Mixed Phytoplankton Research Articles

Elemental composition of the cyanobacterium Anabaena flos-aquae collected from different depths within a stratified lake

The elemental composition of cells of Anabaena flos-aquae was investigated by energy-dispersive electron probe X-ray microanalysis (10 kV) of mixed phytoplankton samples obtained from different depths within a stratified eutrophic freshwater lake. Preliminary studies had indicated that at 10 kV, X-ray information was derived mainly from the peripheral region (up to 1–2 μm) of cells. Routinely detectable elements (present in at least 50% of cells) included Mg (overall mean 112 mmol kg−1 dry mass), Si (1850), P(313), S (113), Cl (92), K (300) and Ca (56). Peaks of Na and Al were also frequently present. Individual elements showed a wide range of intracellular concentrations at each depth within the lake. Si had a clear bimodal distribution at depths of 1–8 m, indicating both low-Si (mean concentrations 54–290–3800 mmol Si kg−1) and high-Si (2770–3800 mmol Si kg−1) cell subpopulations. Low-Si cells had significantly higher concentrations of other detectable elements compared with high-Si cells, but could not be distinguished from the latter in terms of morphology or stage of cell cycle (comparison of dividing and non-dividing cells). High-Si cells were intermixed with low-Si cells in individual Anabaena colonies and decreased proportionally with depth, ranging from approximately 75% in the surface sample to 10% at 8 m. With the exception of Si, mean elemental concentrations of Anabaena populations were closely similar throughout the epilimnion. These differed from the metalimnion sample, which had significantly higher concentrations of Mg, P, S and K, and a lower concentration of Si. Mean ratios of certain elements (Mg, P, S and K) and ion groups (monovalent/divalent cations) were highly constant throughout the sampled water column. At each depth, most of the cell elements were significantly and positively inter-correlated (Pearson analysis), with Mg, P, S and K typically constituting the major group (factor analysis). Correlations with Si were invariably negative, suggesting a separate (possibly cell wall) location of this element in the cell.

Elemental composition of the cyanobacterium Anabaena flos-aquae collected from different depths within a stratified lake

The elemental composition of cells of Anabaena flos-aquae was investigated by energy-dispersive electron probe X-ray microanalysis (10 kV) of mixed phytoplankton samples obtained from different depths within a stratified eutrophic freshwater lake. Preliminary studies had indicated that at 10 kV, X-ray information was derived mainly from the peripheral region (up to 1–2 μm) of cells. Routinely detectable elements (present in at least 50% of cells) included Mg (overall mean 112 mmol kg−1 dry mass), Si (1850), P(313), S (113), Cl (92), K (300) and Ca (56). Peaks of Na and Al were also frequently present. Individual elements showed a wide range of intracellular concentrations at each depth within the lake. Si had a clear bimodal distribution at depths of 1–8 m, indicating both low-Si (mean concentrations 54–290–3800 mmol Si kg−1) and high-Si (2770–3800 mmol Si kg−1) cell subpopulations. Low-Si cells had significantly higher concentrations of other detectable elements compared with high-Si cells, but could not be distinguished from the latter in terms of morphology or stage of cell cycle (comparison of dividing and non-dividing cells). High-Si cells were intermixed with low-Si cells in individual Anabaena colonies and decreased proportionally with depth, ranging from approximately 75% in the surface sample to 10% at 8 m. With the exception of Si, mean elemental concentrations of Anabaena populations were closely similar throughout the epilimnion. These differed from the metalimnion sample, which had significantly higher concentrations of Mg, P, S and K, and a lower concentration of Si. Mean ratios of certain elements (Mg, P, S and K) and ion groups (monovalent/divalent cations) were highly constant throughout the sampled water column. At each depth, most of the cell elements were significantly and positively inter-correlated (Pearson analysis), with Mg, P, S and K typically constituting the major group (factor analysis). Correlations with Si were invariably negative, suggesting a separate (possibly cell wall) location of this element in the cell.

