Variations spatio-temporelles de l'abondance et de la production du bactérioplancton dans un lac humique du Bouclier canadien

1991 ◽  
Vol 37 (1) ◽  
pp. 64-73 ◽  
Author(s):  
Yvon Letarte ◽  
Bernadette Pinel-Alloul
Keyword(s):  
Bacterial Production ◽  
Thymidine Incorporation ◽  
Small Scale ◽  
Bacterial Cells ◽  
Spatiotemporal Variations ◽  
Bacterioplankton Production ◽  
Renewal Time ◽  
Dividing Cells ◽  
Bouclier Canadien ◽  
Bacterioplankton Abundance

We followed the diel and summer variations of bacterioplankton production (estimated from [3H] thymidine incorporation) and abundance (direct count with 4′,6-diamidino-2-phenylindole staining) at four depths in a Canadian Shield humic lake. We found production to be highest and most variable in the epilimnion, but the differences between production estimates made at different times were statistically significant in only 5 out of 16 cases. Production differed significantly among depths in 14 out of 18 trials. The renewal time of the bacterial community varied between 1 and 20 days. Bacterioplankton production and primary production were uncorrelated (r = 0.225; p > 0.2), but bacterial production and chlorophyll a concentration were positively correlated (r = 0.816; p < 0.005). Small coccis (~0.3 – ~0.8 μm) represented between 52 and 80% of the bacterial cells in all the samples. There was no correspondence between bacterial production and frequency of dividing cells. Bacterial production and abundance varied inversely throughout the season, bacteria being two to three times less concentrated in the spring, whereas production was two to three times higher. We found no correlation between bacterioplankton production and abundance (r = 0.012; p > 0.5). Our results demonstrate the importance of small-scale sampling and the difficulty with which bacterioplankton production, its spatiotemporal variations, and the relationships between bacteria and phytoplankton can be predicted. Key words: bacterioplankton, abundance, production, spatiotemporal variations, bacterioplankton–phytoplankton relationships.

scholarly journals Significance of Viral Lysis and Flagellate Grazing as Factors Controlling Bacterioplankton Production in a Eutrophic Lake

1998 ◽  
Vol 64 (2) ◽  
pp. 431-438 ◽  
Author(s):  
Markus G. Weinbauer ◽  
Manfred G. Höfle
Keyword(s):  
Organic Matter ◽  
Bacterial Production ◽  
Eutrophic Lake ◽  
Bacterial Cells ◽  
Viral Lysis ◽  
Thin Sections ◽  
Bacterial Mortality ◽  
Bacterioplankton Production ◽  
Transmission Electron ◽  
Heterotrophic Nanoflagellate

ABSTRACT The effects of viral lysis and heterotrophic nanoflagellate (HNF) grazing on bacterial mortality were estimated in a eutrophic lake (Lake Plußsee in northern Germany) which was separated by a steep temperature and oxygen gradient into a warm and oxic epilimnion and a cold and anoxic hypolimnion. Two transmission electron microscopy-based methods (whole-cell examination and thin sections) were used to determine the frequency of visibly infected cells, and a model was used to estimate bacterial mortality due to viral lysis. Examination of thin sections also showed that between 20.2 and 29.2% (average, 26.1%) of the bacterial cells were empty (ghosts) and thus could not contribute to viral production. The most important finding was that the mechanism for regulating bacterial production shifted with depth from grazing control in the epilimnion to control due to viral lysis in the hypolimnion. We estimated that in the epilimnion viral lysis accounted on average for 8.4 to 41.8% of the summed mortality (calculated by determining the sum of the mortalities due to lysis and grazing), compared to 51.3 to 91.0% of the summed mortality in the metalimninon and 88.5 to 94.2% of the summed mortality in the hypolimnion. Estimates of summed mortality values indicated that bacterial production was controlled completely or almost completely in the epilimnion (summed mortality, 66.6 to 128.5%) and the hypolimnion (summed mortality, 43.4 to 103.3%), whereas in the metalimnion viral lysis and HNF grazing were not sufficient to control bacterial production (summed mortality, 22.4 to 56.7%). The estimated contribution of organic matter released by viral lysis of cells into the pool of dissolved organic matter (DOM) was low; however, since cell lysis products are very likely labile compared to the bulk DOM, they might stimulate bacterial production. The high mortality of bacterioplankton due to viral lysis in anoxic water indicates that a significant portion of bacterial production in the metalimnion and hypolimnion is cycled in the bacterium-virus-DOM loop. This finding has major implications for the fate and cycling of organic nutrients in lakes.

