Bacterial productivity in the Prydz Bay and its adjacent waters,Antarctic     

邱雨生  黄奕普  陈敏  刘广山 《极地研究(英文版)》2004,15(1):14-27

1　IntroductionBacteriaandtheiractivitiesplayanimportantroleintheelementalbiogeochemicalcyclesandenergytransformingintheocean (Zhenetal.1 997) .DortchandPackard(1 989) proposedthatfoodwebsintheeutrophicwatersaredominatedbythebiomassofprimaryproducerswhilefoodwebsintheoligotrophicwatersaredominatedbythebiomassofmicrobes.Heterotrophicbacteriahadbeenshowntoplayanimportantroleinthedecompositionoflarge ,rapidlysinkingorganicparticleswithinandbelowtheeuphot iczone ,andfurthertoaffecttheelementaldyn…  相似文献   

Multiple longshore sand bars in the upper Chesapeake Bay     

Thomas J. Dolan  Robert G. Dean 《Estuarine, Coastal and Shelf Science》1985,21(5):727-743

In the upper Chesapeake Bay (Maryland, U.S.A.) field surveys were conducted at 18 multiple longshore sand bar sites. The multiple bar systems were found in water depths less than approximately 2 m (mean sea level), and exhibited mild bottom slopes of 0·0052 or less. The number of bars composing each system ranged from four to 17 and the spacing between the crests typically increased in the offshore direction, ranging from 12 to 70 m. Bar height also typically increased with distance offshore and ranged from 0·03 to 0·61 m. A grain size analysis of crest and trough sediment did not reveal any significant differences and the sediment was categorized as ‘fine sand’. A review of the literature data indicated that the Chesapeake Bay multiple bars possessed similar characteristics to those found in Gelding Bay (Baltic Sea); similarities in fetch, wave height and tidal range between the two bays may account for this finding. The surf-scaling parameter indicated that the multiple bar systems were extremely dissipative with regard to wave energy, and wave height appeared to be an important factor in controlling bar spacing and bar height. A multiple wave break point hypothesis was discussed as a possible mechanism for the formation of Chesapeake Bay multiple longshore bars, and limited observational evidence appeared to support such a mechanism.  相似文献   

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   

Arsenic incorporation in a salt marsh ecosystem     

James G. Sanders  Richard W. Osman 《Estuarine, Coastal and Shelf Science》1985,20(4):387-392

Replicate portions of a Delaware salt marsh were enclosed in cylindrical microcosms and exposed to elevated levels of inorganic arsenic (arsenate). All biotic and abiotic components in dosed cylinders rapidly incorporated arsenic. Spartina blades showed the greatest arsenic enrichment, with dosed plants incorporating arsenic concentrations an order of magnitude higher than controls. Spartina detritus and sediments also exhibited greatly elevated arsenic concentrations. Virtually all of the arsenic was incorporated into plant tissue or strongly sorbed to cell surfaces. Thus, elevated arsenic concentrations in estuarine waters will be reflected in living and non-living components of a salt marsh ecosystem, implying that increased arsenic will be available to organisms within the marsh ecosystem.  相似文献   

Silicon limitation on primary production and its destiny in Jiaozhou Bay, China——Ⅳ：Study on cross-bay transect from estuary to ocean   总被引：1，自引：0，他引：1  

Yang Dongfang  Chen Yu  Gao Zhenhui  Zhang Jing  Wang Fan 《中国海洋湖沼学报》2005,23(1):72-90

