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In this study, the water quality of four coastal areas in Puerto Princesa Bay, with and without informal settlers, were compared in terms of the phytoplankton composition and density, fecal coliform and physicochemical parameters during a 12-month sampling period. Microscopic examination and identification using phytoplankton monographs showed five harmful algal blooms (HABs) genera (Alexandrium, Dinophysis, Nitzschia, Pseudo-nitzschia, and Pyrodinium) with Dinophysis spp. as the most abundant in coastal areas with informal settlers and Pseudonitzschia spp. in areas without informal settlers. Eight phytoplankton genera (Coscinodiscus, Proboscia, Rhizosolenia, Skeletonema, Ceratium, Prorocentrum, Protoperidinium, and Oscillatoria) reported to have caused algal blooms were also observed with Coscinodiscus spp. as the most abundant in both groups of coastal areas. Multiple-tube fermentation technique showed fecal coliform count ranging from 4 to >1600 most probable number (MPN)/100 ml in the coastal areas with informal settlers and from <1.8 to 295 MPN/100 ml in areas without informal settlers. Multiprobe measurements showed that both groups of coastal areas have similar physicochemical characteristics with only the dissolved oxygen failing to meet the Philippine standards for class SB waters. There was a significant difference (P < 0.05) in water quality between the coastal areas with and without informal settlers in terms of fecal coliform and the density of four phytoplankton genera (Pseudo-nitzschia, Skeletonema, Alexandrium and Ceratium). However, there is no significant difference in terms of the physicochemical parameters. Regression analysis indicates that the presence of informal settlers could affect water quality in terms of fecal coliform and the five phytoplankton genera (Coscinodiscus, Pseudo-nitzschia, Skeletonema, Alexandrium and Ceratium). [ABSTRACT FROM AUTHOR]

The phytoplankton in the inner Neva Estuary is described from data obtained from 1996 to 2000. The seasonal dynamics of the phytoplankton biomass are characterized by a bimodal curve with a summer maximum. The average seasonal biomass was approximately3 mg l-1, the maximum biomass was 8-11 mg l-1. The species composition and quantitative parameters were compared to those observed in the 1980s. A notable, nearly 1.5-2 fold, increase in the biomass in the summer-autumn period and the predominance of Oscillatoria species among the blue-greenalgae were observed. A decline in the nutrient load in the water body at the end of the 1990s appeared to be insufficient to bringabout a decrease in the proportion of Oscillatoria algae in the total species composition or a decline in the biomass ofthe entire phytoplankton community. In 2000 a certain change in the structural composition of the phytoplankton complex was noted. Species that had been predominantin the 1980s and had lost their advantage in the early 1990s, regained their earlier status.

Abstract: Shallow lakes and ponds are often characterised either by clear water with abundant submerged macrophytes or by turbid water with abundant phytoplankton. Blooms of toxic filamentous blue-green algae (cyanobacteria) often dominate the phytoplankton community in eutrophic lakes, which threatens ecological functions and biodiversity of freshwater ecosystems. We studied a simple lake model in order to evaluate individual and combined suppressive effects of rooted submerged and rooted floating-leaved macrophytes on algal blooms. Floating-leaved plants are superior competitors for light, whereas submerged plants absorb and reduce available phosphorus in a water column that rooted floating-leaved plants exploit to a lesser extent. We found that mixed vegetation that includes both submerged and floating-leaved plants is more resistant than vegetation comprised by a single plant type to algal invasion triggered by phosphorus loading. In addition, competitive exclusion of submerged plants by floating-leaved plants may promote an algal bloom. These predictions were confirmed by the decision tree analysis of field data from 35 irrigation ponds in Hyogo Prefecture, Japan. [Copyright &y& Elsevier]

This study determines the efficiency of polyaluminium chloride application on phytoplankton species as a consequence of five reservoir restorations in the Czech Republic during the years 2005 and 2008, including the first ever large-scale application. Although polyaluminium chloride has been used in water treatment plants across the world, information about its application toward cyanobacterial blooms in nature is poor. Although the application of polyaluminium chloride did not cause any fundamental long-term changes in the composition of phytoplankton species or phosphorus load, instead causing fast and acute removal of the phytoplankton community, it may act as an algicidal compound with fast removal efficiency. All treated water bodies described in our study remained unaffected by cyanobacterial blooms and the hygienic limit for the purposes of recreation was not exceeded in any particular season. This article should serve as notice of the advantages and disadvantages of polyaluminium chloride application, and also warn against the uniform usage of this chemical as a method of reducing phytoplankton species in all types of water bodies where cyanobacteria are present. Moreover, data about the effects on non-target (invertebrates) species and microcystin release from cyanobacterial cells are also mentioned. [ABSTRACT FROM PUBLISHER]

