共查询到20条相似文献，搜索用时 46 毫秒
1.
2.
虫黄藻、细菌和造礁石珊瑚有着密切的共生关系, 但虫黄藻藻际细菌群落尚未得到广泛研究。本研究对5个属的6株虫黄藻进行了离体培养, 其中2株为悬浮型虫黄藻(E型), 4株为贴壁型虫黄藻(A—D型)。通过采集藻株培养物3种粒径的样本开展细菌群落分析, 分别为0.2~3μm(自由生活)、>3μm(附着于藻体或颗粒物)与Settling(沉底贴壁藻体上)。结果发现, 2种生活方式的藻株藻际细菌群落具有显著差别, 贴壁型藻株细菌群落的物种丰富度显著高于悬浮型藻株。发现7个属的细菌广泛存在于所有的藻株中, 它们代表了A—E型虫黄藻藻际细菌的核心类群。对3种粒径样本的核心细菌群落比较发现, 自由生和颗粒附着生的核心细菌群落十分相似, 但均与沉底贴壁样本差异明显。 相似文献
3.
不同氮源对微小亚历山大藻生长和毒素产生的影响 总被引：12，自引：0，他引：12
通过尿素、氯化铵、酵母浸出粉和硝酸钠等氮源对微小亚历山大藻(Alexandrium minutum)生长及毒素产生的影响研究,分析了微小亚历山大藻对不同氮源利用状况的差异.结果表明,在氮饥饿条件下,加入硝酸钠和酵母浸出粉能显著促进微小亚历山大藻的生长;高浓度的氯化铵在加入后对微小亚历山大藻有一定的毒性效应,表现为生长停滞,但毒性效应在5 d后消失,并得到与添加硝酸钠及酵母浸出粉相似的增长速率0.21 d-1;添加尿素对微小亚历山大藻的生长没有显著促进作用.在四种氮源中,尿素对微小亚历山大藻毒素产生的刺激作用也最弱,在稳定期每个细胞藻细胞毒素含量维持在6.00~8.00 fmol;添加硝酸钠、氯化铵和酵母浸出粉的藻细胞在稳定期毒素含量分别达到11.85,12.86和14.64 fmol.硝酸钠和氯化铵刺激藻毒素产生的效果比酵母浸出粉更为直接.四种含氮营养盐对微小亚历山大藻毒素组成的影响都很小. 相似文献
4.
胶州湾东北部养殖海域夏季营养盐分布特征及其对浮游植物生长的影响 总被引：1，自引：0，他引：1
以2000年夏季胶州湾东北部养殖海域(女姑山)的现场调查为基础,结合前3年的调查结果和相关的历史资料,对该海域夏季营养盐含量分布特征及其对浮游植物生长的可能限制因子进行了分析和探讨。研究结果表明,胶州湾东北部典型养殖海域夏季表层水体各种营养盐含量高于胶州湾全湾夏季及全年的平均值,铵氮是总溶解态无机氮的主要组成形态,硝态氮次之。该海域的环境因素适宜浮游植物的生长,相关分析显示:叶绿素a与pH及DO呈显著正相关,与PO4、SiO3、NH4、DIN呈负相关。通过分析营养盐对浮游植物生长的限制因素发现,该海域各种营养盐含量相对较高,无机氮不会成为浮游植物生长的限制因素,磷酸盐有限制的可能性,而浮游植物生长受控于硅酸盐的几率最大。 相似文献
5.
