The effect of zinc oxide nano- and microparticles and zinc ions on freshwater organisms of different trophic levels

Data on the effects of various forms of zinc compounds on the biological parameters of freshwater animals (Ceriodaphnia affinis Lillijeborg, 1862; Chironomus riparius Meigen, 1804; and Brachydanio rerio Hamilton-Buchanan, 1822) are presented. Crustacean Ceriodaphnia affinis is the most sensitive test object studied.     

Molecular comparisons of freshwater and marine isolates of the same morphospecies of heterotrophic flagellates

Heterotrophic flagellates are key components of all ecosystems. Understanding the patterns of biodiversity of these organisms is thus particularly important. Here we analyzed the intraspecific diversity of 10 morphospecies of heterotrophic flagellates comprising representatives of the Apusozoa (2 morphospecies) and Kinetoplastea (8 morphospecies), all belonging to the most common flagellates with worldwide distribution. Most morphospecies showed a mixing of lineages isolated from diverse habitats, indicating that some lineages of these morphospecies had been able to colonize different habitats several times. Furthermore, our results revealed remarkable levels of genetic divergence within most of the morphospecies studied, underlining the difficulty of correctly determining species by means of morphology alone. Many cryptic or pseudocryptic species seem to occur. Our results revealed clear divergence between marine and freshwater lineages of the morphospecies Ancyromonas sigmoides, showing that freshwater lineages have not been able to colonize marine environments and marine lineages have not been able to colonize freshwater environments for a long time.     

Distribution and abundance of uncultured heterotrophic flagellates in the world oceans

Heterotrophic flagellates play fundamental roles in marine ecosystems as picoplankton grazers. This recognized importance contrasts with our ignorance of the taxonomic composition of this functional group, which remains mostly unidentified by microscopical and culturing approaches. Recent molecular marine surveys based on 18S rDNA genes have retrieved many sequences unrelated to cultured organisms and marine stramenopiles were among the first reported uncultured eukaryotes. However, little is known about the organisms corresponding to these sequences. Here we determine the abundance of several marine stramenopile lineages in surface marine waters using molecular probes and fluorescent in situ hybridization. We show that these protists are free-living bacterivorous heterotrophic flagellates. They were widely distributed, occurring in the five world oceans, and accounted for a significant fraction (up to 35%) of heterotrophic flagellates in diverse geographic regions. A single group, MAST-4, represented 9% of cells within this functional assemblage, with the intriguing exception of polar waters where it was absent. MAST-4 cells likely contribute substantially to picoplankton grazing and nutrient re-mineralization in vast areas of the oceans and represent a key eukaryotic group in marine food webs.     

Grazing on bacteria by flagellates and cladocerans in lakes of contrasting food-web structure

We tested the hypothesis that grazing on bacteria would varybetween lakes with differing plankton community structures.Paul and Tuesday lakes (Gogebic County, MI) are respectivelydominated by piscivorous and planktivorous fish. Consequently,zooplankton in Paul are primarily large daphnids, while zooplanktonin Tuesday are primarily small cladocerans and copepods. Wemeasured flagellate grazing on bacteria using a fluorescentminicell method, while cladoceran grazing was estimated fromthe relationship between body length and filtering rate. Wepredicted that cladoceran grazing on bacteria would be higherin Paul, and flagellate grazing would be higher in Tuesday.Cladoceran grazing on bacteria was important in both lakes contraryto our initial expectation. Large populations of the small cladoceran,Bosmina longirostris, in Tuesday exerted a grazing pressure(0.18–35x10⁶ bacteria 1^–1 h^–1) approximatelyequal to that of the large cladoceran, Daphnia pulex, in Paul(0.34–30x10⁶ bacteria 1^–1 h^–1). Flagellategrazing was higher in Tuesday as predicted (range: Paul, 0.1–6x10⁶bacteria 1^–1 h^–1; Tuesday, 0.2–20x10⁶ bacteria1^–1 h^–1). However, there was not a simple relationshipbetween total abundance of flagellates and total grazing rates.High community grazing by flagellates occurred when attachedchoanoflagellates were present. These flagellates had higheringestion rates than free forms. We find no clear evidence thatdifferences in food-web structure between the two lakes influencethe process of grazing on bacteria. Instead, our results emphasizethe significance of cladocerans and attached flagellates asconsumers of bacteria in freshwater ecosystems.     

