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1.
This study showed how the daytime length in Jiaozhou Bay affected the water temperature, which in turn affected the phytoplankton growth when solar radiation was sufficient for phytoplankton photosynthesis. Jiaozhou Bay observation data collected from May 1991 to February 1994 were used to analyze the daytime length vs water temperature relationship. Our study showed that daytime length and the variation controlled the cycle of water temperature flunctuation. Should the cyclic variation curve of the daytime length be moved back for two months it would be superimposed with temperature change. The values of daytime length and temperature that calculated in the dynamical model of daytime length lag vs water temperature were consistent with observed values. The light radiation and daytime length in this model determined the photochemistry process and the enzymic catalysis process of phytoplankton photosynthesis. In addition, by considering the effect of the daytime length on water temperature and photosynthesis, we could comprehend the joint effect of daytime length, water temperature, and nutrients, on the spatiotemperal variation of primary production in Jiaozhou Bay.  相似文献   

2.
A simple diagnostic simulation of the annual cycling of the surface specific photosynthesis rate (SPR) in Jiaazhou Bay is described in this paper. Light intensity, temperature and nutrients(nitrate ammonia, phosphate) were considered as main factors controlling photosynthesis of phytoplankton and were introduced into the model by different function equations. The simulated variation ofspecific photosynthesis rate coincided with the measured data. Analysis of the effect of every factor onphotosynthesis indicated that the variation of photosynthesis rate was controlled by all these three factors,while temperature showed good correlation with SPR as measurement showed. This diagnostic simulationyielded the values of some parameter relating with the photosynthesis in Jiaozhou Bay.  相似文献   

3.
ＩＮＴＲＯＤＵＣＴＩＯＮＴｈｅｐｒｏｄｕｃｔｉｏｎｏｆｐｈｙｔｏｐｌａｎｋｔｏｎｉｓｔｈｅｆｉｒｓｔｔａｃｈｅｉｎｔｈｅｐｒｏｄｕｃｔｉｏｎｂｙｍａｒｉｎｅｏｒｇａｎｉｓｍｓａｎｄｉｎｔｈｅｍａｒｉｎｅｆｏｏｄｃｈａｉｎ .Ｋｎｏｗｌｅｄｇｅｏｆｐｒｉｍａｒｙｐｒｏｄｕｃｔｉｏｎｉｎｍａｒｉｎｅｗａｔｅｒｓｉｓｐｒｅｒｅｑｕｉｓｉｔｅｆｏｒｅｘｐｌｏｉｔａｔｉｏｎａｎｄｍａｎａｇｅｍｅｎｔｏｆｔｈｅｏｃｅａｎ’ｓｌｉｖｉｎｇｒｅｓｏｕｒｃｅｓ.Ｔｈｅｐｒｉｍａｒｙｐｒｏｄｕｃｔｉｏｎｉｎｍａｒｉｎ…  相似文献   

4.
Jiaozhou Bay data collected from May 1991 to February 1994, in 12 seasonal investigations, and provided the authors by the Ecological Station of Jiaozhou B ay, were analyzed to determine the spatiotemporal variations in temperature, light, nutrients (NO-3-N, NO-2-N, NH+4-N, SiO2-3-Si, PO3-4-P), phytoplankton, and primary production in Jiaozhou Bay. The results indicated that only silicate correlated well in time and space with, and had important effects on, the characteristics, dynamic cycles and trends of, primary production in Jiaozhou Bay. The authors developed a corresponding dynamic model of primary production and silicate and water temperature. Eq.(1) of the model shows that the primary production variation is controlled by the nutrient Si and affected by water temp erature; that the main factor controlling the primary production is Si; that water temper ature affects the composition of the structure of phytoplankton assemblage; that the different populations of the phytoplankton assemblage occupy different ecologica l niches for C, the apparent ratio of conversion of silicate in seawater into phytoplankton biomas and D, the coefficient of water temperature's effect on phytoplankton biomass. The authors researched the silicon source of Jiaozhou Bay , the biogeochemical sediment process of the silicon, the phytoplankton predominan t species and the phytoplankton structure. The authors considered silicate a limit ing factor of primary production in Jiaozhou Bay, whose decreasing concentration of silicate from terrestrial source is supposedly due to dilution by current and up take by phytoplankton; quantified the silicate assimilated by phytoplankton, the intrins ic ratio of conversion of silicon into phytoplankton biomass, the proportion of silicate uptaken by phytoplankton and diluted by current; and found that the primary production of the phytoplankton is determined by the quantity of the silicate assimilated by them. The phenomenon of apparently high plant-nutrient concentrations but low phytoplankton biomass in some waters is reasonably explained in this paper.  相似文献   