A brief history of South African research on and management of algae-, phytoplankton- and eutrophication-related problems is presented, including their ecological, social and economic impacts, which provides a basis for formulation of future research needs. The contributions of southern African research on different groups of algae and cyanobacteria are discussed. The role of algal and phytoplankton research and the focus shift to cyanobacteria, because of eutrophication in South African aquatic systems, are highlighted, which indicates the different modelling and management methods that have been used and tested. Recommendations are made for future research. [ABSTRACT FROM PUBLISHER]

Abstract: Cyanobacterial toxins constitute one of the most high risk categories of waterborne toxic biological substances. For this reason there is a clear need to know which freshwater environments are most susceptible to the development of large populations of cyanobacteria. Phytoplankton data from 134 UK lakes were used to develop a series of Generalised Additive Models and Generalised Additive Mixed Models to describe which kinds of lakes may be susceptible to cyanobacterial blooms using widely available explanatory variables. Models were developed for log cyanobacterial biovolume. Water colour and alkalinity are significant explanatory variables and retention time and TP borderline significant (R2-adj=21.9%). Surprisingly, the models developed reveal that nutrient concentrations are not the primary explanatory variable; water colour and alkalinity were more important. However, given suitable environments (low colour, neutral-alkaline waters), cyanobacteria do increase with both increasing retention time and increasing TP concentrations, supporting the observations that cyanobacteria are one of the most visible symptoms of eutrophication, particularly in warm, dry summers. The models can contribute to the assessment of risks to public health, at a regional- to national level, helping target lake monitoring and management more cost-effectively at those lakes at the highest risk of breaching World Health Organisation guideline levels for cyanobacteria in recreational waters. The models also inform restoration options available for reducing cyanobacterial blooms, indicating that, in the highest risk lakes (alkaline, low colour lakes), risks can generally be lessened through management aimed at reducing nutrient loads and increasing flushing during summer. [Copyright &y& Elsevier]

This study investigated the seasonal development of phytoplankton and potential microcystin (MC)-producing cyanobacteria and MC concentrations in freshwater lakes in Uganda. During 1 year (May 2007-April 2008), monthly measurements were made of chemical and physical characteristics, phytoplankton composition and MC concentrations in a hypertrophic crater lake (Lake Saka), in shallow eutrophic lakes (Lakes Mburo, George and Edward) and in Lake Victoria (Murchison Bay, Napoleon Gulf). Throughout the study period, cyanobacteria (composed of the genera Anabaena, Aphanocapsa, Chroococcus, Cylindrospermopsis, Microcystis, Planktolyngbya and Planktothrix) dominated, always contributing >50% to the total phytoplankton biovolume. All samples from all sampling sites were found to contain MC. Samples from Lake Saka had the maximum MC concentration (10 μg L) in July 2007. The minimum concentration (0.02 μg L) was recorded in Lake George for the months of May and June 2007 and January and April, 2008. Intermediate MC concentrations (0.1-2.5 μg MC-LR eq. L) were observed at all the sampling sites in the other three lakes. Highly significant positive linear relationships between the total MC concentration and Microcystis cell numbers were observed for all sampling sites. Relating the total MC concentrations to Microcystis cells revealed a >100-fold variation in the average MC contents per cell between lakes. While Microcystis from Lake George exhibited the lowest MC cell quotas (0.03-1.24 fg cell), Microcystis from Lake Saka consistently exhibited maximum MC cell contents (14-144 fg cell). It was concluded that MC production was because of the occurrence of Microcystis at all sampling sites. The populations differed consistently between sites and independent of the season in their average MC content per cell. [ABSTRACT FROM AUTHOR]

