海洋中的凝集网与透明胞外聚合颗粒物

透明胞外聚合颗粒物(TEP)是海洋中大量存在的能被爱尔新蓝(alcian blue)染色的由酸性多糖组成的透明胶状颗粒物,主要来源于浮游植物,由于其透明的特性而被长期忽视。TEP同时具有胶体和颗粒物的特性。作为胶体,TEP为细菌提供了栖息场所与降解基质,同时TEP可以吸收痕量元素,以改变这些元素的生物地球化学过程。作为颗粒物,TEP可以聚集并沉降,由于其高的碳含量,会在很大程度上影响海洋的碳通量。由于TEP可以被中型浮游动物所摄食,所以TEP可以连接并缩短微食物环和经典食物链,在海洋生态系统中起很重要的作用。介绍了TEP的定义、测量方法、来源、形成、及其与浮游植物的关系和其生态功能。     

Biogenic particles and nano/picoplankton in water masses over the Scotia-Weddell Sea Confluence,Antarctica

Summary We studied the particle composition in the ocean surface layer (20–100 m), in terms of non-living versus living particles (< 20 m), along a transect over the Scotia Sea/Weddell Sea transition. The data are related to characteristics of the phytoplankton community and used in a Principal Component Analysis to differentiate between water masses. There was a striking change in particle community characteristics from Scotia Sea to Weddell Sea waters, especially clear at shallow depths (20 m). Total particle concentration decreased greatly moving south over the Confluence but the proportion of living particles increased enormously. This paralleled a change in the composition of the phytoplankton community, from a bloom to a regenerating system, with a striking reduction in the prominence of non-living particles. Densities of auto- and heterotrophic nanoflagellates and bacteria reached maximal values towards the southern end of the transect (8.0 × 10³cm^–3,4.6 × 10³cm^–3,1.0 × 10⁶cm^–3). The PCA based on particle characteristics and chlorophyll a, POC and PON values, distinguished Scotia from Weddell Sea waters and separated shallow from deeper stations.Data presented here were collected during the European Polarstern Study (EPOS) sponsored by the European Science Foundation     

Flow cytometry: instrumentation and application in phytoplankton research

In flow cytometry, light scattering and fluorescence of individual particles in suspension is measured at high speed. When applied to planktonic particles, the light scattering and (auto-)fluorescence properties of algal cells can be used for cell identification and counting. Analysis of the wide size spectrum of phytoplankton species, generally present in eutrophic inland and coastal waters, requires flow cytometers specially designed for this purpose. This paper compares the performance in phytoplankton research of a commercial flow cytometer to a purpose built instrument. It reports on the identification of phytoplankton and indicates an area where flow cytometry may supersede more conventional techniques: the analysis of morphological and physiological characteristics of subpopulations in phytoplankton samples.     

Effects of phytoplankton species composition on absorption spectra and modeled hyperspectral reflectance

Understanding the spectral characteristics of remotely-sensed reflectance by different phytoplankton species can assist in the development of algorithms to identify various algal groups using satellite ocean color remote sensing. One of the main challenges is to separate the effect of species composition on the reflectance spectrum from other factors such as pigment concentration and particle size structure. Measuring the absorption spectra of nine different cultured algae, and estimating the reflectance of the different species, provides a useful approach to study the effects of species composition on the bio-optical properties. The results show that the absorption spectra of different species exhibit different spectral characteristics and that species composition can significantly change the absorption characteristics at four main peaks (438, 536, 600 and 650 nm). A ‘distance angle index’ was used to compare different phytoplankton species. Results indicate that this index can be used to identify species from the absorption spectra, using a database of standard absorption spectra of known species as reference. By taking into account the role of species composition in the phytoplankton absorption model, the performance of the model can be improved by up to 5%. A reflectance-species model is developed to estimate the remotely-sensed reflectance from the absorption spectra, and the reflectance of different phytoplankton species at the same chlorophyll-a concentration is compared, to understand effects of species composition on the reflectance spectra. Different phytoplankton species can cause up to 33% difference in the modeled reflectance at short wavelengths under the condition of the same chlorophyll-a concentration, and variations in the reflectance spectrum correspond to the colors of the algae. The standard deviation of the reflectance among different species shows that the variations from 400 to 450 nm are sensitive to species composition at low chlorophyll-a concentrations, whereas variations in the 510 to 550 nm range are more sensitive under high chlorophyll-a concentrations. For this reason, the green bands may be more suitable for estimating species composition from hyperspectral satellite data during bloom conditions, whereas the blue bands may be more helpful in detection of species under low chlorophyll-a concentrations. In this theoretical approach, variations in reflectance at the same chlorophyll-a concentration can be used to identify phytoplankton species. Another approach to identify phytoplankton species from remotely-sensed hyperspectral reflectance measurements would be to derive the absorption spectra of phytoplankton from the reflectance measurements, and compare these with a standard database of absorption spectra.     

