A study of changes between years in the structure of plankton community in a newly-flooded reservoir

Thouvenot, Antoine; Debroas, Didier; Richardot, Mathilde; Jugnia, Louis B.; Dévaux, Jean

doi:10.1127/archiv-hydrobiol/149/2000/131

Cited by 28 publications

(32 citation statements)

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“…Indeed, according to those authors who have also used the CTC method during their investigation, the proportion of active cells may increase from values typical of ultra-oligotrophic openocean areas (< 5%) to highly productive estuaries (> 50%). The study of the temporal changes in the Sep Reservoir showed, firstly, a lowering in the DOM concentration with time and, secondly, a decrease in the proportion of heterotrophic organisms, such as bacteria, and mixotrophic organisms, which were progressively replaced by strictly autotrophic organisms (Thouvenot et al 2000). The low number of CTC-active bacteria determined at this site during our study could in part be related to changes in this ecosystem.…”

Section: Methodological Aspects and Quantitative Importance Of Ctc-pomentioning

confidence: 80%

“…With an area of 33 ha and a mean depth of 14 m, this reservoir has a catchment of 27 km 2 whose vegetation consists of oak and beech forests and grasslands. The reservoir, which is oligomesotrophic in status, was completely filled for the first time in January 1995 and its mean residence time is 220 d. Temporal changes since flooding have shown evidence for a decrease in the proportion of heterotrophic and mixotrophic organisms in the planktonic biomass, these being progressively replaced by strictly autotrophs (Thouvenot et al 2000).Sampling was carried out at a permanent station situated at the deepest zone of the reservoir near the dam. Water samples from 1 m below the surface were collected every 2 wk in April and weekly from May to August 1997 with a Van Dorn water sampler.…”

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confidence: 99%

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Variations in the number of active bacteria in the euphotic zone of a recently flooded reservoir

Jugnia¹,

Richardot²,

Debroas³

et al. 2000

Aquat. Microb. Ecol.

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Using the CTC (5-cyano-2, 3-ditolyl tetrazolium chloride) method, we estimated the active fraction of bacterioplankton in the euphotic zone of the recently flooded Sep Reservoir, France, with the aim of evaluating its importance and dynamics in relation to temperature and some components of dissolved organic matter (DOM) (i.e. dissolved combined amino acids: DCAA; dissolved free monosaccharides: DFCHO; dissolved combined monosaccharides: DCCHO), and its metabolic significance in conjunction with a bacterial growth indicator:14 C-glucose uptake. From our results, it appears that only a small fraction (0.04 to 3.23%) of total bacterial count in this reservoir was metabolically active. Recorded correlations and multivariate regression analysis suggest that temporal variations in the number of active bacteria are mainly (80%) governed by temperature, together with the high concentrations of those components of DOM, which were present in this ecosystem but which apparently were not always available for bacterial metabolism. We also found a positive relation between the number of active bacteria and the potential heterotrophic activity, which suggest that CTC-positive bacteria are responsible for the bulk of bacterial community metabolism in this recently formed reservoir.KEY WORDS: Active bacteria · CTC · Dissolved organic matter · Temperature · Bacterial activity · New reservoir Resale or republication not permitted without written consent of the publisherAquat Microb Ecol 22: [251][252][253][254][255][256][257][258][259] 2000 fraction of bacterioplankton (e.g. Thom et al. 1993), whereas others have suggested temperature (Tabor & Neihof 1984, Robarts & Sephton 1988, Sommaruga & Conde 1997, lysis (Proctor & Fuhrman 1990), grazing (Gasol et al. 1995) and resource availability (del Giorgio & Scarborough 1995, Choi et al. 1999. In terms of resource availability, a wide variety of sources including phytoplankton excretion and lysis (Cole et al. 1988, Maurin et al. 1997) and grazing and release by zooplankton (e.g. Hygum et al. 1997) have been identified as producing dissolved organic matter (DOM) that fuels bacterioplankton metabolism. Inputs of allochthonous DOM and physical disaggregation of detrital particles (Hadas et al. 1990) are also likely to be significant energy sources for bacterial activities. However, nearly all these studies have been conducted in natural or stabilized artificial lake ecosystems. To our knowledge, no information is available on fluctuations in the number of active bacteria in recently flooded reservoirs that are expected to contain large quantities of terrestrial detritus and organic matter, which is known to efficiently regulate bacterial activity (Paterson et al. 1997).The aim of this study was to determine the importance of the active fraction of bacterioplankton in a recently flooded reservoir, the main variables controlling their abundance (especially temperature and DOM) and their metabolic significance in conjunction with a growth indicator:14 C-glucose uptake. The numbe...

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Section: Methodological Aspects and Quantitative Importance Of Ctc-pomentioning

confidence: 80%

mentioning

confidence: 99%

Variations in the number of active bacteria in the euphotic zone of a recently flooded reservoir

Jugnia¹,

Richardot²,

Debroas³

et al. 2000

Aquat. Microb. Ecol.

