Seasonal phytoplanktonic diversity of Kitham lake, Agra

Two years (Jan. 2000 - Dec. 2001) data on the seasonal studies of phytoplanktonic diversity of Kitham lake (Sur Sarovar) Agra revealed the presence of 73 algal species. A limited number of these were recorded throughout the year, while others were distributed in different seasons mainly in winter and summer seasons. During winters, Chlorophyceae was the most dominant group followed by Bacillariophyceae. On the other hand, Cyanophyceae and Euglenophyceae were the most dominant during summers. Certain species e.g. Pandorina morum, Pediastrum tetras, Gonium sp., Chlorella vulgaris, Scendesmus quadricauda, Oedogonium cardiocum, Synedra ulna, Oscillatoria agardhii and Euglena gracillis were recorded throughout the year. Chlorella, Stigeoclonium, Pandorina, Micratinium, Oscillatoria, Anacystis, Nitzschia and Cymbella were found to be good indicators of water pollution.     

Effect of pH on biologic degradation of Microcystis aeruginosa by alga-lysing bacteria in sequencing batch biofilm reactors

In this paper, the effect of pH on biological degradation of Microcystis aeruginosa by alga-lysing bacteria in laboratory-scale sequencing batch biofilm reactors (SBBRs) was investigated. After 10 d filming with waste activated sludge, the biological film could be formed, and the bioreactors in which laid polyolefin resin filler were used to treat algal culture. By comparing the removal efficiency of chlorophyll a at different aerobic time, the optimum time was determined as 5 h. Under pH 6.5, 7.5, and 8.5 conditions, the removal rates of Microcystis aeruginosa were respectively 75.9%, 83.6%, and 78.3% (in term of chlorophyll a), and that of Chemical Oxygen Demand (COD_Mn) were 30.6%, 35.8%, and 33.5%. While the removal efficiencies of ammonia nitrogen (NH ₄ ⁺ - N) were all 100%. It was observed that the sequence of the removal efficiencies of algae, NH ₄ ⁺ - N and organic matter were pH 7.5>pH 8.5>pH 6.5. The results showed that the dominant alga-lysing bacteria in the SBBRs was strain HM-01, which was identified as Bacillus sp. by Polymerase Chain Reaction (PCR) amplification of the 16S rRNA gene, Basic Local Alignment Search Tool (BLAST) analysis, and comparison with sequences in the GenBank nucleotide database. The algicidal activated substance which HM-01 strain excreted could withstand high temperature and pressure, also had better hydrophily and stronger polarity.     

Antioxidant enzyme activities of <Emphasis Type="Italic">Microcystis aeruginosa</Emphasis> in response to nonylphenols and degradation of nonylphenols by <Emphasis Type="Italic">M. aeruginosa</Emphasis>

The aim of this study was to examine the effects of chemical nonylphenols (NPs) on the antioxidant system of Microcystis aeruginosa strains. The degradation and sorption of NPs by M. aeruginosa were also evaluated. High concentrations of NPs (1 and 2 mg/l) were found to cause increases in superoxidase dismutase (SOD) and glutathione-S-transferase (GST) activities and in glutathione (GSH) levels. These results suggest that toxic stress manifested by elevated SOD and GST levels and GSH contents may be responsible for the toxicity of NPs to M. aeruginosa and that the algal cells could improve their antioxidant and detoxification ability through the enhancement of enzymatic and nonenzymatic prevention substances. The observed elevations in GSH levels and GST activities were relatively higher than those in SOD activities, indicating that GSH and GST contributed more in eliminating toxic effects than SOD. Low concentrations of NPs (0.05–0.2 mg/l) enhanced cell growth and decreased GST activity in algal cells of M. aeruginosa, suggesting that NPs may have acted as a protecting factor, such as an antioxidant. The larger portion of the NPs (>60%) disappeared after 12 days of incubation, indicating the strong ability of M. aeruginosa to degrade the moderate persistent NP compounds. The sorption ratio of M. aeruginosa after a 12-day exposure to low nominal concentrations of NPs (0.02–0.5 mg/l) was relatively high (>30%). The fact that M. aeruginosa effectively resisted the toxic effects of NPs and strongly degraded these pollutants indicate that M. aeruginosa cells have a strong ability to adapt to variations in environmental conditions and that low and moderate concentrations of organic compounds may favor its survival. Further studies are needed to provide detailed information on the fate of persistent organic pollutants and the survival of algae and to determine the possible role of organic pollutants in the occurrence of water blooms in eutrophic lakes.     

