Kinetic model of algal growth incorporating intracellular carbohydrate and phosphorus pools

A series of studies on a kinetic model of photosynthesis, nutrient ingestion, and metabolism for algal growth were conducted. Coefficients included in the proposed model were examined referring to experimental data on growth of Chlorella sp. It was shown that the proposed model can simulate the mechanism of algal growth, change of intracellular phosphorus content, change of intracellular carbohydrate content, and effects of nutrients on algal growth.     

Interacting limits to algal growth: Light, phosphorus, and carbon dioxide availability

Most studies of limiting factors to algal growth seek to quantify the effect of individual factors. However, rates and amounts of photosynthetic carbon fixation in laboratory cultures of Anacystis nidulans show simultaneous dependence on the availability of phosphorus, carbon dioxide, and light. Thus, not all limiting factors may act independently to control algal growth in aquatic systems, and further research into the extent of such interactions is needed.     

The use of algal assays for determining the effect of iron and phosphorus compounds on the growth of various algal species

Algal assays were performed with unialgal cultures of Oscillatoria rubescens. Asterionella formosa, Synedra acus. Haematococcus pluvialis and Scenedesmus quadricauda. The method we used differs in some important respects from the methods described in literature on this subject and these differences are explained in detail.The agal crop, measured as μg 1⁻¹ chlorophyll α was used to determine the productivity of the water samples tested. The following were tested: (1) untreated Wahnbach water; (2) Wahnbach water treated in a pilot plant for elimination of phosphorus and turbid materials; (3) water samples from the pre-reservoir effluent of the Wahnbach Reservoir; and (4) water samples from the Wahnbach Reservoir taken from near the dam.The fertility of the water samples decreased in all the test series in the following order: untreated Wahnbach water > pre-reservoir effluent > water from the Wahnbach reservoir > Wahnbach water treated in the pilot plant. The productivity of the water samples rich in turbid materials and algae, was higher in heat sterilized samples than those prepared by filtration. There is a clear correlation between the productivity of unfiltered sterilized water samples and their iron and total phosphorus content.Using algal assays we proved that the large decrease in productivity resulting from treating the Wahnbach, the main reservoir inflow, is chiefly due to the removal of phosphorus compounds, but also to the removal of iron and other unknown substances. There are indications that the amount of iron required for growth, as compared to that of phosphorus, varies greatly depending on the individual algal species.The significance of the algal assay and their results relating to measures for limiting eutrophication using phosphorus removal plants is discussed.     

Experience with algal blooms and the removal of phosphorus from sewage

The growth of algae and occurrence of algal “blooms” in a number of different waters are described.They cover the period 1930–1940 when only natural phosphates would be present.The waters were drawn from either protected catchments or from a fully treated domestic supply.Spasmotic blooms in a fully treated domestic supply suggest that the mechanism which “triggers” the start of an algal bloom may be neither nutrient concentration nor the concentration of organic matter.It is considered that the pH, alkalinity, carbon dioxide equilibrium condition is a major factor, not only in promoting, but also in maintaining algal blooms.     

No-effect concentrations in algal growth inhibition tests

We propose three simple models for effects of chemical compounds on the growth of batch cultures of algae that allow the estimation of the no-effect concentration. The growth model assumes that the costs for growth is proportional to the concentration that exceeds the no-effect level. The hazard model assumes that the hazard rate is proportional to the concentration that exceeds the no-effect level. The adaptation model is similar to the hazard model, but the effects only occur at the start. The no-effect concentrations of the three models turn out to be very similar.     

The retardment of algal growth in maturation ponds

During recent times inhibition of planktonic algal growth was found to prevail at Windhoek and other localities both in South West Africa and the Republic of South Africa. The phenomenon has important implications with respect to sewage treatment in ponds, particularly maturation pond systems. Inhibition of algal growth in case of the Windhoek maturation ponds appears to be caused by increased sedimentation of algal cells, by depression of the algal growth rate, or by both.     

