Lake Bacterioplankton Research Articles

Effects of Resources and Trophic Interactions on Freshwater Bacterioplankton Diversity

In a study of bacterioplankton in an oligotrophic lake in northern Wisconsin, a community fingerprinting technique, automated ribosomal intergenic spacer analysis (ARISA), was used to determine the effect of resources and trophic interactions on bacterioplankton diversity. Inorganic nitrogen and phosphorus (NP), carbon in the form of glucose (G) or dissolved organic matter extracted from peat (DOM), and carbon and NP in combination were added to two types of experimental systems. Ten-liter mesocosms contained all components of the original aquatic community except for large zooplankton. One-liter dilution cultures were prepared so that the effects of grazers and phytoplankton were removed. During a 3-day incubation, bacterial production showed the greatest response to the carbon plus NP treatment in both experimental systems, but bacterial diversity was strikingly different between them. In the mesocosms, the number of ARISA-PCR fragments averaged 41 per profile, whereas the dilution culture communities were highly reduced in complexity, dominated in most cases by a single PCR fragment. Further analysis of the mesocosm data suggested that whereas the NPDOM addition caused the greatest aggregate bacterial growth response, the addition of NP alone caused the largest shifts in community composition. These results suggest that the measurement of aggregate responses, such as bacterial production, alone in studies of freshwater bacterial communities may mask the effects of resources on bacterioplankton.

Bioavailability and sources of DOC and DON in macrophyte stands of a tropical coastal lake

Dissolved organic carbon (DOC) and nitrogen (DON) derived from aquatic and terrestrial vascular plants provide a major energy and nutrient source for freshwater and coastal marine biota. The bioavailability of this material may to a large extent depend on plant species. In this study, we have compared the bioavailability of DOC and DON sampled in two distinct stands of Typha domingensisand Eleocharis mutatain a coastal tropical lake and in the adjacent ocean in the state of Rio de Janeiro, Brazil. Bioavailability of organic matter was assessed by regrowth bioassays using natural bacterial inocula. Nutrients were added to achieve carbon or nitrogen limitation. At all sampling sites, DON comprised over 95% of the total bioavailable nitrogen, suggesting its dominant role as a nitrogen source. The bioavailability of lacustrine DON (22% in the Typhastand and 34% in the Eleocharisstand) exceeded the bioavailability of DOC (8 and 10%, respectively) and exhibited a larger difference between the stands. 3H-leucine incorporation studies showed that lake bacterioplankton had a well balanced supply of C, N and P. Therefore, an accumulation of labile DON due to an excess nitrogen supply is not probable. We propose that a substantial part of the lake DON was newly formed within the macrophyte stands, while DOC was predominantly of terrestrial origin and more diagenetically changed.

