, 145, 110, and 84 g C m⁻² yr⁻¹ in the inner shelf, the middle shelf, the outer shelf, the shelf break, and oceanic region, respectively. High annual rates of primary production over the inner shelf can be attributed to continuous summer production based on regenerated nitrogen and/or a continuous supply of nitrogen at the inner front region, and to fall production. There were some possibilities of underestimation of annual primary production over the entire shelf due to lack of measurement in early spring and fall, which may be more apparent over the shelf break and oceanic region than the inner shelf, the middle, and the outer shelf. This study suggests that the response of primary production by climate change in the southeastern Bering Sea shelf can be misunderstood without proper temporal and seasonal measurement.  相似文献   

Direct effects of Daphnia-grazing, not infochemicals, mediate a shift towards large inedible colonies of the gelatinous green alga Sphaerocystis schroeteri     

Heike Kampe  Marie König-Rinke  Jürgen Benndorf 《Limnologica》2007,37(2):137-145

The influence of Daphnia galeata×hyalina grazing and of infochemicals released by the daphnids on the colony size and growth rate of the colonial gelatinous green alga Sphaerocystis schroeteri (Chlorococcales) was investigated in laboratory batch experiments run for 96 h. High zooplankton grazing pressure was exerted by a final concentration of 100 daphnids L⁻¹ in the Daphnia treatments. Infochemicals were obtained by filtration (0.2 μm) of water from D. galeata×hyalina cultures (200 ind. L⁻¹ exposed for 24 h). This filtrate was added to the S. schroeteri cultures in two concentrations corresponding to 7 and 50 daphnids L⁻¹, respectively. The growth rate of S. schroeteri was neither affected significantly by direct Daphnia grazing nor by the presence of Daphnia infochemicals, in comparison to the control. However, the portion of inedible S. schroeteri colonies (diameter>50 μm) increased under direct grazing pressure, whereas the Daphnia infochemicals did not influence the colony size significantly. We conclude that the shift in colony size by direct zooplankton grazing denotes an effective defence mechanism against size selective feeding for colonial gelatinous green algae. This effective defence in combination with unchanged growth rates of the larger colonies (under non-limiting nutrient and light conditions) falsifies the assumption of a trade-off between minimising grazing losses and maximising growth by optimising the colony size.  相似文献   

南极菲尔德斯半岛六种藻类和地衣植物的X荧光分析   总被引：2，自引：2，他引：2       下载免费PDF全文

沈显生  孙立广  张莉  尹雪斌  康士秀  吴自勤  巨新  黄宇营 《极地研究》2001,13(3):187-194

为了研究南极的植物与环境间的关系 ,探讨植物在南极环境监测中的作用 ,在无标样条件下 ,利用微束 X荧光分析法对南极菲尔德斯半岛的 6种藻类和地衣植物进行了元素分析。其中藻类植物有孔石莼 (Ulva pertusa)、海膜 (H alymenia sp.)和大型鞘丝藻 (Lyngbya major) ,地衣植物有筛石蕊 (Cladonia borealis)、喇叭石蕊 (C.fimbriata)和松萝 (Usnea sp.)。研究结果发现 ,不同的藻类植物对各种元素的吸收能力不同 ,在 XRF(X射线荧光 )谱中 ,孔石莼比海膜含有更多的元素 ,象 As、Br和 Rb,Cu和 Zn的含量也较高。在大型鞘丝藻中 ,K比 Ca少 ,Zn的含量较高。在 3种地衣植物中 ,其 XRF谱中的元素种类组成非常相似 ,只是 Mn、Fe、Cu和 Zn等元素的相对含量有些差异  相似文献   

The generation of phytoplankton patchiness by mesoscale current patterns   总被引：1，自引：0，他引：1  