Microzooplankton grazing and selectivity of phytoplankton in coastal waters

Microzooplankton grazing activity in the Celtic Sea and Carmarthen Bay in summer 1983 and autumn 1984 was investigated by applying a dilution technique to high-performance liquid chromatographic (HPLC) analysis of photosynthetic pigments in phytoplankton present within natural microplankton communities. Specific grazing rates on phytoplankton, as measured by the utilisation of chlorophyll a, were high and varied seasonally. In surface waters during the autumn, grazing varied between 0.4 d^-1 in the bay and 1.0 d^-1 in the Celtic Sea, indicating that 30 and 65% of the algal standing stocks, respectively, were grazed daily. Grazing rates by microzooplankton within the thermocline in summer suggest that 13 to 42% of the crop was grazed each day. Microzooplankton showed selection for algae containing chlorophyll b, in spite of a predominance of chlorophyll c within the phytoplankton community. Changes in taxon-specific carotenoids indicated strong selection for peridinin, lutein and alloxanthin and selection against fucoxanthin and diadinoxanthin. This indicates a trophic preference by microzooplankton for dinoflagellates, cryptophytes, chlorophytes and prasinophytes and selection against diatoms, even when the latter group forms the largest crop within the phytoplankton. Interestingly, those algal taxa preferentially grazed also showed the highest specific growth-rates, suggesting a dynamic feed-back between microzooplankton and phytoplankton. Conversion of grazing rates on each pigment into chlorophyll a equivalents suggests firstly, that in only one experiment could all the grazed chlorophyll a be accounted for by the attrition of other chlorophylls and carotenoids, and secondly that in spite of negative selection, a greater mass of diatoms could be grazed by microzooplankton than any other algal taxon. The former may be due either to a fundamental difference in the break-down rates of chlorophyll a compared to other pigments, or to cyanobacteria forming a significant food source for microzooplankton. In either case, chlorophyll a is considered to be a good measure of grazing activity by microzooplankton.     

Seasonal study of phytoplankton pigments and species at a coastal station off Sydney: Importance of diatoms and the nanoplankton

Phytoplankton pigments and species were studied at a coastal station off Sydney (New South Wales, Australia) over one annual cycle. Sudden increases in chlorophyll a (up to 280 mg m^-2), due to short-lived diatom blooms, were found in May, July, September, January and February. These were superimposed upon background levels of chlorophyll a (20 to 50 mg m^-2), due mostly to nanoplankton flagellates, which occurred throughout the year. The nanoplankton (<15 m) accounted for 50 to 80% of the total phytoplankton chlorophyll, except when the diatom peaks occurred (10 to 20%). The annual cycle of populations of 16 dominant species-groups was followed. Possible explanations as to alternation of diatom-dominated and nanoplankton-dominated floras are discussed. Thin-layer chromatography of phytoplankton pigments was used to determine the distribution of algal types, grazing activity, and phytoplankton senescence in the water column. Chlorophyll c and fucoxanthin (diatoms and coccolithophorids) and chlorophyll b (green flagellates) were the major accessory pigments throughout the year, with peridinin (photosynthetic dinoflagellates) being less important. Grazing activity by salps and copepods was apparent from the abundance of the chlorophyll degradation products pheophytin a (20 to 45% of the total chlorophyll a) and pheophorbide a (10 to 30%). Chlorophyllide a (20 to 45%) was associated with blooms of Skeletonema costatum and Chaetoceros spp. Small amounts of other unidentified chlorophyll a derivatives (5 to 20%) were frequently observed.     

