The microbial food web in the recently flooded sep reservoir: Diel fluctuations in bacterial biomass and metabolic activity in relation to phytoplankton and flagellate grazers

Jugnia, Louis‐B.; Tadonléké, Rémy D.; Sime-Ngando, Télesphore; Dévaux, Jean

doi:10.1007/s002480000056

Cited by 22 publications

(16 citation statements)

References 62 publications

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“…Our calculations, based on the daily mean values of growth efficiency of nanoflagellates during the period from June to October, ranged from 43% to 50.5% (mean 44.5%; Table 1). Our estimates were close to those reported by Jugnia et al (2000), implying that bacteria and Synechococcus spp. were the dominant prey for nanoflagellates during the period from June to October.…”

Section: Diel Variation Of Picoplankton Carbon Flux From August Tosupporting

confidence: 90%

“…Although bacterial production was found to have significant diel variations, bacterial abundance did not (Fig. 6), a finding similar to those of other studies on the stability of the bacterial community (Torreton and Dufour 1996;Jugnia et al 2000). Nanoflagellate preference for grazing on larger bacteria (Chrzanowski and Š imek 1990) might contribute to observed patterns.…”

Section: Causes Of Diel Variations In Picoplankton Abundance-supporting

confidence: 87%

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Seasonal diel variations of picoplankton and nanoplankton in a subtropical western Pacific coastal ecosystem

et al. 2005

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We analyzed seasonal and diel fluctuation patterns of heterotrophic bacteria, Synechococcus spp., and nanoflagellates at a coastal station at the southern edge of the East China Sea. Synechococcus spp. and nanoflagellates exhibited diel fluctuation at water temperatures above 25ЊC. Cell concentrations of Synechococcus spp. were significantly higher during the evening, whereas those of nanoflagellates were higher during the day. The day and night amounts of heterotrophic bacteria did not differ significantly, and we did not observe diel rhythms in these organisms below 25ЊC. The fractionation experiments we performed between August and October showed that growth rates of bacteria were high (0.73-1.00 g C L Ϫ1 h Ϫ1) during the day. However, because there was an increase in nanoflagellate grazing, there was no change in the abundance of bacteria over the day. Synechococcus spp. was not actively consumed by nanoflagellates during the day, but its rate of production was exceeded by the rate of grazing by nanoflagellates during the night. This out-of-phase Synechococcus spp. growth and mortality caused by grazing created diel variations in its abundance. We also found that picoplankton contributed 24-36 g C L Ϫ1 d Ϫ1to the microbial loop, and Synechococcus spp. and bacteria contributed equally to this carbon flux.

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Section: Diel Variation Of Picoplankton Carbon Flux From August Tosupporting

confidence: 90%

Section: Causes Of Diel Variations In Picoplankton Abundance-supporting

confidence: 87%

Seasonal diel variations of picoplankton and nanoplankton in a subtropical western Pacific coastal ecosystem

et al. 2005

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“…Diel changes in dissolved organic carbon (DOC) have also been reported in river systems, due to autotrophic and heterotrophic metabolism (Kaplan & Bott, 1989;Spencer et al, 2007;Watras et al, 2015;Wilson & Xenopoulos, 2013). In addition, in marine and lentic systems, diel changes in microbial activity have been linked to DOC patterns throughout the daily cycle (Gasol et al, 1998;Jugnia, Tadonl ek e, Sime-Ngando & Devaux, 2000). However, knowledge remains limited and unclear on diel changes in river sediment microbial function, which might be significantly affected by warming diel cycles.…”

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confidence: 99%

Warmer night‐time temperature promotes microbial heterotrophic activity and modifies stream sediment community