The use of algal bioassays to predict the short- and long-term changes in algal standing crop which result from altered phosphorus and nitrogen loadings

Bioassays were performed on filtered water from Jackson Lake, Wyoming, using the Algal Assay Procedure-Bottle Test with Selenastrum capricornutum as the assay organism. It is hypothesized that (i) short- and long-term additions of phosphorus (P) and nitrogen (N) to waters should be evaluated separately, and (ii) only bioassay treatments of lake water plus phosphorus plus nitrogen (LW + P + N) should be used to predict the effect of long-term phosphorus additions on algal standing crop. Equations are developed directly from the corresponding bioassay responses to predict short-term increases in the lake's algal standing crop. Accepting the hypothesis, an equation describing the response of S. capricornutum to LW + P + N treatments is derived to predict the long-term effects of phosphorus additions on algal standing crop. This equation is then combined with another derived to describe the steady state concentration of phosphorus in lake water. The resultant equation predicts the percent change in algal standing crop as a function of any change in the lake's phosphorus loading. In most cases, use of LW + P rather than LW + P + N treatments to predict changes in algal standing crop will lead to quite different interpretation of bioassay data, and probably to different management decisions.     

The effects of sediment size fraction and associated algal biofilms on the kinetics of phosphorus release

Experiments using flumes containing sediment of three different size fractions, from two sites on the River Tame, investigated the influences of sediment particle size, and an associated biofilm, on sediment-water exchanges in heterogeneous sediment deposits. This is the first study undertaken to understand the kinetics of the release of soluble reactive phosphorus from sediments of natural systems to identify which of the size compartments affected those fluxes most. Samples of fine material (<2 mm), gravel (2-20 mm), and stones (>20 mm) were collected over a period of several weeks and brought to a fluvarium where they were placed in artificial, controlled flow, and flume channels. Synthetic solutions of similar ionic strength to the river were prepared using calcium chloride. Temperature, pH, and dissolved oxygen of the solution overlying the sediment were monitored automatically whilst filtered samples were obtained at 2 h intervals over 48 h. The biomass, expressed as mg m(-2) chlorophyll a, of the algal component of the biofilm from the surface of the sediment was estimated using methanol extraction. Differences in the responses were observed between the sediment size fractions and the two sites, where contaminant concentrations varied. The equilibrium phosphate concentration and a phosphorus transfer index were used to establish that there was a net uptake of phosphorus by all three sediment size fractions, from both sites, at the time of sampling. The kinetic results showed very fast initial reactions of phosphorus release from the larger size fractions with a well-developed filamentous algal growth present implying a different mechanism than diffusion being involved. The stones and associated biofilms also released more phosphorus than the fine fraction, e.g. final release concentrations for the most contaminated site were: fines approximately 2.5 microM, gravel approximately 6.5 microM, and stones approximately 65.0 microM (expressed as soluble reactive phosphorus). Phosphorus fluxes, calculated assuming the concentration of phosphorus in the sediment was less than the equilibrium concentration, were a maximum at the most contaminated site, e.g. fines 6.4 nmol m(-2) s(-1), gravel 27 nmol m(-2) s(-1), and stones 109 nmol m(-2) s(-1) (normalised with respect to the river bed area). These results confirm that sediment having a biofilm and associated particulate material results in a greater flux than fine sediment, which does not support a filamentous biomass. Removal of the fine particulates trapped in the algal growth reduced soluble phosphorus release. These factors demonstrate that both gravel and stone substrates have an important control over the release of soluble reactive phosphorus.     

Response variable in algal growth inhibition tests—Biomass or growth rate?

A number of response variables can be derived from growth inhibition toxicity experiments with microorganisms; currently, there is a controversy regarding which variable to specify in standardized test protocols with algae. Yield or biomass at a specified time is the variable used most frequently. Specific average growth rate is a debated alternative, and appreciable differences may exist between EC figures derived from the same set of data using either test endpoint.The problem is reviewed and analysed mathematically. It is concluded that from a theoretical point of view, growth rate is a better response variable than biomass, e.g. because EC figures estimated from growth rates are less dependent on particular test system parameters. However, as the use of both methods to analyse data will probably continue, it is important to be aware of the potential differences between estimated EC figures.     

