温州蜜柑果实发育进程中光合产物运输分配及糖积累特性

测定了温州蜜柑果实发育进程中糖的积累动态,并用14C示踪方法研究了果实发育不同阶段源叶的光合产物在果实中的运输分配特性.结果表明(1)果实组织中的糖含量随果实发育持续上升,果皮以积累己糖为主而其它组织则以积累蔗糖为主或略多.(2)在果实完熟之前,汁囊分配到的光合产物均占果实的50%以上,为果实中的光合产物分配中心;而到完熟阶段分配到汁囊的14C光合产物与其它组织接近,不再有明显的分配中心.(3)汁囊中的14C放射性比活度随着果实发育呈下降趋势,尤其在后期下降极为明显.(4)维管束/囊瓣表皮和囊瓣表皮/汁囊的14C放射性比活度的比率都随果实发育进程而增大,但后者的比率要大大高于前者,表明韧皮部后运输是光合产物进入汁囊的限速阶段.(5)输入到汁囊的14C光合产物主要以蔗糖形式存在,说明光合产物是以蔗糖为主体输入汁囊参与糖积累和代谢的.     

A study of spatial and temporal variability in the adenine nucleotides of lake phytoplankton during a diel cycle (Lac Pavin — France)

A study of diel variations in the adenine nucleotide concentrations of natural phytoplanktonic populations led to the following conclusions:There are significant diel variations in cellular ATP concentrations. However, this temporal variability is not as great as the spatial variability between the various sampling depths, characterized by different phytoplankton populations. Within a globally stable pool of adenine nucleotides, diel variations inside the algal cell mainly take place at the expense of ATP and AMP, while ADP concentrations remain relatively stable.The statistical relationship between algal biomass obtained from cell counts and from adenine nucleotides also confirms maximum stability for ADP and (ATP + ADP + AMP). The diel variations in adenine nucleotide cell concentrations gradually become smaller with depth. This probably reflects the importance of light in causing such variability.     

Variabilités verticale et temporelle des acides gras d'un phytoplancton lacustre au cours d'un cycle nycthéméral

Vertical and temporal variability in the content and composition of fatty acids in the lake phytoplankton were studied during a diel cycle (48 h). There is temporal variability in total fatty acid (FA) content per biomass unit but it is not strictly diurnal. In contrast, polyunsaturated FA with 20–22 C chains and unsaturated FA/ saturated FA ratio are higher during the day than during the night.The temporal variability was not as great as the variability is between sampling depths characterized by different phytoplankton assemblages. Phytoplankton composition and physiological state were the principal factors affecting FA composition. Thus, a C16:1w7/C18:1w9 ratio distinguishes between diatoms, with a high level of C16 unsaturated FA, and dinoflagellates with C18 unsaturated FA. This ratio was different at the surface and at 20 m depth, where the phytoplankton had the same taxonomic composition but a different physiological activity.

     

Diel changes in dark respiration in a plankton community

The dark respiration of a natural plankton community from an eutrophic lake was studied in a laboratory scale enclosure (LSE), exposed to illumination which simulated natural light conditions in the water column. The dark respiration was measured continuously for 2 hours in samples obtained from the LSE each hour for 26 hours. The relationships between dark respiration rates, carbohydrate concentrations and other parameters were investigated.The dark respiration rate showed an exponential decrease with time in the dark in all light period incubations with a time coefficient of 0.3 h^–1. The decrease in respiration rate in the dark period was much slower, reaching an approximately constant level at the end of the night. The overall dark period decline in respiration rate also exhibited an exponential pattern, but with a much lower time coefficient (0.04 h ^–1) than for the light period incubations. A linear relationship was found between dark respiration rate and carbohydrate concentration at night time but no relationship was apparent during the day. A comparison between these data and data from the literature show that this pattern of dark respiration rate decrease with time in the dark may have some general applications for dense phytoplankton communities.     

Diel periodicity in phytoplankton productivity

Daily variation in phytoplankton productivity influences the dynamics and linkages between several large scale processes in aquatic ecosystems. As part of an opening address to the 5th International workshop for the Group for Aquatic Productivity (GAP), the daily patterns of variability in photosynthesis for different algal classes was introduced and accompanied by a discussion of the sources of environmental and endogenous regulation of repeating biological oscillations that occur in phytoplankton on timescales of one day. It is suggested that one way to develop a database that serves to sort and predict phytoplankton variability over the day may be to encourage the creation of a temporal library. Such a library would be comprised of temporally fixed maps of circadian clock-controlled rhythms for individual species, as well as temporally variable maps of diel periodicities that only can be defined for a selected set of environmental conditions.     