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“…In this study, the water was prefiltered through 5-m-pore-size filters according to the methods of Díez et al (20) and Lòpez-Garcia et al (34) in order to take into account most of the small eukaryotic cells observable by standard epifluorescence microscopy but usually considered unidentified Protista and which have been reported to represent a large proportion of microorganisms in lakes (12,60). To study these organisms, we chose T-RFLP (33) as a fingerprinting method.…”

Section: Discussionmentioning

confidence: 99%

“…Metazooplankton was made more visible by staining with a few drops of rose Bengal. If the density of organisms in a sample was too high, a subsample was taken with a Motoda box (60). Phytoplankton was counted monthly using Utermöhl's method (1958) with a Leitz-type inverted microscope (Wild M40).…”

Section: Methodsmentioning

confidence: 99%

Succession and Regulation Factors of Small Eukaryote Community Composition in a Lacustrine Ecosystem (Lake Pavin)

Lepère

Boucher

Jardillier

et al. 2006

Appl Environ Microbiol

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107

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The structure and dynamics of small eukaryotes (cells with a diameter less than 5 m) were studied over two consecutive years in an oligomesotrophic lake (Lake Pavin in France). Water samples were collected at 5 and 30 m below the surface; when the lake was stratified, these depths corresponded to the epilimnion and hypolimnion. Changes in small-eukaryote structure were analyzed using terminal restriction fragment length polymorphism (T-RFLP) and cloning and sequencing of the 18S rRNA genes. Terminal restriction fragments from clones were used to reveal the dominant taxa in T-RFLP profiles of the environmental samples. Spumellalike cells (Chrysophyceae) did not dominate the small eukaryote community identified by molecular techniques in lacustrine ecosystems. Small eukaryotes appeared to be dominated by heterotrophic cells, particularly Cercozoa, which represented nearly half of the identified phylotypes, followed by the Fungi-LKM11 group (25%), choanoflagellates (10.3%) and Chrysophyceae (8.9%). Bicosoecida, Cryptophyta, and ciliates represented less than 9% of the community studied. No seasonal reproducibility in temporal evolution of the small-eukaryote community was observed from 1 year to the next. The T-RFLP patterns were related to bottom-up (resources) and top-down (grazing) variables using canonical correspondence analysis. The results showed a strong top-down regulation of small eukaryotes by zooplankton, more exactly, by cladocerans at 5 m and copepods at 30 m. Among bottom-up factors, temperature had a significant effect at both depths. The concentrations of nitrogenous nutrients and total phosphorus also had an effect on small-eukaryote dynamics at 5 m, whereas bacterial abundance and dissolved oxygen played a more important structuring role in the deeper zone.Small phototrophic and heterotrophic eukaryotes (Ͻ5 m) are found throughout the world's oceans and lakes at concentrations between 10 2 and 10 4 cells ml Ϫ1 in the photic zone (11). Small eukaryotes are known to be essential components in marine trophic food webs (20). The small-eukaryote assemblage is formed by picoalgae, which participate in primary production (55), by colorless heterotrophic cells, mostly flagellates, which are considered to be important grazers of prokaryotic and eukaryotic cells (11) and also play a significant role in the mineralization of organic matter, and finally by some small eukaryotes which can be mixotrophs. Despite the ecological importance of small eukaryotes and the general lack of distinct morphological features of these small cells, they have only recently been studied from a molecular perspective (20, 37). Thanks to these techniques, recent studies, conducted in various environments, have revealed a surprisingly high diversity of small eukaryotes and the existence of novel lineages (39). For example, the genetic diversity of small eukaryotes from coastal waters showed the dominance of novel alveolates (from 36% to 62% of total sequences obtained in their libraries) and the importance of novel stramenopiles, ...

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“…If the density of animals in a sample was too high, a subsample was taken with a Motoda box. Rotifers were counted in a Sedgewick-Rafter cell, after subsampling (Thouvenot et al 2000).…”

Section: Methodsmentioning

confidence: 99%

Bottom-up and top-down control of bacterial community composition in the euphotic zone of a reservoir

Jardillier¹,

Basset²,

Domaizon³

et al. 2004

Aquat. Microb. Ecol.

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Temporal changes in the bacterial community composition (BCC) and the impact of resources and predation on this community composition have been studied in the euphotic zone of the Sep reservoir (France), using terminal-restriction fragment length polymorphism (T-RFLP) and fluorescent in situ hybridization (FISH) for Eubacteria (EUB338) and eubacterial subgroups. Net growth and grazing rates of the various subgroups were computed from experiments conducted in dialysis bags in the presence or absence of predators. There was a significant difference between the grazing rates of different bacterial groups and subclasses, the alpha-proteobacteria (ALF1b) were subjected to the highest grazing rate (max. 1.76 d -1 ). In contrast, the beta-proteobacteria (BET42a) seemed to be little consumed by bacterivorous organisms, and predation led to large variations in the grazing rates of Cytophaga-Flavobacterium (CF319a). The different composition of bacterial consumers (Dinobryon sp. and Cladocera) during the study could explain the observed differences in grazing impact. The mean net growth rates of total bacteria, EUB338, BET42a ALF1b, and CF319a in dialysis bags without predators were 0.21, 0.69, 0.45, 0.50 and 0.84 d -1 , respectively. Various statistical analyses indicated that the BCC could depend on the organic matter excreted by the phytoplankton. There were also positive correlations not only between net growth and/or net production of ALF1b and CF319a with the primary production and biomass of the main phytoplankton groups, but also between phytoplankton biomass, primary production (PP) and some operational taxonomic units (OTUs). Among the physical variables, input and output of water in the reservoir seem to play a role in determining the BCC in this ecosystem. The results suggest that the BCC depends on the combined impact of dominant substrate sources and selective predation by bacterial consumers.

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A study of changes between years in the structure of plankton community in a newly-flooded reservoir

Cited by 28 publications

References 0 publications

Variations in the number of active bacteria in the euphotic zone of a recently flooded reservoir

Variations in the number of active bacteria in the euphotic zone of a recently flooded reservoir

Succession and Regulation Factors of Small Eukaryote Community Composition in a Lacustrine Ecosystem (Lake Pavin)

Bottom-up and top-down control of bacterial community composition in the euphotic zone of a reservoir

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