滇池水体磷的时空变化与藻类生长的关系

水体磷的时空变化与藻类生长的关系对研究水体富营养化具有十分重要的作用。采用GPS定位,对滇池海埂、斗南、罗家村、新街、昆阳等5个代表性位点监测断面水体总磷、可溶性磷及叶绿素a含量进行了为期1年（2003年5月至2004年5月）的动态研究,并在滇池海埂位点进行了日变化试验,全面分析了滇池不同区域、不同层次、不同时期水体总磷和可溶性磷的年变化、日变化及水体氮/磷比对藻类生长的影响。结果表明,滇池水体磷与藻类生长呈现显著的年变化和日变化特征,显示了滇池全湖水体总磷与叶绿素a周年变化呈显著正相关,水体可溶性磷与叶绿素a呈正相关趋势;海埂位点水体总磷与叶绿素a日变化呈显著正相关,水体可溶性磷与叶绿素a日变化呈显著的负相关,水体氮磷比与叶绿素a呈显著正相关。表明水体磷负荷对藻类生长影响呈现显著的水体区域性和水层差异性和季节性,藻类生长主要吸收水体中的可溶性磷,暗示了滇池水体磷是藻类生长的主要限制因子之一。     

Profiles of photosynthetic pigments in the ocean using thin-layer chromatography

Phytoplankton pigments at a coastal station off Sydney, Australia, were studied by cellulose thinlayer chromatography. The chromatographic procedure distinguished chlorophylls a, b and c, chlorophyllide a, pheophytin a and pheophorbide a, and the major carotenoids carotene, astaxanthin, fucoxanthin, peridinin, diadinoxanthin and neoxanthin. Chlorophyllide a and pheophorbide a were the most significant chlorophyll-a degradation products in the water column, chlorophyllide a coming from chlorophyllase activity of senescent diatoms, and pheophorbide a from faecal pellets of copepods. Chlorophyll c occurred in every sample, even where there was no trace of chlorophyll a. Because of the greater chemical and biological stability of chlorophyll c compared to chlorophyll a, high chlorophyll c:a ratios result from a large proportion of senescent or detrital material in the samples. Determining the position of patches of copepods, diatoms, green algae and dinoflagellates in the water column was easily done by noting the presence of definitive pigments on the chromatograms.     

Light absorption by a marine diatom: experimental observations and theoretical calculations of the package effect in a small Thalassiosira species

The relationship between in vivo light absorption efficiency of whole cells and in vitro absorption efficiency of algal pigments has been examined experimentally in the marine diatom Thalassiosira sp. In vitro absorption spectra were obtained for cells disrupted by either ultrasonic treatment or high-pressure shearing stress in a low-temperature (-40°C) pressure cell. A dimensionless measure of the magnitude of the package effect (Q _a ^*), calculated from the ratio of whole-cell to disrupted-cell absorption, ranged from about 0.5 at the blue absorption peak of chlorophyll a (λ=435 nm) to 0.7 at the red chlorophyll a peak (λ=670 nm) to 1.0 at the absorption minimum (λ=600 nm). Cell diameter was found to be an inappropriate measure of size for assessing the magnitude of the package effect. Instead, the effective optical diameter for calculation of intracellular self-shading was found to be less than the cell diameter. This observation is consistent with the fact that most algal pigments are contained within chloroplasts, and that chloroplast volume is necessarily smaller than cell volume.     