5.
The phytoplankton reproduction capacity (PRC), as a new concept regarding chlorophyll-a and primary production (PP) is described. PRC is different from PP, carbon assimilation number (CAN) or photosynthetic rate ( P^B ) . PRC quantifies phytoplankton growth with a special consideration of the effect of seawater temperature. Observation data in Jiaozhou Bay, Qingdao, China, collected from May 1991 to February 1994 were used to analyze the horizontal distribution and seasonal variation of the PRC in Jiaozhou Bay in order to determine the characteristics, dynamic cycles and trends of phytoplankton growth in Jiaozhou Bay; and to develop a corresponding dynamic model of seawater temperature vs. PRC. Simulation curves showed that seawater temperature has a dual function of limiting and enhancing PRC. PRC‘s periodicity and fluctuation are similar to those of the seawater temperature. Nutrient silicon in Jiaozhou Bay satisfies phytoplankton growth from June 7 to November 3. When nutrients N, P and Si satisfy the phytoplankton growth and solar irradiation is sufficient, the PRC would reflect the influence of seawater temperature on phytoplankton growth. Moreover, the result quantitatively explains the scenario of one-peak or two-peak phytoplankton reproduction in Jiaozhou Bay, and also quantitatively elucidates the internal mechanism of the one- or two-peak phytoplankton reproduction in the global marine areas.  相似文献   

6.
Sharpies‘ 1-D physical rrozlel maploying tide-wind driven turbulence closure and surface heating-cooling physics, was coupled with an eculogical rnodet with 9-biochemical components: phytoplankton, zooplankton, shellfish, autotmphic and heterotrophic bacterioplankton, dissolved organic carbon (DOC), suspended detritus and sinking particles to simulate the armual evolution of ecosystem in thecentral part of Jiaozhou Bay. The coupled modeling results showed that the phytoplankton shading effectcould reduce seawater temperamre by 2℃, so that photosynthesis efficiency should be less than 8% ; that the loss of phytoplankton by zooplankton grazing in winter tended to be compensated by phytoplankton advection and diffusion from the otrtside of the Bay; that the incidem irradiance intensity could be the mostimportant factor for phytoplankton grcr, wth rate; and that it was the bacterial secondary prnduction that maintained the maximum zooplankton biomass in winter usually observed in the 1990s, indicating that themicrobial food loop was extremely important for ecosystem study of Jiaozhou Bay.  相似文献   

7.
Jiaozhou Bay data collected from May 1991 to February 1994, in 12 seasonal investigations, and provided the authors by the Ecological Station of Jiaozhou Bay, were analyzed to determine the spatiotemporal variations in temperature, light, nutrients (NO3^--N, NO2^--N, NH4^ -N, SIO3^2--Si, PO4^3--P), phytoplankton, and primary production in Jiaozhou Bay. The results indicated that only silicate correlated well in time and space with, and had important effects on, the characteristics, dynamic cycles and trends of, primary production in Jiaozhou Bay. The authors developed a corresponding dynamic model of primary production and silicate and water temperature. Eq. ( 1 ) of the model shows that the primary production variation is controlled by the nutrient Si and affected by water temperature; that the main factor controlling the primary production is Si; that water temperature affects the composition of the structure of phytoplankton assemblage; that the different populations of the phytoplankton assemblage occupy different ecological niches for C, the apparent ratio of conversion of silicate in seawater into phytoplankton biomas and D, the coefficient of water temperature‘s effect on phytoplankton biomass. The authors researched the silicon source of Jiaozhou Bay, the biogeochemical sediment process of the silicon, the phytoplankton predominant species and the phytoplankton structure. The authors considered silicate a limiting factor of primary production in Jiaozhou Bay, whose decreasing concentration of silicate from terrestrial source is supposedly due to dilution by current and uptake by phytoplankton; quantified the silicate assimilated by phytoplankton, the intrinsic ratio of conversion of silicon into phytoplankton biomass, the proportion of silicate uptaken by phytoplankton and diluted by current; and found that the primary production of the phytoplankton is determined by the quantity of the silicate assimilated by them. The phenomenon of apparently high plant-nutrient concentTations but low phytoplankton biomass in some waters is reasonably explained in this paper.  相似文献   

