Merismopedia Tenuissima Research Articles

Ecological performance of an integrated ex-situ rice-fish co-culture system

Rice-fish co-culture system (RFCS) is an eco-friendly agricultural mode, but traditional RFCS has revealed many deficiencies. In this study, we constructed a new system of ex-situ rice-fish co-culture (ESRF) and evaluated its performance in ecological advantages. Chemical environmental factors, plankton and microorganisms, as well as ecology and economic benefits, were analyzed in the ESRF system. Results showed that 23.6% fertilizer and 47.5% water were saved in ESRF compared with rice monoculture. After wastewater in the fish ponds flowed through the paddy fields, the concentrations of TN, TP, CODMn, NH4+-N, NO2−-N and DIP decreased 72.78%, 63.81%, 53.32%, 45.54%, 51.31% and 44.05%, respectively through the absorption by rice. The phytoplankton abundance of cyanobacteria in wastewater, mainly Microcystis and Merismopedia tenuissima decreased significantly in ESRF system in July. Rotifer was the most dominant zooplankton in all samples and its abundance decreased significantly in ESRF system. After the aquaculture wastewater flowed through the paddy fields, the relative abundance of several bacteria with the ability of transforming nitrogen and phosphorus increased, such as Vogesella, Comamonadaceae, Flavobacterium, Sphingobium, Brevundimonas and Sphingomonas. These results suggest that ESRF is an eco-friendly and economical agricultural production mode and worthy of application in agriculture production.

PHYTOPLANKTON IN THE LAKES OF THE REPUBLIC OF BASHKORTOSTAN

The phytoplankton in a number of lakes in the Bashkir Trans-Urals (Atavdy, Sultankul (2017), Bursunsy, Kuldybay (2019), Bolshiye Uchaly, Uzunkul (2021)) and Bashkir Pre-Urals (Bolshoy Tolpak, 2022)) was studied. As a result of the study, the taxonomic structure, quantitative characteristics, dominant species, distribution features of main algal groups were reveald, and their ecological and geographical characteristics werre identified. 257 species and intraspecific taxa of algae from 9 divisions were registered in the algal flora. Green algae (33%), cyanoprokaryotes and diatoms (21% each of total species number) show the highest species diversity in the lakes. The algal flora is specific for each lake and has low degree of floristic similarity (0.13–0.57 according to Sørensen coefficients). In the ecological and geographical terms, the algal floras of lake plankton is represented by typical planktonic species, widespread in waterbodies of the globe, indifferent to water salinity, living only in fresh waterbodies and preferring neutral waters. Quantitative indicators of phytoplankton varied in a wide range of values: number of cells from 4.4 to 344 mln cells/L, biomass from 0.23 to 22.97 mg/L. Dominant species in terms of abundance are represented predominantly by cyanoprokaryotes (Snowella lacustris, Aphanocapsa delicatissima, A. incerta, Aphanizomenon flos-aquae, Gloeotrichia echinulata, Merismopedia tenuissima, Pseudanabaena galeata, Planktolyngbya limnetica, Woronichinia compacta, Anathece clathrata, Rhabdoderma lineare), in terms of biomass by green (Oocystis lacustris, O. borgei, O. marssonii, Scenedesmus apiculatus), dinophyte (Peridinium cinctum, Gymnodinium sp., Ceratium furcoides), desmidium algae (Staurodesmus cuspidatus, Cosmarium contractum, C. cucumis) and cyanoprokaryotes (Pseudanabaena galeata, Aphanizomenon flos-aquae, Gloeotrichia echinulata). According to the value of the saprobity index (Pantle – Bucc by number 1.57–2.80), the lake waters correspond to β- and α-mesosaprobic types of waterbodies with III and IV water quality classes (moderately polluted or dirty water).