Temperature control of bacterioplankton growth in a temperate large lake

AME Aquatic Microbial Ecology Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsSpecials AME 16:119-130 (1998) - doi:10.3354/ame016119 Temperature control of bacterioplankton growth in a temperate large lake Meinhard Simon*, Christine Wünsch Limnological Institute, University of Constance, PO Box 5560, D-78457 Konstanz, Germany *Present address: Institute for Chemistry and Biology of the Marine Environment (ICBM), University of Oldenburg, PO Box 2503, D-26111 Oldenburg, Germany. E-mail: m.simon@icbm.uni-oldenburg.de ABSTRACT: In order to examine the significance of temperature in controlling growth of bacterioplankton in a large lake with a pronounced pelagic zone we performed 12 temperature shift-up experiments year-round in mesotrophic Lake Constance, Germany, with samples from 1, 6, 10 or 20 and 50 m depth. We measured incorporation of 14C-leucine (Leu) and 3H-thymidine (TdR) at 5, 10, 15, 20 and 25°C including the in situ temperature ±2°C. The results show that during most of the year bacteria at 1 and 6 m were well adapted to the ambient temperature, ranging between 4 and 23°C, because in situ and optimum growth temperatures agreed within 1 to 5°C. At 20 and 50 m, in situ and optimum growth temperatures usually diverged by more than 5°C, and often by more than 10°C, indicating that bacterial growth at these depths was clearly limited by temperature. Hence, in the upper water column, temperature controlled bacterial growth by selecting for a well-temperature-adapted community whereas in the lower part of the water column temperature directly controlled bacterial growth. In several experiments we observed 2 temperature optima. We interpret this observation as an indication of the existence of 2 different subpopulations with different temperature preferences. Q10 values of Leu incorporation and TdR incorporation, ranging from 1.4 to 42.5, exhibited systematic differences. At 1, 6 and 10 m, Q10 of Leu was higher than that of TdR except in 3 cases, whereas at 20 and 50 m Q10 of TdR was higher than that of Leu except in 3 cases. This observation suggests that protein synthesis (Leu) and DNA replication (TdR) are controlled differently by temperature in differently adapted bacterial communities. In order to test the hypothesis that utilization of the most important substrates is optimized at the optimum growth temperature we carried out 5 additional experiments in which we measured uptake and respiration of dissolved free amino acids and monosaccharides. In 3 experiments we found that the fraction of amino acids respired had a distinct minimum at the optimum growth temperature whereas respiration of monosaccharides had such a minimum only in 1 experiment. The experiments gave no indication of enhanced respiration percentages at minimum growth temperatures. KEY WORDS: Temperature · Bacterial production · Amino acid uptake · Monosaccharide uptake · Respiration · Large lake Full text in pdf format PreviousNextExport citation RSS - Facebook - Tweet - linkedIn Cited by Published in AME Vol. 16, No. 2. Publication date: November 27, 1998 Print ISSN: 0948-3055; Online ISSN: 1616-1564 Copyright © 1998 Inter-Research.

Size-specific mortality of lake bacterioplankton by natural virus communities

AME Aquatic Microbial Ecology Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsSpecials AME 15:103-113 (1998) - doi:10.3354/ame015103 Size-specific mortality of lake bacterioplankton by natural virus communities Markus G. Weinbauer*, Manfred G. Höfle GBF-National Research Center of Biotechnology, AG Microbial Ecology, Mascheroder Weg 1, D-38124 Braunschweig, Germany *E-mail: mgw@gbf.de ABSTRACT: The potential effect that viral lysis has on the cell size distribution of bacterioplankton was investigated during late summer stratification in Lake Plußsee, Germany. Size-specific bacterial mortality due to viral lysis was estimated from in situ samples by a transmission electron microscopy based examination of visibly infected cells (VIC) and in an experiment with varying concentrations of the natural virus community. In all depth layers the highest percentage of cells was found in a cell length class that was smaller for the entire bacterial community (0.3-0.6 μm) than for VIC (0.6-0.9 μm). For cells <2.4 μm the highest frequency of VIC (FVIC) was detected in the size classes 0.6-0.9 and 0.9-1.2 μm, and the FVIC was high in the size classes 1.2-1.5 (all depth layers) and 1.5-1.8 μm (meta- and hypolimnion). The estimated mortality due to viral lysis in these size classes was significant with maxima of 29 to 55% in the epilimnion, 30 to 59% in the metalimnion and 56 to 107% in the hypolimnion. In all depth layers the FVIC of bacteria <0.3 μm in length was ca 30% of that averaged for the entire bacterial community, and in the experiment the percentage of cells <0.3 μm was highest in enclosures with high viral activity. In the experiment the average cell size was smaller in enclosures with high than in that with low viral activity. The data demonstrate that being small could be a strategy of cells to reduce mortality due to viral lysis probably by reducing the contact rates with viruses. Thus, viral lysis could be one of the mechanisms keeping the cell size small in aquatic ecosystems. In oxic water cells in the largest size class (>2.4 μm) were not infected with viruses, and in enclosures with epilimnetic lake water the percentage of cells >2.4 μm was highest in enclosures with highest viral abundance, suggesting that resistance against infection favored large cells. However, in the meta- and hypolimnion the FVIC was high for cells >2.4 μm and, since the burst size increased with bacterial cell size, lysis of large cells could contribute significantly to viral production. Also, a major portion of biomass was found in cells >2.4 μm. The finding that viral lysis is size-specific and can affect the cell size distribution of bacteria in lake water has important implications for our understanding of the mechanisms which regulate bacterial production and nutrient cycling in pelagic environments. KEY WORDS: Bacterioplankton size structure · Size-specific viral lysis · Lake Plußsee Full text in pdf format NextExport citation RSS - Facebook - Tweet - linkedIn Cited by Published in AME Vol. 15, No. 2. Publication date: July 02, 1998 Print ISSN: 0948-3055; Online ISSN: 1616-1564 Copyright © 1998 Inter-Research.