Fate and effects of nonylphenol in the presence of the cyanobacterium Microcystis aeruginosa

Interactions of nonylphenol (NP), a toxic and oestrogenic degradation product of widely used non-ionic surfactants, with the cyanobacterium Microcystis aeruginosa were studied. Batch cultures were incubated for 10 days with NP concentrations between 10 and 570 nM. NP was removed more quickly in the presence of M. aeruginosa (half-life 2.7–5.2 days) than in its absence (half-life 6.7–10.2 days) at all concentrations tested. At the end of the experiment, NP could not be found in the biomass, so the biotic removal is due to uptake and chemical transformation, and not to physical binding on the cells. The observed effective concentrations, EC₅₀ and EC₂₀, were 0.45 and 0.25 μ M, respectively. Therefore, NP is expected to have toxic effects on M. aeruginosa only in very contaminated surface waters. However, for concentrations that go far beyond environmental levels, cyanobacteria are able to cope with NP toxicity by internalising the compound in a less toxic form. Therefore, the presence of cyanobacteria may increase the rate of NP removal from the aquatic environment.     

Annual cycles of phytoplankton community-structure and bloom dynamics in the Neuse River Estuary, North Carolina

The spatiotemporal distributions of major phytoplankton taxa were quantified to estimate the relative contribution of different microalgal groups to biomass and bloom dynamics in the eutrophic Neuse River Estuary, North Carolina, USA. Biweekly water samples and ambient physical and chemical data were examined at sites along a salinity gradient from January 1994 through December 1996. Chemosystematic photopigments (chlorophylls and carotenoids) were identified and quantified using high-performance liquid chromatography (HPLC). A recently-developed factor-analysis procedure (CHEMTAX) was used to partition the algal group-specific chlorophyll a (chl a) concentrations based on photopigment concentrations. Results were spatially and temporally integrated to determine the ecosystem-level dynamics of phytoplankton community-constituents. Seasonal patterns of phytoplankton community-composition changes were observed over the 3 yr. Dinoflagellates reached maximum abundance in the late winter to early spring (January to March), followed by a spring diatom bloom (May to July). Cyanobacteria were more prevalent during summer months and made a large contribution to phytoplankton biomass, possibly in response to nutrient-enriched freshwater discharge. Cryptomonad blooms were not associated with a particular season, and varied from year to year. Chlorophyte abundance was low, but occasional blooms occurred during spring and summer. Over the 3 yr period, the total contribution of each algal group, in terms of chl a, was evenly balanced, with each contributing nearly 20% of the total chl a. Cryptomonad, chlorophyte, and cyanobacterial dynamics did not exhibit regular seasonal bloom patterns. High dissolved inorganic-nitrogen loading during the summer months promoted major blooms of cryptomonads, chlorophytes, and cyanobacteria. Received: 12 September 1997 / Accepted: 12 December 1997     

Short-term variations in the pigment composition of a spring phytoplankton bloom from an enclosed experimental ecosystem

Phytoplankton samples taken during the spring bloom in the experimental enclosed ecosystem bags at Loch Ewe, Scotland, during 1983 were analysed for carotenoids and chlorophyll compounds using high-performance liquidchromatography (HPLC). Changes in the relative proportions of these pigments were related to day-to-day changes in the composition of the bloom and the physiological state of the algae. There is clear evidence for a change in the chlorophyllide a:chlorophyll a ratio, which reached a maximum as nutrient limitation occurred. No major qualitative changes in the carotenoid components were seen during the bloom; the relative proportion, however, of some carotenoids does provide useful information on the relative abundance of certain algal type in the phytoplankton.     

Relationships between nutrients and macroalgal biomass in a brazilian coastal lagoon: the impact of a lock construction

The Piratininga Lagoon is a coastal, choked, and brackish ecosystem in SE Brazil, where uncontrolled discharge of domestic sewage led to eutrophication, increasing massive proliferation of benthic macroalgae, and decrease of the lagoon mean depth. In 1992, a dam was constructed by the local Municipality at its tidal channel aiming at stabilising its water level. Main physico-chemical parameters, together with macroalgae biomass, nutrient concentrations in the water column, particulate organic carbon, and chlorophyll a were recorded monthly at 4 sampling stations within the Piratininga lagoon from April 1994 to April 1995. The data, compared with “before-lock” existing studies, show that nutrients and chlorophyll a concentrations significantly increased after the lock construction. Based on the functioning of the ecosystem, we propose to harvest the algal mats before their decomposition period in order to partly remove the nutrient stocks from the lagoon and the future ecosystem modelling to predict the impact of natural and anthropogenic eutrophication.     

