ALBERT — All Library Books, journals and Electronic Records Telegrafenberg

1

Electronic Resource

Laboratory experiments on the impact of biofilms on the plankton of a large river (2003)

Weitere, Markus ; Schmidt-Denter, Kerstin ; Arndt, Hartmut

Oxford, UK : Blackwell Science Ltd

Freshwater biology 48 (2003), S. 0

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ISSN: 1365-2427

Source: Blackwell Publishing Journal Backfiles 1879-2005

Topics: Biology

Notes: 1. Benthic organisms can have a strong effect on the plankton in rivers, although normally only members of the macrofauna are considered as important consumers. In the present study we conducted experiments on four different dates (in December, March, June and September) to assess the potential role of periphytic heterotrophic flagellates (HF), ciliates and rotifers in the control of potamoplankton (bacteria, algae, HF and ciliates).2. Natural periphyton was established on the walls of circular flow channels by exposing them to river water (River Rhine, Germany). The experimental channels (with periphyton) and control channels (without periphyton) were filled with riverine water and the increase rates of planktonic bacteria, algae, HF and oligotrich ciliates were determined for the two treatments.3. The abundance of periphytic ciliates and rotifers at the beginning of the four experiments showed large differences with low values in December and March, and high values in June and September. Dominant potential consumers of plankton were the heterotrich ciliate Stentor sp. and bdelloid rotifers.4. The rates of increase of planktonic algae, HF and ciliates were significantly smaller in the presence of periphyton compared with those in their absence. Significant interactions between the treatment (with and without periphyton) and the time of experiment were found for the planktonic HF and algae, indicating that the impact of the periphyton varied temporarily. The planktonic groups responded differently to the periphyton with the planktonic HF showing the highest loss rate. Significant differences were also found among the loss rates of different HF groups and different diatom size classes.5. These laboratory experiments demonstrate that periphytic ciliates and rotifers are potentially important consumers of different planktonic groups. The quantitative impact of periphyton on plankton with respect to the selective feeding needs further attention.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1046/j.1365-2427.2003.01144.x

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2

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Taxonomic composition and biomass of heterotrophic flagellates in relation to lake trophy and season (2001)

Auer, Brigitte ; Arndt, Hartmut

Oxford UK : Blackwell Science Ltd

Freshwater biology 46 (2001), S. 0

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ISSN: 1365-2427

Source: Blackwell Publishing Journal Backfiles 1879-2005

Topics: Biology

Notes: 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.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1046/j.1365-2427.2001.00730.x

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3

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Benthic–pelagic coupling: a comparison of the community structure of benthic and planktonic heterotrophic protists in shallow inlets of the southern Baltic (2000)

Garstecki, Tobias ; Verhoeven, Richard ; Wickham, Stephen A. ; [et al.]

Oxford, UK : Blackwell Science Ltd

Freshwater biology 45 (2000), S. 0

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ISSN: 1365-2427

Source: Blackwell Publishing Journal Backfiles 1879-2005

Topics: Biology

Notes: 1. The taxonomic composition, abundance and biomass of heterotrophic protists (ciliates, heterotrophic flagellates (HF), rhizopods and actinopods) in the sediment and water column of shallow inlets of the Southern Baltic was studied under a variety of environmental conditions during 1996–1997. A shallow, highly eutrophic station and a deeper, less eutrophic station were compared.  2. Community biomass ranged from 0.12 to 0.34 μg C cm−3 in the water column and from 1.5 to 105 μg C cm−3 in the sediment. Heterotrophic protists dominated zooplankton biomass at both stations (73% and 84% mean contribution), while they were of minor importance within the zoobenthos. Expressed per unit area, benthic biomass contributed a significant part (44% and 49%) to the total heterotrophic protistan community at both stations.  3. Although the methodology for counting ciliates and HF was focussed on a high taxonomic resolution, the results reveal some general trends in the distribution of heterotrophic protists: protozooplankton biomass was dominated by flagellates (80% mean biomass contribution) at the shallow station and by ciliates (73% mean biomass contribution) at the deep station. In the benthos at both stations, ciliates were the dominant protozoans, followed by the hitherto little-studied rhizopods (25% and 35% mean biomass contribution) and flagellates.  4. The degree of benthic–pelagic coupling differed between taxonomic groups. Benthic and pelagic communities of ciliates showed little taxonomic overlap. In contrast, many heterotrophic flagellate species were found both in the benthos and in the pelagic. These benthic–pelagic species contributed significantly to the biomass of HF in the water column. The planktonic rhizopod community consisted of a subset of those species found in the benthos.  5. The abundance of benthic and pelagic protists was positively correlated at the shallow station, but taxonomic data indicate that the direct exchange between benthic and pelagic communities was only partly responsible.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1046/j.1365-2427.2000.00676.x