The phytoplankton lake community model PROTECH (Phytoplankton RespOnses To Environmental CHange) was applied to the eutrophic lake, Esthwaite Water (United Kingdom). It was validated against monitoring data from 2003 and simulated well the seasonal pattern of total chlorophyll, diatom chlorophyll and Cyanobacteria chlorophyll with respective R2-values calculated between observed and simulated of 0.68, 0.72 and 0.77 (all P<0.01). This simulation was then rerun through various combinations of factorized changes covering a range of half to double the flushing rate and from −1 to +4 °C changes in water temperature. Their effect on the phytoplankton was measured as annual, spring, summer and autumn means of the total and species chlorophyll concentrations. In addition, Cyanobacteria mean percentage abundance (%Cb) and maximum percentage abundance (Max %Cb) was recorded, as were the number of days that Cyanobacteria chlorophyll concentration exceed two World Health Organization (WHO) derived risk thresholds (10 and 50 mg m−3). The phytoplankton community was dominated in the year by three of the eight phytoplankton simulated. The vernal bloom of the diatom Asterionella showed little annual or seasonal response to the changing drivers but this was not the case for the two Cyanobacteria that also dominated, Anabaena and Aphanizomenon. These Cyanobacteria showed enhanced abundance, community dominance and increased duration above the highest WHO risk threshold with increasing water temperature and decreasing flushing rate: this effect was greatest in the summer period. However, the response was ultimately controlled by the availability of nutrients, particularly phosphorus and nitrogen, with occasional declines in the latter's concentration helping the dominance of these nitrogen-fixing phytoplankton. [ABSTRACT FROM AUTHOR]

A numerical model was developed to simulate water quality and algal species composition in a deep lake. As artificial destratification is widely used in the lakes, a destratification (bubble plume) model was incorporated with the ecological model to simulate the dynamic responses of different species under artificial mixing. The ecological model predicts concentrations of PO4-P, NH4-N, NO3-N, DO and pH throughout the water column, all of which have a significant influence on the growth of different algal species. The model has been calibrated using data from Uokiri Lake (Japan) for two different species (Diatom and Cyanobacteria) with and without artificial mixing. The calibrated model was used to simulate different conditions of artificial mixing within the lake over a period of five months. The simulation results show that artificial mixing favors non-motile heavier species, such as Diatom, while preventing the growth of Blue-green algae. It is also demonstrated that intermittent operation of the artificial mixing is better for water quality amelioration than continuous operation. [ABSTRACT FROM AUTHOR]

Abstract: Algae are aquatic organisms classified separately from plants. They are known to cause many hazards to humans and the environment. Algae strands contain nitrogen-producing cells that help them float (heterocysts). It is hypothesized that if the membranes of these cells are disrupted by means of ultrasound, the gas may be released analogous to sonic cracking, causing the strands to sink. This is a desirable ecological effect, because of the resulting suppressed release of toxins into the water. We subjected small quantities of blue-green algae of the Anabaena sphaerica species to ultrasound of frequencies and pressures in the clinical diagnostic range, and observed the changes in brightness of these solutions over time. Blue-green algae were forced to sink at any ultrasonic frequency we studied, supporting our hypothesis that heterocysts release nitrogen under ultrasound insonification in the clinical diagnostic range. Although the acoustic fields we used to eradicate blue-green algae are perfectly safe in terms of mechanical index, the acoustic pressures surpass the NURC Rules and Procedures by over 35dB. Therefore, caution should be taken when using these techniques in a surrounding where aquatic or semi-aquatic animals are present. [Copyright &y& Elsevier]

The relationships among environmental conditions and phytoplankton assemblages were characterized during late summer (2003-2005) in Saginaw Bay, Lake Huron. Differences among sampling stations, arising primarily from spatial disparities in water-column optical properties and nutrient availability, were evident. Cyanobacteria and diatoms dominated phytoplankton assemblages, with the greatest total chlorophyll a concentrations occurring at the innermost portions of the Bay. Microcystis abundance was greatest in the Bay's upper reaches and decreased with increasing distance from the mouth of the Saginaw River. A suite of variables, indicative of annually-distinct meteorological and hydrological conditions and phosphorus-laden inflows, were identified to (collectively) best 'group' stations in a manner consistent with that of phylogenetic-group chlorophyll a concentrations and cyanobacterial biovolumes. However, a great deal of variability between abiotic and biotic patterns remained unexplained and several abiotic variables singularly corresponded with Microcystis abundance. Taken together, it appears that multiple environmental conditions (including annual/episodic meteorological patterns, seasonal/intermittent riverine inflows, annual phosphorus loading, etc.) interact with taxon-specific physiological traits to holistically influence late-summer phytoplankton abundance throughout inner Saginaw Bay. [ABSTRACT FROM AUTHOR]