In most natural sedimentary systems labile and refractory organic material (OM) occur concomitantly. Little, however, is known on how different kinds of OM interact and how such interactions affect early diagenesis in sediments. In a simple sediment experiment, we investigated how interactions of OM substrates of different degradability affect benthic nitrogen (N) dynamics. Temporal evolution of a set of selected biogeochemical parameters was monitored in sandy sediment over 116 days in three experimental set-ups spiked with labile OM (tissue of Mytilus edulis), refractory OM (mostly aged Zostera marina and macroalgae), and a 1:1 mixture of labile and refractory OM. The initial amounts of particulate organic carbon (POC) were identical in the three set-ups. To check for non-linear interactions between labile and refractory OM, the evolution of the mixture system was compared with the evolution of the simple sum of the labile and refractory systems, divided by two. The sum system is the experimental control where labile and refractory OM are virtually combined but not allowed to interact. During the first 30 days there was evidence for net dissolved-inorganic-nitrogen (DIN) production followed by net DIN consumption. (Here ‘DIN’ is the sum of ammonium, nitrite and nitrate.) After 30 days a quasi steady state was reached. Non-linear interactions between the two types of OM were reflected by three main differences between the early-diagenetic evolutions of nitrogen dynamics of the mixture and sum (control) systems: (1) In the mixture system the phases of net DIN production and consumption commenced more rapidly and were more intense. (2) The mixture system was shifted towards a more oxidised state of DIN products [as indicated by increased (nitrite + nitrate)/(ammonium) ratios]. (3) There was some evidence that more OM, POC and particulate nitrogen were preserved in the mixture system. That is, in the mixture system more particulate OM was preserved while a higher proportion of the decomposed particulate N was converted into inorganic N. It can be concluded that during the first days and weeks of early diagenesis the magnitude and composition of the flux of decompositional dissolved N-compounds from sediments into the overlying water was influenced by non-linear interactions of OM substrates of different degradability. Given these experimental results it is likely that the relative spatial distributions of OM of differing degradability in sediments control the magnitude and composition of the return flux of dissolved N-bearing compounds from sediments into the overlying water column. 相似文献
6.
7.
The aim of the present study was to investigate seasonal and spatial patterns of soil oxygen consumption, nitrification, denitrification and fluxes of dissolved inorganic nitrogen (DIN) in a tidal salt marsh of the Lagoon of Venice, Italy. In the salt marsh, intact soil cores including overlying water were collected monthly at high tide from April to October in salt marsh creeks and in areas covered by the dominant vegetation, Limonium serotinum. In May, cores were also collected in areas with vegetation dominated by Juncus maritimus and Halimione portulacoides. In laboratory incubations at in situ temperature in the dark, flux rates of oxygen and DIN were monitored in the overlying water of the intact cores. 15N-nitrate was added to the overlying water and nitrification and denitrification were measured using isotope-dilution and -pairing techniques. The results show that highest soil oxygen consumption coincided with the highest water temperature in June and July. The highest denitrification rates were recorded in spring and autumn coinciding with the highest nitrate concentrations. Soil oxygen consumption and nitrification rates differed between sampling sites, but denitrification rates were similar among the different vegetation types. The highest rates were recorded in areas covered with L. serotinum. Burrowing soil macrofauna enhanced oxygen consumption, nitrification and denitrification in April and May. The data presented in this study indicate high temporal as well as spatial variations in the flux of oxygen and DIN, and nitrogen transformations in the tidal salt marshes of the Venice lagoon during the growth season. The results identify the salt marshes of the Venice lagoon as being metabolically very active ecosystems with a high capacity to process nitrogen. 相似文献
8.
Yasuo Nakamura 《Journal of Oceanography》1985,41(1):33-38
Ammonium uptake kinetics and interactions between nitrate and ammonium uptake were examined inChattonella antiqua. After the addition of ammonium to the culture ofC. antiqua, the ammonium concentration decreased linearly with time. The ammonium uptake rate as a function of ammonium concentration followed the Michaelis-Menten equation; the maximal uptake rate was 2.0 pmol cell–1hr–1 and the half saturation constant, 2.2M. Although the ammonium uptake was not affected by nitrate, uptake of nitrate was rapidly (15min) suppressed by ammonium and a 50% reduction in nitrate uptake was observed at an ammonium concentration ofca. 2M. 相似文献
9.
