Isotopic and Elemental Variations of Carbon and Nitrogen in a Mangrove Estuary   总被引：6，自引：0，他引：6  

L.A. Cifuentes  R.B. Coffin  L. Solorzano  W. Cardenas  J. Espinoza  R.R. Twilley 《Estuarine, Coastal and Shelf Science》1996,43(6):781-800

Variations in elemental and isotopic ratios of suspended particulate matter (SPM) were investigated in the Guayas River Estuary Ecosystem (GREE) that empties into the Gulf of Guayaquil, Ecuador. Detritus in the system was identified on the basis of extremely high carbon:chlorophyll aratios (>1000). This material had mean δ¹³C of −26·4±0·3, δ¹⁵N of +4·8±0·2, and (C:N)_atomicof 14·1±0·9. The isotopic data were comparable to measurements reported for fresh and degrading mangrove leaves, whereas the elemental ratio was comparatively enriched in nitrogen. Isotope measurements of SPM throughout the GREE were more similar to values for riverine material and detritus compared with that for the coastal end-member. Values indicative ofin situproduced algae, sewage and shrimp pond effluent were only found at selected sites. Bacterial bioassays, which were used to document potential sources of dissolved organic matter in the GREE, were isotopically similar to SPM. This correspondence coupled with the relatively low (C:N)_aof SPM could be explained by bacterial immobolization of nitrogen onto detritus. Finally, tidal variations of (C:N)_aand δ¹³C at a brackish mangrove site were similar in magnitude to spatial variations encountered throughout the GREE. Based on these results, the authors caution that care must be taken when samples are taken for food-web studies in these systems.  相似文献   

牙鲆鱼耗氧率、氮排泄率与体重及温度的关系   总被引：2，自引：0，他引：2  

张兆琪  张美昭  李吉清  郑春波 《中国海洋大学学报(自然科学版)》1997,(4)

对个体重２．５～３４．５ｇ的牙鲆幼鱼在不同水温（１２、１７、２２、２７℃）下的耗氧率和氮排泄率进行了测试和分析。结果表明，牙鲆幼鱼的耗氧率和氮排泄率均随体重的增加而增加，其差异均达到极显著水平（Ｐ＜０．０１）；牙鲆幼鱼的耗氧率随水温上升而增加，但仅２７℃组与其他３个温度梯度组分别比较，出现差异极其显著（Ｐ＜０．０１），后３个温度梯度组之间的差异则不显著（Ｐ＞０．０５）；牙鲆幼鱼的氮排泄率也随温度的提高而增加，其差异亦达到极显著水平（Ｐ＜０．０１）。作者认为，在牙鲆养殖生产过程中，养殖水体溶解氧应维持在３ｍｇ／Ｌ以上，养殖水温以不超过２７℃为宜。  相似文献   

Seasonal Changes in Nitrogen, Free Amino Acids, and C/N Ratio in Mediterranean Seagrasses   总被引：2，自引：0，他引：2  

Helmut  Pirc Bernd  Wollenweber 《Marine Ecology》1988,9(2):167-179

Abstract. Seasonal changes in nitrogen, free amino acids, and carbon were investigated in the three Mediterranean seagrasses Posidonia oceanica, Cymodocea nodosa , and Zostera noltii. Leaves, rhizomes, roots, as well as dead plant material were analysed separately. Highest N-concentrations were obtained in the winter months, regardless of species or plant part. In contrast to the other two species, the N-content in Posidonia was higher in the rhizomes than in the leaves.
In the investigated species, marked differences in the free amino acid (FAA) composition were detected between species: Proline, lacking in Posidonia , was the main component in Cymodocea. In Posidonia , FAA decreased from 320umol g^-1 (dry wt) in leaf sheaths to 1.5 umol g^-1 (dry wt) in the leaf tips. The function of proline as a possible storage and/or stress metabolite is discussed.
High C/N values in dead P. oceanica and C. nodosa rhizomes as well as in P. oceanica wrack seem to be related to considerable resistance to decomposition. Low C/N ratios did not increase in detached C. nodosa and Z. noltii leaves, which began to decompose shortly after detachment from the plants.  相似文献   