The structure of extrusive organelles in alveolate and other heterotrophic flagellates

The structure of ejective organelles (extrusomes) in 12 species of heterotrophic flagellates belonging to 8 taxonomic groups is considered. Trichocysts of various structures have been found in colpodellids, Spumella and Metromonas. Kinetocysts of amoeboid flagellates, thaumatomonads, contain a cylindrical element. These kinetocysts are attached to bacteria after discharge. When being discharged, trichocysts of colpodellids produce filaments which have transversal striation. Discobolocysts have been found in excavate flagellate Reclinomonas, and ejectisomes--in Goniomonas. Toxicysts have been marked in carnivorous alveolate flagellate Colponema. The most of studied extrusomes lie inside the cytoplasm, while exstrusomes in chrysomonad Spumella are also found inside the nucleus. Trichocysts of colpodellids and Metromonas as well as ejectisomes of Goniomonas are located near the branches of Golgi apparatus. The comparison of the data obtained confirms the hypothesis about the correlation of taxonomic position of flagellates and the structure of their extrusomes that allows in some cases using these features as phylogenetic markers.     

A study on biological activity measurements and heterotrophic bacteria in a small freshwater lake

A 6-m-deep lake has been sampled to measure the temporal and depth-wise distribution of heterotrophic bacteria and biological activity in the water. Surface, mid-depth and bottom waters were analysed at monthly intervals for a period of one year. The coefficient of heterotrophic activity, alkaline phosphatase activity and biological oxygen demand are used as an index of biological activity. The bacterial community was at maximum during spring, coinciding with high values of biological activity. Highest biological activity was observed in the bottom waters. Dissolved organic carbon showed a significant positive correlation with most of the biological activity parameters. This suggests that biological activity, as measured by the coefficient of heterotrophic activity, was more closely related to the concentration of substrates than to population density of heterotrophic bacteria.     

Distribution patterns of heterotrophic flagellates and bacteria in acidic and neutral Karelian lakes

The abundance and taxonomic and trophic structures of the community of planktonic heterotrophic nanoflagellates, as well as the quantitative distribution of bacteria as their main object of food, have been studied in six lakes of Karelia with differing pH values, concentrations and compositions of organic substances, and degrees of anthropogenic load. Thirty-eight species and forms of colorless flagellates from seven orders and groups of uncertain taxonomic statuses have been recorded. Most of them belong to the trophic group of bacteriodetritophages. The minimal abundance and the lowest diversity of flagellates have been documented in clear- and brown-water lakes with low pH values, and maximal values have been observed in the polluted Kondopoga Bay in Lake Onega.     

Taxonomic composition and biomass of heterotrophic flagellates in relation to lake trophy and season

1. Taxonomic composition and abundance of heterotrophic flagellates (HF) were studied in 55 lakes with different trophy in northern Germany using a live-counting technique.
2. Mean abundances and biomasses of HF ranged from 169 cells L⁻¹ and 22 μg L⁻¹ in mesotrophic lakes to 2439 cells mL^–1 and 475 μg L⁻¹ in hypertrophic lakes, respectively. Highest values were generally observed in spring, but mesotrophic lakes showed maximum values in early summer.
3. The taxonomic composition of HF was not significantly influenced by lake trophy and season. The major fraction of HF consisted of chrysomonads and Protista incertae sedis; other important groups were choanoflagellates and bicosoecids. The size distribution of HF changed with lake trophy and season, with a higher proportion of large HF (> 10 μm) in hypertrophic lakes and in spring, respectively.
4. Correlation analyses revealed a strong negative impact of cladocerans on total HF biomass and especially on large HF. Ciliates and large bacteria (> 10 μm) were strongly positively correlated with HF biomass; small bacteria (< 2 μm) showed a weak positive correlation.
5. Analyses at the level of species and genera revealed distinct distribution patterns of some taxa. Paraphysomonas , Aulacomonas and Quadricilia as large-bodied HF showed highest abundance in hypertrophic lakes and in spring. Attached taxa (e.g. Monosiga , Salpingoeca amphoridium ) were highly abundant in late summer and autumn, whereas Spumella and Kathablepharis occurred frequently in most samples.     