Kinetics of phosphorus release from a natural mixed grain-size sediment with associated algal biofilms

Experiments using flumes containing mixed grain-size sediment with an associated algal biofilm, from two sites on the R. Tame, investigated the sediment-water exchanges in heterogeneous sediment deposits. These results were considered in the light of findings of a companion study [Gainswin BE, et al. The effects of sediment size fraction and associated algal biofilms on the kinetics of phosphorus release. Sci Total Environ, this issue.] by considering this natural system in relation to the effects of the different sizes of material comprising the sediment. Sediment samples were collected in trays installed in the river over a period of one growth cycle (March 2001-April 2002) and placed in flume channels with controlled water flow. The temperature, pH, and dissolved oxygen of the solution overlying the sediment were monitored automatically whilst filtered samples were obtained at 2-0h intervals over 48 h. The biomass, expressed as chlorophyll a, of the algal component of the biofilm from the surface of the sediment was estimated using methanol extraction. The composition of the sediment, viz. size fractions, organic matter and porosity, were determined at the end of the experiments. The equilibrium phosphate concentration and a phosphorus transfer index were used to establish that a net uptake of phosphorus by some of the samples that occurred at the time of sampling. The results were modelled using a Diffusion Boundary Layer model and the maximum flux from the sediment (or limiting diffusion flux) compared for each of the samples. The limiting diffusion flux was highest at the most contaminated site--reaching approximately 180 nmol m(-2) s(-1) (normalised with respect to the river bed area). The limiting diffusion flux calculated for the composite samples was in agreement with the flux estimated from the contributions expected from the individual size fractions [Gainswin BE, et al. The effects of sediment size fraction and associated algal biofilms on the kinetics of phosphorus release. Sci Total Environ, this issue.]. The dominance of the flux contribution from the stones size fraction (>20 mm) confirms that sediment having a filamentous biofilm and associated particulate material results in a greater flux than a silt sediment without such a biomass.     

The effect of photochemical treatment of water on algal growth

A new method for the destruction of algae in surface waters by dye-sensitized photooxidation is described. The algae (Peridinium, Pediastrum and Cosmarium) used as test organisms were inoculated in an artificial culture medium, containing a dye-sensitizer, with subsequent incubation in a controlled environment (20 ± 2°C, 14 h light, 10 h darkness). Water samples from Peridinium bloom in Lake Kinneret underwent similar treatment. The algicidal effect of various sensitizer concentrations and of different sunlight exposure times was investigated. Complete destruction of algae was obtained in about 2 weeks of incubation after exposure to solar radiation for 30–60 min in the presence of 0.25, 0.15 and 0.75 mg 1⁻¹ methylene blue or 0.5, 0.8 and 0.8 mg 1⁻¹ rose bengal in Peridinium, Pediastrum and Cosmarium cultures, respectively.     

The evaluation of algal growth potential by cultivation on solid media

An evaluation of algal growth potential and toxicity by cultivation on solid media has been completed. The growth rates of colonies are independent of the external strength of nutrients until 150 h of cultivation; this is due to the inner nutrient pools of cells. Thereafter, cells become more dependent on external nutrient sources and the growth rates of colonies are controlled by diffusion of nutrients from the plate to the growth zone i.e. to the perimeter of the colony. At the end of 400 h colony growth decreases at a rate proportional to the concentration of nutrients. The final size of colonies is proportional to the strength of nutrients, ranging from concentrations characteristic of oligotrophic waters to those of sewage.Yield of dense periphyton on a plate is proportional to the initial nutrient content until about 1500 mg l⁻¹ dry weight has been achieved. Higher yields are limited by cell density or light penetration. The yield constant is inversely proportional to the solution strength.The results of a new procedure are convertible into the yields of dry weights obtained by cultivation in aerated liquid suspension. Sixty-six 9 cm diameter Petri dishes can be placed in a cultivation unit with an area of only 0.7 m². The use of microtitration plates for immunology, with 96 wells in a plate 9 × 13 cm, can extend the number of variants up to about 3000 colonies in the same cultivation unit. Evaluation is quick, simple and precise. The coefficient of variation is about 10%. Yield is measured by sizing under a microscope or by dry weight evaluation on filter discs.     

