High-West and Low-East Distribution Patterns of Chlorophyll a, Primary Productivity and Diatoms in the Subarctic North Pacific Surface Waters, Midwinter 1996   总被引：1，自引：0，他引：1  

Akihiro Shiomoto  Hiroki Asami 《Journal of Oceanography》1999,55(4):493-503

We have determined chlorophyll a (Chla) concentration, primary productivity, cell density and species composition of diatoms, and the number of microzooplankton at the surface in the subarctic North Pacific in January 1996. The wet weight of copepods obtained by vertical tows from 150 m to the surface was also measured during the cruise. Chla concentration and primary productivity tended to be higher in the region west of 180°, the western subarctic North Pacific (WSNP), than east of 180°, the eastern subarctic North Pacific (ESNP). The same results were observed for the total diatom cell densities and for the genera Thalassiosira and Denticulopsis. Significant linear relationships were observed between the Thalassiosira cell density and Chla concentration and primary productivity, indicating that Thalassiosira contributes to the high-WSNP and low-ESNP distribution patterns of Chla concentration and primary productivity. Moreover, naked ciliate abundance tended to be lower in the WSNP than in the ESNP, whereas copepod biomass showed an inverse trend. Significantly negative Spearman rank correlations were found between the Thalassiosira cell density and the number of naked ciliates and between the number of naked ciliates and the wet weight of copepods. These results indicate that copepod grazing indirectly controls Thalassiosira cell density via predation on the naked ciliates. We conclude that the high copepod biomass in the WSNP is a factor controlling the high-WSNP and low-ESNP Thalassiosira abundance and hence Chla concentration and primary productivity patterns.  相似文献   

湖北梁子湖近百年来环境演变历史及驱动因素分析     

张清慧  董旭辉  羊向东 《湖泊科学》2016,28(3):545-553

湖泊生态系统的修复必须建立在历史生态环境演化过程与驱动机制认识的基础之上.针对草型湖泊演化历史研究相对不足的现状,以长江中游典型草型湖泊梁子湖为研究对象,结合210Pb和137Cs年代测试,通过对沉积柱高分辨率的多指标分析(硅藻、元素地球化学和粒度)以及流域历史资料重建近百年来梁子湖生态环境的演化过程,并在此基础上利用冗余分析定量区分影响该湖泊生态环境演化的关键驱动因子.结果显示,沉积物总磷和重金属元素Cu是影响该湖泊生态环境演化的2个显著变量,它们分别单独解释硅藻组合的12.7%和8.5%变率.这表明近百年来人类活动引起的营养输入对梁子湖生态环境演化起关键性作用,而重金属污染也是影响梁子湖环境演变的重要因子.本研究结果可以为梁子湖及长江中下游其他类似湖泊的环境治理提供科学依据.  相似文献   

Adaptations of araphid pennate diatoms to a planktonic existence     

Wiebe H. C. F. Kooistra  Gandi Forlani  & Mario De Stefano 《Marine Ecology》2009,30(1):1-15

Pennate diatoms are monophyletic. Their principal cell wall elements, called valves, are shaped like a ship's hull. Within the pennates, the araphids are paraphyletic; they possess rimoportulae and pore fields located at the valve apices. The pore fields exude mucilage pads with which cells attach to one another to form chains. Many taxa use the pads also for attachment to substrata. Only a few genera are truly planktonic. The main question addressed in this study is whether the planktonic lifestyle is ancestral or derived. Phylogenies inferred from nuclear SSU rDNA gene sequences of diatoms indicated that the attached lifestyle is ancestral among the araphids, whereas a typically planktonic lifestyle seems to have developed at least three times and possibly four times independently. Acquisition of a planktonic lifestyle from benthic ancestry was accompanied by a reduction in the silicification of cell-wall elements, but changes in morphological characters shared by all four clades were not detected. The reason why only three or four araphid pennate clades have adopted a planktonic lifestyle may be related to constraints associated to their sexual reproduction mode. Partner cells of opposite mating type align with one another and produce isogametes. These gametes lack flagella; they move to one another in an amoeboid fashion, which functions well on surfaces, but seems a liability in a turbulent water column. The planktonic lineages must have overcome this constraint, e.g. by sinking to the bottom, or aggregating, to perform sexual reproduction. Members of the four araphid pennate lineages are now common constituents of the plankton, suggesting that they are ecologically successful.  相似文献   

