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Tatiana F. Maria André M. EstevesJan Vanaverbeke Ann Vanreusel 《Estuarine, Coastal and Shelf Science》2011,94(3):272-280
The effect of an abundant sandy beach polychaete, Scolelepis squamata, on the colonisation of defaunated sediments by marine nematodes indicates that sandy beach fauna can be partially controlled by biological interactions within and across size groups. Experimental cores, equipped with windows allowing infaunal colonisation, were filled with defaunated sandy beach sediment containing two different treatments with and without S. squamata. These cores were inserted into microcosms filled with sediment with indigenous meiofauna collected from the field. The treatments were incubated in the laboratory at ambient temperature and salinity for 2, 7, 14 and 21 days, in order to follow the colonisation process of the defaunated sediments by the indigenous nematode fauna over time. Nematodes initially colonised both treatments, with abundances of up to 10% of the densities in the control; after 2 weeks, nematode densities in the cores without S. squamata surpassed the control densities. Nematode assemblages in both treatments were not species rich, and also differed in composition from the natural assemblages. The most successful colonising species, Enoplolaimus litoralis, was rare in the surrounding sediment, suggesting that colonisation was determined by species-specific characteristics such as body size, motility and feeding strategy. Initially the presence of macrofauna did not affect the nematode community composition, but after 2 weeks of the experiment, the presence of the polychaete seemed to facilitate the earlier establishment of non-opportunistic species. 相似文献
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2002-05-20-26在东海进行小尺度船基浮游生物生态系围隔实验,研究浮游动物的群落结构、组成与环境之间的关系,探讨了优势种群的自然繁殖发育期。结果表明,浮游动物的种类组成较简单,优势种明显。浮游动物生物量、丰度及优势种群丰度三者的变化呈逐渐增加趋势。在实验期的1～5d,小拟哲水蚤的无节幼虫和早期幼体占绝对优势,该自然种群的丰度不断增加;随时间推移,无节幼虫逐渐发育为桡足幼体,而后又逐渐发育为成体。因此,本次实验期是实验海区优势种小拟哲水蚤种群的自然繁殖发育盛期。 相似文献
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层滑构造在煤层及其顶、底板间普遍发育,它对地质勘探、煤矿生产、矿井工程灾害防治以及煤层气的开发等方面都有着重要影响。本文以淮北煤田海孜煤矿为例,在研究宏观层滑构造带组合特征的基础上,探讨了层滑构造的微观特征和形成机理。构造煤是层滑引起的煤层流变最显著的特征之一。通过对构造煤与构造岩的微观特征测试,发现层滑运动除了产生脆性变形外,还产生较强烈的塑性变形。利用煤镜质组光率体各向异性和构造岩组构,结合层滑构造的实测数据进行了煤岩体应力、有限应变分析。结果表明:层滑构造以顺层剪切为主,煤层受力的主要方向为NW-SE向。 相似文献
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Zhang ZhiJian Wang ZhaoDe Joseph Holden Xu XinHua Wang Hang Ruan JingHua Xu Xin 《水文研究》2012,26(1):15-26
Global warming poses a great threat to wetland ecological stability and water quality improvement. In this paper, we sampled six types of wetlands representing different kinds of land utilisation around the TaiHu Lake Basin in southeast China. An outdoor computerized microcosm was set up in May 2008 to simulate climate scenarios of ambient temperature (control) and a warmed ambient temperature (+5 °C) using a novel minute‐scale daily and seasonal temperature manipulation technology. The 18‐month incubation indicated that warming impaired the ecological sink of sediment (fixing P from porewater) while strengthening the role of the ecological source, moreover, the rate of P release from sediment into porewater (19–113% for total phosphorus) was much stronger than from top sediment into overlying water. Warming enhanced the activity of neutral and alkaline phosphatases for P‐deficient wetland sediments and neutral phosphatases for P‐rich sediments, at the 14th month of incubation. A significant increase in total phospholipid fatty acids (PLFAs) occurred under warming in sediments with relatively low levels of PLFAs, but bacterial abundance in the sediment biomass tended to decrease (18%) along with an increase (4·5%) of the fungi‐to‐bacteria ratio. The variations of carbon consumption and availability indicated by measured dissolved organic carbon in sediment may have contributed to P release from sediments to water. Copyright © 2011 John Wiley & Sons, Ltd. 相似文献
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Astrid E. Schwarz 《Limnologica》2003,33(1):62-73