Biological indicators as tools for monitoring water quality of a hot spot area on the Egyptian Mediterranean Coast

El-Mex Bay is a semi-sheltered coastal embayment located west of Alexandria, the Egyptian Mediterranean Sea. It is considered as a hot spot area receiving industrial, agricultural, and domestic wastes from the adjacent Lake Mariut through El-Umum Drain. To evaluate the water quality of the bay, phytoplankton and macroalgae as biological tools were investigated seasonally concerning physicochemical parameters from 2018 to 2019. The results indicated that the Bay harbored a diversified phytoplankton community (162 species), comprising 99 freshwater forms, 38 marine, 22 euryhaline, and only 3 brackish forms. The total average phytoplankton abundance was 419,414 unit/L. Few species were responsible for the main bulk of phytoplankton namely Merismopedia tenuissima, Cylindrotheca closterium, Cyclotella sp., Skeletonema costatum, Scenedesmus quadricauda, Scenedesmus bijugus, and Tetradesmus dimorphus. During the study period, El-Mex Bay was affected by the presence of 13 harmful and /or toxic algal species, among which the mediophyte species Skeletonema costatum was responsible for the peak occurring during autumn (2018). The results of the recorded nutrients indicated that the Bay is highly loaded, where NH4, NO2, NO3, PO4, and SiO4 attained 141.68 µM, 25.61 µM, 151.16 µM, 10.73 µM, and 232.86 µM, respectively. The macroalgal flora was represented only by the two opportunistic species (Ulva fasciata and Ulva intestinalis). Both species could survive in freshwater conditions exhibiting very broad salinity tolerance (6.51–38.41‰) and a high level of nitrogenous compounds. Those results revealed that El-Mex Bay suffers from pollution and deterioration of water quality.

Effects of the herbicides metazachlor and flufenacet on phytoplankton communities – A microcosm assay

Agrochemicals are the main pollutants in freshwater ecosystems. Metazachlor and flufenacet are two common herbicides applied in fall (i.e., August–October) to agricultural fields in Northern Germany. High concentrations of these herbicides are often found in adjacent aquatic ecosystems. Phytoplankton are one of the highly susceptible non-targeted aquatic organismal groups for herbicides and effects on phytoplankton may initiate a chain of consequences in meta communities through trophic interactions. Few studies have focused on responses of the phytoplankton community for metazachlor and, no studies have focused on flufenacet. We studied the effects of metazachlor and flufenacet on the phytoplankton community by conducting a microcosm experiment exposing natural fall phytoplankton communities to environmentally realistic concentrations as 0 (control), 0.5, 5 and 50 µg L−1 of metazachlor and flufenacet treatments over a 4-week period. We measured changes in density, composition (i.e., in phyla and species level), taxonomic diversity indices, and functional features of phytoplankton communities as a response to herbicides. A reduction in the density of Chlorophyta species (e.g., Koliella longiseta, Selenastrum bibraianum) and Cyanobacteria species (e.g., Merismopedia tenuissima and Aphanocapsa elegans) was observed in herbicide treatments compared to controls. The phytoplankton community shifted towards a high density of species from Bacillariophyta (e.g., Nitzschia fonticola and Cyclotella meneghiniana), Miozoa (i.e., Peridinium willei), and Euglenozoa (i.e., Trachelomonas volvocina) in herbicide treatments compared to controls. Metazachlor and flufenacet showed significant negative effects on taxonomic diversity indices (e.g., species richness, the Shannon-Wiener index) and functional features (e.g., functional dispersion and redundancy) of the phytoplankton communities, with increasing herbicide concentrations. Our study provides insights into direct, selective, and irrecoverable effects of metazachlor and flufenacet on phytoplankton communities in the short-term. The comprehensive understanding of these effects of environmentally realistic herbicide concentrations on aquatic biota is essential for a sustainable management of aquatic ecosystems in agricultural areas.

Optimization of biomass and some metabolites productivity of Merismopedia tenuissima and Spirulina (Arthrospira) platensis grown under stress conditions