The trophic role of glycolic acid in coastal seawater. II. Seasonal changes in concentration and heterotrophic use in Ipswich Bay,Massachusetts, USA

Glycolic acid is a known algal excretory product which is found in marine waters and is readily metabolized by marine bacteria. The following parameters were measured over the course of a year in Ipswich Bay: chlorophyll a, temperature, viable bacteria, heterotrophic uptake of glycolate, and glycolate concentrations. The latter two were combined to give estimates of the flux of glycolate for a station 3 km out in the bay and for an inshore station. Pronounced seasonal changes were found for all parameters. Statistically significant correlations between heterotrophic V _max and glycolic acid concentrations and temperature were found, but not between planktonic chlorophyll a and any of the other parameters. Measurements of glycolic acid flux yielded an annual flux of 2.84 g m^-2 for the bay station, which is about 0.5% of the bay phytoplankton production. Glycolic acid turns over roughly 12 times per year in the bay. It contributes perhaps as much to bacterial metabolism as any other single substrate, but is apparently not of dominating importance.     

Aspects of water column primary productivity in the Chukchi Sea during summer

Measurements of primary productivity, chlorophyll a, incident solar radiation, phosphate-P, silicate-Si, nitrate-N, nitrite-N, ammonium-N, temperature and salinity were made in the Marginal Ice Zone of the Chukchi Sea in summer 1974. Low to moderate levels of primary productivity (0.07 to 0.97 g C m^-2 half-day^-1) were observed; primary productivity exceeded 3 g C m^-2 half-day^-1 at two stations. Surface primary productivity was nitrogen-limited at most stations. Mean chlorophyll a concentration in the photic zone varied from 0.4 to 17.8 mg m^-3. Higher concentrations and significant subsurface accumulation of chlorophyll a, reaching 40 mg m^-3, were observed in July at stations near the ice-edge than those in open water. No chlorophyll maximum was noted in September, when values ranged from 0.4 to 2.2 mg m^-3. It is postulated that the contribution of sea-ice algae to the total chlorophyll content can be substantial, but that the stay of these cells in the water column may not be long. Non-linear regression estimates from solar radiation and chlorophyll-specific primary productivity data showed a maximal photosynthetic rate of 18 mg C mg chlorophyll a ^-1 half-day^-1, an optimal light intensity of 54 langleys half-day^-1, and markedly reduced primary productivity at moderately higher light intensities. These features indicate that phytoplankton was shade-adapted.     

Effect of epibionts on the microdistribution of chlorophyll in corals and its detection by fluorescence spectral imaging

The spatial distribution of chlorophyll in three coral species carrying invertebrate symbionts was determined using spectral imaging techniques. From each pixel of the image, full fluorescence spectral data was obtained as well as comparative ratios of fluorescence. The multipixel fluorescence map and the relative-intensity fluorescence ratios demonstrated a high concentration of chlorophyll a next to the pits of Cryptochirus coralliodytes in Favites halicora. Spectral similarity maps of Goniastrea retiformis infested with Lithophaga lessepsiana and of Millepora dichotoma infested with Savignium milleporum revealed relatively higher chlorophyll concentrations in these two corals next to the symbionts. We hypothesize that the invertebrate symbionts fertilize their immediate surroundings with their excreta, enhancing algal growth. The spectral analysis system used in this study made it possible to distinguish such changes by spatial quantitation of the fluorescence emitted from small surface areas.     