Phytoplankton succession in Lake Valencia,Venezuela

Phytoplankton counts and supporting physical and chemical data were taken on Lake Valencia, Venezuela, over a five-year interval. The data are used to test the validity of a successional paradigm for class-level taxa. According to the paradigm, formulated from previous studies of Lake Lanao, Philippines, and from data on temperate lakes, the order of taxa from early to late succession is: diatoms, chlorophytes, blue-green algae, dinoflagellates. A successional episode is considered to begin when stability of a water column is restored after deep mixing. As the episode progresses, there is a steady decrease in concentration of the limiting macronutrient (in this case, N). In a test of the validity of the paradigm for Lake Valencia, dates of exceptional population increase or decrease were obtained for each taxon. Since nitrate concentration declines steadily as succession progresses, the entry of a given taxon into the successional sequence is indicated quantitatively by the mean nitrate concentration on dates of exceptional increase in population density, and exit from the successional sequence is indicated by mean nitrate concentration on dates of exceptional population declines. The successional position of each major taxon, bounded by its entry and exit in the sequence, can be mapped on the complete spectrum of nitrate concentrations observed in the lake. For Lake Valencia, the nitrate mapping procedure agrees exactly with the predictions based on the successional paradigm. Conformance of Lake Valencia phytoplankton with predictions made a priori suggests that there is a generalized pattern in the phytoplankton succession of the mixed layers of temperate and tropical lakes.     

Phytoplankton production and growth rate in Lake Tanganyika: evidence of a decline in primary productivity in recent decades

1. This study focused on phytoplankton production in Lake Tanganyika. We provide new estimates of daily and annual primary production, as well as growth rates of phytoplankton, and we compare them with values published in former studies.
2. Chlorophyll- a (chl- a ) in the mixed layer ranged from 5 to 120 mg chl- a  m⁻² and varied significantly between rainy and dry seasons. Particulate organic carbon concentrations were significantly higher in the south basin (with 196 and 166 mg C m⁻³ in the dry and the rainy season, respectively) than in the north basin (112 and 109 mg C m⁻³, respectively).
3. Carbon : phosphorus (C : P) ratios varied according to season. Phosphorus limitation seemed to occur more frequently than nitrogen limitation, especially during the rainy season. Severe P deficiencies were rare.
4. Measured particulate daily primary production ranged from 110 to 1410 mg C m⁻² day⁻¹; seasonal contrasts were well marked in the north basin, but less in the south basin, where primary production peaks occurred also in the rainy season. Estimates of annual primary production, based on daily primary production calculated from chl- a and water transparency, gave values lower than those reported in previous studies. Picophytoplankton accounted on average for 56% of total particulate production in the south basin during the wet season of 2003.
5. Phytoplankton growth rates, calculated from primary production, ranged from 0.055 to 0.282 day⁻¹; these are lower than previously published values for Lake Tanganyika.     

Diel migration and vertical distribution of Cladocera in Lake D. Helvecio (Minas Gerais,Brazil)

Six genera of Clad ocera (Diaphanosoma, Daphnia, Ceriodaphnia, Moina, Bosmina, Bosminopsis), each of them usually with only one species were found in Lake D. Helvecio, a natural valley lake located in the eastern part of Brazil. Diurnal migratory movements of the organisms observed in this lake showed a different pattern in different species. Closely related species, which explore the same food source, live in different layers, thus avoiding interspecific competition. The migratory behaviour of the species was studied mainly in relation to temperature and oxygen distribution in the lake. Thus, analyses were made in the summer (January, 1978) when a strong stratification occurs with the establishment of a thermocline and an oxycline. Comparisons were made also with the data obtained in winter (July, 1978), when a complete mixing of water occurs.     