The attention to using cyanobacteria as a nutrient supplement has increased due to their nutritional value and high bioactive metabolites contents. The reason behind designing such a study is to illustrate and clarify stress conditions effects like nitrogen and phosphorus supplementation and deficiency, salinity stress, and different pH values on the biomass, lipid, protein, amino acid, and carbohydrate productivities of Merismopedia tenuissima and Spirulina (Arthrospira) platensis.  The obtained results revealed that an increase in sodium nitrate by 100% caused an improvement in biomass, protein, and amino acid’s productivity of S. platensis  and M. tenuissima by 7.02 % and 7.05, 9.2% and 47.5%, 11.8% and19.5, respectively while 100% nitrogen deficiency enhanced lipid productivity of S. platensis  and M. tenuissima to 41% and 94%. Moreover, phosphorus limitation led to a reduction in biomass, protein, amino acid, and carbohydrate S. platensis to 24.3%, 21.1%, 43.3%, and 28.1%, respectively. However, phosphorus-free medium showed an increase in lipid productivity of S. platensis and M. tenuissima by 46.8% and 81.8%, respectively. The addition of 0.05 M NaCl concentration to S. platensis  medium stimulates the biomass, protein, and carbohydrate productivity by 6%, 7.75%, and 18.1%, respectively, whilst, among all concentration, zero M NaCl (control) resulted in increasing biomass, protein, and amino acids, whilst, high concentration (0.3M) of NaCl enhanced lipid productivity to 125.9% and 153.5% at S. platensis  and M. tenuissima, respectively. Applications of high alkalinity (pH 9) increased the productivities of all studied metabolites in S. platensis and reduction of all mention metabolites in M. tenuissima.

The impact of nitrogen concentrations on production and quality of food and feed supplements from three cyanobacteria and potential application in biotechnology

Abstract Primary metabolites (carbohydrates, proteins and amino acids) as well as growth and total dry mass displayed species and nitrogen dose dependency. Secondary metabolites, namely, phycobilins (contents and fractions) and lipids (contents and fractions) were also variably altered in the studied organisms. Three strains of cyanobacteria were isolated, purified and identified using the morphological approach and confirmed using 16S r- RNA. Namely, Anabaena sp., Merismopedia tenuissima and Arthrospira (Spirulina) platensis were cultivated under various nitrogen concentrations. Growth curves were followed for 14 days using chlorophyll (Chl.) a contents, which showed a gradual increase with time till the 12thday (stationary phase started); after that Chl. a contents were sharply decreased. Nitrogen deficiency enhanced growth (Chl. a, dry weight and rate) of Anabaena, Merismopedia and Arthrospirain comparison with the control (100% N), may be due to their coherent ability to fix atmospheric nitrogen. However, 100% nitrogen deficiency decreased growth of the three studied cyanobacteria, probably indicating insufficiency of nitrogen fixation to fulfill their cellular needs. Photosynthesis and respiration as the source as influenced by nitrogen availability as the sink were also concerned with in this work.

Drivers of cyanobacterial blooms in lakes and reservoirs in Jinan City, China

Cyanobacterial blooms are a serious issue and frequently occur in lakes and reservoirs. Understanding how topography and human activities affect cyanobacterial dominance and blooms can greatly enhance the success of restoration projects to reduce blooms. Therefore, in this study the dominant species of cyanobacteria were determined by calculating the break point of the cumulative dominance curve for multiple sites in Jinan, China. In addition, the key drivers affecting the dominant cyanobacteria species were identified by canonical correspondence analysis and correlations between topography, human activities and the key drivers of the dominant cyanobacteria were investigated using random forests analysis. Merismopedia glauca, Merismopedia tenuissima, Microcystis aeruginosa, Oscillatoria tenuis, Phormidium tenus and Raphidiopsis sinensia were determined to be the dominant species. The key drivers of cyanobacterial bloom development were total phosphorus (TP), ammonium nitrogen (NH3-N), water temperature and total hardness. Topography and human activities were highly correlated with the key driving factors. The higher the altitude, the greater the effect of water temperature on the cyanobacteria community. In the area where sewage irrigation was present and a large amount of chemical fertiliser was used, total hardness had a greater effect on the cyanobacteria community. In areas where the population was more concentrated, TP and NH3-N had greater effects on the cyanobacteria community.