Can Simple Empirical Equations Describe the Seasonal Dynamics of Bacterioplankton in Lakes: An Eight-Year Study in Shallow Hypertrophic and Biologically Highly Dynamic Lake Sobygard, Denmark

Seasonal variation in bacterioplankton abundance, biomass, and bacterioplankton production was studied over eight years in hypertrophic Lake Sobygard. Biologically, the lake is highly variable; this is due mainly to large interannual variation in fish recruitment. Bacterioplankton production was low during winter, typically 1–3 × 107 cells l−1 h−1, and high during summer, albeit greatly fluctuating with maximum rates typically ranging from 60 to 90 × 107 cells l−1 h−1 (or 0.4 to 0.6 mg C l−1 day−1). Less pronounced variations were found in bacterioplankton abundance, which typically ranged from 3–8 × 109 cells l−1 in winter to 15–30 × 109 cells l−1 during summer. The specific growth rate of bacterioplankton varied from 0.02–0.2 d−1 in winter to 0.5–2.3 day−1 during summer. Interpolated mean bacterioplankton production, in terms of carbon, ranged from 0.08 to 0.16 mg C l−1 day−1, corresponding to 1.6–5.5% of the phytoplankton production, while biomass ranged from 0.28 to 0.36 mg C l−1, corresponding to 1.9–4.6% of the phytoplankton biomass. We conducted regression analysis, relating the bacterioplankton variables to a number of environmental variables, and evaluated the interannual parameter variability. Chlorophyll a and phytoplankton production contributed less to the variation in the bacterioplankton variables than in most previous analyses using data from less eutrophic systems. We suggest that the proportion of phytoplankton production that is channelized through bacterioplankton in lakes decreases with increasing trophic state and decreasing mean depth. This probably reflects a concurrent increase in fish predation on macrozooplankton and loss by sedimentation. An important part of the residual variation in the equations hitherto proposed in the literature could be explained by variation in macrozooplankton biomass and pH > 10.2. A negative effect of high pH on bacterioplankton production was confirmed by laboratory experiments. The impact of different zooplankton varies considerably, with Daphnia seeming to have a negative impact on bacterioplankton abundance and, thereby, indirectly on bacterioplankton production, while Bosmina, rotifers, and cyclopoid copepods seem to stimulate both abundance and production. Bosmina apparently also stimulate the bacterioplankton specific growth rate.

Autotrophic carbon sources for heterotrophic bacterioplankton in a floodplain lake of central Amazon

The relative contribution of autotrophic carbon sources (aquatic macrophytes, flooded forest, phytoplankton) for heterotrophic bacterioplankton was evaluated in a floodplain lake of the Central Amazon. Stable carbon isotopes (δ13C) were used as tracers. Values of δ13C of different autotrophic sources were compared to those of dissolved organic carbon (DOC) and those of bacterially produced CO2.

Flow cytometric determination of bacterial abundance in lake plankton with the green nucleic acid stain SYTO 13

We have developed a protocol for the cytometric enumeration of bacterioplankton in lakes with the nucleic acid stain SYTO 13; our protocol can be used with any standard bench‐top flow cytometer equipped with an argon laser with excitation at 488 nm. The protocol performs well in the range of bacterial densities from 105 to 106 ml−1. Estimates of bacterial abundance using the cytometric technique ranged from 72 to 141% of the epifluorescence estimates with DAPI staining. The average C.V. of replicate cytometric counts was 2.4%, and the average C.V. for cytometric counts in replicate water samples was 6.7%. The precision of cytometric counts was 10‐fold higher than corresponding epifluorescence bacterial counts, and the sample processing time is decreased by 10–15‐fold relative to the epifluorescence technique. This cytometric protocol can be applied to samples from a wide variety of lakes and offers an accurate, precise, and fast alternative to standard epifluorescence bacterial counts.