南黄海表层沉积物中氮的区域地球化学特征   总被引：5，自引：0，他引：5  

吕晓霞  宋金明 《海洋科学进展》2003,21(2):174-180

通过分级浸取分离的方法获得了南黄海表层沉积物不同形态的氮，首次探讨其分布的区域性特征：南黄海表层沉积物中各形态氮在不同测线上均呈现出波状分布。B测线的基本上呈现出中部海域高，两边海域低，而西部海域又略高于东部海域的趋势，D和E测线的基本上呈现出西高、东低的趋势，C测线的则呈现出西低、东高的趋势，F测线的变化趋势比较平缓，从整体上看，SOEF—N和TN的分布呈现出西部海区比东部海区低的趋势。受各测线上沉积物种类差异的影响，自北向南各形态氮的变化幅度逐渐减小，其中SOEF-N在各测线上的变化幅度最大，且自北向南降幅最大。受水动力及沉积物粒度的影响，不同形态氮在黄海槽内各站位沉积物中的含量较高。沉积物中各形态氮在不同测线上的分布还表明，陆源输入对南黄海沉积物中氮测线分布有较小的影响，海洋自生氮对南黄海表层沉积物中氮的形态、含量与分布具有重要影响。  相似文献   

Community Structure and Dynamics of Phytoplankton in the Western Subarctic Pacific Ocean: A Synthesis   总被引：1，自引：1，他引：1  

Hongbin Liu  Koji Suzuki  Hiroaki Saito 《Journal of Oceanography》2004,60(1):119-137

The phytoplankton community in the western subarctic Pacific (WSP) is composed mostly of pico- and nanophytoplankton. Chlorophyll a (Chl a) in the <2 μm size fraction accounted for more than half of the total Chl a in all seasons, with higher contributions of up to 75% of the total Chl a in summer and fall. The exception is the western boundary along the Kamchatka Peninsula and Kuril Islands and the Oyashio region where diatoms make up the majority of total Chl a during the spring bloom. Among the picophytoplankton, picoeukaryotes and Synechococcus are approximately equally abundant, but the former is more important in term of carbon biomass. Despite the lack of a clear seasonal variation in Chl a concentration, primary productivity showed a large seasonal variation, and was lowest in winter and highest in spring. Seasonal succession in the phytoplankton community is also evident with the abundance of diatoms peaking in May, followed by picoeukaryotes and Synechococcus in summer. The growth of phytoplankton (especially >10 μm cell size) in the western subarctic Pacific is often limited by iron bioavailability, and microzooplankton grazing keeps the standing stock of pico- and nano-phytoplankton low. Compared to the other HNLC regions (the eastern equatorial Pacific, the Southern Ocean, and the eastern subarctic Pacific), iron limitation in the Western Subarctic Gyre (WSG) may be less severe probably due to higher iron concentrations. The Oyashio region has similar physical condition, macronutrient supply and phytoplankton species compositions to the WSG, but much higher phytoplankton biomass and primary productivity. The difference between the Oyashio region and the WSG is also believed to be the results of difference in iron bioavailability in both regions. This revised version was published online in July 2006 with corrections to the Cover Date.  相似文献   

渤海生态动力过程的模型研究 Ⅱ.营养盐以及叶绿素a的季节变化          下载免费PDF全文

刘浩  尹宝树 《海洋学报》2007,29(4):20-33

利用在本系列研究第一部分中所建立的耦合的生物物理模型,模拟了渤海浮游植物生物量和营养盐含量的年度循环特征.模拟结果显示:藻类的春季水华是由经过一冬积累在水体中的营养盐导致,而水华开始的时间在浅水区明显早于深水区,对此深水区水体层化结构的形成可能起着重要作用;另一方面,河载营养盐与悬起的沉积物所释放的营养盐是诱发夏季水华的共同原因.基于模型结果,我们还发现:渤海的浮游植物动力特性就整体而言依然受无机氮限制,但是在莱州湾,磷限制特性表现得非常明显,这主要是由于每年黄河都要携带大量的无机氮进入海水,从而导致莱州湾营养盐的氮磷比已远远超过16.  相似文献   