Patterns of the quantitative distribution of plankton heterotrophic flagellates in the high-mountain Lake Sevan (Armenia)

Patterns of the quantitative development and spatial distribution of heterotrophic flagellates have been studied in Lake Sevan (Armenia). The abundance and biomass of flagellates is lower in summer than in autumn, but on the whole these parameters correspond to the quantitative parameters in oligotrophic lakes. Differences in the vertical and horizontal distribution of flagellates have been found during summer stratification and autumn homothermy.     

Characterization of aerobic heterotrophic bacteria in cold and nutrient-poor freshwater ecosystems

Aerobic heterotrophic bacteria present in the surface water of three cold and nutrient-poor lakes in the Chilean Patagonia (Alto Reino, Las Dos Torres and Venus) were analysed for genetic similarity and metabolic diversity using 16S ribosomal DNA and the Biolog EcoPlate^TM system, respectively. Bacterial fingerprints of water samples in enriched and non-enriched nutrient broth demonstrated a >50% fingerprinting similarity between the lakes. Metabolic activity was also similar. However, the Biolog EcoPlate^TM system carbon substrates revealed functional diversity. Lake Las Dos Torres showed the most fingerprinting similarity between enriched and non-enriched cold water samples. The amounts of living and viable bacteria were also higher in this lake’s water sample, suggesting a predominance of facultative oligotrophic groups. DNA sequencing analysis demonstrated the presence of phylum Bacteroidetes in Lake Alto Reino; phyla Bacteroidetes and Gammaproteobacteria in Lake Las Dos Torres; and phyla Bacteroidetes, Alphaproteobacteria, and Gammaproteobacteria in Lake Venus. Although each lake had a unique bacterial community structure, the different bacterial groups may be performing similar metabolic functions, given the similarity in extreme environmental conditions.     

Steric effect and effect of metal coordination on the reactivity of nitric oxide with cysteine-containing proteins under anaerobic conditions

A comparison is made between the reactivity of nitric oxide (NO) with cysteine, bovine serum albumin (BSA) and metallothionein-1 (MT1) at pH 7 under strictly anaerobic conditions. The rate of reaction of NO with these amino acid/proteins was found to be of the order: cysteine > BSA > MT1, in clear disparity with the size of the reactants. The difference in the reaction rates is attributed to steric effects due to the high molecular size in the case of BSA and to effects of metal coordination proper as well as to steric effects associated with the closed dual shell-like structure resulting from the tight coordination of the thiolate groups with Zn2+ in MT1. The mechanisms of the reaction of NO with cysteine, BSA and MT and its possible implication for the rate of the respective reactions are discussed.     

A comparison of the trophic transfer of fatty acids in freshwater plankton by cladocerans and calanoid copepods

1. Analyses of zooplankton fatty acid (FA) composition in laboratory experiments and samples collected from lakes in New Zealand spanning a wide gradient of productivity were used to assess the extent to which FAs might infer their diet. We used the cladocerans, Daphnia and Ceriodaphnia, and the calanoid copepod, Boeckella, as test organisms, and monocultures of cryptophytes, chlorophytes and cyanobacteria as food. Based on reproductive success, cryptophytes were the highest food quality, chlorophytes were intermediate and cyanobacteria the poorest. 2. Several FA groups were highly correlated between zooplankton and their diets. They were monounsaturated fatty acids (MUFAs), and ω3 and ω6 polyunsaturated fatty acids (PUFAs) for cladocerans, and saturated fatty acids (SAFAs) and ω3 PUFAs for copepods. Several FAs varied significantly less in the zooplankton than in their monoculture diets, e.g. MUFAs in Daphnia, and ω3 and ω6 PUFAs in Ceriodaphnia, despite clear dietary dependency for these FAs. 3. Zooplankton collected from lakes in New Zealand had more eicosapentaenoic acid (EPA) (Daphnia), more highly unsaturated ω3 and ω6 FAs (C₂₀, C₂₂; Daphnia, Ceriodaphnia, Boeckella) and less ω3 C₁₈ PUFAs (Daphnia, Ceriodaphnia, Boeckella) and ω6 C₁₈ PUFAs (Daphnia, Ceriodaphnia) than measured in the same species reared on phytoplankton in the laboratory. 4. Analyses of FA composition of seston and freshwater zooplankton globally showed that, in general, zooplankton had a significantly higher proportion of arachidonic acid and EPA than seston, and copepods also had a higher percentage of docosahexaenoic acid than seston. 5. These results suggest that zooplankton selectively incorporate the most physiologically important FAs. This could be a consequence of preferential assimilation, selective feeding on more nutritious cells or locating and feeding within higher food quality food patches.     