The exchange and growth potential of phosphorus in algae cultures

This laboratory study was undertaken as an effort to provide information which might lead to the establishment of defined relationships existing between phosphorus and eutrophication.

The applicability to eutrophication of the Watt‐Hayes Steady State Model describing phosphorus transfer and exchange has been determined for the selected conditions of this study. By determining inorganic, particulate and organic steady state phosphorus concentrations and exchange rates resulting from various phosphorus inputs, equations enabling one to predict exchange rates, steady state phosphorus concentrations and maximum algal growth have been developed.     

A simple cultivation unit for the evaluation of algal growth potential and toxicity of water

The design presented here enables a makeshift cultivation unit to be assembled for AGP evaluation after Lukavský (Lukavský J. Water Res. 17, 549–558, 1983) i.e. using solid media in a microtitration plate. The unit consists of common laboratory components and is very cheap and reliable.     

柴油清净剂研究与应用展望

对国内外柴油清净剂的研究进展和应用现状进行调研,结果表明其大都停留在第三代清净剂水平。对国内市场上两款知名柴油清净剂进行分析,概述和对比不同柴油清净剂的清净效果,并对其存在的问题进行剖析,提出应发展全面解决发动机积炭的第五代复合型清净剂,制定柴油清净剂相关标准。     

Temporal variability of dissolved P speciation in a eutrophic reservoir--implications for predicating algal growth

Weak-anion exchange chromatography was used to explore the temporal variability in the speciation of dissolved P in the surface layer of a eutrophic reservoir. Authentic free ortho-P ion was the most common form of P on three of the five sampling occasions-including during a bloom of the green algae Botryococcus braunii indicating that the bloom was not P limited. Conversely, the absence of authentic ortho-P during a bloom of the dinoflagellate Ceratium hirundinella suggested the bloom was either P limited or co-limited. These observations were confirmed by algal-growth bioassay experiments.     

藻类有机物的特性研究

以铜绿微囊藻为对象,考察了蓝藻细胞胞外有机物(EOM)及胞内有机物(IOM)的荧光特性、分子量分布及可同化有机碳特性。EOM有1个典型荧光基团,代表可溶性生物代谢产物,IOM有4个典型荧光基团,分别代表芳香结构蛋白、生物代谢产物、类腐殖酸及类富里酸有机质。EOM及IOM有机氮区域的有机物分子量较大,而有机碳区域的有机物分子量小于1 k Da。EOM中AOC含量较低,而IOM中AOC含量较高,且在藻细胞生长过程中浓度较稳定。     

Algae as a chemical speciation monitor—I A comparison of algal growth and computer calculated speciation

An alga, Selenastrum capricornutum, was used to monitor the relationship between metal speciation and toxicity. The principal effect of copper on the algae was a decrease in growth rate constant as the total concentration of copper increased. A 24-h growth experiment was used to monitor the effect of metal on the algae. Chlorophyll measurements at 17 and 23 h were used to estimate the growth rate constant. A plot of growth rate constant versus the speciation variable (total copper, pCu, pCuL, etc.) was used to determine the toxic species and the algicidal concentrations. Solutions containing EDTA, TRIEN, NTA, HIMDA and bicine became algicidal at pCu of 8.0 whereas solutions containing ethylenediamine and citric acid became algicidal at pCu 8.65 and 9.5, respectively. A comparison of growth and calculated speciation suggests that Cu en⁺² and Cu CIT OH⁻² were toxic species.