1. Loch Leven is a shallow, eutrophic lake in Scotland, U.K. It has experienced much change over the 30 years that it has been studied; this has primarily been due to reduced nutrient loads to the lake through active catchment management. Its recovery has been slow and, therefore, we used a phytoplankton community model (PROTECH) to test its sensitivity to changing nutrient loads and water temperature. 2. PROTECH was initialized to simulate the observed phytoplankton community in 1995 and was then repeatedly run through a combination of step-wise changes in water temperature and nutrient load (two treatments were simulated for nutrient load: one changing both nitrate and phosphorus, and one changing just phosphorus). The effect on total chlorophyll- a concentration, cyanobacteria abundance and phytoplankton diversity was examined. 3. Whilst changes in temperature had little effect, variations in the nutrient load produced a range of responses. Increasing only the phosphorus load caused a large increase in Anabaena abundance and total chlorophyll- a concentration. However, the opposite response was recorded when nitrate load was changed as well, with Anabaena increasing its biomass under reduced nutrient load scenarios. 4. The key factor determining the type of response appeared to be nitrogen availability. Anabaena, a nitrogen fixer, could exploit the phosphorus resource of Loch Leven under limiting nitrogen conditions, allowing it to dominate under most of the scenarios tested apart from those supplying extra nitrogen to the lake. The model predictions agree with the observed data, which show that Anabaena continues to dominate the summer phytoplankton bloom in Loch Leven despite the considerable reduction in phosphorus supply from the catchment. This research provides a possible explanation for this. [ABSTRACT FROM AUTHOR]

Saladito Reservoir, located in Cienfuegos Province in Cuba, lies in an intermediate position between tropical and subtropical climatic conditions. Although Cuba only had 13 reservoirs before 1959, the government has constructed 229 reservoirs since that time, with a total storage capacity of 8.81 km3, administered by the National Hydraulic Resources Institute. In 1995, it was proposed to use waste water from the Swinish Farm to fertilize small reservoirs, providing nitrogen and phosphorus to increase primary production in the reservoirs as a means of facilitating high fish production levels. Saladito Reservoir, with a hydrographic basin of 34.5 km2, a mean depth of 3.4 m and a water retention time of 2 years, was constructed as the final part of the wastewater treatment system for Swinish Farm in the Palmyra Municipality. The main objective of this study is to determine the level of eutrophication in the reservoir after it had received waste water from the Farm for 17 months, based on relevant biological (phytoplankton), chemical and physical indicators sampled at five stations on 22 and 23 May 1995. Based on the measured parameters, the concentration of dissolved salts was generally high, with calcium and bicarbonate being the dominant ions. The nitrite-nitrogen and nitrate-nitrogen concentrations were relatively low at the surface, increasing with depth, while the ammonium-nitrogen concentrations were extremely high, likely related to the high organic content of the reservoir. The total phosphorus concentration also exhibited high values, indicating the possible existence of soluble phosphorus in a complex with iron, which would allow algae to assimilate it like phosphate. The water transparency, measured as Secchi disk, was 0.2 m at all sampling stations. The chlorophyll-a concentration ranged from 111 µg L−1 in the surface water to 50 µg L−1 at the bottom depth. The phytoplankton cell counts identified 27 algal species contained in five classes. The dominant group was Cyanophyceae, with Oscillatoria sp. being the largest contribution to the reservoir biomass. Twenty-seven taxa were present in the reservoir in concentrations of at least 1 mg m−3. The results of this study indicate that Saladito Reservoir is hyper-eutrophic, based on its measured biomass (cell counts), and chlorophyll-α, inorganic nitrogen and total phosphorus concentrations. The possible production of algal toxins from blue-green algal growths also could be affecting the productivity of Saladito Reservoir. [ABSTRACT FROM AUTHOR]