Influence of light on bacterioplankton in a tropical lake

Bacterial abundance and production in a vertical profile in Lake Kariba (17dgS), Zimbabwe, were affected by solar irradiance. At the surface, 1.87 × 109 bacteria 1−1 were found and abundance peaked at 10 m (2.5 × 109 bacteria l-1), then decreasing with depth. Bacterial reproduction at the surface(0.145 µg C1−1 h−1) was nearly four times less than the production at 10 m although bacterial numbers were only 26% less. Thus, bacterial production per cell was lower at the surface than deeper down, suggesting that bacterial production is inhibited at the surface.

Fish-induced changes in zooplankton grazing on phytoplankton and bacterioplankton: a long-term study in shallow hypertrophic Lake Søbygaard

The impact of fish-mediated changes on the structure and grazing of zooplankton on phytoplankton and bacterioplankton was studied in Lake S0bygaard during the period 1984-92 by means of in vitro grazing experiments (C-labelled phytoplankton, H-labelled bacterioplankton) and model predictions. Measured zooplankton clearance rates ranged from 0-25 ml I' h on phytoplankton to 0-33 ml H h on bacterioplankton. The highest rates were found during the summer when Daphnia jpp. were dominant. As the phytoplankton biomass was substantially greater than that of bacterioplankton throughout the study period, ingestion of phytoplankton was 26-fold greater than that of bacterioplankton. Multiple regression analysis of the experimental data revealed that Daphnia spp., Bosmina longirostru and Cyclops vidnus, which were the dominant zooplankton, all contributed significantly to the variation in ingestion of phytoplankton, while only Daphnia spp. contributed significantly to that of bacterioplankton. Using estimated mean values for clearance and ingestion rates for different zooplankters, we calculated zooplankton grazing on phytoplankton and bacterioplankton on the basis of monitoring data of lake plankton obtained during a 9 year study period. Summer mean grazing ranged from 2 to 4% of phytoplankton production and 2% of bacterioplankton production to maxima of 53 and 88%, respectively. The grazing percentage decreased with increasing density of planktrvorous fish caught in August each year using gill nets and shore-line electrofishing.The changes along a gradient of planktivorous fish abundance seemed highest for bacterioplankton. Accordingly, the percentage contribution of bacterioplankton to the total ingestion of the two carbon sources decreased from a summer mean value of 8% in ZJap/tnia-dominated communities at lower fish density to 0.7-1.1% at high fish density, when cyclopoid copepods or Bosmina and rotifers dominated. Likewise, the percentage of phytoplankton production channelled through the bacteria varied, it being highest (5-8%) at high fish densities. It is argued that the negative impact of zooplankton grazing on bacterioplankton in shallow lakes is highest at intermediate phosphorus levels, under which conditions Daphnia dominate the zooplankton community.

Population dynamics of bacterioplankton in an oligotrophic lake

Population dynamics of bacterioplankton in an oligotrophic lake

The dynamics of heterotrophic nanoflagellates and bacterioplankton in a large ultra-oligotrophic Antarctic lake