Phytoplankton community structure of Lake Wushan stocked densely with planktivorous filter-feeding bighead and silver carp, middle and lower reaches of the Yangtze River

武山湖是紧邻长江的通江型富营养化湖泊，是国家级湿地公园.为切实了解该湖在以鲢、鳙养殖为主的情况下浮游植物结构特征，于2017年9月-2018年8月对其浮游植物群落结构特征及水质开展了监测.监测结果表明武山湖水质全年处于轻度富营养到重度富营养水平之间；12次共采集浮游植物7门100种（属），浮游植物优势种共有23种，其中蓝藻门有9种，绿藻门有8种，硅藻门和隐藻门各有3种.夏季和秋季蓝藻门优势种最多且优势度高，冬季和春季绿藻门和硅藻门优势种多且优势度高.武山湖浮游植物每月优势度最大的种类主要有蓝藻门微囊藻和细小平裂藻、绿藻门小球藻以及硅藻门小环藻.浮游植物生物量峰值出现在6月，达34.77 mg/L；丰度峰值出现在7月，达341.46×10⁶ cells/L.冗余分析（RDA）和线性相关分析均表明浮游植物丰度和生物量与总磷、温度和pH均呈显著正相关，且蓝藻门生物量和丰度以及优势属与总磷和温度均呈显著正相关.研究结果表明武山湖浮游植物丰度和生物量在夏季均很高，发生蓝藻水华的风险较大.相对于氮，磷是更重要的限制浮游植物生长的营养元素.;Lake Wushan is a highly eutrophic, shallow lake connected to the Yangtze River, and a national wetland park. In order to study phytoplankton structural characteristics in the lake stocked densely with silver carp (Hypophthalmichthys molitrix) and bighead carp (Aristichthys nobilis), we conducted a field survey on the phytoplankton community and lake trophic status from September 2017 to August 2018. Trophic status indices (TLI) showed the water quality was between mesotrophic and heavy eutrophic state. A total of 100 phytoplankton species (genera) belonging seven phyla were identified; twenty-three dominant species including nine species of Cyanophyta, eight species of Chlorophyta and both three species of Bacillariophyta and of Cryptophyta were observed. The dominant groups were Cyanophyta in summer and autumn, Chlorophyta and Cryptophyta in winter and spring. The phytoplankton size distribution had a trend biased toward miniaturization. Microcystis sp., Merismopedia tenuissima, Chlorella chlorophylla, Chlorella sp., and Cyclotella sp. were the predominant species in our 2017-2018 annual survey. The peak biomass appeared in June, reaching 34.77 mg/L, and the peak abundance appeared in July, reaching 341.46×10⁶ cells/L. Both of redundancy analyses and linear correlation analyses showed that total phosphorus, temperature and pH were positively correlated with phytoplankton abundance and biomass, and total phosphorus and temperature were also positively correlated with the biomass and abundance of Cyanophyta and the dominant genus. Our results showed that the abundance and biomass of phytoplankton were high, indicating high risks of cyanobacterial water blooms in summer months. Nitrogen was at least as important as phosphorus in limiting phytoplankton production in Wuhan lakes.

Application of Three Cyanobacteria in Foods and Feeds Biotechnology: Phosphorus Affects.

Cyanobacteria grown under abiotic stress affect on some metabolites that used as promising for foods and feeds biotechnology. Thus, the objective of the study was to evaluate the 3 local cyanobacteria isolates for production of foods and feeds under various concentration of phosphorus. Cyanobacteria namely; Anabaena sp., Merismopedia tenuissima and Spirulina platensis were grown photoautotrophically in modified medium. The growth pattern in the medium containing various phosphorus concentrations were followed and harvested around 14 days. A decrease in phosphorus concentrations by 50% led to an increase in chlorophyll-a of M. tenuissima and S. platensis. The application of high concentration of phosphorus (+100%) to the culture of Anabaena sp. led to an increase in dry weight and growth rate by 0.382 mg mL-1 and 0.013 h-1, respectively. The deficiency of phosphorus concentrations led to a decrease in carbohydrate contents of Anabaena, Merismopedia and Spirulina with compared to the control culture. In general, the total lipid contents of Anabaena sp. and M. tenuissima were stimulated by phosphorus deficiency. The phosphorus-free media and increase in phosphorus concentration by 100% resulted in an increase in protein fractions such as soluble, insoluble, globulins, prolamines, glutelins and total protein content of Anabaena sp. The application of high concentration of phosphorus (+100%) to the culture of S. platensis led to an increase in total lipid contents in comparison to control. The highest phycobiliprotein contents of S. platensis were recorded at 50% phosphorus deficiency. Cyanobacteria has a soft cell wall that makes it especially easy to digest and is additionally full of live active enzymes which further enhances metabolism and the efficient intake of nutrients.