ABSTRACT Dissolved nutrient uptake and metabolism by periphyton in a central North Island gravel-bed river were investigated using recirculating in-situ chambers. Dissolved inorganic nitrogen (DIN) uptake was correlated with photosynthesis and chlorophyll but N uptake and carbon fixation were partly de-coupled indicating storage. Dissolved reactive phosphorus (DRP) uptake was only weakly correlated with photosynthesis. Diatoms and green algae relied on DRP in the water, but Cyanobacteria met part of their P needs from storage. Dissolved organic nutrients were excreted in both light and dark incubations, with approximately 50% of DIN uptake during photosynthesis excreted as DON. To simulate diurnal variations in nutrients, oxygen and pH existing computer models need to de-couple photosynthesis from nutrient uptake, allow for variable stoichiometry and better quantify recycling of organic nutrients. 相似文献
10.
Distribution of nitrogenous nutrients and denitrifiers strains in estuarine sediment profiles of the Tanshui River, northern Taiwan 总被引：1，自引：1，他引：1
Chemical profiles of both oxidized (nitrate and sulfate) and reduced (ammonium, sulfide, acid-volatile sulfide [AVS], and pyrite) materials and the corresponding distribution of denitrifier microbial communities were measured at low tide in sediments at Guandu in the estuary of the Tanshui River, northern Taiwan in August 2002. Denitrifier strains were isolated for physiological and phylogenic analyses. Based on the distribution of nitrogenous compounds and denitrifier abundances, the vertical profile of Guandu sediments could be separated into four layers: a mixed layer (the top 1 cm of depth, respectively containing 0.82–2.37 and 535.9–475.0 μM of nitrate and ammonium), a nitrate-concentrated layer (1–5 cm in depth, 2.37–0.53 and 475.0–1192.1 μM, respectively), a denitrifier-aggregation layer (5–7 cm in depth, 0.53–0.72 and 1192.1–1430.1 μM, respectively), and an ammonium-enriched layer (7–12 cm in depth, 0.72–0.78 and 1430.1–2196.6 μM, respectively). Denitrifier strains were detected in all layers except for the mixed layer. A variety of metabolic processes by these strains may occur in different layers. Bacillus jeotgali-, Bacillus sphaericus-, and Bacillus firmus-related strains isolated from the nitrate-concentrated layer may be involved in the nitrification-denitrification coupling process due to the relatively low nitrate concentrations (maximum = 2.37 μM), and may contribute to denitrification not nitrification. Bacillus bataviensis- and B. jeotgali-related strains isolated from the denitrifier-aggregation layer comprised the predominant denitrifier population (3.64 × 104 cells/g of denitrifier abundance). They possess the ability of dissimilatory nitrate reduction to ammonium (DNRA). Bacillus jeotgali-related strains and two newly identified strains of GD0705 and GD0706 isolated from the ammonium-enriched layer possibly use fermentative processes as the main metabolic pathway instead of denitrification when nitrate is scarce, and this further supports the high ammonium concentrations (up to 2.20 mM) found in the Guandu sediments. In addition, spore formation also enhances the chance of survival of these strains in the face with such a nitrate-deficient environment. 相似文献
11.
本文研究了水体中不同形式溶解无机氮(NH_4~+,NO_3~-,NH_4~++NO_3~-)及其含量对牟氏角毛藻和钙质角毛藻胞内活性氮组分(NH_4~+,NO_3~-,AA,Pr,RNA及DNA)的影响。结果表明:角毛藻胞内无机氮储量的大小体现了水体中无机氮的营养水平;培养角毛藻采用混合无机氮比之单一无机氮,其胞内AA和Pr含量较高,AA/Pr值可定量标志水体无机氮的营养水平及藻类本身氮的营养状况;RNA/DNA值是藻类生长增殖状况的指标之一。 相似文献
12.