Synchrotron-based Fourier-transform infrared (FTIR) microspectroscopy was used to characterize micropopulations of the cyanobacteria Anabaena flos-aquae and Aphanizomenon flos-aquae in mixed phytoplankton samples taken from the epilimnion and hypolimnion of a stratified eutrophic lake (Rostherne Mere, UK). All FTIR spectra (normalized to amide I) showed a closely similar sequence of 10 bands over the wavenumber range 4,000–900&ThickSpace;cm -1 and were assigned to a range of vibrationally active chemical groups. Interspecific differences between Anabaena and Aphanizomenon were revealed using correlation and multivariate analysis (principal component analysis, PCA) of the set of individual band intensities. Differences between species (separately for epilimnion and hypolimnion) were also analysed by comparing band intensity means, and by performing PCA over a broad spectral region (1,750–900&ThickSpace;cm -1 ). Comparison of intensity means showed that spectra obtained from epilimnetic algae had significant differences in bands 5–7 and in bands 4, 9 and 10. However, in the spectra obtained from the hypolimnion algae, a different pattern was observed, with significant differences between the species restricted to bands 7–10. PCA of the spectral region 1,750–900&ThickSpace;cm -1 also demonstrated interspecific differences in relation to carbohydrate and protein concentrations, with Anabaena displaying higher carbohydrate levels in both the epilimnion and hypolimnion. Intraspecific comparisons of band intensity means for epilimnion and hypolimnion subpopulations demonstrated clear differences in Aphanizomenon , where significant differences were observed between epilimnion (higher carbohydrate concentration compared with protein) and hypolimnion (lower carbohydrate concentration compared with protein) subpopulations. Anabaena however showed only minor differences. PCA comparison of the spectral region 1,750–900&ThickSpace;cm -1 , followed by data visualization using scores plots and loading plots, also demonstrated quantitative differences. Scores plots resolved the epilimnion and hypolimnion subpopulations in Aphanizomenon (but not Anabaena ), with the loading plot showing large differences in carbohydrates, supporting the analysis using discrete peak intensities. [ABSTRACT FROM AUTHOR]

Silver carp Hypophthalmichthys molitrix (Valenciennes) were co-cultured with channel catfish Ictalurus punctatus (Rafinesque) in 0.4 ha earthen ponds to determine the impacts of carp grazing on pond phytoplankton communities and cyanobacterial off-flavours in catfish. Carp were stocked at densities of 0, 75, or 250 fish ha−1 in seven replicate ponds per treatment. The mean chlorophyll a concentrations (a measure of phytoplankton standing crop) steadily increased in all treatments from about 100 μg L−1 in April to more than 400 μg L−1 by mid-October. Silver carp had no affect ( P>0.1) on chlorophyll a concentrations across all sampling dates (April though October) or for sampling dates late in the growing season (August–October) when the prevalence of cyanobacterial off-flavours among catfish populations is usually greatest. Silver carp did not eliminate odour-producing cyanobacteria from pond phytoplankton communities: on sampling dates in September and October, three to six ponds in all treatments contained populations of the odour-producing cyanobacteria Oscillatoria perornata, Anabaena spp., or both. Failure of silver carp to eliminate odour-producing cyanobacteria resulted in a relatively high incidence in all treatments of ponds with off-flavoured catfish. On sampling dates in September and October, catfish in three to five ponds in each treatment were tainted with either musty (2-methylisoborneol) or earthy (geosmin) off-flavours. The presence of silver carp had no obvious effect on off-flavour intensity: on each sampling date, at least three ponds in each treatment contained catfish described as distinctly to extremely off-flavored. Apparently, hypertrophic conditions in catfish ponds overwhelm the effect of silver carp grazing at the low carp densities used in this study. [ABSTRACT FROM AUTHOR]

1. Linking a regional climate model (RCM) configured for contemporary atmospheric greenhouse gas concentrations, with a phytoplankton community model (PROTECH) produced realistic simulations of 20 years of recent phytoplankton data from Bassenthwaite Lake, in the North-West of England. 2. Meteorological drivers were derived from the RCM to represent a future climate scenario involving a 1% per annum compound increase in atmospheric CO2 concentrations until 2100. Using these drivers, PROTECH was run for another 20 year period representing the last two decades of the 21st century. 3. Comparison of these present and future simulations revealed likely impacts on the current seasonal phytoplankton development. Under future climate conditions, the simulated spring bloom showed an increase in cyanobacteria dominance caused by greater success of Planktothrix. Also, the summer cyanobacteria bloom declined earlier because of nutrient limitation caused by the increased spring growth. Overall productivity in the lake did not change. 4. Analysis showed that these predicted changes were driven by changes in water temperature, which were in turn triggered by the higher air temperatures predicted by the RCM. [ABSTRACT FROM AUTHOR]