Katja Fennel 《Ocean Dynamics》2001,52(2):58-70

 Elken et al. (1994) suggested that phytoplankton patchiness can be generated by mesoscale eddies in light-limited, nutrient-replete environments. This hypothesis is explored using two ecological models of different physical complexity. The model results support the idea that the coupling of mesoscale eddy circulation and phytoplankton growth leads to differential growth rates and thus generates variability in phytoplankton distributions. The specific circulation of a cyclonic eddy isolates a phytoplankton population in its core. Due to the reduced vertical mixing, a higher growth rate is supported in the core, and phytoplankton concentrations increase compared to the surrounding environment. A one-dimensional model is used to explore the hypothesis in general and to perform sensitivity studies. A more realistic simulation uses a coupled three- dimensional model for the western Baltic Sea. Starting from vertically and horizontally homogeneous distributions for nutrients and plankton, the models generate patchiness due to the proposed mechanism. The described mechanism may apply for other mesoscale variable environments during light-limited growth periods as well, e.g., the frontal region of the Southern Ocean. Received: 31 March 2001 / Accepted: 31 August 2001  相似文献   

浑江末前寒武纪丝状藻类及其环境意义   总被引：10，自引：1，他引：10  

高林志  乔秀夫 《地质论评》1992,38(2):140-148

本文初步探讨了吉林浑江晚前寒武纪丝状藻类与沉积环境的关系。这些丝状藻类产自晚前寒武纪不同层位,大多属蓝绿藻类。通过对丝状藻类整体面貌和个体丰度的分析,笔者将其划分为三类即:藻席型、孤立生存型和其间的过渡类型。根据对现代丝状藻类生态及环境的研究,采取比较古生物学的方法,具体讨论了浑江地区晚前寒武纪丝状藻类的指相意义。根据沉积学与事件地层记录分析的沉积环境模式与对丝状藻类环境分析的结果是一致的。  相似文献   

蓝藻聚铁作用的模拟实验   总被引：3，自引：0，他引：3       下载免费PDF全文

刘志礼  杜汝霖 《地质科学》1993,28(1):79-86

实验模拟前寒武纪大气的高二氧化碳分压(P_CO2),低氧浓度条件下,加入较低浓度(6μg/g)铁的Zarronk培养液培养蓝藻Spirulina platensis,观察铁的沉淀与凝聚。藻在生长过程中不断改变环境的离子平衡系统以及pH,Eh等,造成铁的氧化、还原、络合和Fe³⁺沉淀。实验组与未加蓝藻的对照组有显著差别。实验证实藻在聚铁和铁矿形成中起重要作用。  相似文献   

Organic Material and Trace Elements of Bituminous Rocks in the Ozankiiy Field, Ankara, Turkey          下载免费PDF全文

Saday Azadoglu ALIYEV Ali SARI 《《地质学报》英文版》2007,81(4):658-667

Bituminous rocks in the Ozankoey （Ankara） field are different from those of the Paleocene- Eocene Mengen and Giineytepe （Bolu） regions in metal enrichment levels. Organic carbon （Corg） content of organic material-rich rocks in the Ozankoey （Ankara） field is 3.66-40.72% wt averaging 14.34%. The dominant organic materials are algae/amorphous accompanied by minor amount of herbaceous material （The dominant kerogen type is Type-I with a limited amount of Type-Ⅱ kerogen.）. The bituminous rocks in the Ozankoey field are enriched in heavy metals such as Ni, Mn, As and Cr. In comparison with the average enrichment values of dements, Ni, Mn, As and Cr in bituminous shales of the Ozankoey field are as about 4.38, 14.93, 10.90 and 5.58 times as average values. The average concentrations of these heavy metals are also as high as 215× 10^-6, 828 × 10^-6, 58.54 × 10^-6, and 148 × 10^-6 respectively. In addition, sorption properties of day and organic materials are also important for metal enrichments in the bituminous shales.  相似文献   

Organic Material and Trace Elements of Bituminous Rocks in the Ozank(?)y Field,Ankara,Turkey          下载免费PDF全文

