Observations on the ecological importance of salt marshes in the Cumberland Basin,a macrotidal estuary in the Bay of Fundy     

Donald C. Gordon  Peter J. Cranford  Con Desplanque 《Estuarine, Coastal and Shelf Science》1985,20(2):205-227

The Cumberland Basin, a 118 km² estuary at the head of the Bay of Fundy which has an average tidal range of about 11m, contains large tracts of salt marsh (15% of the area below highest high water). Low marsh (below about 0·9 m above mean high water) is composed almost exclusively of Spartina alterniflora while the vegetation on high marsh is more diverse but dominated by Spartina patens. Because of its higher elevation, high marsh is flooded infrequently for short periods by only extreme high tides. Low marsh is inundated much more frequently by water as much as 4m deep for periods as long as 4 h per tide. Temporal variability in the occurrence of extreme tides influences the flooding frequency of high marsh for any given month and year. Using a modification of Smalley's method, the mean annual net aerial primary production (NAPP) of low and high marsh is estimated to be 272 and 172 g C m^?2, respectively. Vegetation turnover times average 1·0 and 2·0 y for low and high marsh, respectively. Because of abundant tidal energy, much of the low marsh production appears to be exported and distributed widely about the estuary. Since high levels of turbidity suppress phytoplankton production, salt marshes produce approximately half of the carbon fixed photosynthetically in the Cumberland Basin. It is concluded that salt marshes play a major ecological role in the Cumberland Basin.  相似文献   

VERTICAL PROFII,ES OF CHL-A AND PRIMARY PRODUCTIVITY IN THE MIDDLE CONTINENTAL SHELF AREA AND EDDY AREA OF THE EAST CHINA SEA     

Wu Yu-lin  Zhou Cheng-xu  Zhang Yong-shan 《中国海洋湖沼学报》2002,20(1):74-80

Vertical profiles of chl-a and primary productivity in the middle continental shelf area and eddy area of the East China Sea were studied using data from a cruise in the East China Sea in February to March, 1997 and a cruise in July, 1998. The results showed that chl-a vertical distribution closely related to in situ hydrological and nutrient conditions. Chla-a concentration ranged from 0.22 to 0.35 mg/m³ and 0.93–1.09 mg/m³ in the eddy area and in the middle continental shelf area, respectively. In both areas, chl-a concentrations in deep layers were slightly higher than those in shallow layers, but was of the same order of magnitude. In summer, when a thermocline existed in the water column, highest chl-a concentrations appeared at the base of the thermocline layers in both areas. In the eddy area, chl-a concentration maximized at 31.743 mg/m³, and averaged 1.143 mg/m³ below 30 m depth. In the middle continental shelf area, the highest chl-a concentration was 2.120 mg/m³, the average was 1.168 mg/m³. The primary productivity reached 1418.76 mgC/(m²·d) in summer and 1360.69 mgC/(m²·d) in winter. In the eddy area, the primary productivity was 787.50 mgC/(m²·d) in summer and 159.04 mgC/(m²·d) in winter. Vertical carbon sinking rate from the deep layer to the bottom in both areas is also discussed in this paper. Contribution NO. 4183 from the Institute of Oceanology, Chinese Academy of Sciences. Project No. 49636210 supported by NSFC.  相似文献   

沉积钙质白云石带状面缺陷的择优取向     

胡梅生  唐玉梅等 《矿物学报》1991,11(1):9-12,T003,T004

作者用透射电子显微镜研究了沉积钙质白云石中的带状面缺陷。在衍衬象中面缺陷呈现出特有的条纹衬度,并具有一定的择优取向,它们沿着｛018｝面排列。面缺陷也可分叉,分枝部分平等于｛2－／10｝面。根据白云石面缺陷的取向,本文提出了鞍状白云石宏观弯曲面和微观面缺陷的取向关系。  相似文献   