一种腐屑食性鱼类对生态系统氮循环的影响     

线薇薇  孙松  刘瑞玉 《中国海洋大学学报(自然科学版)》2004,34(4):549-554

研究表明 :腐屑食性鱼类——梭鱼对环境中有机氮的摄入能力随体重的增加而增加 ,随温度的升高 ,体重系数显著减少。摄入氮 (CN,mg/ d)与体重 (W,g)和温度 (T,℃ )的数值关系可用如下模型表示 :CN=0 .6 370 W1 .0 642 ln(3.70 0 8T)。体重为 1 0 0 g的梭鱼每日可消耗环境中 332 mg氮有机质。梭鱼氮的吸收效率主要受温度的影响 ,而氮的转化效率与体重呈显著的正相关关系。随体重的增加 ,排泄氮所占比例降低  相似文献   

中国南极长城湾及附近海区1993/1994年夏季表层水样无机氮、磷酸盐的浓度及其分布状况     

陈皓文  朱明远  洪旭光  陆华  袁峻峰 《海洋湖沼通报》1996,(4)

1993／1994年南极夏季对中国南极长城湾及附近海区表层海水四种营养盐浓度及其分布状况作了调查。结果表明，NH4－N、NO3－N、NO2－N及PO4－P的大致浓度分别是2．13、7．07、0．74和1．12μg·dm-3。一般来说，湾内高于湾外氮盐于12月份常出现高值。四种形态的无机盐类之最高、最低浓度出现的时间和站位不尽一致。∑N／P递减次序大致是12月，2月，1月。水温变化与NH4－N、PO4－P浓度和∑N／P的变化常较一致，而与NO2－N则常不一，一些站位上营养盐浓度偏低可能与浮游植物摄取有关。结果显示了调研海区的浅水内湾特征。浮游植物所需营养充分。该湾仍维持正常状态。  相似文献   

Nutrient budgets and trophic state in a hypersaline coastal lagoon: Lagoa de Araruama, Brazil     

Marcelo F. L. Souza  Bjrn Kjerfve  Bastiaan Knoppers  Weber F. Landim de Souza  Raimundo N. Damasceno 《Estuarine, Coastal and Shelf Science》2003,57(5-6):843-858

Lagoa de Araruama in the state of Rio de Janeiro, Brazil, is a hypersaline lagoon with salinity varying spatially from 45 to 56. We collected water samples during monthly cruises throughout the lagoon, and along the streams feeding the system, from April 1991 to March 1992. Nutrients and other water quality parameters exhibited great spatial and temporal variations. Mass balance calculations indicate large amounts of anthropogenic nutrient inputs. The data indicate that the lagoon currently is oligotrophic but is in a state of transition to become a mesotrophic system. Molar dissolved inorganic nitrogen:dissolved inorganic phosphorus (DIN/DIP) varied between 2.2:1 and 659:1 with a volume-weighted average of 22:1. The high DIN/DIP ratio contrasts with that found in nearby lagoons, suggesting that phytoplankton primary production is limited by phosphorus in Lagoa de Araruama. The major loss of DIP is apparently driven by biological assimilation and diagenic reactions in the sediments. Calculations indicate that the lagoon is slightly net autotrophic at +0.9 mol C m⁻² yr⁻¹. This suggests that the biomass of the primary producers is restricted by phosphorus availability. Phosphorus retention in the sediment and the hypersaline state of the lagoon prevent changes in autotrophic communities and the formation of eutrophic conditions.  相似文献   

长江和长江口高含量无机氮的主要控制因素   总被引：41，自引：6，他引：41  

沈志良  刘群  张淑美  苗辉  张平 《海洋与湖沼》2001,32(5):465-473

根据1998－1998年长江和长江口河水和雨水的现场调查、历史资料以及相关文献，定量分析长江流域无机氮的主要来源和输送调查。估算表明，降水无机氮、农业非点源氮（化肥和土壤流失的氮）和点源污水氮的输入分别占长江口无机氮输出通量的62．3％、18．5％和14．4％。氮的降水输入是长江口高含量无机氮的主要来源，进入长江的降水氮仅仅大约占长江流域全部降水氮的36．8％。降水米要受控于化肥气态损失、化石燃料及动植物过程中释放的物质等。实际上，化肥N的气态损失和农业非点源流失大约占长江流域年化肥N使用量的60％，这是控制长江口高含量无机氮的关键因素。  相似文献