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Claire E. Reymond Konny‐Sebastian Zihrul Jochen Halfar Bernhard Riegl Alexander Humphreys Hildegard Westphal 《Sedimentology》2016,63(4):940-958
Strongly influenced by seasonal and interannual (i.e. El Niño‐Southern Oscillation) upwelling, the equatorial setting of the Galápagos Archipelago is divided into well‐defined temperature, nutrient and calcium carbonate saturation (Ωaragonite) regions. To understand the relationship between oceanographic properties and sediment grain associations, grain size, carbonate content and components from sea floor surface samples were analysed, representing the main geographical regions of the Galápagos Archipelago. The shallow‐water rocky reefs of the Galápagos Archipelago are characterized by mixed carbonate–siliciclastic slightly gravelly sands. Despite minor differences in carbonate content, major differences exist in the distribution and composition of key carbonate producing biota. Halimeda is absent and benthic foraminifera occur in extremely low abundance. The western side of the Galápagos Archipelago is strongly influenced by nutrient‐rich, low‐Ωaragonite, subtropical water, which generates a heterozoan carbonate biofacies in a tropical realm resembling cold‐water counterparts (i.e. serpulid, echinoderm, gastropod, barnacle and bryozoan‐rich facies). The Central East region is composed of a transitional‐heterozoan biofacies. Biofacies observed in the northern region have an increased occurrence of tropical corals, albeit with a minor overall contribution to the carbonate components. Although the temperature gradient would allow for a broader distribution of photozoan biofacies, the increased nutrient concentration and related reduced light penetration from the upwelled waters favour heterozoan carbonate factories, mimicking cool‐water, deeper or higher latitude environments. The recent sedimentary record of the Galápagos Archipelago presents a range of tropical heterozoan carbonate communities, responding to more than simply latitude or temperature but a much more complex mixture of physical, evolutionary and geological processes. 相似文献
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浙江瓯江开潭水库库区浮游植物与水质的关系 总被引：1，自引：0，他引：1
通过2001年7月-2002年6月对瓯江开潭水库库区水体浮游植物的调查，以及对溶解氧和叶绿素a等理化指标的逐月测定，结果表明：该水域共有浮游植物7门40属82种(包括变种)，其中以绿藻门和硅藻门的种类占优势，浮游植物的群落类型为绿藻型和硅藻型为主，种类和数量随季节和水域不同而呈现差异，水体营养特征为浮游植物响应型，水体向中营养化发展趋势明显，部分水体受到不同程度污染． 相似文献
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The molecular weight distributions and hydrolysable neutral sugar composition of dissolved organic carbon (DOC) was investigated
in four maritime Antarctic lakes on Signy Island of different trophic status; Heywood Lake (eutrophic), Light Lake (oligo-mesotrophic),
Sombre Lake and Moss Lake (both oligotrophic). Tangential flow ultra-filtration (TFU) was used to separate DOC into high molecular
weight (HMW; >1000 Da) and low molecular weight (LMW; < 1000 Da) size fractions. Pulsed amperometric detection-high performance
liquid chromatography (PAD-HPLC) was used to determine the hydrolysable neutral sugar molecular composition of each size fraction.
Total DOC concentrations defined the trophic trend in the four lakes and ranged from 8 to 303 μM. The <1000 Da fraction of all the lakes dominated the DOC distribution, comprising 76% in Light Lake which also had the
highest chl-a concentrations. Heywood Lake was relatively enriched in >1000 Da total organic carbon and had extremely high concentrations
of total hydrolysable neutral sugars (11 μM) corresponding to 43% of total DOC. However, no clear pattern was apparent with regard to lake trophic status and potential
sources of DOC, and the measured variations in individual aldose concentration, composition and their various molecular weight
fractions. 相似文献
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Two nanociliates of the order Prostomatida,Pseudobalanion planctonicum (12–18 µm) andUrotricha furcata (12–21 µm), were found to be the most abundant ciliates in the epilimnion of Piburger See, a small mesotrophic lake. Temperature and food availability were the main factors controlling the sudden increase in abundance, which reached a maximum of 101 cell ml–1 at the beginning of summer. During their exponential development in numbers and biomass, a strong decrease in chlorophylla and in the abundance of phytoplankton, especiallyRhodomonas, was observed. We assume, therefore, thatPseudobalanion planctonicum andUrotricha furcata together with rotifers, mainlyPolyarthra dolichoptera, are able to reduce the phytoplankton biomass in the upper epilimnion to the same level as found during the clearwater phase. Preliminary results of grazing on bacteria suggest that these nanociliates are omnivorous, although their impact on bacterial assemblages was low (3.1% of the standing stock grazed per day). Feeding on the base of the food web combined with their high abudance at certain times makes them an important link for higher trophic levels. This study constitutes the second report onPseudobalanion as an important component of the microbial food web in lakes. 相似文献
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藻类异常增殖引发的水华是威胁我国水源地水库的主要生态问题之一。探究水源水库中藻类异常增殖的促发因素是防控藻类水华水质问题的前提。本文以太湖流域两个大(Ⅱ)型中营养水库为例,通过周年浮游植物细胞密度、生物量及相关环境因子逐月监测,分析影响水库有害藻类生物量季节性异常增殖特征及其促发条件。结果表明,地处亚热带季风区的两个水源水库均存在蓝藻和硅藻阶段性异常增殖的风险,老石坎水库5月暴发了以曲壳藻为绝对优势种的重度硅藻水华现象,硅藻细胞密度达到6232×104 cells/L,赋石水库则在6和9月均出现了蓝藻细胞数达到水华级别的异常增殖现象。冗余分析表明,总磷、水温和水位是影响水库硅藻、蓝藻异常增殖的关键因素。非线性回归等统计分析表明,两个水库中水体总磷浓度显著影响藻类异常增殖强度的临界值为0.024 mg/L,而水温高于16℃时,硅藻水华事件可能发生,硅藻水华发生的最佳温度为22℃水温高于20℃时,蓝藻水华事件可能发生,蓝藻水华发生的最佳温度为30℃持续低水位或水位快速波动过程中藻类水华暴发的风险较高。研究表明,太湖流域中营养水源水库藻类异常增殖或藻类水华的发生往往是营... 相似文献
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