A comparison of different methods used for the quantitative evaluation of biomass of freshwater phytoplankton

Although in a strict sense the term phytoplankton biomass only refers to living algal material, in aquatic ecology the term has been associated with a variety of biological and biochemical procedures used to quantify the particulate matter suspended in natural waters. Relative merits of different biomass characteristics have been studied in three Dutch freshwater lakes with great differences in absolute biomass. Parallel determinations have been made of seston dry weight and supplementary elementary and caloric analyses of seston, of chlorophyll-a concentration and supplementary paper chromatographic analyses of pigment extracts, of particle concentration and particle size distribution as studied with an electronic particle counter, and of phytoplankton cell volume as calculated from the results of microscopic enumeration and sizing of algae. In this way an attempt was made to create a detailed picture of the nature of the seston of the three freshwater lakes.Different analytical techniques give strikingly different information, the accuracy of any method is largely dependent on the circumstances present, and different biomass characteristics therefore are only of value in limited spheres. It is suggested to distinguish between total seston characteristics (e.g. seston dry weight, particulate organic carbon, total particle volume) and strictly algological biomass characteristics (e.g. chlorophyll-a concentration, phytoplankton cell volume). The pattern of growth of phytoplankton populations shown by e.g. chlorophyll-a concentration may differ markedly from that indicated by e.g. total particle volume or seston dry weight. Also, to more or less extent the wax and wane of phytoplankton populations may go undetected among the total seston. Apparently, there is no one method of estimating biomass and no conversion factor that may serve for general purposes. In general, unambiguous information on the nature of the seston of natural waters may only be obtained by estimating total seston characteristics and algological biomass characteristics simultaneously. Depending on the objective of the investigation supplementary component analyses should be carried out to guarantee the correct interpretation of the results.     

A study of absorption characteristics of chromophoric dissolved organic matter and particles in Lake Taihu,China

Absorptions by non-phytoplankton particles and phytoplankton, and chromophoric dissolved organic matter (CDOM) were measured at 50 sites in large, shallow, Lake Taihu in winter and summer 2006 to study their seasonal and spatial variations, and their relative contributions to total absorption. The CDOM absorption was significantly higher in winter than in summer, due to degradation and release of fixed carbon in phytoplankton and submerged aquatic vegetation (SAV). The hyperbolic model was used to model the spectral absorption of CDOM, and the mean spectral slope of 6.38 nm⁻¹ was obtained. At most sites, the spectral absorption of non-phytoplankton particles was similar to that of the total particles, demonstrating that the absorption of the total particles is dominated by the absorption of non-phytoplankton particles. In summer, phytoplankton absorption increased markedly, due to frequent algal blooms especially in Meiliang Bay. In winter, the significant increase in non-phytoplankton particle absorption resulted from the increase of inorganic particulate matter caused by sediment resuspension. Strong linear relationships were found between a _d(440) and total suspended matter (TSM), organic suspended matter (OSM), and inorganic suspended matter (ISM). Strong linear relationships were also found between a _ph(440), a _ph(675) and chlorophyll a (Chl-a) concentration. The total relative contributions of non-phytoplankton particles over the range of photosynthetically active radiation (PAR) (400–700 nm) were 48.4 and 79.9% in summer and winter respectively. Non-phytoplankton particle absorption dominated the total absorption, especially in winter, in Lake Taihu, due to frequent sediment resuspension in the large shallow lake as a result of strong windy conditions. The results indicate that strong absorption by CDOM and non-phytoplankton particles at the blue wavelength has an impact on the spectral availability, and acts as a selection factor for the composition of the phytoplankton community, with cyanobacteria being the dominate species in Lake Taihu. Handling editor: L. Naselli-Flores     