Elemental composition of depth samples of Ceratium hirundinella (Pyrrophyta) within a stratified lake: an X-ray microanalytical study

AME Aquatic Microbial Ecology Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsSpecials AME 19:177-187 (1999) - doi:10.3354/ame019177 Elemental composition of depth samples of Ceratium hirundinella (Pyrrophyta) within a stratified lake: an X-ray microanalytical study David C. Sigee*, Eugenia Levado, Andrew J. Dodwell School of Biological Sciences, The University of Manchester, 3·614 Stopford Building, Oxford Road, Manchester M13 9PT, United Kingdom *E-mail: david.sigee@man.ac.uk ABSTRACT: The elemental composition of Ceratium hirundinella cells was investigated in mixed phytoplankton samples collected from the water column of a stratified lake. X-ray microanalysis (XRMA) routinely detected Mg, Si, P, Cl, K and Ca with occasional peaks of Na, Al and Fe. Cell concentrations of most elements showed no significant variation within the epilimnion, but Mg, P, Cl and K were significantly lower (and Si higher) in cells from the metalimnion. Ratios of Mg/K, P/K, Mg/P, monovalent/divalent cations and diffusible anions/cations were constant throughout the sampled water column. Within depth populations of Ceratium, concentrations of each element varied considerably, approximating (except Si) to a normal distribution. Approximately 5% of all cells had abnormally low concentrations of K and were possibly undergoing senescence. Correlation and factor analysis demonstrated a major statistical association between Mg, P, S and K in Ceratium cells throughout the depth samples. The XRMA results suggest an underlying homogeneity in the population of Ceratium throughout the sampled water column, consistent with the known high mobility and rapid migration of these cells within the water body. KEY WORDS: Phosphorus · X-ray microanalysis · Ceratium · Dinoflagellates · Water column · Anions · Cations Full text in pdf format PreviousNextExport citation RSS - Facebook - Tweet - linkedIn Cited by Published in AME Vol. 19, No. 2. Publication date: October 01, 1999 Print ISSN: 0948-3055; Online ISSN: 1616-1564 Copyright © 1999 Inter-Research.

From algal competition to animal production: Enhanced ecological efficiency of Brachionus plicatilis with a mixed diet

The food ‐chain transmission of mineral nutrient effects to zooplankton production via phytoplankton competition was studied by two ‐stage experiments with a mixed phytoplankton assemblage from the Indian Ocean and the rotifer species Brachionus plicatilis. Phytoplankton species composition was steered by nutrient competition in the first stage of the cultures. High atomic Si:N ratios (>1:1) in the medium resulted in diatom dominance, and low ones resulted in flagellate dominance. Medium Si:N ratios (0.3–0.6:1) resulted in even mixtures of both types of algae. The phytoplankton assemblage resulting from competition was used as food for Brachionus. An even mixture between diatoms and flagellates in the food resulted in higher Brachionus production than one sided food mixtures.

Elemental concentrations, correlations and ratios in micropopulations of Ceratium hirundinella (Pyrrhophyta): an X-ray microanalytical study

The elemental composition of Ceratium hirundinella was determined in mixed phytoplankton samples collected over a 2-month period (late June to early September 1995). Electron probe X-ray microanalysis spectra of single cells routinely showed clear peaks of monovalent (Na, K) and divalent (Mg, Ca) cations, plus Si, P, S and Cl. Considerable variation in elemental concentrations occurred both within and between samples (20 cells). The overall ratio of monovalent to divalent cations was relatively constant at about 1.3. Intracellular concentrations of anions/cations and electronegative/electropositive elements were significantly correlated in most samples, suggesting a controlled internal balance of these ionic groups. Correlation analysis of elemental concentrations revealed clear patterns of statistical association within individual samples, with significant positive correlations between particular pairs of elements (Mg–P, K–Cl and K–P). Some pairs of highly correlated elements (particularly Mg–P) occurred in defined ratios throughout the samples, while others (e.g. K–Cl, Na–Mg) were variable. Factor analysis showed that elemental associations were determined by two Principal Factors in most samples, possibly related to insoluble and soluble components of cells. Decrease in the level of available P in lake water was associated with a sharp decrease in the intracellular P concentration and the concentration of other correlated elements. The estimated C/P ratio markedly differed from the classical (Redfield) value at times of low P availability. The concentration of P in cells of Ceratium was approximately 10% times greater than in the surrounding water medium (total P) compared with values of 102–103 for K.