8.
1 INTRODUCTION In a marine area, temporal and special variation in phytoplankton growth is closely related with that of light, water temperature and nutrient. The key study in this paper is how environmental factors in- cluding light, water temperature an…  相似文献   

9.
Analysis and comparison of Jiaozhou Bay data collected from May 1991 to February 1994 revealed the spatiotemporal variations of the ambient Si(OH)4:NO3 (Si:N) concentration rations and the seasonal variations of (Si:N) ratios in Jiaozhou Bay and showed that the Si:N ratios were <1 throughout Jiaozhou Bay in spring, autumn, and winter. These results provide further evidence that silicate limits the growth of phytoplankton (i.e. diatoms) in spring, autumn and winter. Moreover, comparison of the spatiotemporal variations of the Si:N ratio and primary production in Jiaozhou Bay suggested their close relationship. The spatiotemporal pattern of dissolved silicate matched well that of primary production in Jiaozhou Bay. Along with the environmental change of Jiaozhou Bay in the last thirty years, the N and P concentrations tended to rise, whereas Si concentration showed cyclic seasonal variations. With the variation of nutrient Si limiting the primary production in mind, the authors found that the range of values of primary production is divided into three parts: the basic value of Si limited primary production, the extent of Si limited primary production and the critical value of Si limited primary production, which can be calculated for Jiaozhou Bay by Equations (1), (2) and (3), showing that the time of the critical value of Si limitation of phytoplankton growth in Jiaozhou Bay is around November 3 to November 13 in autumn; and that the time of the critical value of Si satisfaction of phytoplankton growth in Jiaozhou Bay is around May 22 to June 7 in spring. Moreover, the calculated critical value of Si satisfactory for phytoplankton growth is 2.15–0.76 μmol/L and the critical value of Si limitation of phytoplankton growth is 1.42–0.36 μmol/L; so that the time period of Si limitation of phytoplankton growth is around November 13 to May 22 in the next year; the time period of Si satisfactory for phytoplankton growth is around June 7 to November 3. This result also explains why critical values of nutrient silicon affect phytoplankton growth in spring and autumn are different in different waters of Jiaozhou Bay and also indicates how the silicate concentration affects the phytoplankton assemblage structure. The dilution of silicate concentration by seawater exchange affects the growth of phytoplankton so that the primary production of phytoplankton declines outside Jiaozhou Bay earlier than inside Jiaozhou Bay by one and half months. This study showed that Jiaozhou Bay phytoplankton badly need silicon and respond very sensitively and rapidly to the variation of silicon. This study was funded by NSFC (No. 40036010) and subsidized by Special Funds from National Key Basic Research Program of P. R. China (G19990437), the Postdoctoral Foundation of Ocean University of Qingdao, the Director's Foundation of the Beihai Monitoring Center of the State Oceanic Administration and the Foundation of Shanghai Fisheries University.  相似文献   