Optical plankton analyser: a flow cytometer for plankton analysis, II: Specifications

An analysing flow cytometer, the optical plankton analyser (OPA), is presented. The instrument is designed for phytoplankton analysis, having a sensitivity comparable with commercially available flow cytometers, but a significantly extended particle size range. Particles of 500 microns in width and over 1,000 microns in length can be analysed. Sample flow rates of up to 55 microliters/s can be used. Also, the dynamic range of the instrument is significantly increased for particles larger than about 5 microns. The optics, hydraulics, and electronics of the instrument are described, including the best form for a low fluid shear cuvette. The new pulse quantification technique we call digital integration is presented. This technique is essential for the instrument to handle both short and very long particles with a large dynamic range. Test measurements demonstrating particle size range and dynamic range are presented. Dynamic ranges of 10,000 and 100,000 were typically observed, measuring field samples with Microcystis aeruginosa colonies, whereas one sample showed a dynamic range of 10(6). A simple method for interpretation of time of flight (TOF) data in terms of particle morphology is presented. The specifications of the instrument are given.     

Change in the concentrations of iron in different size fractions during a phytoplankton bloom in controlled ecosystem enclosures

To observe micronutrient dynamics in the plankton ecosystem, controlled ecosystem enclosure (CEE) experiments were conducted in Saanich Inlet, B.C., Canada. Two CEEs (2.5 m in diameter, 16 m in length, one for Fe studies and the other for biological studies) were launched for the period 22 July to 5 August 1996 and enriched with 10 μM nitrate and 5.2 nM Fe (13% of total Fe) on day 1. Sampling from three integrated depths, intervals 0-4, 4-8 and 8-12 m, was performed on days 0, 1, 2, 3, 4, 5, 7, 9 and 11. Iron concentrations were measured for five size fractions: >25 μm particles, 2-25 μm particles, 0.2-2 μm particles, 0.2 μm-200 kDa small colloidal particles and <200 kDa soluble species. The sediment in the Fe enclosure was also collected on every sampling day after day 2 and its Fe was determined. Size-fractionated particulate organic carbon and total chlorophyll-a were also analyzed.The Fe in small colloidal particles (200 kDa-0.2 μm) comprised 78% of the traditionally defined dissolved phase (<0.2 μm) on day 1. Of all the size fractions of Fe, the small colloidal particulate fraction decreased most significantly during the phytoplankton bloom. In the dissolved fraction (<0.2 μm), the small colloidal particle fraction comprised 79% of the decrease. The decrease in concentration of Fe in small colloidal particles was larger than that of total Fe from day 1 to day 4. In contrast, the >25 μm Fe particles increased over the same period. These results suggest that Fe in small colloidal particles changed to >25 μm Fe particles during phytoplankton growth. A large amount of Fe was kept in the surface layer with the phytoplankton, and transported to the deep layer by phytoplankton sedimentation, at the end of the bloom. From these results, the small colloidal particulate Fe seems to be the most dynamic size fraction and a high percentage of Fe in small colloidal particles changed to large particles due to chemical/physical aggregation and/or physical adsorption to suspended particles such as phytoplankton cells.     