Microbially mediated carbonates in the Holocene deposits from Sarliève, a small ancient lake of the French Massif Central, testify to the evolution of a restricted environment     

JEAN-GABRIEL BRÉHÉRET  AGATHE FOURMONT  JEAN-JACQUES MACAIRE  PHILIPPE NÉGREL† 《Sedimentology》2008,55(3):557-578

Both the mineralogy and facies of lacustrine bio‐induced carbonates are controlled largely by hydrological factors that are highly dependent upon climatic influence. As such they are useful tools in characterizing ancient lake environments. In this way, the study of the sedimentary record from the small ancient Sarliève Lake (Limagne, Massif Central, France) aims to reconstruct the hydrological evolution during the Holocene, using petrographical, mineralogical and geochemical analyses. The fine‐grained marls, mainly calcitic, display numerous layers rich in pristine Ca‐dolomite, with small amounts of aragonite, which are clearly autochthonous. As these minerals are rather unusual in the temperate climatic context of western Europe, the question arises about their forming conditions, and therefore that of the lacustrine environment. Ca‐dolomite prevails at the base of the sequence as a massive dolomicrite layer and, in the middle part, it builds up most of the numerous laminae closely associated with organic matter. Scanning electron microscope observations reveal the abundance of tiny crystals (tens to hundreds of nanometres) mainly organized as microspheres looking like cocci or bacilli. Such a facies is interpreted as resulting from the fossilization of benthic microbial communities by dolomite precipitation following organic matter consumption and extracellular polymeric substance degradation. These microbial dolomites were precipitated in a saline environment, as a consequence of excess evaporation from the system, as is also suggested by their positive ?¹⁸O values. The facies sequence expresses the following evolution: (i) saline pan, i.e. endorheic stage with a perennial lowstand in lake level (Boreal to early Atlantic periods); (ii) large fluctuations in lake level with sporadic freshening of the system (Atlantic); (iii) open lake stage (sub‐boreal); and (iv) anthropogenic drainage (sub‐Atlantic).  相似文献   

软玉子料的形状规律及其应用   总被引：2，自引：1，他引：1  

李平  李凌丽 《岩矿测试》2008,27(5):395-396

通过对软玉子料形状总结,发现子料多呈扁平状,其长宽比较小,磨圆好的子料形状可分为11类。这些特征可用于子料鉴别与特殊材料制作。  相似文献   

贵州绥阳双河洞国家地质公园洞穴基本特征及成因探讨   总被引：7，自引：0，他引：7  

刘平 《贵州地质》2008,25(4)

106地质大队于1959～1960年曾对双河洞石膏矿进行过地质勘查。1986年～2006年4月,先后有中、法、日等国专家19次进双河洞考察,初步查明了该洞总长度为105.7km,是亚洲第二长洞,在世界上排名第16位。该洞不仅规模宏大,网络复杂,且有一定数量的次生淋滤型石膏矿分布,成为国内外罕见的独特洞穴景观。双河洞自2004年荣获国家地质公园称号以来,已引起国内外专家的广泛关注。该洞的形成,与该区域大范围内下寒武统清虚洞组上部至中寒武统平井组下部白云岩中,含大量硬石膏层有着密切的成因联系。  相似文献   

1999年渤海浮游植物生物量的数值模拟   总被引：6，自引：1，他引：6  

高会旺  王强 《中国海洋大学学报(自然科学版)》2004,34(5):867-873

以浮游植物量、浮游动物量、营养盐浓度 (包括无机氮和无机磷 )以及碎屑量为生态变量 ,在HAMSOM水动力学模式的基础上构建了 1个三维浮游生态动力学NPZD模型。采用此模型研究了渤海 1999年浮游植物量和初级生产力的变化情况 ,模拟结果与实测基本相符。模拟结果表明 :1999年渤海浮游植物量的变化大致呈双峰分布 ,春季水华出现在4,5月份 ,秋季水华出现在 9,10月份 ;受透明度和局地水深的影响 ,渤海湾和辽东湾北部浮游植物量的年变化呈夏季大、冬季小的单峰分布。 1999年渤海不同海区初级生产力的变化特征是 :除莱州湾一年中有春、夏 2个峰值外 ,其它 3个海区都是夏季高、冬季低的单峰分布 ;1999年整个渤海年平均的初级生产力为 2 5 7mgC/m2 /d。  相似文献   