Diel changes in the biochemical composition of the particulate matter coupled with several parameters in the hypereutrophic Villerest reservoir (Roanne,France)

The diel changes of the biochemical composition of particulate matter was studied in Villerest reservoir (located on the Loire river, near the city of Roanne, France) during July 92. Several biomass and metabolic indicators (proteins, carbohydrates, lipids, chlorophyll a and primary production) were assessed bihourly over 2 days.Since the P/C is largely recognized as a good integrator of the metabolic functions of the cells, we examined its distribution pattern concomitantly with aforementioned parameters. The results demonstrated enhanced P/C ratios clearly indicating that nutrients were sufficiently available for growth. In addition, this index showed a diel significant variation with levels higher in the night than in the day. Moreover, these results suggest that phytoplankton species during the night used the day-synthesized carbohydrates to insure the cell metabolic functioning.     

Field and Laboratory Studies on Nile Phytoplankton in Egypt IV. Phytoplankton of Aswan High Dam Lake (Lake Nasser)

Seasonal, local and monthly vertical variations in chlorophyll a concentration and in qualitative and quantitative counts in Aswan High Dam Lake (AHDL) phytoplankton were followed from March 1982 to February 1984. The chlorophyll a values correlated more or less with the total phytoplankton counts. Total algal counts exhibited considerable local variations in the different seasons and tended to decrease in the most southern part of AHDL, especially during the flood period. The temporal course of algal development showed an almost inverse trend to that of dissolved nitrate-nitrogen. The possibility of nitrogen limitation of algal growth was verified. Diatoms and blue-green algae alternated in the dominance of the phytoplankton community. The genera Cyclotella and Anabaenopsis respectively were the most predominant genera among the diatoms and blue-greens and consequently in the phytoplankton community.     

淀山湖浮游植物群落特征及其演替规律

为探明淀山湖浮游植物群落结构演变与富营养化之间的关系,于2004-2006年对上海市最大天然淡水湖泊淀山湖的浮游植物进行逐月采样调查,分析其群落结构特征.共采集到淀山湖浮游植物84属205种,主要由绿藻(种类数占50%)、硅藻(20%)、蓝藻(13%)、裸藻(13%)等组成.相邻两月之间种类相似性系数呈现冬春季高、夏秋季低的趋势:优势种为银灰平裂藻(Merismopedia glauca)、小席藻(Phormidium tenus)、铜绿微囊藻(Microcystis aeruginosa)、具缘微囊藻(M.marginata)、湖泊鞘丝藻(Lyngbya limnetica)、微小色球藻(Chroococcus minutus),颗粒直链藻最窄变种(Melosira granulata var.angustissima )、啮蚀隐藻(Cryptomonas erosa)、小球藻(Chlorella vulgate)和四尾栅藻(Scenedesmus quadricauda)等.浮游植物群落细胞数量主要由蓝藻(42.73%)、绿藻(37.75%)、硅藻(12.67%)和隐藻(6.06%)组成;生物量主要由硅藻(36.75%)、蓝藻(16.78%)、绿藻(16.36%)和隐藻03.53%)等组成.淀山湖浮游植物群落结构季节演替模式不同于PEG(Plankton Ecology Group)模型,其中蓝藻从春末开始大量出现,夏季大量繁殖,一直延续到秋初.综合文献资料看出,淀山湖浮游植物群落已从1959年的硅藻一金藻型、1987-1988年的隐藻-硅藻型演变为2004-2006年的蓝藻-绿藻型;数量由1959年的103 ind./L上升至2004-2006年的1.11×107 cells/L.演替的总体趋势表现为:贫中营养型的金藻、甲藻比例下降,富营养型的蓝藻、隐藻和微型绿藻增加.浮游植物数量和群落结构的演变指示了淀山湖水体的富营养化进程.     

Diel changes in the alkaline phosphatase activity of bacteria and phytoplankton in the hypereutrophic Villerest reservoir (Roanne,France)

The diel changes of the size fractioned alkaline phosphatase activity (APA) were studied in relation to several abiotic and biotic factors in Villerest reservoir (located on the Loire river, near the city of Roanne, France), bihourly during two days in July 1992. The APA measured in this work exceeded considerably those reported in the literature, suggesting that dissolved mineral phosphorus was not available to microorganisms. At 1 m, the APA was primarily due to bacteria which actively assimilated organic P compounds released by photosynthetic algal metabolism. At 5, 10 and 20 m, the APA was predominantly algal. The high concentrations in SRP (soluble reactive phosphorus) would indicate that orthophosphates were not bioavailable. The reverse (i. e availability to phytoplankton) would have resulted in undetectable levels of P-PO_inf4^sup3–due to the massive proliferation of algae in Villerest reservoir.     