Generation of equally sized particle plaques using solid-liquid suspensions

A device is presented for the generation of equally sized plaques of sensitive particles in a 96-well format. The resulting particle plaques can be used for the measurement of adsorption isotherms and uptake kinetics in protein chromatography or for immobilization reactions. The particle plaques are formed from suspensions with a vacuum device that is designed as a reusable sandwich module. The particles are retained by a mesh while the solvent is removed by the vacuum. As most particles used for protein chromatography are sensitive to mechanical stress and dehydration, the vacuum device is gentle enough to allow the use of these particles, thus eliminating the uncertainty of slurry preparation and pipetting. Apparatus characteristics and preparation procedures are described precisely. The physical intactness of the particles after the preparation procedure is proved by microscopic analysis. Data on the uniformity of the obtained resin plaques with respect to the reproducibility of their adsorption performance is given. Finally, adsorption isothermal and kinetic data of BSA on an ordinary HIC system obtained by high-throughput measurements are shown as an application example.     

Residence time and exposure time of sinking phytoplankton in the euphotic layer

The residence time of a sinking particle in the euphotic layer is usually defined as the time taken by this particle to reach for the first time the bottom of the euphotic layer. According to this definition, the concept of residence time does not take into account the fact that many cells leaving the euphotic layer at some time can re-enter the euphotic layer at a later time. Therefore, the exposure time in the surface layer, i.e. the total time spent by the particles in the euphotic layer irrespective of their possible excursions outside the surface layer, is a more relevant concept to diagnose the effect of diffusion on the survival of phytoplankton cells sinking through the water column.While increasing the diffusion coefficient can induce both a decrease or an increase of the residence time, the exposure time in the euphotic layer increases monotonically with the diffusion coefficient, at least when the settling velocity does not increase with depth. Turbulence is therefore shown to increase the total time spent by phytoplankton cells in the euphotic layer.The generalization of the concept of exposure time to take into account the variations of the light intensity with depth or the functional response of phytoplankton cells to irradiance leads to the definition of the concepts of light exposure and effective light exposure. The former provides a measure of the total light energy received by the cells during their cycling through the water column while the latter diagnose the potential growth rate.The exposure time, the light exposure and the effective light exposure can all be computed as the solution of a differential problem that generalizes the adjoint approach introduced by Delhez et al. (2004) for the residence time. A general analytical solution of the 1D steady-state version of this equation is derived from which the properties of the different diagnostic tools can be obtained.     

The role of phytoplankton in the removal of arsenic by sedimentation from surface waters

The role of phytoplankton in the removal of arsenic (As) by particle adsorption and sedimentation was investigated in Moira Lake, Canada. Sampling water and suspended particles over one year illustrated significant variation in As partitioning between particulate and aqueous phases, but failed to establish a correlation between the partition coefficient, K _d, and indicators of phytoplankton biomass. A highly significant inverse logarithmic relationship was noted between K _d and the concentration of suspended particles (log K _d = 5.1 – 1.4 log SS; p = 0.0001) in an apparent demonstration of the particle concentration effect (O' Connor & Connolly, 1980).Particle deposition, measured by means of sediment traps, appeared to include a substantial component of resuspended surficial sediment making sediment trap results unreliable for quantifying the removal of substances from the water column. The As concentration of particles from deep traps deployed during late summer and early fall exceeded the As concentrations of suspended particles and surficial sediment, and may indicate that a highly contaminated nepheloid layer acts as a temporary sink for As.     

Magnetic particle motions within living cells. Physical theory and techniques.

Body tissues are not ferromagnetic, but ferromagnetic particles can be present as contaminants or as probes in the lungs and in other organs. The magnetic domains of these particles can be aligned by momentary application of an external magnetic field; the magnitude and time course of the resultant remanent field depend on the quantity of magnetic material and the degree of particle motion. The interpretation of magnetometric data requires an understanding of particle magnetization, agglomeration, random motion, and both rotation and translation in response to magnetic fields. We present physical principles relevant to magnetometry and suggest models for intracellular particle motion driven by thermal, elastic, or cellular forces. The design principles of instrumentation for magnetizing intracellular particles and for detecting weak remanent magnetic fields are described. Such magnetic measurements can be used for noninvasive studies of particle clearance from the body or of particle motion within body tissues and cells. Assumptions inherent to this experimental approach and possible sources of artifact are considered and evaluated.     