The preferential inorganic nitrogen source for the seagrass Zostera noltii was investigated in plants from Ria Formosa, South Portugal. Rates of ammonium and nitrate uptake were determined at different concentrations of these nutrients (5, 25 and 50 μm ), supplied simultaneously (NH4NO3) or separately (KNO3 and NH4Cl). The activity of the enzymes nitrate reductase (NR) and glutamine synthetase (GS) was also assessed. The results showed that ammonium is the preferential inorganic nitrogen source for Z. noltii, but, in the absence of ammonium, the species also has a high nitrate uptake capacity. The simultaneous availability of both inorganic nitrogen forms enhanced the uptake rate of ammonium and decreased the uptake rate of nitrate compared to when only one of the nitrogen forms was supplied. The activity of both enzymes was much higher in the leaves than in the roots, highlighting the importance of the leaves as primary reducing sites in the nitrogen assimilation process. 相似文献
13.
溶解态无机氮（dissolved inorganic nitrogen, DIN）主要由亚硝酸盐-氮（NO-2-N）、硝酸盐-氮（NO-3-N）和铵氮（NH+4-N）组成,它们在海洋的生物地球化学循环过程中起重要作用。但人类活动向海洋输入了大量无机氮,导致一系列环境问题。为了更好地开展海洋氮循环研究和环境污染管理,需对海水中的DIN进行测定。在众多分析方法中,光谱法因其通用性好、适用范围广、所需设备简单,成为测定海水DIN的首选。本文总结了近10年来基于光谱法测定海水DIN的研究进展,包括紫外分光光度法测定NO-3-N、萘乙二胺分光光度法测定NO-2-N和NO-3-N、次溴酸盐氧化-分光光度法测定NH+4-N、靛酚蓝分光光度法测定NH+4-N、酸碱指示剂-分光光度法测定NH+4-N、荧光法和化学发光法测定DIN等,比较了各分析方法的特点,并展望了光谱法测定海水DIN的发展趋势。总的来说,在分析方法上,新试剂的使用以及一些新合成材料的出现,丰富了DIN的分析手段;在分析仪器上,以流动分析技术为基础的分析仪器在DIN的实验室及现场分析中得到了广泛应用。DIN的分析方法均朝着简单便捷、全自动化、分析速度快、精确度高、可适用范围广的方向发展。 相似文献
14.
Many tropical cnidarians, including anemones and corals, contain symbiotic dinoflagellates known as zooxanthellae. Photosynthesis by symbiotic dinoflagellates benefits the animal host and the proficiency of host metabolism also plays an important role in the nutrient status of the photosynthetic dinoflagellates. We aimed to determine the responses of symbiotic dinoflagellates to host starvation. The ultrastructure and some physiological indicators of symbiotic dinoflagellates (Symbiodinium sp., zooxanthellae) were examined in starved sea anemones (Stichodactyla mertensii; 3‐, 45‐ and 280‐day starvation). The cell size of zooxanthellae was not affected by starving the host; however, the ultrastructure and other physiological indicators of the zooxanthellae were affected. The photochemical efficiency of symbiotic dinoflagellates from anemones after 280 days of starvation was significantly (P < 0.01) higher than that of symbiotic dinoflagellates from anemones after 3‐ and 45‐day starvation. The number of symbiotic dinoflagellates from anemones decreased with increasing starvation duration. Generally, the chlorophyll a and c content of symbiotic dinoflagellates decreased significantly with longer anemone starvation. The tentacles of 3‐day starved anemones contained the most zooxanthellae, some of which were dividing and still enclosed within one periplast, and some had split entirely within one host vacuole. Moreover, each cell from 3‐day starved anemone contained up to five or six more mitochondria than those from 45‐ to 280‐day starved anemones. More lipid granules appeared in the zooxanthellae from 45‐ to 280‐day starved anemones. Pyrenoids, lobed accumulation bodies and calcium oxalate crystals existed in the symbiotic dinoflagellates from anemones at different starvation stages, which suggested that their existence had no correlation with host starvation. These findings contribute to an improved mechanistic understanding of the symbiotic relationship between zooxanthellae and anemones. 相似文献
15.