The abundance of both heterotrophic nanoflagellates (HNAN) and bacterioplankton in a large (9km2) ultraoligotrophic Antarctic lake (Crooked Lake) were investigated from December 1992 until November 1993. HNAN abundance peaked in spring, summer and autumn, falling to lowest numbers during the winter. Numbers ranged between 0 and 50.9×104 l−1. Bacterioplankton abundance was highest during the late summer and then fell progressively towards winter and autumn (range 1.19–4.46×106 l−1) In contrast to numbers, mean cell volumes (MCV) of the bacteria reached their highest in spring, and consequently highest bacterial biomass occurred at this time. MCV ranged between 0.052 and 0.224μm3. Bacterial production measurements following the incorporation of [3H] thymidine into DNA and [14C] leucine into protein using a doubling-labelling procedure were undertaken in January, June, August, October and November. Rates varied between 2.8 and 52 ng C l1 h1. On occasions, a significant difference in production rates based on the uptake of leucine and thymidine was observed, suggesting unbalanced growth. Highest rates of production coincided with times of high dissolved organic carbon levels in the water column and lowest production with low levels of DOC. HNAN grazing rates were measured by following the uptake of fluorescently labelled bacteria and averaged 4.8 bacterial cells individual1 day1 at 2 and 4°C. Specific growth rates (h1) ranged around 0.00070–0.00077 in both the field and laboratory, giving doubling times of 37.3 and 41.0 days, respectively. These low rates of grazing and growth indicate that there is no adaptation to low temperatures in these freshwater protists. Based on these data, the gross production efficiency is 24%. HNAN removed between 0.1 and 9.7% of bacterial production per day.

Role of Anaerobic Ciliates in Planktonic Food Webs: Abundance, Feeding, and Impact on Bacteria in the Field

We studied the dynamics of two populations of anaerobic ciliates, Plagiopyla sp. and Metopus sp., and of their potential prey, heterotrophic and phototrophic purple bacteria, in Lake Cisó throughout a 1-year cycle. The abundance of both ciliates was very low (less than 2 individuals per ml). During mixing, Plagiopyla ciliates exhibited high clearance rates (about 100 nl ciliate h), its integrated abundance increased with a net doubling time of 47 days, and its potential doubling times, as calculated from the number of bacteria consumed, ranged between 5 and 8 days. During stratification, the activity of Plagiopyla ciliates was reduced and the population decreased; this was related to the higher amounts of sulfide present. The impact of predation by the Plagiopyla population on bacterioplankton was found to be insignificant, less than 0.1% of bacterial biomass consumed per day. Thus, anaerobic ciliates cannot control the bacterioplankton in Lake Cisó because of both the low abundance over the period studied and the low feeding rates during certain periods. A review of available field studies suggests that this conclusion can be extrapolated to most other anoxic systems.

Assessing the impact of copper on DNA and protein synthesis of lake bacterioplankton assemblages

Assessing the impact of copper on DNA and protein synthesis of lake bacterioplankton assemblages

Direct and Indirect Evidence of Size-Selective Grazing on Pelagic Bacteria by Freshwater Nanoflagellates

Size-selective grazing of three heterotrophic nanoflagellates (with cell sizes of 21, 44, and 66 mum) isolated from Lake Arlington, Texas was examined by using a natural mixture of fluorescence labelled lake bacteria. Sizes of ingested bacteria in food vacuoles were directly measured. Larger bacterial cells were ingested at a frequency much higher than that at which they occurred in the assemblage, indicating preferential flagellate grazing on the larger size classes within the lake bacterioplankton. Water samples were collected biweekly from June through September, 1989, fractionated by filtration, and incubated for 40 h at in situ temperatures. The average bacterial size was always larger in water which was passed through 1-mum-pore-size filters (1-mum-filtered water) (which was predator free) than in 5-mum-filtered water (which contained flagellates only) or in unfiltered water (in which all bacterivores were present). The increase of bacterial-cell size in 1-mum-filtered water was caused by a shift in the size structure of the bacterioplankton population. Larger cells became more abundant in the absence of flagellate grazing.