Abundance, size distribution and bacterial colonization of transparent exopolymeric particles (TEP) during spring in the Kattegat

The abundance, size distribution and bacterial colonizationof transparent exopolymeric particles (TEP) were monitored inthe Kattegat (Denmark) at weekly intervals throughout the spring(February-May) encompassing the spring diatom bloom. These recentlydiscovered particles are believed to be formed from colloidalorganic material exuded by phytoplankton and bacteria, and mayhave significant implications for pelagic flux processes. Duringthis study, the number concentration of TEP (>1 µm)ranged from 3 x 10³ to 6 x 10⁴ ml^–1 and the volume concentrationbetween 0.3 and 9.0 p.p.m.; they were most abundant in the surfacewaters subsequent to the spring phytoplankton bloom. The rangeof TEP (encased) volume concentration was similar to that ofthe phytoplankton, although at times TEP volume concentrationexceeded that of the phytoplankton by two orders of magnitude.The TEP size distribution followed a power law, with the abundanceof particles scaling with particle diameter^–(ß+1).The seasonal average estimate of ß (2.3) was not significantlydifferent from three, consistent with TEP being formed by shearcoagulation from smaller particles. However, date-specific estimatesof ß differed significantly from three, probably becauseTEP are fractal. All TEP were colonized by bacteria, and bacteriawere both attached to the surface of and embedded in TEP. Yetthe number of attached bacteria per TEP was related neitherto the surface area nor the volume, but rather scaled with TEPsize raised to an exponent of     

Interpretation of particle spectra of electronic counters by microscopical methods

1. Using monocultures or single species dominated natural phytoplankton, cell counts and volume estimations obtained by visual and electronic methods show reasonable agreement. Calibration seems possible (Figs. 1–2).
2. Further examples given (Fig. 3–4) show that microscopical identification of the volume peaks in electronic counter spectra of natural seston is not quite simple. Phytoplankton peaks may not be detected in the Coulter spectrum. Shifts of Coulter peaks to the left side of the visual spectrum may be found when cylindrical, elongated or needle-like phytoplankton dominate the sample.
3. Both visual and electronic methods include potentially large errors. Possibly particle volume is either overestimated by the microscope and/or underestimated by the Coulter counter (Figs. 1a, 2, 3b, 4b, c; Table 2). In grazing studies both methods should be employed. Mutual corrections may be possible, based on the type of the seston present (size and nature of phytoplankton cells and detritus particles). In each case both techniques can yield complementary information about the seston investigated. When performing multitube analysis, screening tests of the samples as described by VANDERPLOEG (1981) are recommended.
4. Detritus, especially the different types of aggregated particles, offers severe problems. In the analysis of detritus-rich samples both methods give unreliable results.
5. In most cases estimates of volume, obtained by microscopical and electronic methods, are used as auxiliary parameters. It is the relation between microscopical or Coulter volume and other parameters (e.g. Coulter volume versus POC and phytoplankton volume versus chlorophyll content) that can give useful ecological information.

     

Relation of light penetration to particle distribution in vertically mixed lacustrine environments

The penetration of natural light into a vertically mixed reservoir in the Thames Valley was compared with particle distribution as determined by a Coulter Counter. Attenuation coefficients determined using blue, green, yellow and red filters were correlated with Total Particulate Volume and Total Particulate Surface Area. While there was a low but acceptable correlation of light attenuation with Total Particulate Volume, there was a high correlation of light attenuation with Total Particulate Surface area. Theoretical aspects of this correlation are discussed with reference to the moderate production of phytoplankton in vertically mixed reservoirs of the Thames Valley. The Coulter Counter can give absolute measures of turbidity resulting from suspended particles of a diameter exceeding 3 µm.     