细菌对海水中各形态氮的影响 总被引：1，自引：0，他引：1
海洋细菌生长过程中,不但能利用体系中的有机物质,而且也能利用无机营养盐。本论文通过小麦岛细菌接种实验发现,细菌大量繁殖时吸收利用体系中的营养物质,生成颗粒态氮(PN)和溶解有机氮(DON),体系中溶解无机氮(DIN)、总溶解氮(TDN)降低至最低值。进入细菌指数生长期和稳定期后,颗粒态和有机态氮不断降解向体系中释放出无机营养盐,DIN和TDN呈现回升趋势,颗粒氮(PN)与细菌数量变化正相关。体系中,初始氮源的量决定了细菌体内POC/PN的比值,氮源充足,细菌繁殖数量多,POC/PN值低,氮源不足,细菌数量相对较少,POC/PN比值高。 相似文献
16.
Nitrogen uptake in light versus darkness of the seagrass Zostera noltei: integration with carbon metabolism 
下载免费PDF全文
下载免费PDF全文 We conducted a study that shows that light and dark conditions do not affect the uptake rates of ammonium and nitrate by the seagrass Zostera noltei. This is an important advantage over some seaweed species in which these rates are severely reduced at night. In the light, the ammonium uptake rates were initially higher (15 and 20 μmol·g?1·h?1) and stabilized at a rate of 5 μmol·g?1·h?1 after 1 h, whereas in the dark the rates remained constant at a rate of 10 μmol·g?1·h?1 over the first 180 min of incubation. The rates of nitrate uptake in the light were high within the first 120 min of incubation (7.2–11.1 μmol·g?1·h?1) and decreased afterwards to lower values (0.8–3.9 μmol·g?1·h?1), whereas in the dark the rates fluctuated around 0.0–11.1 μmol·g?1·h?1 throughout the whole incubation time (7 h). The soluble sugar content of Z. noltei leaves increased significantly with both ammonium and nitrate incubations in the light, indicating the metabolic outcome of photosynthesis. In the dark, there was no significant variation in either the soluble sugar or in the starch content of leaves, rhizomes or roots in either the ammonium or nitrate incubations. However, the total starch content of plants decreased at night whereas the total soluble sugars increased, suggesting a process of starch catabolism to generate energy with the consequent production of smaller monosaccharide products. The starch content of rhizomes decreased significantly during the light incubations with nitrate but not with ammonium. These results suggest that carbohydrate mobilization is necessary for Z. noltei to account for extra energetic costs needed for the uptake and assimilation of nitrate. Furthermore, our results suggest that nitrate uptake, at least during the day, requires the mobilization of starch whereas the uptake of ammonium does not. 相似文献
17.
Krishnan KP Fernandes SO Loka Bharathi PA Krishna Kumari L Nair S Pratihary AK Rao BR 《Marine environmental research》2008,65(5):445-455
Studies on the Arabian Sea coastal anoxia have been of immense interest, but despite its ecological significance there is sparse understanding of the microbes involved. Hence, observations were carried out off Goa (15 degrees 30'N, 72 degrees 40'E to 15 degrees 30'N, 72 degrees 59'E) to understand the processes that mediate the changes in various inorganic nitrogen species in the water column during anoxia. Water column chemistry showed a clear distinct oxic environment in the month of April and anoxic condition in October. Our study based on microbial signatures indicated that oxygen deficit appeared as a well-defined nucleus almost 40 km away from the coast during the oxic period (April) and spreads there after to the entire water column synchronizing with the water chemistry. Striking results of net changes in inorganic nitrogen species in nitrification blocked and unblocked experimental systems show that denitrification is the predominant process in the water column consuming available nitrate ( approximately 0.5 microM) to near zero levels within approximately 72 h of incubation. These observations have been supported by concomitant increase in nitrite concentration ( approximately 4 microM). Similar studies on denitrification-blocked incubations, demonstrate the potential of nitrification to feed denitrification. Nitrification could contribute almost 4.5 microM to the total nitrate pool. It was found that the relation between ammonium and total dissolved inorganic nitrogen (DIN) pool (r=0.98, p<0.001, n=122) was significant compared to the latter with nitrite and nitrate. The occurrence of high ammonium under low phosphate conditions corroborates our observations that ammonium does not appear to be locked under low oxygen regimes. It is suggested that ammonium actively produced by detrital breakdown (ammonification) is efficiently consumed through nitrification process. The three processes in concert viz. ammonification, nitrification and denitrification appear to operate in more temporal and spatial proximity than hitherto appreciated in these systems and this gives additional cues on the absence of measurable nitrate at surface waters, which was earlier attributed only to efficient algal uptake. Hence we hypothesize that the alarming nitrous oxide input into the atmosphere could be due to high productivity driven tighter nitrification-denitrification coupling, rather than denitrification driven by extraneous nitrate. 相似文献
18.