Most scientists tend to ignore the history of their own discipline, at best it occurs as a sort of ‘big names history’. History is thought to be useless or at least irrelevant for the own scientific work. In the following it is questioned, whether this is an indispensable assumption of productive and progressive science. Some propositions will be discussed, what a positive historical perspective could mean for the current limnological research. It is claimed that it could be not only interesting but even exciting for limnologists to deal with their own history. One important argument is that limnology not only has a history but also is history: the ‘discovery’ of new methods, theories, concepts and instruments depends on the forgoing. Consequently, scientific progress is related to the history and progress of a particular discipline. This means in same time that the historical reflection could be an important issue to a more complete ‘explanation’ and understanding of this progress.Another reason to overcome the traditional separation into actual and historical knowledge and acting could be the hybrid character of ecology. In ecology, and consequently also in limnology, several elements of opposite scientific methodologies are merged together. Therefore the discussions on the saprobial system, an ecosystem ‘lake’ and the ‘microbial loop’ differ fundamentally. Turned positively it means that limnology should be skilled in handling with different systems of knowledge. This skills should be accessible by approaching the own history in a selfconcious way. Of course the internal view alone is not sufficient to write a history of the discipline, which aims to demonstrate the movement of progress, the relation between science and society as well as science and technics. Its history must be studied from the perspective and with the methods of the history and philosophy of science. In doing so there should be a common objective for historians and scientists that is the amelioration of the science ‘limnology’. 相似文献
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利用2007—2010年CloudSat卫星资料,对青岛地区（35.583°～37.150°N,119.050°～121.000°E）云特征参量进行了统计分析。结果表明：单层云出现频率为39%左右,多层云主要以2层云为主,出现频率均为18%左右;月平均云量在64.1%～77.6%之间,从1月至12月呈递减趋势;卷云、高层云、高积云和层积云平均频率之和为86.5%,其他类型的云出现的频率均不高;云水路径在4、5月和8、9月较大,分别达到了200 g·m-2以上和350 g·m-2以上;云液态有效粒子半径在6～16 μm之间,春、夏、秋季高值区位于云体中部至上部;云冰晶有效粒子半径在20～120 μm之间,高值区位于云体中部至底部;青岛南部,即近海区域云有效粒子半径和云水含量大于北部。 相似文献
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Effects of Wastewater-borne Heavy Metals on Mangrove Plants and Soil Microbial Activities 总被引：11，自引：0，他引：11
Effects of wastewater-borne heavy metals on growth of young plants (9-month-old Bruguiera gymnorrhiza) and soil microbial activities in mangrove microcosms were evaluated. During the 26-week loading period, each mangrove microcosm received 31.2 litres synthetic wastewater of three strengths: normal, medium (5 times of normal strength) and strong (10 times of normal strength). Normal strength wastewater had Cu, Zn, Cd, Cr and Ni concentrations of 3, 5, 0.2, 2 and 3 mg l−1, respectively. Plant growth and total plant biomass in wastewater-treated microcosms were lower than that in the control, and the maximum reduction was found in microcosms receiving strong wastewater. Alkaline phosphatase activity and ATP contents of the mangrove soils receiving wastewater were also reduced. More than 95% reduction in these two parameters was found in soils loaded with strong wastewater. Microtox test demonstrated that soil elutriates obtained from microcosms receiving strong wastewater were of the greatest toxicity (EC50 was 23%). These results show that high concentrations of heavy metals present in strong wastewater were toxic and posed negative effects to both mangrove plants and soil microbial activities. Microbial activities were generally more sensitive to the toxicity of heavy metals than plants. 相似文献
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The impact of several types of reed-protecting structures on hydrodynamic conditions, sediment properties and littoral water quality were investigated. All types of embankment lead to a dissipation of wave energy. The embankment with fagots (type 1) shows a limited porosity in contrast to the other types examined. All kinds of embankment enhance the accumulation of organic matter at the land/water-interface. Hence, they protect littoral accumulation zones from erosion. The embankment with fagots causes changes in sediment properties at the seaward side of reed belts. The surface of mineral sediments is turned into a fine-grained mud, with a high content of organic matter. Accelerated sedimentary microbial processes (oxygen demand) are produced by increasing nutrient availability (carbon, nitrogen). As a result, the O2-saturation of water bodies is significantly reduced. This is in contrast to the embankment with wooden partitions and palisades (type 2 and 3), which had no significant effects on sediment conditions and water quality. The consequences of changes in type 1-protected reed stands are discussed. Practical recommendations are given for the further use of reed-protecting structures. 相似文献
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