Phytoplankton community variations in tropical coastal area affected where submarine groundwater occurs     

Luis Troccoli-Ghinaglia  Jorge A. Herrera-Silveira  Francisco A. Comín  José Rafael Díaz-Ramos 《Continental Shelf Research》2010

The influence of subterranean water discharge on phytoplankton was studied at two localities (Progreso and Dzilam) on the northern coast of the Yucatan Peninsula. Hydrographic and phytoplankton samples were taken monthly between September 1998 and August 1999. High concentration of silicate (>65 μmol L⁻¹) and nitrate (>80 μmol L⁻¹) and low salinity showed the influence of submerged groundwater discharge (SGD) in the area. In Dzilam, hydrological conditions shows low salinity and high concentration of nitrate and silicate favored from the SGD. Meanwhile, high concentrations of ammonium, nitrite, and phosphate at Progreso (>150 000 inhabitants) suggest mixing of SGD and domestic waste waters. Thick-valve pennate diatoms dominated at Dzilam while dinoflagellates dominated in Progreso. Hydrological differences in both study zones suggest that local forcings, and interaction between coastal water masses and SGD plays an important role in hydrological conditions and primary productivity in the coastal zone of Yucatan. The anthropogenic modified SGD in Progreso may affect the nutrient regime and phytoplankton community structure, and may be used as indicator of eutrophication.  相似文献   

Effect of submerged aquatic vegetation on turbulence induced by an oscillating grid   总被引：1，自引：0，他引：1  

Dolors Pujol  Jordi ColomerTeresa Serra  Xavier Casamitjana 《Continental Shelf Research》2010

In wetlands wind-induced turbulence significantly affects the bottom boundary, and the interaction between turbulence and plant canopies is therefore particularly important. The aim of this study is to advance understanding of the impact of this interaction in submerged aquatic vegetation (SAV)¹ on vertical mixing in a fluid dominated by turbulence. Wind-generated turbulence was simulated in the laboratory using an oscillating grid. We quantify the vertical distribution of turbulent kinetic energy (TKE)² above and within different types of vegetation, measured by an acoustic Doppler velocimeter. Experimental conditions are analysed in two canopy models (rigid and semi-rigid) with seven solid plant fractions (SPFs)³, three stem diameters (d)⁴ and three oscillation grid frequencies (f)⁵ and four natural SAVs (Cladium mariscus, Potamogeton nodosus, Myriophyllum verticillatum and Ruppia maritima).  相似文献   

气候变化对植被和土壤的影响效应     

陈重潘 《云南地理环境研究》2010,22(2):39-42

全球气候变化已是当今世界研究的热点。近年来,气候变化对陆地植被以及土壤的影响研究已经广泛开展。通过系统收集和整理气候变化对植被和土壤影响国内外相关研究结果,有利于进一步认识气候变化给生存环境带来的影响。大量野外定量分析以及经验模型预测等方法研究表明:气候变化对陆地植被产生了重要影响,主要表现在植被分布范围、生产力以及多样性的改变。气候变化也会使土壤基本性质发生变化,同时土壤作为全球碳循环过程中重要的中间碳库,土壤有机碳库与气候变化有着密切的关系,气候变暖与土壤有机碳库的分解互为反馈。  相似文献   

我国滨海核电站防护工程设计标准研究     

刘德辅  史宏达  刘桂林  王风清 《海洋工程》2017,35(4):135-146

面对全球极端气候频发的趋势,国内外核电站海岸防护工程普遍采用"可能最大台风暴潮"、"设计基准洪水"等具有含混性的规定作为确定防灾设计标准的依据,其内涵的各种不确定性因素必然会对防灾决策带来重大的致灾隐患。按照国务院核电站安全规划(2011-2020)提出的"必须按照全球最高安全要求",全面开展滨海核电站防护工程设计标准研究己势在必行。使用多维复合极值分布理论及双层嵌套多目标联合概率模式,将核电站水文与气象的研究标准合二为一,对IAEA及我国滨海核电站防护工程设计标准进行了风险评估,供有关部门参考。  相似文献   

荒漠植物枝系构型影响因素分析   总被引：13，自引：2，他引：11  

何明珠  张景光  王辉 《中国沙漠》2006,26(4):625-630

荒漠植物的枝系构型的影响因素包括各级分枝角度、各级分枝长度、枝径比、逐步分枝率和总体分枝率、树冠分维数、分枝分维数和计盒维数等17个指标。采用主成分分析（PCA）方法对50种典型荒漠植物的17个构型指标进行分析,结果表明：第一主成分的贡献率十分高,达到77.0％,其中2级分枝长度和3级分枝长度是影响枝系构件的主要因素;第二主成分的贡献率只有11.3％,主要综合了3级分枝角度、2级分枝角度和1级分枝角度三个因素。对枝系构型因素进行PCA排序可将其划分为三类：第一类包括各级分枝长度;第二类包括逐步分枝率和分形维数;第三类包括各级分枝角度和枝径比等。通过第一和第二主成分分析体现了荒漠植物的两种不同的生态适应机制,即在分枝长度上和分形维数上,趋于增加和减小两种趋势,但在分枝角度方面,都有趋于增大的趋向。  相似文献   