Thymidine incorporation into lake water bacterioplankton and pure cultures of chemolithotrophic (CO, H2) and methanotrophic bacteria

Incorporation of [3H]methyl thymidine into bacterial DNA was measured using samples of bacterioplankton from Lake Constance and pure cultures of CO, H2 and CH4-oxidizing bacteria. Thymidine was incorporated by Pseudomonas carboxydovorans, Paracoccus denitrificans, Methylosinus trichosporium, Methylomonas agile, and by various chemolithotropic or methylotrophic isolates from Lake Constance. Thymidine incorporation by bacterial cultures was stimulated by increasing concentrations of CO or H2. Increased CH4 concentrations stimulated thymidine incorporation by Ms. trichosporium only if the cells had been starved. In contrast to bacterial cultures, thymidine incorporation by bacterioplankton samples was not stimulated by increasing

Abundance and activity of bacterioplankton in warm lakes

Abundance and activity of bacterioplankton in warm lakes

Thymidine incorporation by littoral and pelagial bacterioplankton in a mesohumic lake

Thymidine incorporation by littoral and pelagial bacterioplankton in a mesohumic lake

Coupling of the seasonal patterns of bacterioplankton and phytoplankton in a eutrophic lake

Developments of bacterial and phytoplankton biomass were assessed during an annual sampling cycle in a eutrophic lake (Lake Aydat, France). Bacterial abundance, estimated by epifluorescence microscopy counting, varied from 0.61 to 12.72 × 106 cells/mL, confirming the eutrophic status attributed to this lake. Cellular densities were nearly homogeneously distributed in the water column. Mean values for bacterial abundance, obtained from three sampling depths (2, 7, and 14 m) were 3.70, 4.23, and 3.66 × 106 cells/mL. In the epilimnion, phytoplankton productivity and community composition, as well as temperature, appeared to control bacterial development. Bacterial biomass varied from 0.5 to 43.5 × 10−2 mg C/L. Mean values for the three sampling depths were 8.1, 10.1, and 9.1 × 10−2 mg C/L. Although bacterial biomass was significantly correlated with bacterial abundance, only 45 to 65% of its variation could be explained by abundance. Individual cell biovolumes varied up to sixfold, from 0.014 μm3 in spring and autumn to 0.090 μm3 in summer. The largest bacterial cells and the most elevated bacterial biomass were reached when bacteria were attached to phytoplankton or detrital organic matter, primarily during summer. Mucilaginous phytoplankton, such as Gomphosphaeria and Sphaerocystis, was found to be particularly good substrate available for the development of large and attached bacteria.Key words: eutrophic lake, bacterioplankton, phytoplankton, seasonal coupling, bacterial attachment.

Zooplankton grazing on lake bactenoplankton and phytoplankton

Grazing experiments with the calanoid Calamoecia lucasi and the cladoceran Ceriodaphnia dubia feeding on free lake bacterioplankton produced artificially high clearance rates by the acridine orange direct count method (AODC), but lower and more conservative clearance rates by labelling bacteria with [ 3 H]thymidine. A comparison of zooplankton carbon requirements and bacterial biomass suggests that even at maximal filtration rates bacterioplankton can only be a minor constituent of the diet. Bacterioplankton and phytoplankton do not provide adequate carbon to satisfy the daily requirement for respiration let alone for growth and reproduction. This suggests that: (i) predation of small zooplankton occurs; (ii) stress depresses the clearance rates; or (iii) the values obtained are at the low end of the diel range of feeding rates.

Effect of temperature on the mineralization of organic phosphorus compounds by certain aquatic bacteria

Summary“Yellow pigmented” bacteria chiefly consisting of Flavobacterium species and nonfruiting myxobacteria have been observed as an essential constituent of bacterioplankton in lakes. In eutrophic Mindel Lake (near Constance, BRD) aerobic myxobacteria of allochthonous origin had produced a bacterial waterbloom which persisted longer than 2 months.Isolated strains did not form fruiting bodies under the employed culture conditions and were in most features identical to “Sporocytophaga cauliformis” Knorr & Gräf. These bacteria did not only grow at 0° C, but had a continuous optimum for growth below 20° C.Producing an overplus of alkaline phosphatases they had a marked effect on hydrolysis of phosphates. In spite of their psychrophilic habit synthesis of alkaline phosphatases did not vary at different growth temperatures, and optimum activities were found near 36° C.Pure culture experiments were undertaken to estimate catalytic efficiencies of phosphate mineralization which could be attributed to standing crops of Myxobacteria in lake water.