Characteristics of Phytoplankton Community and Its Relationship with Environmental Factors in Different Regions of Yilong Lake, Yunnan Province, China

Yilong Lake, a shallow, plateau lake, is the ninth largest water body in the Yunnan Province, China. In order to figure out the characteristics of phytoplankton communities in different regions of this lake, the phytoplankton and environmental factors in the west region, east region, and in a submerged macrophytes restoration demonstration region were monthly investigated and analyzed from August 2013 to July 2014. The results showed that the habitats in different regions were spatially heterogeneous. Total nitrogen (TN), total phosphorus (TP), ammonia nitrogen (NH4+-N), five-day biochemical oxygen demand (BOD5), transparency (SD), turbidity (Turb.), and electrical conductivity (EC) had no significant differences between the demonstration region and the west region, but these two regions showed significant differences in comparison with the east region (P<0.05). The largest phytoplankton density was Cyanophyta and the dominant species in the three regions were different. Mersmopedia tenuissima had the highest dominance in the west region; Cylindrospermopsis raciborskii and Pseudanabaena limntica were the most dominant taxa in the east region; while Merismopedia tenuissima and Anabaenopsis sp. were dominant in the O. uminata restoration demonstration region. PCoA compared the β diversity of phytoplankton communities in the three different regions based on the entire year investigations. It was found that the community structures of the west region and O. uminata restoration demonstration region were similar (P>0.05), but they were significantly different from the community from the east region (P<0.01). Redundant analysis (RDA) showed that TN, TP, BOD5, and SD were the main environmental factors affecting the distribution of phytoplankton community in Yilong Lake. In addition, NH4+-N, EC, permanganate index, and pH also have a certain effect on the phytoplankton community.

Removal efficiency of phosphorus, cyanobacteria and cyanotoxins by the “flock & sink” mitigation technique in semi-arid eutrophic waters

Geoengineering techniques have been used to control phosphorus and cyanobacteria in lakes promising greater and quicker chemical and ecological recovery. Techniques that use coagulants and clays to remove particulates and dissolved phosphorus from the water column have received great. In this study, bench-scale “flock & sink” assays were carried out to evaluate the efficiency of the coagulants aluminium sulphate (SUL), polyaluminium chloride (PAC) and chitosan (CHI), alone and combined with natural bentonite clays (BEN) and lanthanum-modified bentonite (LMB), to remove of phosphorus from a eutrophic reservoir in a semi-arid region of Brazil. In addition, the study seeks to assess the effects on the cyanobacteria density and the intra- and extracellular concentrations of cyanotoxins after the application of these geoengineering materials. The SUL and PAC coagulants effectively reduced the total phosphorus (TP), reactive soluble phosphorus (SRP), turbidity, chlorophyll-a, cyanobacteria density and intracellular microcystin, whereas CHI showed a low removal efficiency. Lanthanum-modified bentonite proved to be more effective than BEN; however, the application of the coagulants only was sufficient to successfully remove phosphorus and cyanobacteria from the water column. In addition, the efficiency of the “flock & sink” technique in cell removal varied among the cyanobacteria species. Small colonial species such as Aphanocapsa delicatissima, Merismopedia glauca and Merismopedia tenuissima were removed regardless of the treatment used, including those with CHI and BEN. As for the filamentous cyanobacteria, Cylindrospermopsis raciborskii, Geitlerinema amphibium, Planktothrix agardhii and Pseudanabaena catenata, removal was achieved only using PAC, SUL and LMB alone or when combined. The intracellular concentrations of saxitoxin and cylindrospermopsin and the extracellular fraction of these cyanotoxins and of microcystin were not influenced by the application of coagulants and clays. This indicates that cell lysis did not occur with the addition of the geoengineering materials. These results demonstrate that the “flock & sink” technique could be used for restoration of eutrophic waters.