Between 1991 and 1993, Saginaw Bay experienced an invasion by zebra mussels, Dreissena polymorpha, which caused a significant perturbation to the ecosystem. Blooms of Microcystis, a toxin-producing blue-green alga, became re-established in the bay after the zebra mussel invasion. Microcystis blooms had all but been eliminated in the early 1980s with controls on external phosphorus loadings, but have re-occurred in the bay most summers since 1992. An apparent paradox is that these recent Microcystis blooms have not been accompanied by increases in external phosphorus loadings. An ecosystem model was used to investigate whether the re-occurrence of Microcystis could be due to changes caused by zebra mussels that impacted phytoplankton community structure and/or internal phosphorus dynamics. The model was first used to establish baseline conditions in Saginaw Bay for 1991, before zebra mussels significantly impacted the system. The baseline model was then used to investigate: (1) the composite impacts of zebra mussels with average 1991-1995 densities; (2) sensitivity to changes in zebra mussel densities and external phosphorus loadings; and (3) three hypotheses on potential causative factors for proliferation of blue-green algae. Under the model assumptions, selective rejection of blue-green algae by zebra mussels appears to be a necessary factor in the enhancement of blue-green production in the presence of zebra mussels. Enhancement also appears to depend on the increased sediment-water phosphorus flux associated with the presence of zebra mussels, the magnitude of zebra mussel densities, and the distribution of zebra mussel densities among different age groups. [ABSTRACT FROM AUTHOR]

Responses of plankton and fish communities to mass removal of cyprinid fishes were studied in a two-basin lake, Äimäjärvi, in southern Finland during 1997–2001. Fish were removed from the lake with fyke nets and seining. By spring 2001, the cumulative catches were 276 kg ha-1 in the northern and 226 kg ha-1 in the southern basin. Roach dominated the catches of both basins. From summer 1997 to 2001 the total biomass of phytoplankton decreased from 10–30 to 5–13 mg l-1 in the more eutrophic northern basin and from 5–19 to 2-4 mg l-1 in the southern basin, respectively. The occurrence of maximum biomass of blue-green algae moved from July to August towards autumn during the study period. The mean biomass of cladoceran crustaceans in July to August showed a slightly increasing trend from 100–150 to 150–200 μg C l-1. The biomasses of Daphnia spp. and Bosmina coregoni were higher in 2000 and 2001 compared to earlier years. The annual mean total catches of multimesh gillnets, dominated by roach, were 3.9–5.1 kg net-1 in the northern and 1.8–2.6 kg net-1 in the southern basin. A slight decrease took place in the gillnet catches in the southern basin but not in the northern. The increased growth of young perch and roach in the last years of the study period was attributed to the thermal conditions rather than to the fish removal. [ABSTRACT FROM AUTHOR]

Biological systems are variable and there are fundamental limits on the predictability of, e.g. phytoplankton concentrations in rivers and lakes. How does inherent uncertainties in empirical data constrain our approaches to prediction? This paper addresses this question in discussing one of the most fundamental concepts in predictive ecosystem modelling, the uncertainty in the empirical y-variable used to validate model predictions. So, the focus of this paper is not on concentrations but on coefficients of variation (CV: S.D./MV; S.D.: standard deviation, MV: mean value). The CV-values regulate the theoretically highest predictive power of models and the reliability of data used for model validations. We have collected an extensive data-base from the River Danube (at a site close to Regensburg) as a basis for these analyses. The water samples have been analysed using delayed fluorescence (DF), a technique which makes it possible to obtain compatible data on the five algal variables used in this study, green algae, diatoms, cryptophytes and blue-greens (cyanobacteria) as well as total chlorophyll. We have also compared these results on CVs with results from other river sites and lakes. This study shows that: (1) The monthly variations in CV based on data from several years show similar patterns for the five algal variables, but the CVs are generally somewhat higher for all five variables in September and October and lower in April and May. (2) The monthly CVs do not seem to be significantly related to the mean values or the flow velocity. (3) There are no significant differences in monthly CVs among the five variables, although the blue-greens may have the highest CV and cryptophytes and green algae the lowest. (4) The daily, weekly, monthly (based on individual months, e.g. January a given year), monthly (based on data from several years, e.g. January for several years) and yearly CVs increase from 0.3, 0.35, 0.55, 0.80 to 0.95, respectively, for chlorophyll (and similar values also apply to the four other algal variables). This means that it is unlikely that a model for monthly chlorophyll concentrations in rivers would yield r2-values higher than about 0.6. This information is of great importance in science and water management since it means that we can never expect to derive models that could predict monthly chlorophyll concentrations in rivers well. (5) The mean CV for chlorophyll based on all data from the Regensburg site is 0.96, which is close to the median value from 19 rivers sites in the UK. (6) The correlation between the monthly mean values and the monthly peak values were found to be strong, but this is partly spurious. [Copyright &y& Elsevier]