Diel changes in phytoplankton photosynthetic efficiency in Brackish waters

From 18 to 23 September 1974, investigations on the diel changes in phytoplankton were carried out in the Baltic Sea. Every 4 h, water samples were collected from 2 and 15 m, and PO₄, chlorophyll a, temperature, salinity, pH, phytoplankton composition and phytoplankton light photosynthesis relationship were determined. Continuous measurements of surface irradiance and some estimations of zooplankton were also made. P ^B (photosynthesis per unit chlorophyll a at low light levels of 2·10^-2 cal cm^-2 min^-1) revealed only random variation during the sampling period, i.e., 1.0 to 1.6 mg C (mg chlorophyll a)^-1 h^-1. P _m ^B (Light-saturated photosynthesis per unit of chlorophyll a) displayed pronounced diel fluctuations with the highest value of about 6 mg C (mg chlorophyll a)^-1 h^-1 around noon, and the lowest value of about 2.5 mg C (mg chlorophyll a)^-1 h^-1 during the night, during which latter period the value of P _m ^B was more or less constant. Reasons for the diel fluctuations are discussed, and an equation which describes these fluctuations is proposed. Using this equation, the daily phytoplankton production estimated in incubators by a previously described method can be corrected for the time of day at which samples are collected.     

Characterization of in vivo absorption features of chlorophyte,phaeophyte and rhodophyte algal species

Despite the plentiful diversity of macroalgae in coastal environments, few studies have examined the in vivo absorption features of common marine macrophytes. Here we report on results of a survey of 12 central California common intertidal and subtidal taxa, representing Chlorophyta, Phaeophyta and Rhodophyta carried out in the summer of 1988. Computer-assisted analyses were used to obtain fourth-derivative spectra from in vivo absorption spectra determined at room temperature to obtain spectral diagnostics for the different algal divisions and to provide a means to determine whether spectral features could be used to identify stress responses among these plants. Among the Chlorophyta, characteristic maxima for chlorophylls a and b were resolved in all species examined, and a spectral component attributable to siphonaxanthin-like carotenoid(s) was observed in two Ulva species and the coenocytic alga Derbesia marina. Representatives of the Phaeophyta were characterized by similar maxima for chlorophyll a and c, and for fucoxanthin. Among the Rhodophyta, maxima for chlorophyll a, as well as B- and R-type phycoerythrin were resolved. Differences in in vivo absorption features were detected for two tidal populations of Porphyra perforata and Mastocarpus papillatus. High-tidal thalli absorb less green light in regions characterized by phycoerythrin, but have enhanced carotenoid absorption compared with lowtidal thalli. Resolution of spectra by fourth-derivative analysis revealed significant differences in phycoerythrin and carotenoid contents. The spectral changes observed appear to reflect environmental and possibly populational characteristics of these algae. The spectral analyses described here provide robust, non-invasive means to characterize subtle responses of macroalgae to environment in ways not possible previously. Additional merits of these fourth-derivative analyses for use in environmental studies are discussed.This contribution is dedicated to the memory of Professor L. R. Blinks, a pioneer in photosynthesis research and algal physiology     

Natural diet of larval Penaeus merguiensis (Decapoda: Penaeidae) and its effect on survival

The relationship between Penaeus merguiensis protozoea larvae and their phytoplankton diet was examined using seasonal plankton surveys and in situ rearing experiments. Larval abundance, phytoplankton community structure, and chlorophyll a concentration in Albatross Bay, Gulf of Carpentaria, were monitored monthly for 2 yr. Larval abundance peaked in November (spring) and March (autumn), at which times diatoms were the most abundant group in net samples of phytoplankton and in the guts of larvae. During November 1989 and March 1990, larvae were reared in nylon mesh enclosures positioned throughout the water column at three depths: 0 to 3 m, 3 to 6 m and 6 to 9 m. Overall, larval survival and gut fullness were both higher in November than in March. In both months, larval survival was lower at the surface than at other depths. This correlated with lower chlorophyll a concentrations, but lower total cell densities were not detected. During the in situ experiments, diatoms were the most abundant phytoplankton group in the water column and in the guts of larvae and, therefore, appeared to be the principal diet of larvae. Pigment analysis demonstrated that while gut contents generally reflected the composition of the phytoplankton community, the larvae were not feeding exclusively on diatoms. They also ingested green algae and possibly seagrass detritus. The in situ experiments demonstrated that the predominantly diatom flora in Albatross Bay can provide a nutritionally adequate environment for prawn larvae even at seasonally low levels. It is unlikely, therefore, that starvation is a major cause of mortality of P. merguiensis larvae during either of the biannual peaks in their abundance in Albatross Bay, Gulf of Carpentaria.     