The authors analyzed the data collected in the Ecological Station Jiaozhou Bay from May 1991 to November 1994, including 12 seasonal investigations, to determine the characteristics, dynamic cycles and variation trends of the silicate in the bay. The results indicated that the rivers around Jiaozhou Bay provided abundant supply of silicate to the bay. The silicate concentration there depended on river flow variation. The horizontal variation of silicate concentration on the transect showed that the silicate concentration decreased with distance from shorelines. The vertical variation of it showed that silicate sank and deposited on the sea bottom by phytoplankton uptake and death, and zooplankton excretion. In this way, silicon would endlessly be transferred from terrestrial sources to the sea bottom. The silicon took up by phytoplankton and by other biogeochemical processes led to insufficient silicon supply for phytoplankton growth. In this paper, a 2D dynamic model of river flow versus silicate concentration was established by which silicate concentrations of 0.028–0.062 μmol/L in seawater was yielded by inputting certain seasonal unit river flows (m³/s), or in other words, the silicate supply rate; and when the unit river flow was set to zero, meaning no river input, the silicate concentrations were between 0.05–0.69 μmol/L in the bay. In terms of the silicate supply rate, Jiaozhou Bay was divided into three parts. The division shows a given river flow could generate several different silicon levels in corresponding regions, so as to the silicon-limitation levels to the phytoplankton in these regions. Another dynamic model of river flow versus primary production was set up by which the phytoplankton primary production of 5.21–15.55 (mgC/m²·d)/(m³/s) were obtained in our case at unit river flow values via silicate concentration or primary production conversion rate. Similarly, the values of primary production of 121.98–195.33 (mgC/m²·d) were achieved at zero unit river flow condition. A primary production conversion rate reflects the sensitivity to silicon depletion so as to different phytoplankton primary production and silicon requirements by different phytoplankton assemblages in different marine areas. In addition, the authors differentiated two equations (Eqs. 1 and 2) in the models to obtain the river flow variation that determines the silicate concentration variation, and in turn, the variation of primary production. These results proved further that nutrient silicon is a limiting factor for phytoplankton growth. This study was funded by NSFC (No. 40036010), and the Director's Fund of the Beihai Sea Monitoring Center, the State Oceanic Administration.  相似文献   

Hydrodynamic control of phytoplankton in low salinity waters of the James River estuary,Virginia, U.S.A.     

Margaret J. Filardo  William M. Dunstan 《Estuarine, Coastal and Shelf Science》1985,21(5):653-667

Autotrophic biomass and productivity as well as nutrient distributions and phytoplankton cell populations in the James River estuary, Virginia, were quantified both spatially and temporally over a 17-month period. Emphasis was placed on the very low salinity region of the estuary in order to gain information on the fate of freshwater phytoplankters. Differing amounts of freshwater plant biomass are advected into the estuary as living material, DOC or POC and the demonstrated variability of this input must play an important role in marine biogeochemical cycling.Late summer and fall maxima in both chlorophyll a and the photosynthetic production of particulate organic carbon in very low salinity regions were inversely correlated with river discharge.During periods of low river discharge greater than 50% of the chlorophyll a biomass measured at 0‰ disappeared within a narrow range of salinity (0–2‰). Cell enumeration data suggest that species introduced from the freshwater end-member tend to comprise the bulk of the biomass removed. Confounding factors, which may contribute to the regulation of both the abundance and species of phytoplankters mid-river, include the flocculation of colloidal material with phytoplankton cells, the presence of the turbidity maximum and the growth of endemic phytoplankton populations.An inverse relationship exists between the phytoplankton abundance in very low salinity waters and the abundance of biomass measured in the lower portion of the river (estuary). Thus, autotrophic production in the fresh and very low salinity areas may indirectly regulate the onset on the spring bloom in the estuary by controlling the amount of nutrients available.  相似文献   

Long-chain alkenones and U₃₇′ variability along a south–north transect in the Western Pacific Ocean     

Ilhem Bentaleb  Michel Fontugne  Luc Beaufort 《Global and Planetary Change》2002,34(3-4)

In this paper, we present 50 surface water samples collected during the IMAGES III cruise (June–July 1997) along a transect from New Zealand to the China Sea (42°S–178°E, 21°N–120°E) covering a temperature range from 13.3 to 30.4 °C. A very worthwhile aspect of this study is a coupling of both biomarker (alkenone) and coccolithophorid counting. We show that the U₃₇^k′–temperature relationship is very similar to the Prahl et al. [Geochim. Cosmochim. Acta 52 (1988) 2203] culture calibration and to the global core top calibration of Müller et al. [Geochim. Cosmochim. Acta 62 (1998) 1757]. However, in the warmest surface waters of the Western Pacific ocean (>26.4 °C) where Gephyrocapsa oceanica is likely the most widespread species, the associated U₃₇^k′ has a constant value of 1.0. The consequence is that above this temperature threshold, U₃₇^k′ cannot be used as an accurate paleothermometer.  相似文献   