Saday Azadolu ALYEV  Ali SARI 《《地质学报》英文版》2007,81(4)

Bituminous rocks in the Ozank(?)y(Ankara) field are different from those of the Paleocene- Eocene Mengen and Güineytepe(Bolu) regions in metal enrichment levels.Organic carbon(C_(org)) content of organic material-rich rocks in the Ozank(?)y(Ankara) field is 3.66-40.72% wt averaging 14.34%.The dominant organic materials are algae/amorphous accompanied by minor amount of herbaceous material(The dominant kerogen type is Type-Ⅰwith a limited amount of Type-Ⅱkerogen.). The bituminous rocks in the Ozank(?)y field are enriched in heavy metals such as Ni,Mn,As and Cr.In comparison with the average enrichment values of elements,Ni,Mn,As and Cr in bituminous shales of the Ozank(?)y field are as about 4.38,14.93,10.90 and 5.58 times as average values.The average concentrations of these heavy metals are also as high as 215×10~(-6),828×10~(-6),58.54×10~(-6),and 148×10~(-6) respectively.In addition,sorption properties of clay and organic materials are also important for metal enrichments in the bituminous shales.  相似文献   

从孢粉、藻类研究看马桥先人的生活环境     

张玉兰 《上海国土资源》2007,(2):1-4

马桥遗址经多次发掘,取得了很多成果。本次采集了2005年发掘的05MMT4探方样品,进行孢粉、藻类研究。根据孢粉、藻类成分特征,划分出了3个孢粉组合带,它们分别是:1带是以Quercus(evergreen)-Gramineae-Typha-Pi-nus-Polypodiaceae-Concentricystes为主孢粉带;2带是以Concentricystes-Quercus(evergreen)-Salvinia-Polypodiace-ae-Typha-Gramineae为主孢粉带;3带是以Pinus-Salix-Quercus(evergreen)-Chenopodiaceae-Pteridium-Polyp-odiaceae-Concentricystes为主孢粉带,并以此恢复了当时古植被和古地理环境。且对马桥先人的生活环境、农耕发展作了探讨,为上海地区文化发展及文明化进程提供了新资料。  相似文献   

DNA barcode assessment of Ceramiales (Rhodophyta) in the intertidal zone of the northwestern Yellow Sea   总被引：1，自引：0，他引：1  

杜国英  吴菲菲  郭皓  薛红凡  茅云翔 《中国海洋湖沼学报》2015,33(3):685-695

A total of 142 specimens of Ceramiales(Rhodophyta) were collected each month from October 2011 to November 2012 in the intertidal zone of the northwestern Yellow Sea. These specimens covered 21 species,14 genera,and four families. Cluster analyses show that the specimens had a high diversity for the three DNA markers,namely,partial large subunit r RNA gene(LSU),universal plastid amplicon(UPA),and partial mitochondrial cytochrome c oxidase subunit I gene(COI). No intraspecific divergence was found in our collection for these markers,except for a 1–3 bp divergence in the COI of Ceramium kondoi,Symphyocladia latiuscula,and Neosiphonia japonica. Because short DNA markers were used,the phylogenetic relationships of higher taxonomic levels were hard to evaluate with poor branch support. More than half species of our collection failed to find their matched sequences owing to shortage information of DNA barcodes for macroalgae in Gen Bank or BOLD(Barcode of Life Data) Systems. Three specimens were presumed as H eterosiphonia crispella by cluster analyses on DNA barcodes assisted by morphological identification,which was the first record in the investigated area,implying that it might be a cryptic or invasive species in the coastal area of northwestern Yellow Sea. In the neighbor-joining trees of all three DNA markers,H eterosiphonia japonica converged with D asya spp. and was distant from the other Heterosiphonia spp.,implying that H. japonica had affinities to the genus Dasya. The LSU and UPA markers amplified and sequenced easier than the COI marker across the Ceramiales species,but the COI had a higher ability to discriminate between species.  相似文献