Application of functional data analysis to investigate seasonal progression with interannual variability in plankton abundance in the Bay of Fundy,Canada     

Takayoshi Ikeda  Michael Dowd  Jennifer L. Martin 《Estuarine, Coastal and Shelf Science》2008

The statistical technique of functional data analysis (FDA) is applied to a time series analysis of plankton monitoring data. The analysis is focused on revealing patterns in the seasonal cycle to assess interannual variability of several different taxonomic groups of plankton. Cell concentrations of diatom, dinoflagellate and zooplankton abundances from the Bay of Fundy, Canada provide the observations for analysis. FDA was performed on the log-transformed abundance data as a new approach for treating such types of sparse and noisy data. Differences in the seasonal progression were seen, with peak numbers, timings and abundance levels varying for the three groups as determined by curve registration and higher order derivatives using the objectively fit FDA curves. Nonmetric multidimensional scaling was used to capture seasonal variation among years. These results were further assessed in terms of dominant species and the relationships between groups for different seasons and years. It is anticipated that the easy to use, general and flexible technique of FDA could be applied to a wide variety of marine ecological data that are characterized by missing values and non-Gaussian distributions.  相似文献   

Changes in the Composition of the Diatom Flora During the Last Century Indicate Increased Eutrophication of the Oder Estuary, South-western Baltic Sea   总被引：1，自引：0，他引：1  

E. Andrn 《Estuarine, Coastal and Shelf Science》1999,48(6):665

Four short sediment cores from the Oder estuary, south-western Baltic Sea, were studied with respect to their siliceous microfossil and organic carbon content. The sediments were dated by²¹⁰Pb. The objective was to detect and date changes in the composition of the diatom flora and link these changes to increased human impact in the drainage area during recent centuries. Two of the cores showed an unperturbed sedimentary sequence representing a complete historical record. A change in the composition of the diatom assemblages attributable to anthropogenic factors was recorded. This was dated to about 1900 in the Oderhaff. The change consisted of an increase in species that thrive in eutrophic waters and those indicating increased salinity or the availability of inorganic nutrients.  相似文献   

A paleolimnological record of anthropogenic disturbances at Holmes Lake,Adirondack Mountains,New York     

Thomas E. Rhodes 《Journal of Paleolimnology》1991,5(3):255-262

Holmes Lake, Adirondack Mountains, New York, is a clear-water acidic lake that was treated with lime in 1983 to permit stocking of trout. Diatom assemblages in dated sediments reflect three anthropogenic modifications of the lake ecosystem: 1) assemblages from the mid- and late 1800's are associated with historical and sedimentary records of forest clearance, and indicate slightly increased pH; 2) acidobiontic species increase in sediments from the mid-1900's, a period of local reforestation and regionally increasing anthropogenic acid loading; 3) liming caused large increases of circumneutral periphytic species in the first growing season, and decreases of acidobiontic species by the second.  相似文献   

Effects of canopy removal and nitrogen enrichment on a Distichlis spicata-edaphic diatom complex     

Michael J. Sullivan 《Estuarine, Coastal and Shelf Science》1981,13(2):119-129

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Importance of diffuse nutrient loading and lake level changes to the eutrophication of an originally oligotrophic boreal lake: a palaeolimnological diatom and chironomid analysis     

Jarmo J. Meriläinen  Juhani Hynynen  Arja Palomäki  Pasi Reinikainen  Anssi Teppo  Kaj Granberg 《Journal of Paleolimnology》2000,24(3):251-270