10.
ＩＮＴＲＯＤＵＣＴＩＯＮＮａｎｄＰｉｎｐｕｔｔｅｄｉｎｔｏＪｉａｏｚｈｏｕＢａｙｂｙｒｉｖｅｒｓａｎｄｂｙｓｅｗａｇｅｅｆｆｌｕｅｎｔｓｏｆｃｉｔｉｅｓ ,ｈａｖｅｍａｄｅｔｈｅＢａｙｂｅｃｏｍｅｍｏｒｅａｎｄｍｏｒｅｅｕｔｒｏｐｈｉｃｄａｙｂｙｄａｙ .Ｓｈｅｎ ( 1994)ｔｈｏｕｇｈｔｔｈａｔｐｈｙｔｏｐｌａｎｋｔｏｎｇｒｏｗｔｈｗａｓｌｉｍｉｔｅｄｂｙｔｈｅｃｈａｎｇｅｆｒｏｍｎｉｔｒｏｇｅｎｔｏｐｈｏｓｐｈｏｒｏｕｓ ;ａｎｄｔｈａｔｔｈｅｓｉｌｉｃａｔｅｃｏｎｃｅｎｔｒａｔｉｏｎｉｎＪｉａｏｚｈ…  相似文献   

11.
Analysis and comparison of Jiaozhou Bay data collected from May 1991 to February 1994 (12 seasonal investigations) provided by the Ecological Station of Jiaozhou Bay revealed the characteristic spatiotemporal variation of the ambient concentration Si∶DIN and Si∶16P ratios and the seasonal variation of Jiaozhou Bay Si∶DIN and Si∶16P ratios showing that the Si∶DIN ratios were <1 throughout the year in Jiaozhou Bay; and that the Si∶16P ratios were <1 throughout Jiaozhou Bay in spring, autumn and winter. The results proved that silicate limited phytoplankton growth in spring, autumn and winter in Jiaozhou Bay. Analysis of the Si∶DIN and Si∶P ratios showed that the nutrient Si has been limiting the growth of phytoplankton throughout the year in some Jiaozhou Bay waters; and that the silicate deficiency changed the phytoplankton assemblage structure. Analysis of discontinuous 1962 to 1998 nutrient data showed that there was no N or P limitation of phytoplankton growth in that period. The authors consider that the annual cyclic change of silicate limits phytoplankton growth in spring, autumn and winter every year in Jiaozhou Bay; and that in many Jiaozhou Bay waters where the phytoplankton as the predominant species need a great amount of silicate, analysis of the nutrients N or P limitation of phytoplankton growth relying only on the N and P nutrients and DIN∶P ratio could yield inaccurate conclusions. The results obtained by applying the rules of absolute and relative limitation fully support this view. The authors consider that the main function of nutrient silicon is to regulate and control the mechanism of the phytoplankton growth process in the ecological system in estuaries, bays and the sea. The authors consider that according to the evolution theory of Darwin, continuous environmental pressure gradually changes the phytoplankton assemblage's structure and the physiology of diatoms. Diatoms requiring a great deal of silicon either constantly decrease or reduce their requirement for silicon. This will cause a series of huge changes in the ecosystem so that the whole ecosystem requires continuous renewal, change and balancing. Human beings have to reduce marine pollution and enhance the capacity of continental sources to transport silicon to sustain the continuity and stability in the marine ecosystem. This study was funded by the NSFC (No. 40036010) and subsidized by Special Funds from the National Key Basic Research Program of P. R. China (G199990437), the Postdoctoral Foundation of Ocean University of Qingdao, the Director's Foundation of the Beihai Monitoring Center of the State Oceanic Administration and the Foundation of Shanghai Fisheries University.  相似文献   

12.
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   

13.
Statistical analysis on data collected in the Jiaozhou Bay (Shandong, China) from May 1991 to February 1994 and those collected in Hawaii from March 1958 to December 2007 shows dynamic and cyclic changes in atmospheric carbon in the Northern Pacific Ocean (NPO), as well as the variation in space-time distribution of phytoplankton primary production and atmospheric carbon in the study regions. The study indicates that the human beings have imposed an important impact on the changing trends of the atmospheric carbon. Primary production in the Jiaozhou Bay presents a good example in this regard. In this paper, dynamic models of the atmospheric carbon in the NPO, the cyclic variations in the atmospheric carbon, and primary production in the Jiaozhou Bay are studied with simulation curves presented. A set of equations were established that able to calculate the rate and acceleration of increasing carbon discharged anthropologically into the atmosphere and the conversion rate of phytoplankton to atmospheric carbon. Our calculation shows that the amount of atmospheric carbon absorbed by one unit of primary production in the Jiaozhou Bay is (3.21−9.74)×10−9/(mgC·m−2d−1), and the amount of primary production consumed by a unit of atmospheric carbon is 102.66–311.52 (mgC·m−2d−1/10−6). Therefore, we consider that the variation of atmospheric carbon is a dynamic process controlled by the increase of carbon compound and its cyclic variation, and those from anthropologic discharge, and phytoplankton growth.  相似文献   