Heterotrophic flagellates, centrohelid heliozoa and filose amoebae from marine and freshwater sites in the Antarctic

Heterotrophic flagellates, centrohelid heliozoa and filose amoebae were recorded from cultures derived from water collected at marine and freshwater sites in the Antarctic. Marine samples were collected in the vicinity of Prydz Bay, southeast Antarctica and freshwater samples from Sombre Lake on Signy Island and Crooked and Druzhby Lakes in the Vestfold Hills. Thirty-five species were identified. One new species, Kiitoksia kaloista (Protista incertae sedis), is described. The other species have been previously reported from other geographic locations, providing no evidence for endemism in protozoan species found in Antarctica. Received: 23 September 1996 / Accepted: 28 December 1996     

白洋淀异养鞭毛虫群落特征及其与环境因子的相关性

于2010年4月至2011年3月调查了白洋淀3个典型湖区表层水体异养鞭毛虫丰度和生物量及环境因子的周年变化,分析了异养鞭毛虫群落与环境因子的相关关系。白洋淀表层水体异养鞭毛虫的丰度和生物量分别介于100-3200 个/mL和35.98-2328.85 μg/L之间,周年平均值分别为1054 个/mL和532.93 μg/L。白洋淀小型异养鞭毛虫(＜7 μm)的丰度占总丰度的47.11%,而生物量只占总生物量的6.82%;中型异养鞭毛虫(约7-14 μm)的丰度占总丰度的37.42%,生物量占总生物量的39.21%;大型异养鞭毛虫(＞14 μm)的丰度虽只占总丰度的15.47%,却贡献了53.97%的生物量。相关性分析表明,异养鞭毛虫丰度与总氮和氨氮呈显著性负相关,与pH值、细菌丰度、纤毛虫丰度及叶绿素a含量呈显著性正相关;异养鞭毛虫生物量与pH值、溶解氧、纤毛虫丰度及叶绿素a含量显著正相关,与总氮、氨氮呈显著负相关。结果表明异养鞭毛虫群落在微食物环中起着枢纽作用。     

Effects of NaCl salinity on the population dynamics of freshwater zooplankton (rotifers and cladocerans)

Salinization of freshwater bodies due to anthropogenic activity is currently a very serious problem in Mexico. One of the consequences may be changes in the rotifer and cladoceran populations, both of which are generally abundant in freshwater bodies. Under laboratory conditions we evaluated the effect of different salt (sodium chloride) concentrations (0–4.5 g l⁻¹) on the population dynamics of ten freshwater zooplankton species (rotifers: Anuraeopsis fissa, Brachionus calyciflorus, B. havanaensis, B. patulus and B. rubens; cladocerans: Alona rectangula, Ceriodaphnia dubia, Daphnia pulex, Moina macrocopa and Simocephalus vetulus). All of the zooplankton species tested were adversely affected by 1.5–3.0 g l⁻¹ NaCl. In the range of salt concentrations tested, the population growth curves of B. patulus and B. rubens showed almost no lag phase and reached peak abundances within a week or two; A. fissa had a lag phase of about a week, while both B. calyciflorus and B. havanaensis started to increase in abundance immediately following the initiation of the experiments. Increased NaCl levels reduced the population abundances of A. fissa, B. calyciflorus and B. havanaensis at or beyond 1.5 g l⁻¹. NaCl at 1 g l⁻¹ had little effect on the population growth of cladocerans. M. macrocopa, which was more resistant to NaCl than the other cladoceran species, showed positive population growth even at 4.5 g l⁻¹. The rates of population increase (r, day⁻¹) were generally higher for rotifers than for cladocerans. Depending on the NaCl concentration, the r of rotifers ranged from +0.57 to −0.58 day⁻¹, while the r for cladocerans was lower (+0.34 to −0.22 day⁻¹).     