三门湾秋季浮游植物现存量和初级生产力   总被引：3，自引：0，他引：3  

刘镇盛  蔡昱明  刘子林  郝锵 《海洋学研究》2003,21(2):30-36

对1987年9月浙江三门湾海区浮游植物细胞丰度、叶绿素a浓度和初级生产力的分布特征及其与环境的关系进行了研究。结果表明,调查海区的浮游植物细胞丰度、叶绿素a浓度和初级生产力均具有明显的空间区域性分布特征。叶绿素a浓度高值区位于三门湾顶部和健跳港口,从湾顶部往湾口海区方向,叶绿素a浓度逐渐下降。初级生产力的分布趋势与叶绿素a浓度的分布趋势一致。表层水浮游植物平均细胞丰度为(3.36±1.39)×103个/dm3,表、底层平均叶绿素a浓度分别为(1.47±0.42)μg/dm3和(1.12±0.19)μg/dm3,平均初级生产力为(36.0±29.5)mg/(m2·d)。  相似文献   

Fluid flow equations governing primary oil migration as a separate phase     

Ismail Ozkaya 《Marine and Petroleum Geology》1989,6(4)

A mathematical model of primary oil migration as a separate phase out of compacting shales is presented. During burial and oil generation, source rock porosity decreases and oil saturation increases until residual oil saturation is reached. At this stage oil is expelled out by capillary and excess fluid pressure gradients. The model is a system of differential equations which relate changes in oil and water saturation in time to water and oil flow out of the source rock during burial. An additional set of equations for periods of erosion of overburden are also provided. The equations can be numerically solved by finite difference method. If oil and water flow is to be simulated during oil generation, then at each time step, changes by oil generation in oil and water saturations and porosity must be calculated. The solution procedure is briefly outlined.  相似文献   

Seasonal Variations in Benthic Community Metabolism and Nitrogen Dynamics in a Shallow, Organic-Poor Danish Lagoon     

Erik Kristensen 《Estuarine, Coastal and Shelf Science》1993,36(6)

The dynamics of benthic primary production and community respiration in a shallow oligotrophic, marine lagoon (Fællestrand, Denmark) was followed for 1·5 years. The shape of the annual primary production cycle was explained primarily by seasonal changes in temperature (r² = 0·67-0·72) and daylength (r² = 0·63), whereas temperature almost explained all variation in benthic community respiration (r² = 0·83-0·87). On a daily basis the benthic system was autotrophic during spring and summer supplied by 'new' and 'regenerated' nitrogen and predominantly heterotrophic during fall and winter caused by light and nutrient limitation. The linear depth-relationship between porewater alkalinity and ammonium indicated that the C:N ratio of mineralized organic matter is low in spring and summer (3-6) and high in fall and winter (9-16). This is inversely related to net primary production and thus the input of labile, nitrogen-rich algal cells. Accordingly, mineralization occurred predominantly in the upper 2-5 cm of the sediment. The pool of reactive material (microalgal cells) was estimated to account for 12% of total organic carbon in the upper 3 cm, and had an average turnover time of less than 1 month in summer. Assimilation of organic carbon by benthic animals was equivalent to about 30% of the annual gross primary production. Grazing reduced chlorophyll a concentration in the sediment during summer and spring to values 30-40% lower than in winter, but maintained a 3-4 times higher specific microalgal productivity. The rapid turnover of organic carbon and nitrogen, and important role of benthic microalgae showed that the benthic community in this oligotrophic lagoon is of a very dynamic nature.  相似文献