长白山野生经济植物中4种微量元素的含量与变异因素   总被引：1，自引：0，他引：1  

崔晓阳  宋金凤  张韫 《山地学报》2003,21(6):653-661

对长白山不同垂直景观带141个野生植物样品中Fe、Zn、Se、Ge的含量进行了分析。结果表明,本区供试野生经济植物含Fe1003 24±674 54μg/g、Zn69 28±46 06μg/g、Se0 111±0 071μg/g、Ge2 63±2 40μg/g。平均来说,植物的Fe、Zn含量都是较丰富的,而Se、Ge则含量不高。不同植物样品中微量元素含量差异相当大,各元素的总体变异系数(Cv)高达0 64～0 91。这种差异主要来自生物性因素(种间差异、部位差异);环境因素(母岩、土壤、气候)也有显著影响,不同垂直景观带间有显著差异。就供试植物样品总体而言,不同元素间都表现出正相关趋势,其中Fe与Zn、Zn与Se、Zn与Ge、Se与Ge之间的正相关皆达显著或极显著水平。根据相对富集系数(Re)和生物吸收系数(Ac),筛选出了"微量元素相对富集型"药用和食用植物若干种。  相似文献   

EXCITATION ENERGY TRANSFER IN VITRO BETWEEN PHYCOBILIPROTEINS AND THYLAKOID PHOTOSYSTEM Ⅱ OF HIGHER PLANTS     

仵小南  曾呈奎 《中国海洋湖沼学报》1992,(4)

The excitation energy transfer from phycobiliproteins to thylakoid PSII of higher plants was investigated. When incubated with spinach thylakoids, phycobiliproteins isolated from red and blue- green algae transferred light energy absorbed to spinach PSII. The efficiency of energy transfer was dependent on the kind of phycobiliproteins used. If spinach thylakoids were replaced by the thylakoids of Brassica chinensis, R phycoerythin or C- phycocyanin did not transfer their excitation energy to PSII of Brassica chinensis unless allophycocyanin was present.  相似文献   

REGIONAL AND TEMPORAL TRENDS IN POWER PLANT UNIT SITING, 1912–1978*     

Robert Q. Hanham  Frank J. Calzonetti 《The Professional geographer》1983,35(4):416-426

Regional trends in the siting of U.S. coal, gas, oil, and nuclear power plant units from 1912 to 1978 are examined. Results of a multivariate statistical analysis indicate that while these trends are comparatively individualistic, they tend to be governed more by factors affecting the choice of fuel than by regional differences in the siting process.  相似文献   

荒漠植物种子萌发研究进展   总被引：62，自引：22，他引：62  

张勇  薛林贵  高天鹏  晋玲  安黎哲 《中国沙漠》2005,25(1):106-112

 对种子自身结构,水分、温度、光照、沙埋深度等对荒漠植物种子萌发的影响进行了综述。硬实种子的不透水性、不透气性以及物理障碍是影响种子萌发的重要因素,通过热水浸种、擦破种皮或果皮、浓硫酸浸泡、低温或辐射处理可以破除硬实的影响。有些荒漠植物果皮或种皮外包有粘液层,这种结构对种子的萌发及幼苗生长有促进作用;部分植物的种胚覆盖物含有生长抑制物质而抑制种子萌发;胚休眠与后熟是影响胚萌发的重要生理因素。雨量大小、分布,降雨次数及土壤湿度是决定荒漠植物种子萌发的重要生态因子;温度影响种子的萌发,变温促进萌发;部分荒漠植物种子的萌发需要光照,有些要在暗中萌发,有些则对光无特异的需求;沙埋深度可调节光照、土壤湿度和土壤温度,从而调节种子萌发。应重视荒漠植物种子对严酷环境适应的研究,从分子水平上阐述其对严酷生境的适应机制。  相似文献   

Support for the Giant Wave Hypothesis: evidence from submerged terraces off Lanai,Hawaii     

Jody M. Webster  David A. Clague  Juan Carlos Braga 《International Journal of Earth Sciences》2007,96(3):517-524

The origin of subaerial coral conglomerate deposits on the Hawaiian islands of Lanai and Molokai is controversial, primarily because these deposits are difficult to interpret and the vertical motion of these islands is poorly constrained. Based on bathymetry, dive observations, sedimentary and radiocarbon data from coralline algal dominated deposits from two submerged terraces at −150 and −230 m off Lanai, Lanai has experienced relatively little vertical movement over the last 30 ka. Using internally consistent age versus depth relationships, paleowater depths, and published sea level data, we estimate that Lanai has experienced maximum rates of uplift of 0.1 m/kyr or subsidence of 0.4 m/kyr over this period. Our analysis of possible uplift mechanisms, published geophysical, numerical modelling, and recent tide data suggests that this is also the maximum uplift rate for the last several hundred thousand years. Taken together these data support the interpretation that coral conglomerates at elevations higher than +35 m on Lanai are tsunami deposits with a minimum wave run up > 170 m, rather than shoreline deposits formed during the last two interglacials, then uplifted to their present elevations.  相似文献