The role of plankton biomass in controlling fluctuations of suspended matter in Lake Constance

The concentrations of particulate matter, expressed as dry weight (DW), particulate organic (POM), and inorganic material were measured at regular intervals in Lake Constance between February 1980 and December 1982. Maximum particle concentrations were recorded for the euphotic zone in summer (7 mg l⁻¹), while minima occurred during the early summer and in winter. Annual mean concentrations of DW within the entire water column varied between 0.6 and 0.7 mg l⁻¹. In the euphotic zone nearly 70% of DW is organic material. The inorganic particles originate either from phytoplankton (diatomaceous silicon, biogenic decalcification) or from the tributaries. Although phytoplankton biomass only comprises a relatively small proportion (i.e. 30% at maximum) of organic matter, it is the primary source of POM. Therefore, seasonal variations in phytoplankton control epilimnetic concentrations of POM in Lake Constance. Inorganic material comprises smaller proportions of suspended matter. Seasonal variations are related predominantly to fluctuations in biomass and therefore particulate inorganic matter is suggested to originate mainly from autochthonous sources. At the sampling station concentrations of inorganic particles supported by the main tributary, the Alpenrhein, only occasionally vary concomitantly with runoff.     

Deriving Restoration Goals for Acidified Lakes from Ataxonomic Phytoplankton Studies

The ataxonomic phytoplankton composition and abundance (biomass classes) in lakes of differing acidity were examined by flow cytometry. The ataxonomic parameters applied here were photosynthesis pigments and cellular protein content. Up to 1000 cells per second can be assessed by this method. Consequently, enough cells to create biomass spectra can be counted within only a few minutes. Photosynthesis pigment autofluorescence was used to separate algal cells from detritus and to classify the phytoplankton organisms into different pigment groups. Chlorophyll fluorescence ratio (CFR) at different excitation wave lengths proved to be a sensitive tool. As expected, the diversity of CFR-determined pigment groups decreased with increasing acidification. Some groups were acid-insensitive and occurred even at pH below 3.0. However, picoplanktic cyanobacteria ( Synechoccocus/Synechocystis -like particles [SLPs]) were absent at pHs below 4.5–4.0, with their accompanying high metal concentrations. Thus, the reappearance of cyanobacterial picoplankton may serve as a first major restoration goal in strongly acidified lakes. Protein staining using fluorescein isothiocyanate enables fast estimates of phytoplankton biomass and establishment of biomass spectra as an estimate of the integrity of plankton communities. Although the phytoplankton investigations presented are only snapshots of the situation on the sampling days, the feasibility of flow cytometrical methods for preparing phytoplankton biomass spectra has been demonstrated. The completeness of such biomass spectra, such as the presence or absence of SLP-picoplankters, as well as the variances around regression lines (linear or parabolic), may serve as goals in restoring lakes acidified to different degrees.     

Ultra-high sensitivity multi-photon detection imaging in proteomics analyses

We report on the use of 125I and 131I labeling and of new, multicolor, multi-photon detection (MPD) methods to routinely and quantitatively detect protein spots on two-dimensional gel electrophoresis plates in the zeptomole to attomole range. We demonstrate that the MPD methodology can be used to detect radioactive labels on two-dimensional gels and has several characteristics that are advantageous for functional proteomics. First, by using single particle detectors, the sensitivity for detection of radiolabels can be improved dramatically. Second, because single particle detectors can differentiate the particle energies produced by different decay processes, it is possible to choose combinations of radioisotopes that can be detected and quantified individually on the same 2-D gel. Third, the MPD technology is essentially linear over six to seven orders of magnitude, i.e., it is possible to accurately quantify radiolabeled proteins over a range from at least 60 zeptomoles to 60 femtomoles. Finally for radionuclides that decay by electron capture, e.g., with emission of both beta and gamma rays, co-incident detection of two particles/photons can be used to detect such radionuclides well below background radiation levels. These methods are used to monitor acidic/phosphorylated proteins in as little as 60 ng of HeLa cells proteins.