Freixa

Acuña

Casellas

et al. 2017

Global Change Biology

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Diel temperature patterns are changing because of global warming, with higher temperatures being predicted to be more pronounced at night. Biological reactions are temperature dependent, with some occurring only during the daylight hours (e.g., light photosynthesis) and other during the entire day (e.g., respiration). Consequently, we expect the modification of daily temperature cycles to alter microbial biological reactions in stream sediments. Here, we aimed to study the effect of warming and changes of the diel temperature patterns on stream sediment biofilm functions tied to organic carbon decomposition, as well as on biofilm meiofaunal community structure. We performed an eight-week experiment with 12 artificial streams subjected to three different diel temperature patterns: warming, warmer nights and control. Significant effects of warming on biofilm function and structure were mainly detected in the long term. Our results showed that warming altered biofilm function, especially in the warmer nights' treatment, which enhanced β-glucosidase enzyme activity. Interestingly, clear opposite diel patterns were observed for dissolved organic carbon and β-glucosidase activity, suggesting that, at night, sediment bacteria quickly consume the input of photosynthetic dissolved organic carbon labile compounds created during light-time. The biofilm structure was also altered by warming, as both warming and warmer night treatments enhanced copepod abundance and diminished abundances of turbellaria and nematodes, which, in turn, controlled bacterial, algal and ciliate communities. Overall, we conclude that warming has strong effect on sediment biofilm structure and enhanced microbial organic matter degradation which might, consequently, affect higher trophic levels and river carbon cycling.

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“…Obviously, the absence of direct measurements of grazing rates of flagellates on heterotrophic bacteria communities, for instance using fluorescently labelled bacteria (FLB) [40], prevented us from drawing firm conclusions about the grazing pressure of HNF on bacteria and our results should be considered in light of that. However, it has been suggested that a minimal proportion of 1,000 heterotrophic bacteria for one heterotrophic flagellate is characteristic of microbial food webs in which flagellates preferentially consume bacteria [39,41,42]. The value for this ratio was higher than 1,000 in each treatment (VFA vs. VF) and for each experiment (early spring vs. summer).…”

Section: Discussionmentioning

confidence: 99%

Effect of grazers and viruses on bacterial community structure and production in two contrasting trophic lakes

Berdjeb¹,

Pollet²,

Domaizon³

et al. 2011

BMC Microbiol

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BackgroundOver the last 30 years, extensive studies have revealed the crucial roles played by microbes in aquatic ecosystems. It has been shown that bacteria, viruses and protozoan grazers are dominant in terms of abundance and biomass. The frequent interactions between these microbiological compartments are responsible for strong trophic links from dissolved organic matter to higher trophic levels, via heterotrophic bacteria, which form the basis for the important biogeochemical roles of microbial food webs in aquatic ecosystems. To gain a better understanding of the interactions between bacteria, viruses and flagellates in lacustrine ecosystems, we investigated the effect of protistan bacterivory on bacterial abundance, production and structure [determined by 16S rRNA PCR-DGGE], and viral abundance and activity of two lakes of contrasting trophic status. Four experiments were conducted in the oligotrophic Lake Annecy and the mesotrophic Lake Bourget over two seasons (early spring vs. summer) using a fractionation approach. In situ dark vs. light incubations were performed to consider the effects of the different treatments in the presence and absence of phototrophic activity.ResultsThe presence of grazers (i.e. < 5-μm small eukaryotes) affected viral production positively in all experiments, and the stimulation of viral production (compared to the treatment with no eukaryotic predators) was more variable between lakes than between seasons, with the highest value having been recorded in the mesotrophic lake (+30%). Viral lysis and grazing activities acted additively to sustain high bacterial production in all experiments. Nevertheless, the stimulation of bacterial production was more variable between seasons than between lakes, with the highest values obtained in summer (+33.5% and +37.5% in Lakes Bourget and Annecy, respectively). The presence of both predators (nanoflagellates and viruses) did not seem to have a clear influence upon bacterial community structure according to the four experiments.ConclusionsOur results highlight the importance of a synergistic effect, i.e. the positive influence of grazers on viral activities in sustaining (directly and indirectly) bacterial production and affecting composition, in both oligotrophic and mesotrophic lakes.

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The microbial food web in the recently flooded sep reservoir: Diel fluctuations in bacterial biomass and metabolic activity in relation to phytoplankton and flagellate grazers

Cited by 22 publications

References 62 publications

Seasonal diel variations of picoplankton and nanoplankton in a subtropical western Pacific coastal ecosystem

Seasonal diel variations of picoplankton and nanoplankton in a subtropical western Pacific coastal ecosystem

Warmer night‐time temperature promotes microbial heterotrophic activity and modifies stream sediment community

Effect of grazers and viruses on bacterial community structure and production in two contrasting trophic lakes

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