The specific composition, vertical distribution and daily migration of plankton in a meromictic salt lake, Lake Shira, have been investigated. The main structural components of the ecosystem are bacteria, algae and crustaceans. Since the late 1970s, blue-green algae are reported as dominant. Nowadays the phytoplankton is dominated by Lyngbya contorta, Microcystis ichtyoblabe (Cyanophyta), Cyclotella tuberculata (Bacillariophyta) and Dictyosphaerium tetrachotomum (Chlorophyta). The zooplankton of Lake Shira comprises Arctodiaptomus salinus (Copepoda), Brachionus plicatilis and Hexarthra oxiuris (Rotatoria). Investigation revealed a stratified vertical distribution of all dominant species except Cyclotella with a maximum at a depth of 12–15 m during the summer growth period. Zooplanktons differ in the pattern of distribution and daily migration, but most zooplankton tend to concentrate near the surface. The possible reasons for the vertical distribution of the plankton are discussed. [ABSTRACT FROM AUTHOR]

Epiphyte communities in a phosphorus-limited hard-water lake were compared over a 14-week period from Potamogeton illinoensis and structurally similar artificial plants of different leaf ages. Artificial plants were serially incubated in the lake to simulate the age of natural leave. The physiognomy of loosely attached epiphytes appeared similar on the two substrata. Algal cell number and biovolume were 15-fold and 17-fold higher, respectively, on artificial leaves early in the growing season, but total algal density gradually became similar on natural and artificial plants. In contrast, the taxonomic composition of loosely attached algae became increasingly distinct, and mean cell biovolume on natural leaves was twice that on artificial leaves. Adnate epiphytes on both sub-strata developed from sparse populations of bacteria on new leaves to a community of diatoms, blue-green algae and numerous bacteria on mature and senescent leaves. Adnate community succession on natural leaves in late senescence/death differed from that on artificial leaves colonized for comparable periods in having (1) a marked increase infilamentous blue-green algae, (2) a final fungi-dominated stage. The trends in colonization indicate that macrophytes in this aligotrophic lake provided a distinct habitat from that of artificial substarta for epiphytes throughout the growing season. [ABSTRACT FROM AUTHOR]

Ratios are commonly used to relate taxonomic, physiological and ecological properties of algal cells to variation in cell shape and size. However, ratios can be more difficult to interpret than the original variables. A detailed example of a ratio commonly used in diatom taxonomy is presented. The abundance of a repeated rotational element on a centric diatom valve is of ten expressed as density (e.g. number of marginal spines per μm Of circumference), rather than simply as total number. It is expirically demonstrated that density is often curvilinearly related to diameter, whereas total number is linearly related (when related at all) to diameter. This linear relationship is the basis for on empirical model which accounts for variation in density in real examples. Under this model, density will be a poorer taxonomic character than total number except under rare occasions (e.g. when the slope of the total element versus diameter regression is zero and variance in the numerator is not dependent on the denominator). Other ratios are similarly difficult to interpret. Length / width (or width / length) is often curvilinearly related to width (length) because variation is compounded from several sources. Surface / volume has been employed to investigate the relative contributions of size and shape to phytoplankton sinking. However, the properties of this ratio have not been fully investigated, and the relationship between size, shape and sinking rate has not been fully elucidated for the data set in question. [ABSTRACT FROM AUTHOR]