Polyphasic examination on Merismopedia tenuissima CHAB 7021 from Ganjiang River, China revealed the polyphyly of the genus Merismopedia (Cyanobacteria)

Species in the cyanobacterial genus Merismopedia are present in freshwaters at different trophic levels, with some species even as the components of cyanobacterial blooms. However, species diversity in this genus was not fully verified by molecular investigation and polyphasic taxonomic studies. In this study, Merismopedia-like strain tenuissima CHAB 7021 was isolated from Ganjiang River in Jiangxi Province, China, and polyphasic characterization of this strain was performed by morphological observation, ultrastructural examination, chemical detection of pigments and phylogenetic analysis based on 16S rRNA gene sequences. Morphological identification of the strain was supported by the ultrastructural features, as the tiny species Merismopedia tenuissima Lemmermann. The phylogeny based on 16S rRNA gene sequences revealed at least three clades formed by the strains of Merismopedia. The three M. tenuissima strains including M. tenuissima CHAB 7021 was gathered in clade III with distant relationship to the clade I formed by the six Merismopedia strains including the type species M. punctata, and such a genetic distance may propose Merismopedia tenuissima to separate from Merismopedia genus. However intermixture relationship in between strains of M. punctate and M. glauca in the phylogenetic tree still complicated the taxonomic status in the genus Merismopedia. The process for taxonomic revision in the Merismopedia genus still await for examination and further information on more strains of type species M. punctata.

Cyanobacteria Occurrence in Photosynthetic Stabilization Ponds

Photoautotrophic organisms, particularly cyanobacteria, have great ecological importance due to their photosynthetic capacity, and biosynthetic versatility in diverse and extreme environments. However, photosynthetic ponds, they may be serious and dangerous producers of potentially toxic toxins. Their release and bloom in treated effluent receiving bodies are a major concern because of the negative consequences on aquatic biota and the risks to public health. The aim of this study is to analyze the occurrence, composition, density and spatio-temporal distribution of cyanobacteria in sewage treatment plants by photosynthetic ponds in ten cities located in the central region of the São Paulo State, Brazil. The results recorded high densities of Microcystis sp. with a maximum average of 9.4x105 cells per millilitre (cells/mL); Synechococcus sp., with an average of 7.8x105; Synechocystis aquatilis with 7.2x105; Merismopedia tenuissima with 4.8x105; and Phormidium sp. with 1.9x105. Among these species found, the highest occurrence was M. tenuissima. The high densities show that these ponds are an aquatic environment conducive to the development of cyanobacteria and, potentially, an important source of cyanotoxin production. Therefore, studies and monitoring of the effects on the receiving water bodies are recommended by determining their cyanobacteria densities and investigating the possible presence of cyanotoxins.

Effects of increased zooplankton biomass on phytoplankton and cyanotoxins: A tropical mesocosm study

Zooplankton are important biocontrol agents for algal blooms in temperate lakes, while their potential in tropical and subtropical environments is not well understood. The aim of the present study was to evaluate the influence of increased zooplankton biomass on phytoplankton community and cyanotoxins (microcystins and saxitoxin) content of a tropical reservoir (Ipojuca reservoir, Brazil) using in situ mesocosms. Mesocosms consisted of 50L transparent polyethylene bags suspended in the reservoir for twelve days. Phytoplankton populations were exposed to treatments having 1 (control), 2, 3 and 4 times the biomass of zooplankton found in the reservoir at the beginning of the experiment. Filamentous cyanobacteria such as Planktothrix agardhii and Cylindrospermopsis raciborskii were not negatively influenced by increasing zooplankton biomass. In contrast, the treatments with 3 and 4 times zooplankton biomass negatively affected the cyanobacteria Aphanocapsa sp., Chroococcus sp., Dolichospermum sp., Merismopedia tenuissima, Microcystis aeruginosa and Pseudanabaena sp.; the diatom Cyclotella meneghiniana; and the cryptophyte Cryptomonas sp. Total microcystin concentration both increased and decreased at different times depending on zooplankton treatment, while saxitoxin level was not significantly different between the treatments and control. The results of the present study suggest that zooplankton biomass can be manipulated to control the excessive proliferation of non-filamentous bloom forming cyanobacteria (e.g. M. aeruginosa) and their associated cyanotoxins.