Elemental concentrations, correlations and ratios in micropopulations of Ceratium hirundinella (Pyrrhophyta): an X-ray microanalytical study

The elemental composition of Ceratium hirundinella was determined in mixed phytoplankton samples collected over a 2-month period (late June to early September 1995). Electron probe X-ray microanalysis spectra of single cells routinely showed clear peaks of monovalent (Na, K) and divalent (Mg, Ca) cations, plus Si, P, S and Cl. Considerable variation in elemental concentrations occurred both within and between samples (20 cells). The overall ratio of monovalent to divalent cations was relatively constant at about 1.3. Intracellular concentrations of anions/cations and electronegative/electropositive elements were significantly correlated in most samples, suggesting a controlled internal balance of these ionic groups. Correlation analysis of elemental concentrations revealed clear patterns of statistical association within individual samples, with significant positive correlations between particular pairs of elements (Mg–P, K–Cl and K–P). Some pairs of highly correlated elements (particularly Mg–P) occurred in defined ratios throughout the samples, while others (e.g. K–Cl, Na–Mg) were variable. Factor analysis showed that elemental associations were determined by two Principal Factors in most samples, possibly related to insoluble and soluble components of cells. Decrease in the level of available P in lake water was associated with a sharp decrease in the intracellular P concentration and the concentration of other correlated elements. The estimated C/P ratio markedly differed from the classical (Redfield) value at times of low P availability. The concentration of P in cells of Ceratium was approximately 10% times greater than in the surrounding water medium (total P) compared with values of 102–103 for K.

Is kelp detritus a good food for suspension feeders? Effects of kelp species, age and secondary metabolites

The food quality of detrital particles derived from three species of kelps was evaluated in a laboratory feeding experiment utilizing two species of suspension feeders, the serpulid polychaete Pseudochitonopomaoccidentalis and the mussel Mytilustrossulus. Fresh and aged kelp particles were also evaluated, and growth in all treatments was compared to growth on ad libidum phytoplankton rations. Fresh particles from Laminariagroenlandica, aged particles from Agarumfimbriatum and Alariamarginata, and mixed phytoplankton promoted the highest growth rates in both consumers. Growth was inversely related to total polyphenolic concentration in the fresh kelp particles. The increase in quality of both Agarumfimbriatum and Alariamarginata particles with age corresponded with a rapid loss of polyphenolic secondary metabolites and an increase in total nitrogen.

Changes in the composition of fatty acids in sinking matter during a diatom bloom in a controlled experimental ecosystem

A controlled experimental ecosystem (CEE) was set-up in Saanich Inlet, British Columbia, Canada during the summer of 1986. A mixed phytoplankton bloom (predominated by diatoms) which rapidly resulted after addition of nutrients at the commencement of the experiment, led to high fluxes of total mass and organic carbon to the bottom of the CEE. Suspended particles settling to the bottom of the bag were collected from time to time and analysed for their fatty acids, particulate organic carbon and particulate organic nitrogen content. Fluxes of fatty acids were high when the bloom was in its exponential phase of growth whereas organic carbon increased when the bloom was in its decay phase. The major fatty acids were C14:0, tC16:0 and C16:1, but the overall composition of fatty acids changed extensively as growth of the bloom progressed. The fatty acid C20:5, for example, a characteristic of diatoms, increased rapidly and reached its maximum when the bloom attained its peak. On the other hand, C20:3 acid tended to increase towards the end of the bloom when nutrients in the water column of the CEE were already depleted and nanoflagellates dominated. These systematic changes in the abundance of C20:5 and C20:3 as well as those in the ratios of unsaturated fatty acids (UFA) to saturated fatty acids (SAFA) from the onset of the bloom until its end, suggest that the composition of fatty acids in sinking particles could serve as a useful biological indicator of diatom growth and ecophysiological state of the overlying diatom community.