A Comparison of Phytoplankton and Algae Growing on Plexiglas Slides in an Oligotrophic Lake

This study compares the composition and dynamics of phytoplankton communities and of periphyton communities growing on Plexiglas slides in a temperate oligotrophic lake. Ordination methods were used in the comparisons, which covered a three-month period during the summer. Plankton and periphyton communities differed considerably, and shared only six common taxa. An ephemeral Dinobryon pulse occurred simultaneously in both communities, and represented the largest source of variability in community composition. Recovery from the pulse was faster in the phytoplankton than in the periphyton. Attachment to substrata, through its effect on cell turnover times and nutrient cycling, is hypothesized to provide a temporal refuge for plankton species during periods of unfavorable environmental conditions.     

Short-term variability of chlorophyll a concentrations in Lake Ontario

Research on aquatic ecosystems has shown the presence of diel (24 hour) variations of chlorophylla. In order to investigate this phenomenon in the Great Lakes, an IFYGL program was set up in which 8 cruises were made roughly monthly between April and October 1972. Two Lake Ontario Stations were chosen, one inshore near Oshawa, Ontario and the other mid-lake. Chlorophylla samples were taken approximately every two hours at depths of 1, 5 and 1o m at the inshore station and 1, 10 and 20 m at the mid-lake station.Chlorophylla concentrations at the 1 m depth were reduced during periods of high light intensities, but this phenomenon was observed only during the late June and July cruises at the near-shore station. Apparently, during most cruises, light intensities were too low to produce this effect. Coefficients of variation of chlorophylla concentrations as great as too% occurred at the deeper sampling depth during periods when the thermocline was well developed. This variability was associated with a thermocline motion in which the fixed depths sampled moved from the epilimnion into the thermocline or the hypolimnion and back again over the sampling period. When the lake was not thermally stratified, variability of chlorophylla concentrations was also observed with coefficients of variations between 20–3o%. Horizontal advection by currents, vertical turbulence, and presence of Langmuir cells were possible mechanisms causing such chlorophylla variability.In light of these observations, caution must be used in interpreting spatial and temporal distributions of chlorophylla in lakes. Special care must be taken when sampling at depths near the thermocline due to movements that take place. For this reason, water samples taken from the epilimnion during periods of thermal stratification are recommended as opposed to fixed depth or integrated samples which could be affected by thermocline movements.This study was undertaken as part of the International Field Year for the Great Lakes, a joint Canadian-U.S. contribution to the International Hydrological Decade Program     

Interrelation of Diel and Seasonal Change,Involving Summer Thermal Stratification,Weather Variables and a Mobile Dinoflagellate in a Productive English Lake

A 2-year study was made, using continuous recording, of changes in thermal structure in the upper layer of an English lake during summer stratification. Diel, seasonal and irregular episodic events are related to weather variables. Marked diel change of temperature, with short-term stratification, is associated with high daily input of solar radiation and low daily wind-run. There is further correlation, probably mostly secondary, with high daily maximum air temperature. The diel cycles may be largely repetitive in appropriate weather episodes, or show progressive modification that can, by vertical heat transfer, extend the more persistent seasonal metalimnion and thermocline. Occasional inverse stratification can occur, especially around dawn, with an indication of subsequent penetrative convection. Examples are given in which regular diel patterns of thermal stratification are modified by increased wind stress, including the development of temperature oscillations. Such modification can disperse higher depth-maxima of the dinoflagellate Ceratium, that are capable of later re-formation. Metalimnetic maxima of Ceratium are more persistent.     

Seasonal Periodicity in Lacustrine Phytoplankton and the Theory of Ecological Succession

An attempt has been made to examine the extent to which seasonal periodicity of lacustrine phytoplankton corresponds to the general concepts of the theory of ecological succession. The study was carried out on an eutrophic lake (Aydat, France). As REYNOLDS (1980, 1984) suggests, the seasonal periodicity of phytoplankton is an autogenic succession which may be perturbed by allogenic physical processes that change the initial direction of the succession. Thus, in this lake, only spring succession of phytoplankton can be considered as a true succession, consistent with the theory of ecological succession in that it was a directional and predictable phenomenon leading to an increasing complexity of community.     