The recent environmental history of Lake Lappajärvi in western Finland (63°00 N, 23°30 E, area 149 km²), a humic, brown water lake with an average phosphorus content of ca. 20 g l^–1, was studied from short core sediment samples taken from the two main basins of the lake. Based on the stratigraphy of diatoms and chironomids and the sediment quality it was possible to distinguish four developmental stages during the past century: (1) a pre-industrial stage covering the time up to about 1935; (2) a stage of increasing nutrient loading (ca. 1936–1960); (3) a stage of pronounced erosion from lake level regulation and extensive ditching of the catchment area (ca. 1960–1970); and (4) a meso-eutrophic stage from ca. 1970 onwards.Acidophilous Aulacoseira distans coll. and other species typical of dystrophic, nutrient-poor lakes characterized the diatom assemblages during the first stage, and the profundal zoobenthic assemblages, characterized by Heterotrissocladius subpilosus and Micropsectra, indicated good hypolimnetic oxygen conditions and a low sedimentation of organic matter (approx. less than 50 g m^–2 a^–1). The increased loading rapidly led to changes both in diatoms and chironomids (e.g., to an early extinction of H. subpilosus in the 1950s). The process finally led to eutrophication with a successive proliferation of diatom species such as Asterionella formosa followed by Aulacoseira ambigua, Fragilaria crotonensis, and finally Melosira varians. The relative proportion of alkaliphilous species reached a maximum in the final stage and the original profundal chironomid fauna was replaced by Chironomus anthracinus gr. and C. plumosus which are typical of profundal areas suffering from temporal oxygen deficit. It is notable that the considerable decrease in waste water loading from the point sources (80–86% ) during the past two decades has not led to a recovery in the lake. This highlights the importance of diffuse loading from agriculture, forestry and other human activities even to this comparatively large lake.  相似文献   

琵琶潭瀑布岩溶沉积物生物多样性研究   总被引：4，自引：1，他引：3  

王智慧  张朝晖  李建华 《中国岩溶》2007,26(2):178-182

为了探索瀑布岩溶沉积物中生物多样特征, 2006年12月对贵阳市琵琶潭瀑布岩溶沉积环境进行了野外生态学调查,采集样品和标本25份。经室内初步分析和鉴定, 该瀑布岩溶沉积物中含有5大生物多样性类群共33个物种,它们是蓝细菌( Cya no bacteria) 2个种,原生动物( Pr oto zoan) 12个种,绿藻( Green algae ) 1个种,硅藻( Dia toms) 10个种和苔藓植物( Bry ophy tes) 8个种。生物多样性在琵琶潭岩溶沉积形成中的地质生态学贡献主要表现在: ( 1)生物表面为淡水碳酸钙晶体提供了附着基础; ( 2) 绿色植物光合作用转移了二氧化碳,有助于碳酸钙沉积;( 3)生物群落为瀑布岩溶沉积提供了骨架; ( 4) 生物群落在一定程度上控制和影响了岩溶沉积形态。   相似文献   

Mid-Holocene hemlock decline and diatom communities in van Nostrand Lake, Ontario, Canada     

Jeannine-Marie St. Jacques  Marianne Douglas  J.H. McAndrews 《Journal of Paleolimnology》2000,23(4):385-397

Terrestrial ecosystem disturbances inferred from the fossil hemlock pollen decline (ca. 4,800 BP) and recovery (ca. 3,800 BP) affected van Nostrand Lake, including the diatom communities. Ecological models suggest the lake responded by eutrophying, reflecting higher nutrient influx resulting from increased erosion. A decline in lake productivity followed as the forest vegetation recovered and erosion slowed. Lastly, as the forest switched from early and middle successional species to mature species, lake productivity increased as erosion increased nutrient inflow, especially phosphorus. However, this eutrophication response was delayed or buffered, perhaps due to wetland development surrounding the lake. The lake never fully returned to its initial, pre-hemlock decline state, but oscillated between more eutrophic and more mesotrophic or oligotrophic stages, possibly reflecting other disturbances in the catchment and climatic change.  相似文献