An application of cellular organic matter to coagulation of cyanobacterial cells (Merismopedia tenuissima)

Algae affect the performance of drinking water treatment significantly when they decay and release considerable amounts of cellular organic matter (COM). The study describes the cyanobacterium Merismopedia tenuissima and its COM and investigates the effect of their simultaneous coagulation. As COM is highly complex mixture, we characterised it in terms of hydrophobicity, protein content and molecular weights (MWs). To describe the coagulation mechanisms and molecular interactions in the system, we determined both COM and cell surface charge by means of potentiometric titration and zeta potential analysis, respectively, and performed the jar tests with single components and their mixtures with and without a coagulant (ferric sulphate).The coagulation tests performed with the individual components or with their mixtures proved efficient cell removals (up to 99%) but relatively low COM removals (37 ÷ 57%). This disproportion can be attributed to the prevalence of hydrophilic compounds and to the high portion of low-MW organics in COM. Coagulation of COM/cell mixtures achieved comparable efficacy with single component tests, using even lower coagulant doses. Furthermore, COM presence substantially deviated the pH optimum for cell removal and thus altered coagulation mechanisms. While single cells interacted prevailingly through adsorption onto Fe-oxide-hydroxides at about neutral pH (6.0–7.7), the COM/cell mixtures succumbed to charge neutralisation by Fe-hydroxopolymers within moderately acidic pH range (5.0–6.5). Moreover, COM initiated cell flocculation also at acidic pH in both the presence (pH 3.4–3.9) and the absence of a coagulant (pH 3.6–4.6). This supportive effect is ascribed to relatively high-MW COM (>10 kDa), serving as a natural flocculant through inter-particle bridging mechanism and exhibiting nearly the same COM/cell removals as ferric sulphate.

The Relationship between Phytoplankton Evenness and Copepod Abundance in Lake Nansihu, China.

The relationship between biodiversity and ecosystem functioning is a central issue in ecology. Previous studies have shown that producer diversity can impact the consumer community via predator-prey interactions. However, direct observations of this relationship remain rare, in particular for aquatic ecosystems. In this research, the relationship between phytoplankton diversity (species richness and evenness) and the abundance of copepods was analyzed in Lake Nansihu, a meso-eutrophic lake in China. The results showed that copepods abundance was significantly decreased with increasing phytoplankton evenness throughout the year. However, both species richness and phytoplankton biomass showed no significant relationship with the abundance of copepods. Canonical correspondence analysis revealed that phytoplankton evenness was negatively correlated with Thermocyclops kawamurai, Cyclops vicinus, Eucyclops serrulatus, Mesocyclops leuckarti, Sinocalanus tenellus, Sinocalanus dorrii, Copepods nauplius, but positively correlated with many Cyanophyta species (Chroococcus minutus, Dactylococcopsis acicularis, Microcystis incerta, Merismopedia tenuissima, Merismopedia sinica and Lyngbya limnetica). Based on our results, phytoplankton evenness was a better predictor of copepods abundance in meso-eutrophic lakes. These results provide new insights into the relationship between diversity and ecosystem functioning in aquatic ecosystems.

Factors influencing cyanobacteria community structure in Chara-lakes

For practical reasons, cyanobacteria attract scientific interest in eutrophicated, often degraded water bodies. Much less attention is paid to blue-greens in less fertilized lakes, including a group of macrophytic lakes with vegetation dominated by charophytes (Chara-lakes). In this study, therefore, two small, mid-forest Chara-lakes with negligible recreational use were compared with two large Chara-lakes subject, along with their drainage basin, to higher human pressure. An attempt was made to find out whether there are any differences in the qualitative and quantitative structure of cyanobacteria and in cyanobacteria functional groups between the studied Chara-lakes. In addition, the lakes ecological status was assessed based on their total phytoplankton and cyanobacteria biomass.Small mid-forest Chara-lakes were distinguished by Chroococcales taxa, while Oscillatoriales and Nostocales preferred large recreationally used water bodies with catchment areas changed by human activity. Aphanothece minutissima, Merismopedia tenuissima, Aphanizomenon gracile, Aphanocapsa holsatica and Cyanodictyon planctonicum differentiated among the studied Chara-lakes.Although cyanobacteria dynamics did not differ Chara-lakes from eutrophic water bodies, the dominance of cyanobacteria was only detected in the two large Chara-lakes characterised by a worse ecological status compared to the small mid-forest ones.Alkalinity, water temperature, colour and, to a lesser extent, TP and TN:TP ratio are postulated to be water properties which, in addition to extensive charophyte meadows, control the development of cyanobacteria in the studied Chara-lakes.

