Nitrogen forms and decomposition of organic carbon in the southern Bohai Sea core sediments

Study on form characteristics of nitrogen in marine sediments is the primary method to research its biogeochemical cycling and nitrogen form characteristics in core sediments can reflect the process and results of early diagenesis in a certain degree. In this paper, Sequential extraction process in natural grain size was used for studying the existent forms of nitrogen in five core sediments of the southern Bohai Sea for the first time. Nitrogen was divided into two parts -transferable and fixed based on whether it could be extracted by the reagent. Distributions and early diagenesis of transferable nitrogen forms in the southern Bohai Sea were researched integratedly. Results indicate that IEF - N and OSF-N are predominant forms in transferable part in the studied core sediments. Contents of different nitrogen forms vary differently with depth, and have different diagenesis process. Decomposition constant of organic nitrogen (ON) and OC are about 15.51 × 10~(-3)a~(-1)and 4.79× 10~(-3)a~(-1) respective     

Deposition Rates of Terrestrial and Marine Organic Carbon in the Osaka Bay, Seto Inland Sea, Japan, Determined Using Carbon and Nitrogen Stable Isotope Ratios in the Sediment

Carbon and nitrogen stable isotope ratios (¹³C and ¹⁵N) of surface sediments were measured within Osaka Bay, in the Seto Inland Sea in Japan, in order to better understand the sedimentation processes operating on both terrestrial and marine organic matter in the Bay. The ¹³C and ¹⁵N of surface sediments in the estuary of the Yodo River were less than –23 and 5 respectively, but increased in the area up to about 10 km from the river mouth. At greater distances they became constant (giving ¹³C of about –20 and ¹⁵N about 6). It can be concluded that large amounts of terrestrial organic matter exist near the mouth of the Yodo River. Stable isotope ratios in the estuary of the Yodo River within 10 km of the river mouth were useful indicators allowing study of the movement of terrestrial organic matter. Deposition rates for total organic carbon (TOC) and total nitrogen (TN) over the whole of the Bay were estimated to be 63,100 ton C/year and 7,590 ton N/year, respectively. The deposition rate of terrestrial organic carbon was estimated to be 13,200 (range 2,000–21,500) ton C/year for the whole of Osaka Bay, and terrestrial organic carbon was estimated to be about 21% (range 3–34) of the TOC deposition rate. The ratio of the deposition rate of terrestrial organic carbon to the rate inflow of riverine TOC and particulate organic carbon (POC) were estimated to be 19% (range 3–31) and 76% (range 12–100), respectively.     

胶州湾围隔浮游生态系统氮、磷营养盐迁移-转化模型研究

通过对目前生态动力学模型的总结和综合,以生态系统中氮、磷营养盐循环为主线,建立了适用于海洋围隔浮游生态系统的多变量的营养盐迁移-转化动力学模型.该模型包括浮游植物、浮游动物、溶解无机态营养盐、溶解有机态营养盐和生物碎屑5个模块,涉及溶解无机氮、磷酸盐、溶解有机氮、溶解有机磷、浮游植物、浮游动物和生物碎屑7个状态变量.分别利用1999年秋季和2000年夏季胶州湾围隔生态实验数据进行了模型和验证工作,成功地模拟了富加营养盐条件下围隔浮游生态系统中氮、磷营养盐生物化学迁移-转化过程,并确定了20余个参数的量值.     

Nutrient Limitation in Macroalgae (Ulva and Enteromorpha) from the Rías Baixas (NW Spain)

Abstract.  Photosynthesis and growth rates in samples of two green seaweeds ( Ulva and Enteromorpha ) were monitored in the laboratory. The macroalgae were collected every 15 days from four coastal embayments in Galicia (NW Spain). Ulva samples were found to be nutritionally limited, particularly in summer. The physiological activity of Enteromorpha did not appear to be as affected by nutrient scarcity, although it may have suffered from phosphorus limitation. The subsistence quotas, critical concentrations and storage capacity for N and P in Ulva were comparable to those obtained by other investigators in similar studies. The trace metals analysed apparently did not negatively affect the macroalgae at the measured concentrations; one explanation is that many of these metals function as essential micronutrients. The complex physiological interactions between metals and nutrients, however, may complicate interpretation of the results.     

Processes Causing the Temporal Changes in Si/N Ratios of Nutrient Consumptions and Export Flux during the Spring Diatom Bloom

Two processes are generally explained as causes of temporal changes in the stoichiometric silicon/nitrogen (Si/N) ratios of sinking particles and of nutrient consumption in the surface water during the spring diatom bloom: (1) physiological changes of diatom under the stress of photosynthesis of diatom and (2) differences of regeneration between silicon and nitrogen. We investigated which process plays an important role in these changes using a one-dimensional ecosystem model that explicitly represents diatom and the other non-silicious phytoplankton. The model was applied to station A7 (41°30′ N, 145°30′ E) in the western North Pacific, where diatom regularly blooms in spring. Model simulations show that the Si/N ratios of the flux exported by the sinking particles at 100 m depth and of nutrient consumptions in the upper 100 m surface water have their maxima at the end of the spring diatom bloom, the values and timings of which are significantly different from each other. Analyses of the model results show that the differences of regeneration between silicon and nitrogen mainly cause the temporal changes of the Si/N ratios. On the other hand, the physiological changes of diatoms under stress can hardly cause these temporal changes, because the effect of the change in the diatom's uptake ratio of silicon to nitrogen is cancelled by that in its sinking rate.     

化学生态调控对鳌山湾氮磷营养盐的影响

鳌山湾,是一个营养类型特殊的海湾,湾中基本无径流输入,呈“C”字形,封闭性较强,水较浅,湾内主要有筏式扇贝养殖和底播贝类养殖,沿岸有滩涂池塘养殖.根据1996年11月至1998年5月的调查结果得知,鳌山湾海域为贫营养海域[1,2].为探讨贫营养海域进行化学生态调控的可能性,利用鳌山湾的封闭性,根据其水交换规律[3],于1999年6月首次对鳌山湾进行了全湾规模较大的化学生态调控试验,旨在有效提高鳌山湾的营养水平,为今后在贫营养海域合理发展海水养殖业提供科学依据,获得了十分理想的效果.     

Isotopic and Elemental Variations of Carbon and Nitrogen in a Mangrove Estuary

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.     

砷酸根的液—固界面交换吸附研究——pH和Ca(Ⅱ)的影响

研究ｐＨ和Ｃａ（Ⅱ）对砷酸根在海水与ＮａＣｌ介质中对水合氧化物和粘土矿物上交换吸附的影响：（１）在酸性条件下和海水及ＮａＣｌ介质中，砷酸根在针铁矿上的交换率Ｅ（％）—ｐＨ曲线呈平顶峰型、在δ－ＭｎＯ呈峰型、在粘土上分别呈双峰型和肩峰型。这是砷酸根存在多种形式与固体表面发生离子／配位子交换以及介质中阴离子竞争交换吸附共同作用的结果。（２）在碱性条件下的海水介质中，砷酸根与水合氧化物和粘土矿物的Ｅ（％）—ｐＨ曲线都呈Ｖ型，这是因为生成了具有一定结构的液—固界面三元络合物之故。（３）在ＮａＣｌ介质中，Ｃａ加入起促进作用，再次证明液—固界面三元络合物生成机理与Ｖ型曲线的内在关系