根据 1998年 5月的调查资料 ,分析并讨论了春季黄海南部海区溶解无机氮的分布特征。结果表明 :( 1)因受长江冲淡水及沿岸流的影响 ,NH+4 - N、NO-2 - N浓度的平面分布基本呈周边高、中央低 ,NO-3 - N的浓度则基本呈长江口外海域高、中北部深水区低的分布规律。 ( 2 )调查海域深水区的溶解无机氮存在明显的层化现象 ,且底层等值线上凸密集。 10 m以浅水体 ,NO-3 - N的浓度分布均匀 ,10 m以深水体 ,NO-3 - N的浓度急剧增加 ,且呈现出随深度增加而增加的趋势 ,NH+4 - N、NO-2 - N浓度的垂直分布比较均匀。 ( 3)黄海南部表层叶绿素 a的浓度呈现周边高、中央低的分布特征。 相似文献
19.
Stphane L'Helguen Christian Madec Pierre Le Corre 《Estuarine, Coastal and Shelf Science》1996,42(6):803-818
Uptake rates of ammonium, nitrate, urea and nitrite were measured for 1 year (1988) at a coastal station in the well-mixed waters of the western English Channel. Ammonium was the major form of nitrogen (N) utilized (48%) by phytoplankton, followed by nitrate (32%), urea (13%) and nitrite (7%). Seasonal changes of uptake of ammonium, nitrate and urea showed a broad, intense summer maximum. Nitrite uptake was low throughout the year except for a peak value in June. Uptake rates of ammonium and nitrate were independent of substrate concentrations, whereas those of urea and nitrite were not. The summer maxima of ammonium, nitrate and total N uptake, and the significant relationships of N-uptake index to ambient light, and of chlorophyll-a-specific N uptake to surface-incident light, indicate that light is the major factor controlling N uptake in these waters. This is due to the permanent vertical mixing which reduces the mean light available for N uptake to <15% of the incident light. Mixing also injects regenerated N continuously into the euphotic zone, thus alleviating nitrogen limitation and accounting for the larger proportion of regenerated N uptake in total N uptake. 相似文献
20.
采用高浓度无机三态氮(铵氮4NH?-N、亚硝氮2NO?-N和硝氮3NO?-N)共存的模拟海水体系,在最适生长条件下,研究了小分子有机物(糖类、有机酸、醇、有机氮)和p H对海洋着色菌(Marichromatium gracile)YL28去除水体无机三态氮的影响。结果表明:以葡萄糖、乙酸钠和乙醇为唯一碳源时,水体中的高浓度2NO?-N和3NO?-N均能被完全去除,4NH?-N的去除率分别为93.40%、84.55%和66.63%;碳源为乙酸钠时菌体生长最好,体系中添加蛋白胨或尿素,仅4NH?-N的去除效果明显降低。p H值在6.0—9.0时,该菌株对4NH?-N、2NO?-N和3NO?-N均具有去除能力。由此可知:YL28菌株对模拟海水养殖水体中高浓度无机三态氮具有良好的去除能力,高浓度有机氮化物(蛋白胨和尿素)对4NH?-N的去除能力有明显影响,但对2NO?-N和3NO?-N仍保持高效的去除能力。本研究为不产氧光合细菌制剂在水产养殖中的合理应用提供参考。 相似文献