14.
A zero-dimensional box model (PNCMjzb) with six state variables (ammonium, nitrate, dissolved organic nitrogen, phytoplankton, zooplankton and detritus) was developed to study nitrogen cycling in the Jiaozhou Bay pelagic ecosystem. The dominant processes within these compartments are considered with nitrogen as flow currency. Phytoplankton and zooplankton are treated as separate state variables, assuming that the species composition was dominated by two or three species the dynamic constants of which are similar and that they represent the entire plankton community. The microbial loop has not been integrated explicitly in the model. The turnover of bacteria is included implicitly in processes such as detritus decomposition, DON remineralization, pelagic nitrification and denitrification. The model is driven by two forcing variables, viz. water temperature and light intensity. Historical data from the1980s and 1990s were compiled and used for model calibration. In this paper (part Ⅰ), the consideration of every main compartment in the model is interpreted in detail. And the applied equations and parameters are presented. The main results from the simulations together with discussion about phytoplankton dynamics and primary production in Jiaozhou Bay are presented in the next paper (part Ⅱ).  相似文献   

15.
浮游植物物候能够反映浮游植物的生长变化与湖泊生态系统的变化,水温、营养盐浓度等因素对物候有重要影响。太湖富营养化程度较高,水温的影响作用日趋显著,物候与水温关系的研究对理解、控制和改善太湖生态系统具有重要意义。本研究利用2003—2018年MODIS遥感数据计算浮游植物物候指标和湖泊水表温度（Temperature of Water Surface,LSWT）,通过分析太湖浮游植物物候时空变化特点探究了不同区域的物候特征,并结合LSWT揭示了浮游植物物候对LSWT变化的响应关系。结果表明：① 不同浮游植物物候指标具有不同空间分布特点,水华发生次数、峰值叶绿素a（Chla）浓度和水华总持续时间呈现由西部沿岸向湖心区递减的趋势;浮游植物生长开始时间和峰值Chla发生时间分布复杂但在沿岸区域相对较早;② 太湖可被划分为4种具有不同物候特征的区域,Ⅰ类区域主要位于贡湖湾、东部沿岸以及太湖中部开阔水域,该区Chla浓度范围为50~60 μg/L,且波动平缓,水华发生次数最少、开始最晚、持续时间最短;Ⅱ类区域主要分布于太湖西部沿岸,Chla浓度范围为50~90 μg/L且变化剧烈,该区水华发生次数最多、开始最早、持续时间最长;Ⅲ和Ⅳ类属于过渡区域,前者主要分布于梅梁湾、竺山湾及入湾口,后者主要位于南部沿岸以及太湖中部;③ 浮游植物物候对LSWT变化的响应受营养水平影响,当营养水平较高时,浮游植物的生长受LSWT的促进作用显著,LSWT年际变化的升高趋势对浮游植生长物候提前、生物量增加的影响明显,反之,则LSWT变化对浮游植物生长的影响减弱。  相似文献   

16.
Biogenic silicate accumulation in sediments, Jiaozhou Bay   总被引：1，自引：0，他引：1  
1 INTRODUCTION Silicate, or silicic acid (H4SiO4), is a very im- portant nutrient in the ocean. Unlike other major nu- trients such as phosphate and nitrate or ammonium, which are needed by almost all marine plankton, silicate is an essential chemical req…  相似文献   