Selenium in plankton from the northwestern Mediterranean Sea

Selenium is a multiple oxidation state trace element whose redox chemistry and concentration in sea water can be modified by biological activity in the euphotic zone. A field study was undertaken to examine the effects of oceanographic and biological parameters on the selenium concentration of the coastal plankton. For this purpose, plankton was collected in the Ligurian Sea from October 1990 to December 1991. The samples analyzed were composed of mixed phytoplankton and microzooplankton ranging in size from 50 to 200 μm. The medium selenium concentration measured in microplankton was 1.57 μg Se·g −1 carbon or 0.62 μg Se·g −1 dry weight ( n = 15). Seasonal fluctuations in selenium concentration of microplankton were influenced by hydrodynamic conditions. During strong vertical mixing of the water column, deeper water with high selenite and selenate concentrations may reach the surface and selenium concentration in plankton was found to increase by a factor of eight compared to the median annual value. Under usual hydrodynamic conditions, seasonal fluctuations of the microplankton selenium content were typically low. Such low variations appeared to be due to the specific composition of microplankton. In the case of a phytoplankton bloom, selenium concentration in microplankton increased in proportion to the diatom biomass, whereas in other cases a negative linear relationship was found between selenium content and zooplankton biomass. The biogeochemical cycling of selenium may be influenced by seasonal fluctuations of the plankton selenium content which is controlled by hydrodynamic processes and plankton composition.

Diurnal buoyancy changes of Microcystis in an artificially mixed storage reservoir

In a storage reservoir, which is artificially mixed in order to reduce algal and especially cyanobacterial growth, the cyanobacterium Microcystis is still present. The aim of the research was to investigate why Microcystis was able to grow in the artificially mixed reservoir. From the results it could be concluded that the large shallow area in the reservoir allows this growth. The loss of buoyancy during the day was much higher in this shallow part than in the deep part. Assuming that the loss of buoyancy was the result of a higher carbohydrate content, a higher growth rate in the shallow part may be expected. A higher received light dose by the phytoplankton in the shallow mixed part of the reservoir than in the deep mixed part explains the difference in buoyancy loss. A significant correlation between the received light dose (calculated for homogeneously mixed phytoplankton) and the buoyancy loss was found. Apparently, the Microcystis colonies were entrained in the turbulent flow in both the shallow and the deep part of the reservoir. With a little higher stability on one sampling day, due to the late start of the artificial mixing, the loss of buoyancy at the deep site was higher than on the other days and almost comparable to the loss at the shallow site. Although the vertical biomass distribution and the temperature profiles showed homogeneous mixing, the colonies in the upper layers apparently received a higher light dose than those deeper in the water column. Determination of the buoyancy state of cyanobacteria appeared to be a valuable method to investigate the light history and hence their entrainment in the turbulent flow in the water column.

A Method of in situ Measurement for Counting and Sizing of Blue-Green Alga Particles by the Detection of Fluorescent Components at Two Wavelengths.

To understand the ecosystem of lakes and the ocean, we have developed a new in situ measurement system for counting and sizing alga particles. The system is based on the fact that the laser induced fluorescence from the phytoplankton changes its spectrum according to the phycocyanin quantity which is abundant in blue-green algae. In the system, blue-green algae are discriminated by measuring the ratio of fluorescence components at the two wavelengths (655 nm and 685 nm) emitted from the phytoplankton irradiated with a 532 nm laser beam. The system gives particle size distribution for each alga in the mixed phytoplankton of blue-green and green algae.

Quantitative determination of cyanobacteria in mixed phytoplankton assemblages by an in vivo fluorimetric method

An in vivo fluorimetric method for selectively determining the concentration of cyanobacteria (blue-green algae) in mixed phytoplankton communities was developed. Excitation wavelengths of 620 nm and 440 nm were applied, the former for detecting the cyanobacteria themselves, and the latter for subtracting the interference due to eukaryotic algae present in the sample. The emission fluorescence of the cyanobacteria and eukaryotic algae was measured at 645 nm and 680 nm, respectively. In the range of 0.01 to 10 μg phycocyanin ml −1 a linear relationship between fluorescence intensity and cell concentration was established for all the species examined: Microcystis aeruginosa, Phormidium tenue, Anabaena cylindrica and Spirulina platensis.

Nutrient concentration of aquatic plants: Patterns across species

An extensive compilation of data for 96 phytoplankton species, 46 macroalgal species, 27 seagrass species, 11 species of freshwater angiosperms, and several mixed phytoplankton and macroalgal communities revealed a tendency toward higher concentrations of N and P in phytoplankton compared to those of macrophytes. The depletion of P, and to a lesser extent N, in macrophytes, particularly macroalgae, appears to reflect a greater degree of P and N limitation of growth of natural macrophyte populations, rather than an intrinsic difference in their chemical composition relative to that of phytoplankton. Close associations between nutrients, particularly a strong linear relationship between concentrations of N and P, reflect the similar biochemical basis of the different aquatic plant groups and appear to represent a fundamental characteristic of the plant kingdom. The results obtained indicate, therefore, that aquatic plants form a continuum across a unique pattern of change in nutrient concentrations, despite considerable differences in their architectural, evolutionary, and life histories, and the growth conditions encountered in their habitats.