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4

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Confusing Selective Feeding with Differential Digestion in Bacterivorous Nanoflagellates (2001)

BOENIGK, JENS ; MATZ, CARSTEN ; JÜRGENS, KLAUS ; [et al.]

Oxford, UK : Blackwell Publishing Ltd

The @journal of eukaryotic microbiology 48 (2001), S. 0

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ISSN: 1550-7408

Source: Blackwell Publishing Journal Backfiles 1879-2005

Topics: Biology

Notes: Food selectivity and the mechanisms of food selection were analyzed by video microscopy for three species (Spumella, Ochromonas, Cafeteria) of interception-feeding heterotrophic nanoflagellates. The fate of individual prey particles, either live bacteria and/or inert particles, was recorded during the different stages of the particle-flagellate-interaction, which included capture, ingestion, digestion, and egestion. The experiments revealed species-specific differences and new insights into the underlying mechanisms of particle selection by bacterivorous flagellates. When beads and bacteria were offered simultaneously, both particles were ingested unselectively at similar rates. However, the chrysomonads Spumella and Ochromonas egested the inert beads after a vacuole passage time of only 2–3 min, which resulted in an increasing proportion of bacteria in the food vacuoles. Vacuole passage time for starved flagellates was significantly longer compared to that of exponential-phase flagellates for Spumella and Ochromonas. The bicosoecid Cafeteria stored all ingested particles, beads as well as bacteria, in food vacuoles for more then 30 min. Therefore “selective digestion” is one main mechanism responsible for differential processing of prey particles. This selection mechanism may explain some discrepancies of former experiments using inert particles as bacterial surrogates for measuring bacterivory.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1111/j.1550-7408.2001.tb00175.x

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5

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Particle Handling during Interception Feeding by Four Species of Heterotrophic Nanoflagellates (2000)

BOENIGK, JENS ; ARNDT, HARTMUT

Oxford, UK : Blackwell Publishing Ltd

The @journal of eukaryotic microbiology 47 (2000), S. 0

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ISSN: 1550-7408

Source: Blackwell Publishing Journal Backfiles 1879-2005

Topics: Biology

Notes: . High resolution video-microscopy was used to observe grazing patterns of the heterotrophic nanoflagellates Cafeteria roenbergensis, Bodo sultans, Spumella sp., and Ochromonas sp. Spumella and Ochromonas enclose food particles with pseudopodia while Cafeteria and Bodo engulf particles by invagination of the cell surface. The following parameters of the feeding process were quantified: frequency of flagellar beating, speed of particles in different positions of the feeding current, food size selection, feeding rate, and the time budget for the handling of particles. The mean handling times differed between 94 s for Cafeteria and 4 s for Ochromonas for ingested particles. Handling times for ingested particles were significantly longer than for non-captured particles. Long handling times were calculated to be disadvantageous only for flagellates which propel a high water volume per hour (esp. Ochromonas) or live in a bacteria-rich environment. Our model calculations may provide a reasonable theoretical explanation for a concentration-dependent behavioural variability of the feeding strategy of different heterotrophic nanoflagellates (HNF) species.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1111/j.1550-7408.2000.tb00060.x

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6

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Top-down effects on pelagic heterotrophic nanoflagellates (HNF) in a large river (River Rhine): do losses to the benthos play a role? (2002)