Phycoremediation and adsorption isotherms of cadmium and copper ions by Merismopedia tenuissima and their effect on growth and metabolism.

The current study tends to investigate the removal of cadmium and copper ions by Merismopedia tenuissima, grown in different concentrations of cadmium and copper ions, as well to investigate their effects on growth and metabolism. Sorption isotherms of Langmuir and Freundlich were obtained for the quantitative description of cadmium and copper uptake by M. tenuissima. Langmuir model adequately to describe the data of biosorption for these metals. However, the Freundlich model could work well in case of Cu(2+) only. M. tenuissima appears to be more efficient for removing Cd(2+) ions than Cu(2+). However, the affinity constant of Cu(2+) on the biomass of M. tenuissima was higher than Cd(2+) indicating that M. tenuissima is more tolerant to Cd(2+) phytotoxicity than Cu(2+). FTIR analysis of algae with and without biosorption revealed the presence of carboxyl, amino, amide and hydroxyl groups, which were responsible for biosorption of Cd(+2) and Cu(+2) ions.

Functional diversity and adaptative strategies of planktonic and periphytic algae in isolated tropical floodplain lake

Functional diversity and adaptative strategies of planktonic and periphytic algae in isolated tropical floodplain lake. This study aimed to test the hypothesis that after a great magnitude and high duration of flood pulse in floodplain, functional diversity of phytoplankton and phy- coperiphyton communities will be higher during high water. The strategies' dynamics evaluated during high and low water periods consisted of size classes, life forms, and functional groups. For the phytoplankton, the adaptations to floating, and for phycoperiphyton, the intensity and structure for attachment to substrate were also analyzed. Functional diversity was calculated from functional dendrograms of species. Functional diversity, richness, and density of both communities presented the greatest values during the high waters. In the high waters, Cryptomonas marsonii Skuja was dominant in plankton and Pseudoan- abaena skujae Claus in periphyton, while in the low water, Merismopedia tenuissima Lemm. was dominant in plank- ton and Fragilaria capucina Desm. was dominant in periphyton. Thus, the flood pulse promoted the dominance of free-floating species in plankton, during the high water, and of metaphytic species in periphyton. In the low water, we observed the dominance of species with higher surface/ volume ratio in plankton, and strongly attached in periph- yton. We concluded that, in isolated floodplain lake, possibly the flood pulse directs the functional diversity of phytoplankton and phycoperiphyton.

Phytoplankton Community and the Relationship with the Environment in Nansi Lake, China

This study was carried out from June to October 2008 in Nansi Lake. Based on the data collected from five sampling stations, phytoplankton taxonomic composition, abundance, temporal variations and spatial distribution were examined. About 94 species, including 48 species of Chlorophyta, 22 species of Bacillariophyta, and 1 water bloom causative species were identified. Average phytoplankton diversity index and evenness values were 1.59 and 0.58, respectively, revealing moderate biodiversity of phytoplankton biocoenosis. The phytoplankton abundance averaged 1.52×107 cells/L, and was much higher than previous investigation carried out in the same months in 1995. The species of Chlorophyta, Bacillariophyta dominated phytoplankton community. The main dominant species were Scenedesmus dimorphus, Chlorella vulgaris, Synedra acus, Aulacoseira granulata, Merismopedia tenuissima and Monallantus brevicylindrus. Concerning nutrient stoichiometry, it was suggested that the higher TN: TP ratio indicated potential P-limitation for phytoplankton growth in Nansi Lake. The environmental conditions of water quality and phytoplankton community composition indicated that Nansi Lake was eutrophic in summer.