Bacterivory by microheterotrophic flagellates in seawater samples

Andersen, Per; Fenchel, Tom

doi:10.4319/lo.1985.30.1.0198

Cited by 169 publications

(85 citation statements)

References 4 publications

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“…It must then be assumed that losses of bacterial biomass were negligible during this phase. Two factors able to reduce the bacterial biomass in marine waters are grazing by nano-and microzooplankton (Andersen & Fenchel 1985, Van Duyl et al 1990) and lysis induced by viruses (Proctor & Fuhrman 1990, Heldal & Bratbak 1991. In degradation experiments with marine phyto- also be assumed that viral attack of bacteria is relatively low in an exponentially growing population.…”

Section: Resultsmentioning

confidence: 99%

Aerobic degradation of phytoplankton debris dominated by Phaeocystis sp. in different physiological stages of growth

Osinga¹,

deVries²,

Lewis³

et al. 1997

Aquat. Microb. Ecol.

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ABSTRACT. The aerobic degradation of phytoplankton debris collected in Dutch coastal waters on 2 days in 1991 (15 April and 8 May), representing 2 physiological stages of a phytoplankton spring bloom dominated by Phaeocystis sp., was studied in batch culture experiments. The bacterial production and the concentrations of particulate organic carbon (POC) and dissolved organic carbon (DOC) were monitored over a period of 102 d. Bacterial numbers and biomass were followed for 35 d. All experiments showed a rapid metabolic response of bacteria and a sharp decrease in the concentration of POC and DOC during the first days of the experiments. Thereafter, bacterial production rates remained constant, and POC and DOC decreased slowly. Apparently, the phytoplankton debris consisted of a lablle, rapidly degradable fraction and a refractory, slowly degradable fraction. The labile fraction comprised approximately 50% of the debris, and was degraded with a bacterial carbon conversion efficiency of between 10 and 20%. There were no indications that antibiotic compounds present in the algal debris inhibited the degradation. Acrylate, a proposed antibiotic compound which was present in the algal debris, was rapidly degraded in a control experiment. The percentage of the material that had been degraded after 102 d was highest in the experiment with material collected in May. It was concluded that during the early phase of the bloom, more refractory compounds are produced

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Section: Resultsmentioning

confidence: 99%

Aerobic degradation of phytoplankton debris dominated by Phaeocystis sp. in different physiological stages of growth

Osinga¹,

deVries²,

Lewis³

et al. 1997

Aquat. Microb. Ecol.

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“…This is three times the ratio found in an epipelagic reference data set, 1760 ± 162 (averaged data from the following papers: Kirchman et al, 1989;Cho et al, 2000;Tanaka and Rassoulzadegan, 2002;Yamaguchi et al, 2002Yamaguchi et al, , 2004Tanaka et al, 2005), indicating less protists for a given prokaryote cell in deep waters than at surface. A putative reason for the higher PROK:HP ratio in deep waters would be that the prokaryote abundance in the deep ocean is below the numerical threshold of grazing (Andersen and Fenchel, 1985), thus protists spend a lot of energy (via respiration) in the search for prey and as a result prokaryotes are inefficiently grazed. Alternatively, HP cells could be sustained at low prokaryotic abundances given the micropatch distribution theory (Simon et al, 2002;Baltar et al, 2009) that suggests that most of the interactions between HP and prokaryotes take place in large or small aggregates where prey density is high enough to sustain HP growth.…”

Section: Discussionmentioning

confidence: 99%

Global abundance of planktonic heterotrophic protists in the deep ocean

et al. 2014

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The dark ocean is one of the largest biomes on Earth, with critical roles in organic matter remineralization and global carbon sequestration. Despite its recognized importance, little is known about some key microbial players, such as the community of heterotrophic protists (HP), which are likely the main consumers of prokaryotic biomass. To investigate this microbial component at a global scale, we determined their abundance and biomass in deepwater column samples from the Malaspina 2010 circumnavigation using a combination of epifluorescence microscopy and flow cytometry. HP were ubiquitously found at all depths investigated down to 4000 m. HP abundances decreased with depth, from an average of 72 ± 19 cells ml À 1 in mesopelagic waters down to 11 ± 1 cells ml À 1 in bathypelagic waters, whereas their total biomass decreased from 280±46 to 50±14 pg C ml À 1 . The parameters that better explained the variance of HP abundance were depth and prokaryote abundance, and to lesser extent oxygen concentration. The generally good correlation with prokaryotic abundance suggested active grazing of HP on prokaryotes. On a finer scale, the prokaryote:HP abundance ratio varied at a regional scale, and sites with the highest ratios exhibited a larger contribution of fungi molecular signal. Our study is a step forward towards determining the relationship between HP and their environment, unveiling their importance as players in the dark ocean's microbial food web.

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“…1 and 4c; Table 2). Such curves have been reported from laboratory experiments or experimental enclosures over short incubations (Andersen and Fenchel 1985). Weisse (1990) showed, however, that such inverse relationships between HNF and bacteria may persist longer (weeks or months), not only in experimental systems…”

mentioning

confidence: 98%

Are rapid changes in bacterial biomass caused by shifts from top-down to bottom-up control?

Psenner

Sommaruga

1992

Limnol. Oceanogr.

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In the epilimnion of Mondsee, a mesotrophic hard‐water lake in Austria, bacterial numbers were strongly but inversely correlated with the abundance of heterotrophic nanoflagellates (HNF). The mean size of pelagic heterotrophic bacteria was small (0.04–0.05 µm3) for most of the summer, with short rods and cocci dominating. During the peak of small cyanobacteria which followed a Dinobryon bloom, however, large and elongated bacteria appeared and mean bacterial cell volume increased to 0.19 µm3. This phase lasted several days, then the size structure reverted to the previous condition with small and spherical cells predominating. Bacterial numbers peaked shortly after the decline of the algal bloom, and HNF reached their highest density ∼1 week after the biomass maximum of bacteria. Diel changes of bacterial biomass, however, were of the same order of magnitude as seasonal ones. We hypothesize that small, flagellated predators, but also Dinobryon, were able to control the abundance of pelagic bacterial populations (top down) for almost the whole summer. Bacterial size, on the other hand, was significantly correlated with the abundance of phytoplankton, suggesting that bacterial cell volumes depend primarily on nutrient supply (bottom up). Consequently, the importance of both control modes to the bacterial biomass can change rapidly.

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Bacterivory by microheterotrophic flagellates in seawater samples

Cited by 169 publications

References 4 publications

Aerobic degradation of phytoplankton debris dominated by Phaeocystis sp. in different physiological stages of growth

Aerobic degradation of phytoplankton debris dominated by Phaeocystis sp. in different physiological stages of growth

Global abundance of planktonic heterotrophic protists in the deep ocean

Are rapid changes in bacterial biomass caused by shifts from top-down to bottom-up control?

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