The structure and component characteristics of partial nitrification biofilms under autotrophic and heterotrophic conditions

The differences in the structure and component characteristics of partial nitrification biofilms between autotrophic and heterotrophic conditions were investigated in this work. Three-dimensional excitation–emission matrix fluorescence spectroscopy (EEM), fluorescence staining, and confocal laser scanning microscopy (CLSM) were used to determine differences in the architecture and extracellular polymeric substance (EPS) distribution of the autotrophic and heterotrophic biofilms. Partial nitrification was successfully achieved, and the results demonstrated that an appropriate amount of organic carbon (chemical oxygen demand (COD)/N?=?2.6) is advantageous for obtaining better partial nitrification. The final ammoniation and nitrosation rates achieved were 97 and 99 %, respectively. Proteins (PN) and polysaccharides (PS) were dominant in the tightly bound EPS (TB-EPS) of autotrophic and heterotrophic biofilms, with PN/PS ratios of 0.96 and 0.69, respectively. Proteins, lipids, α-d-glucopyranose polysaccharides, and nucleic acids were mostly present within the layers of biofilms, but they were distributed in the upper-middle portion of the autotrophic biofilm and increased with depth from the upper layer in the heterotrophic biofilms.     

Dynamics and trophic roles of heterotrophic protists in the plankton of a freshwater tidal estuary

Freshwater tidal estuaries comprise the most upstream reaches of estuaries and are often characterised by the presence of dense bacterial and algal populations which provide a large food source for bacterivorous and algivorous protists. In 1996, the protistan community in the freshwater tidal reaches of the Schelde estuary was monitored to evaluate whether these high food levels are reflected in a similarly high heterotrophic protistan biomass. Protistan distribution patterns were compared to those of metazoan zooplankton to evaluate the possible role of top-down regulation of protists by metazoans. Apart from the algivorous sarcodine Asterocaelum, which reached high densities in summer, heterotrophic protistan biomass was dominated by ciliates and, second in importance, heterotrophic nanoflagellates (HNAN). HNAN abundance was low (annual average 2490 cells ml^–1) and did not display large seasonal variation. It is hypothesised that HNAN were top-down controlled by oligotrich ciliates throughout the year and by rotifers in summer. Ciliate abundance was generally relatively high (annual average 65 cells ml^–1) and peaked in winter (maximum 450 cells ml^–1). The decline of ciliate populations in summer was ascribed to grazing by rotifers, which developed dense populations in that season. In winter, ciliate populations were probably regulated `internally' by carnivorous ciliates (haptorids and Suctoria). Our observations suggest that, in this type of productive ecosystems, the microbial food web is mainly top-down controlled rather than regulated by food availability.     

Application of the size-fractionation method to simultaneous estimation of clearance rates by heterotrophic flagellates and ciliates of pico- and nanophytoplankton

To estimate the clearance rates of pico- and nanophytoplankton by heterotrophic nanoflagellates (HNF) and ciliates, the size-fractionation method was employed in combination with a multiple regression analysis. Apparent growth rate of a specific phytoplankton group was decomposed into three terms, net growth rate, grazing rates by HNF and those by ciliates, and the grazing rates were interpreted as a linear function of average cell concentrations of HNF and ciliates. We produced a set of subsamples from a water sample by size-fractionation using three different pore sizes. By measuring phytoplankton and protozoan cell concentrations, apparent growth rate of a specific phytoplankton group was regressed against the average cell concentrations of HNF and ciliates to obtain the net growth rate of the phytoplankton group and the average clearance rates by these two protozoan groups. The estimated values were within the range of those previously reported for cultured and natural protozoan, which supported the feasibility of the present method. The estimated values also suggested that picophytoplankton abundance in Otsuchi Bay in spring is controlled mainly by HNF through active grazing. The present study rediscovered the utility of the size-fractionation method as a method to estimate the clearance rates of different protozoan groups from natural assemblages in a single experiment.