Timing and tectonic setting of Grenvillian metamorphism—constraints from a transect along Georgian Bay,Ontario*     

R. A. JAMIESON  N. G. CULSHAW  N. WODICKA  D. CORRIGAN  J. W. F. KETCHUM 《Journal of Metamorphic Geology》1992,10(3):321-332

Systematic mapping of a transect along the well-exposed shores of Georgian Bay, Ontario, combined with the preliminary results of structural analysis, geochronology and metamorphic petrology, places some constraints on the geological setting of high-grade metamorphism in this part of the Central Gneiss Belt. Correlations within and between map units (gneiss associations) have allowed us to recognize five tectonic units that differ in various aspects of their lithology, metamorphic and plutonic history, and structural style. The lowest unit, which forms the footwall to a regional decollement, locally preserves relic pre-Grenvillian granulite facies assemblages reworked under amphibolite facies conditions during the Grenvillian orogeny. Tectonic units above the decollement apparently lack the early granulite facies metamorphism; out-of-sequence thrusting in the south produced a duplex-like structure. Two distinct stages of Grenvillian metamorphism are apparent. The earlier stage (c. 1160–1120 Ma) produced granulite facies assemblages in the Parry Sound domain and upper amphibolite facies assemblages in the Parry Island thrust sheet. The later stage (c. 1040–1020 Ma) involved widespread, dominantly upper amphibolite facies metamorphism within and beneath the duplex. Deformation and metamorphism recently reported from south and east of the Parry Sound domain at c. 1100–1040 Ma have not yet been documented along the Georgian Bay transect. The data suggest that early convergence was followed by a period of crustal thickening in the orogenic core south-east of the transect area, with further advance to the north-west during and after the waning stages of this deformation.  相似文献   

南极乔治王岛长城湾沿岸固定冰中有色层生态观察          下载免费PDF全文

吕培顶  张坤诚  黄风鹏  渡边研太郎 《极地研究》1991,3(3):56-63

自1988年11月至1989年3月,对南极乔治王岛的长城湾沿岸水域中的海洋生物和环境因子进行了调查,1988年11月20日在2号站采得的冰芯中部有一层约5cm的棕色层,而1988年11月17日、20日和26日在5号站采得的冰芯样中有二层棕色层。固定冰中叶绿素a浓度范围在2.55～56.8mg/m~3之间,而且大部分含量集中在海冰的中间层中,而不象其它海区如昭和、戴维斯、凯西和麦克默多等站,大部分叶绿素a集中在海冰的底部,造成这种差别的原因、可能是由于海冰的结构和形成过程不同所致。  相似文献   

沉积物粒度分析在厦门市第四纪环境研究和地层划分对比中的应用   总被引：6，自引：0，他引：6  

张璞  陈建强  田明中  朱金芳  黄宗林  江春亮 《地球科学与环境学报》2005,27(1):88-94

采用MS2000型激光粒度分析仪进行测试，利用计算机粒度分析软件对数据进行整理和计算，绘制出样品的频率曲线、概率累积曲线以及粒度众数位值曲线等图件并进行沉积环境分析。厦门地区第四纪环境演化经历了中更新世同安组(含泥中粗砂、含泥细中砂、砂为主)海积一冲积一更新统上部龙海组(含泥粗中砂、含泥细中砂、含泥粗砂、粗砂、细中砂、含细砾中粗砂、中细砂等)冲积一洪冲积一更新世上部东山组(砂、砂砾、含泥中粗砂、粗砂、泥质中细砂、细砂、中粗砂等)冲洪积及部分海积(粉砂、细粉砂、含碳质泥、粘土、淤泥质粘土、粉砂质粘土等)一全新世长乐组(粉砂，淤泥质粘土、粉砂质粘土、碳质粘土、含砂淤泥质粘土，粉砂质亚粘土、粉细砂亚粘土等)海湾沉积。在解释环境变化的同时，说明粒度变化曲线在一定程度上可以作为地层划分的依据之一，并以此对研究区地层进行了详细划分。  相似文献