17.
To better understand the spatial-temporal variation in phytoplankton community structure and its controlling factors in Jiaozhou Bay,Qingdao,North China,four seasonal sampling were carried out in 2017.The phytoplankton community structure and various environmental parameters were examined.The phytoplankton community in the bay was composed of mainly diatoms and dinoflagellates,and several other species of Chrysophyta were also observed.Diatoms were the most dominant phytoplankton group throughout the year,except in spring and winter,when Noctiluca scintillans was co-dominant.High Si/N ratios in summer and fall reflect the high dominance of diatoms in the two seasons.Temporally,the phytoplankton cell abundance peaked in summer,due mainly to the high temperatures and nutrient concentrations in summer.Spatially,the phytoplankton cell abundance was higher in the northern part of the bay than in the other parts of the bay in four seasons.The diatom cell abundances show significant positive correlations with the nutrient concentrations,while the dinoflagellate cell abundances show no correlation or a negative correlation with the nutrient concentrations but a significant positive correlation with the stratification index.This discrepancy was mainly due to the different survival strategies between diatoms and dinoflagellates.The Shannon-Wiener diversity index(H')values in the bay ranged from 0.08 to 4.18,which fell in the range reported in historical studies.The distribution pattern of H' values was quite different from that of chlorophyll a,indicating that the phytoplankton community structure might have high biomass with a low diversity index.Compared with historical studies,we believe that the dominant phytoplankton species have been changed in recent years due mainly to the changing environment in the Jiaozhou Bay in recent 30 years.  相似文献   

18.
An environmental capacity model for the petroleum hydrocarbon pollutions (PHs) in Jiaozhou Bay is constructed based on field surveys, mesocosm, and parallel laboratory experiments. Simulated results of PHs seasonal successions in 2003 match the field surveys of Jiaozhou Bay resaonably well with a highest value in July. The Monte Carlo analysis confirms that the variation of PHs concentration significantly correlates with the river input. The water body in the bay is reasonably subjected to self-purification processes, such as volatilization to the atmosphere, biodegradation by microorganism, and transport to the Yellow Sea by water exchange. The environmental capacity of PHs in Jiaozhou Bay is 1500 tons per year IF the seawater quality criterion (Grade Ⅰ/Ⅱ, 0.05 mgL-1) in the region is to be satisfied. The contribution to self-purification by volatilization, biodegradation, and transport to the Yellow Sea accounts for 48%, 28%, and 23%, respectively, which make these three processes the main ways of PHs purification in Jiaozhou Bay.  相似文献   

19.
A one-year field study was conducted to determine the conversion ratio of phytoplankton biomass carbon (Phyto-C) to chlorophyll-a (Chl-a) in Jiaozhou Bay, China. We measured suspended particulate organic carbon (POC) and phytoplankton Chl-a samples collected in surface water monthly from March 2005 to February 2006. The temporal and spatial variations of Chl-a and POC concentrations were observed in the bay. Based on the field measurements, a linear regression model II was used to generate the conversion ratio of Phyto-C to Chl-a. In most cases, a good linear correlation was found between the observed POC and Chl-a concentrations, and the calculated conversion ratios ranged from 26 to 250 with a mean value of 56 μg μg−1. The conversion ratio in the fall was higher than that in the winter and spring months, and had the lowest values in the summer. The ratios also exhibited spatial variations, generally with low values in the near shore regions and relatively high values in offshore waters. Our study suggests that temperature was likely to be the main factor influencing the observed seasonal variations of conversion ratios while nutrient supply and light penetration played important roles in controlling the spatial variations.  相似文献   

20.
Measurements of ammonium and nitrate uptakes by natural phytoplankton assemblages from Jiaozhou Bay at various combinations of ammonium and nitrate concentrations with 15N trace techniques showed that uptake rate of either nitrogen was influenced by the presence of the other but that the influence of ammonium on nitrate uptake was much greater than, that of nitrate on ammonium uptake. The influence mechanism of ammonium on nitrate uptake manifested as competition at lower concentrations and as inhibition at higher concentrations (ammonium concentration >0.6 umol/L), but no total inhibition appeared within the concentration.range of the experiments (0-10umol/L). The influence of nitrate on ammonium uptake seems to be a result of competition for uptake sites on the cell surface. In view of the in situ nutrient concentration in the given marine . environment, it is believed that both nitrogen sources are utilized by phytoplankton. Nitrate uptake in the presence of ammonium and ammonium uptake in the presen  相似文献   

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