Photosynthetic parameters of the entire euphotic phytoplankton of the Bransfield Strait, Summer 1985

The photosynthetic parameters αB, PBm, and Ik were derived from the relationship between primary productivity (P) and irradiance (I) for mixed samples, each mixture consisting of seven samples of phytoplankton collected from different depths, between the surface and 35 m at eight different sampling stations in the Bransfield Strait in January–February 1985. The αB values obtained in this study were considerably higher than those generally reported for phytoplankton from a single depth in polar waters. These higher values may be attributed to the fact that most of the phytoplankton in the mixed samples came from depths with limiting irradiances, which had a greater yield than surface phytoplankton. The PBm value we obtained was lower than that reported by other authors, possibly because the mixed sample phytoplankton have saturation points at low light intensity. Our IK values confirmed the ability of phytoplankton in these latitudes to reach maximum photosynthesis rates with low densities of photonic flux. When treated as independent parameters, the αB and PmBvalues showed a significant correlation for each sampling station. The efficiency of the entire euphotic phytoplankton of the water column, estimated as ∫0euPdz/∫0euBdz or Integral Assimilation Number (IAN), showed a predictable significant correlation with the αB values calculated from the entire euphotic phytoplankton. Areas with high surface biomass were as productive as those with low surface phytoplankton biomass. Areas with low surface phytoplankton biomass showed higher αB values than areas with high surface biomass, which suggests, that, the αB values for the entire photosynthesizing phytoplankton in the water column may have greater predictive value than the αB values for the phytoplankton from a single depth. This finding should be taken into account when satellites are used for studying marine production processes, especially in areas with very different euphotic depths and surface phytoplankton concentrations.

Trace Determination of Domoic Acid in Sea Water and Phytoplankton by High-Performance Liquid Chromatography of the Fluorenylmethoxycarbonyl (FMOC) Derivative

Abstract A method is presented for the trace determination of domoic acid, a neurotoxic amino acid responsible for cases of Amnesic Shellfish Poisoning resulting from the consumption of contaminated shellfish. The method involves pre-column derivatization with 9-fluorenylmethylchloroformate to form the FMOC derivative followed by reversed-phase HPLC with fluorescence detection. The detection limit for domoic acid in seawater and aqueous extracts is 15pg/mL (50 pM) using gradient elution, a 20μL injection volume, and a 2.1mm I.D. microbore column. Use of dihydrokainic acid as an internal standard improved quantitation. The method was applied to the detection of domoic acid in seawater, in phytoplankton cultures (Nitzschia pungens forma multiseries), and in natural mixed phytoplankton assemblages in estuarine waters.

Phosphate Uptake by Eukaryotic Algae in Cultures and by a Mixed Phytoplankton Population in a Lake: Analysis by a Force‐Flow Relationship*

AbstractThe phosphate uptake behaviour of monospecific cultures of green algae in the laboratory and of mixed phytoplankton populations in a mesotrophic lake has been analyzed with the aid of a force‐flow relationship. This analysis yields two parameters: A conductivity coefficient, that characterizes the activity of the phosphate uptake system. An external threshold phosphate concentration, below which uptake of phosphate is excluded on energetic grounds. When the phosphate concentration lies below the threshold value, the algae show an activation of the uptake system, reflected in an increase in the conductivity coefficient. Correspondingly, excess phosphate above the threshold value leads to a diminuation of the conductivity.Using this simple analysis, phosphate discharge into lake water may be readily monitored.