太湖浮游植物群落结构及其与水质指标间的关系

为了探讨太湖浮游植物群落结构时空分布特征、以及太湖浮游植物群落指标与水质指标间的关系,于2013年1月─2013年12月对太湖7个点位浮游植物群落结构和水质指标（水温、透明度、pH、溶解氧、电导率、总氮、总磷、氨氮、高锰酸盐指数、化学需氧量、氟化物、生化需氧量、硝酸盐氮、亚硝酸盐氮、溶解性磷酸盐和叶绿素a）进行月度调查,研究其浮游植物群落结构和湖泊水质的时空分布;并利用Pearson相关性分析浮游植物密度、浮游植物多样性与水质指标间的关系;找出影响太湖浮游植物群落结构的主要水质指标。结果表明：太湖7个点位共获得124种浮游植物物种,其中蓝藻门（Cyanophyta）30种、绿藻门（Bacillariophyta）47种、硅藻门（Chlorophyta）34种、隐藻门（Cryptophyta）3种、裸藻门（Euglenophyta）6种和甲藻门（Dinoflagellate）4种;其中蓝藻门的微囊藻属（Microcystis spp.）为绝对优势种群,优势度为80.8%;太湖浮游植物总密度与蓝藻门密度呈极显著正相关（r=1.000,P＜0.0001）;绿藻门和硅藻门占浮游植物总密度百分比分别和蓝藻门占浮游植物总密度百分比呈极显著负相关（r=-0.497,P＜0.0001;r=-0.814,P＜0.0001）。太湖7个点位水质首要污染物为总氮,其次是总磷和化学需氧量;西太湖污染物浓度最高。从空间上看,太湖浮游植物总密度最高值出现在贡湖湾（远离其入湖口处）,且贡湖湾浮游植物群落多样性相对低于太湖其他点位,同时贡湖湾微囊藻属密度百分比达90.1%,远高于太湖其他点位;从时间上看,太湖浮游植物总密度最高值出现在12月份、其次是6月份;通过浮游植物群落指标与水质指标相关性分析,水温、透明度、总氮、化学需氧量、叶绿素a是影响太湖浮游植物群落结构的主要水质指标。控制太湖入湖口水质污染物浓度排放和修?     

Klebsiella pneumoniae metabolites enhance Microcystis aeruginosa biomass flocculation

Microcystis aeruginosa is a common aquatic toxin-producing cyanobacterium. This study explores M. aeruginosa biomass recovery using bioflocculation. Bioflocculants produced by Klebsiella pneumoniae significantly enhanced aquatic M. aeruginosa flocculation efficiency. Under neutral and acidic conditions, flocculation efficiency reached 90%, whereas flocculation efficiency was 75% under alkaline conditions. M. aeruginosa flocculation was ion dependent, and Ca²⁺ was determined to be the most effective cationic inducer. Negatively charged proteoglycans were identified as the being the functional components in the flocculants. Optimal conditions for M. aeruginosa flocculation were determined using response surface methodology and are as follows: (1) K. pneumoniae bioflocculant dose, 13.3?mg/L; (2) flocculation time, 1.6 hours; and (3) pH?=?5 for flocculation of 10⁹ cells per litre. Bioflocculation using K. pneumoniae represents a promising method to control development of M. aeruginosa blooms. Further in-field investigations are necessary to fully assess its potential.