WEITERE, MARKUS ; ARNDT, HARTMUT

Oxford UK : Blackwell Science Ltd

Freshwater biology 47 (2002), S. 0

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ISSN: 1365-2427

Source: Blackwell Publishing Journal Backfiles 1879-2005

Topics: Biology

Notes: 1. The abundance, production and control of pelagic heterotrophic nanoflagellates (HNF) in the Lower River Rhine (Germany) were investigated. Field samples (live-counting technique) were taken at least every 2 weeks at Cologne (km 685) over a period of 20 months. In addition, Lagrangian sampling was carried out 160 km downstream of Cologne (Kalkar–Grieth, km 845) over a period of 12 months. Potential HNF growth rates and loss rates caused by planktonic predators were estimated in the laboratory (size fractionation experiments) and compared with the changes in HNF-density in a water parcel flowing downstream.2. Mean abundance (±SD) ranged from 7 ± 6 to 4890 ± 560 individuals mL–1 and was positively correlated with discharge. Heterotrophic nanoflagellates abundance increased up to 30-fold during flood events, whereas there were only minor changes in the taxonomic composition.3. HNF growth rate ranged from 0.16 ± 0.12 to 1.98 ± 0.10 day–1. Between 0 and 95% (mean: 32%) of the gross production was lost to planktonic predators; a larger portion between 0 and 195% (mean: 64%) of the HNF gross production was lost by other means.4. There may be an important role for benthic predators in the control of pelagic HNF. First, production of HNF was high and grazing losses to planktonic predators low at times when HNF abundance was low. Secondly, high in situ loss rates (not explicable by planktonic predators), which were positively related to temperature, indicate the importance of biotic interactions. Thirdly, the dependence of HNF abundance on discharge indicated a decrease grazing intensity with rising water levels (increase in water volume/colonised river bed ratio).5. The impact of discharge on planktonic HNF mediated by the grazing impact of benthic predators was modelled, showing a good fit with the field data.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1046/j.1365-2427.2002.00875.x

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7

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Experimental demonstration of chaos in a microbial food web (2005)

Becks, Lutz ; Hilker, Frank M. ; Malchow, Horst ; [et al.]

[s.l.] : Macmillian Magazines Ltd.

Nature 435 (2005), S. 1226-1229

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ISSN: 1476-4687

Source: Nature Archives 1869 - 2009

Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics

Notes: [Auszug] Discovering why natural population densities change over time and vary with location is a central goal of ecological and evolutional disciplines. The recognition that even simple ecological systems can undergo chaotic behaviour has made chaos a topic of considerable interest among theoretical ...

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1038/nature03627

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8

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Rotifers as predators on components of the microbial web (bacteria, heterotrophic flagellates, ciliates) — a review (1993)

Arndt, Hartmut

Springer

Hydrobiologia 255-256 (1993), S. 231-246

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ISSN: 1573-5117

Keywords: rotifers ; feeding ; bacteria ; ciliates ; heterotrophic flagellates ; microbial web

Source: Springer Online Journal Archives 1860-2000

Topics: Biology

Notes: Abstract Recent investigations have shown that processes within the planktonic microbial web are of great significance for the functioning of limnetic ecosystems. However, the general importance of protozoans and bacteria as food sources for rotifers, a major component of planktonic habitats, has seldom been evaluated. Results of feeding experiments and the analysis of the food size spectrum of rotifers suggest that larger bacteria, heterotrophic flagellates and small ciliates should be a common part of the food of most rotifer species. About 10–40 per cent of rotifers' food can consist of heterotrophic organisms of the microbial web. Field experiments have indicated that rotifer grazing should generally play a minor role in bacteria consumption compared to feeding by coexisting protozoans. However, according to recent experiments regarding food selection, rotifers should be efficient predators on protozoans. Laboratory experiments have revealed that even nanophagous rotifers can feed on ciliates. Preliminary microcosm and chemostat experiments have indicated that rotifers, due to their relatively low community grazing rates compared to the growth rates of bacteria and protozoans, should generally not be able (in contrast to some cladocerans) to suppress the microbial web via grazing, though they may structure it. Filter-feeding nanophagous rotifers (e.g. brachionids) seem to be significant feeders on the smaller organisms of the microbial web (bacteria, flagellates, small ciliates), whereas grasping species (e.g. synchaetids and asplanchnids) seem to be efficient predators on larger organisms (esp. ciliates). Another important role of rotifers is their feedback effect on the microbial web. Rotifers provide degraded algae, bacteria and protozoans to the microbial web and may promote microbial activity. Additional experimental work is necessary for a better understanding of the function of rotifers in aquatic ecosystems.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1007/BF00025844

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