Selection of phytoplankton species in culture by gradual salinity changes

Continuous cultures of mixed phytoplankton populations were subjected to gradual salinity changes. The phytoplankton was exposed to defined regimes of high, low or fluctuating salinity, in artificial brackish media. In several experiments ammonium was the limiting nutrient. A rapid selection process was observed in natural phytoplankton assemblages. A gradual freshening caused the dominance of Chaetoceros mülleri at low salinity (S = 5). Skeletonema costatum became dominant at higher, constant or fluctuating salinities, accompanied by Ditylum brightwellii in low cell numbers. Ammonium limitation was not achieved in this experiment. Competition for ammonium was studied in a second experiment, using an inoculum of two species. At S = 18 D. brighwellii became the dominant species in this competition. A minor shift towards S = 15 reversed the affinities for ammonium, and S. costatum won the competition. At S = 8 S. costatum had the highest affinity for ammonium after a period of osmotic adjustment. Ammonium became limiting when salinities arrived at constant meso- or polyhaline levels. Both species were able to grow in fluctuating osmotic environments (S = 5 to 19). The growth of D. brightwellii decreased below S = 8 and after repeated variations of the salinity. These salinity fluctuations suppressed growth and ammonium uptake of both species, thus preventing ammonium limitation. These competition experiments indicate that unstable salinity may stimulate the mass development of S. costatum in brackish lakes.

An in vivo fluorescence response in the Bay of Biscay in June

CONCLUSION AND SUMMARYSurface fluorescence measurements in June in the Bay of Biscay showed little correlation with chlorophyll a measurements due to the presence of a marked diurnal fluorescence rhythm although satisfactory correlations have been obtained at other times of year in the same region (see Fig. 10 of Pingree et al. 1982). By contrast, the beam attenuation coefficient values showed a good correlation with the chlorophyll a measurements and can be used to map the sea surface distribution of chlorophyll a when the diurnal rhythm is present, particularly when the phytoplankton is dominated by a single species. This conclusion may be of considerable practical significance when contemplating synoptic surveys in such situations. As Prezlin & Ley (1980) have observed there is growing awareness that fluorescence per unit chlorophyll a is not a constant that can be used reliably in mixed phytoplankton biomass estimates based on in vivo chlorophyll a fluorescence, and the problem is clearly compounded if some species exhibit a marked diurnal fluorescence rhythm. Furthermore, the present observations support the caveats of Falkowski & Kiefer (1985), that in situ moored fluorometers, the use of air-borne laser-induced fluorescence, or satellite-received passive, solar-induced fluorescence, only measure fluorescence, not chlorophyll per se.The fluorescence response near the shelf-break over a 24 h period following a drogued dahn buoy showed a variation of about a factor of 5 between the day and night fluorescence levels. Beam attenuation coefficient measurements and Coulter Counter analyses showed that these results could not be attributed to the migration of the phytoplankton.

Mesocosm studies of DCMU-enhanced fluorescence as a measure of phytoplankton photosynthesis

When measurements of in-vivo fluorescence are used to estimate photosynthesis in the field, the marked temporal and spatial variations in phytoplankton populations, and their nutrient and light histories, have produced varied results. Natural phytoplankton populations in large, flow-through mesocosms with different controlled nutrient and sewage sludge additions were sampled weekly from June to September 1984. Good correlations were observed between the increase in fluorescence upon the addition of DCMU (ΔF) and both in-situ production and the parameters (Pm and α) of the photosynthesis-irradiance curve for these phytoplankton populations. Good correlations were also obtained between DCMU-enhanced fluorescence (FDCMU) and chlorophyll a concentrations. The relationship between ΔF and in-situ14C production was consistent among mesocosms even in the face of major shifts from diatom-dominated to dinoflagellate-dominated populations. On the other hand, the FDCMU:Chl a relationship was significantly different between mesocosms and related to species composition. It was concluded that ΔF offers the possibility of rapidly and accurately indexing both in-situ production and the photosynthetic capacity of mixed phytoplankton populations.

The response of Asterionella formosa to germanium: implications for the germanium inhibition technique for estimating diatom contribution to community productivity

SUMMARY. 1. The effect of added germanium on the assimilation of carbon by Asterionella formosa Hass. in mixed phytoplankton assemblages was measured weekly from July to December 1981 by auto‐radiography.2. Contrary lo a major assumption of the germanium‐inhibition method of partitioning primary productivity, the germanium‐induced inhibition varied considerably and with no apparent pattern.3. Inhibition values determined for laboratory cultures are probably not indicative of the responses of in situ populations, and serious errors can occur in estimating diatom contribution to total community photosynthesis. This places severe limitations on the use of the method.