Seasonal Distribution of Phytoplankton in Yellowknife Bay,Great Slave Lake

The factors influencing the seasonal distribution of phytoplankton were determined between July 1975 and December 1977 in Yellowknife Bay, Great Slave Lake. The initiation of the spring bloom occurred during April of each year in response to changing light conditions and despite the 0 °C water temperatures. Although the plankton showed some fluctuations in density (100–400 mg/m³) during the summer, there was no vernal decrease in the size of the populations. The end of the growing season was characterized by a sharp drop in numbers near the end of October. Multiple regression analysis indicated that changes in the standing crop of the plankton during the summer were primarily related to temperature (r = 0.60) and the concentrations of NO₃–N (r=–0.74) and SiO₂ (r=–0.82). Changing light conditions probably had little effect on the population during the growing season. Chlamydomonas lapponica was dominant during April of each year. While the growth of this species caused a reduction in the concentrations of total phosphorus and NO₃–N, the level of SiO₂ remained constant and consequently diatoms (Asterionella formosa, Stephanodiscus astraea, Diatoma tenue var. elongatum and Melosira islandica) waxed rapidly during May. By the first of June, nutrient concentrations were low, thereby permitting the development of Dinobryon bavaricum and Dinobryon cylindricum. The extremely rapid decrease in the densities of common species during the fall was probably due to the rapid decline in temperature and light levels and the formation of ice on the bay.     

The Effects of Sampling Intervals on Phytoplankton Growth and Loss Values Derived from Seasonal Phytoplankton Biomass Variations in an Artificial Lake

Detailed vertical phytoplankton sample series with a good resolution were taken every 3–4 days for almost two years from the artificial Lake Saidenbach. The intervals between samplings were systematically increased by regularly “ignoring” certain samples so that six different annual curves based on different sampling frequencies were obtained to describe phytoplankton variations in the course of the year from a single time series. In this way it was possible to study the effect of the interval between samplings on the results of phytoplankton studies and on the rates of change and turnover calculated from the biomass. The results show that the maximum rates of change and turnover values yielded by half-weekly samplings are some 20–30% higher than those yielded by weekly samplings. Sampling intervals smaller than 3–4 days yield not much increased rates of change and turnovers. This implies that short term changes in the phytoplankton are more accurately detected by half-weekly samplings. It is therefore suggested that, depending on the nature and objectives of the investigations, sampling intervals of 3–4 weeks are sufficient for the winter, but during the growth period (spring to autumn) samples should be taken at least once a week or fortnightly.     

柑橘果实的光合特性、产物运输及分配在糖分积累中的作用

测定了温州蜜柑 (CitrusunshiuMarc .cv .Miyagawawase)果实发育进程中干鲜重、果皮光合速率和叶绿素含量的变化 ,并用14 CO2 示踪技术研究了果皮和叶同化生成的光合产物在果实内的运输分配特性。结果表明 :果皮光合速率与叶绿素含量有关 ,随着叶绿素含量的下降 ,果实光合速率也快速下降。在果实完熟之前 ,即使是当果皮积累的干重超过汁囊时 ,叶同化产物仍主要分配到汁囊中 ;而在完熟阶段 ,果皮光合速率接近零 ,果皮成了叶同化产物的主要库。果皮的同化产物 ,主要保留在果皮中 ,输入到汁囊的比率随果实发育而下降 ,但高峰时也有 12 %输入汁囊。与对照相比 ,果实遮光处理后降低了果皮与汁囊的干重和含糖量。上述结果表明果皮光合产物主要用于果皮自身的发育并能减少对叶光合产物的依赖 ,同时也能部分增加汁囊糖的积累     

Changes in the phytoplankton of Lake Trummen induced by restoration

Lake Trummen, previously an oligotrophic lake, was heavily polluted during 1930–1957. The lake was restored by suction dredging of the top sediment layer. After restoration nutrien concentrations and phytoplankton biomass were drastically reduced. Eutrophic species disappeared and more oligotrophic species returned to the lake. The investigation covers 12 years-monthly-bimonthly countings of algae together with electronmicroscopical studies of taxonomically difficult taxa. The investigation was made at the species level (300 species identified and 80 quantitatively recorded).