The Effects of Small-Scale Turbulence on Air–Sea Heat Flux

2011 ◽  
Vol 41 (1) ◽  
pp. 205-220 ◽  
Author(s):  
Fabrice Veron ◽  
W. Kendall Melville ◽  
Luc Lenain
Keyword(s):  
Field Experiments ◽  
Renewal Theory ◽  
Small Scale ◽  
Surface Renewal ◽  
Near Surface ◽  
Turbulence Measurements ◽  
Renewal Time ◽  
Surface Turbulence ◽  
The Mean ◽  
Renewal Events

Abstract The air–sea exchange of heat is mainly controlled by the molecular diffusive layer adjacent to the surface. With an order of magnitude difference between the kinematic viscosity and thermal diffusivity of water, the thermal sublayer is embedded within its momentum analog: the viscous sublayer. Therefore, the surface heat exchange rates are greatly influenced by the surface kinematics and dynamics; in particular, small-scale phenomena, such as near-surface turbulence, have the greatest potential to affect the surface fluxes. Surface renewal theory was developed to parameterize the details of the turbulent transfer through the molecular sublayers. The theory assumes that turbulent eddies continuously replace surface water parcels with bulk fluid, which is not in equilibrium with the atmosphere and therefore is able to transfer heat. The so-called controlled-flux technique gives direct measurements of the mean surface lifetime of such surface renewal events. In this paper, the authors present results from field experiments, along with a review of surface renewal theory, and show that previous estimates of air–sea scalar fluxes using the controlled-flux technique may be erroneous if the probability density function (PDF) of surface renewal time scales is different from the routinely assumed exponential distribution. The authors show good agreement between measured and estimated heat fluxes using a surface renewal PDF that follows a χ distribution. Finally, over the range of forcing conditions in these field experiments, a clear relationship between direct surface turbulence measurements and the mean surface renewal time scale is established. The relationship is not dependent on the turbulence generation mechanism. The authors suggest that direct surface turbulence measurements may lead to improved estimates of scalar air–sea fluxes.

Bacterial production measured by leucine and thymidine incorporation rates in French lakes

1999 ◽  
Vol 42 (3) ◽  
pp. 513-524 ◽  
Author(s):  
Muriel Petit ◽  
Pierre Servais ◽  
Pierre Lavandier
Keyword(s):  
Bacterial Production ◽  
Thymidine Incorporation

scholarly journals Relationships between cytometric characteristics of high and low nucleic-acid bacterioplankton cells, bacterial production and environmental parameters along a longitudinal gradient across the Mediterranean Sea

2010 ◽  
Vol 7 (6) ◽  
pp. 8245-8279 ◽  
Author(s):  
F. Van Wambeke ◽  
P. Catala ◽  
P. Lebaron
Keyword(s):  
Nucleic Acid ◽  
Mediterranean Sea ◽  
Bacterial Production ◽  
Environmental Parameters ◽  
Early Summer ◽  
Bacterial Cells ◽  
Green Fluorescence ◽  
Flow Cytometric ◽  
Chlorophyll Distribution ◽  
The Mediterranean

Abstract. Heterotrophic bacterioplankton abundance and production were determined along vertical (down to bathypelagic layers) and latitudinal (from 4.9° E to 32.7° E) gradients across the Mediterranean Sea in early summer 2008. Abundance and flow cytometric characteristics (green fluorescence and side scatter signals) of high nucleic acid (HNA) and low nucleic acid (LNA) bacterial cells were investigated using flow cytometry. Contrarily to what is generally observed, the percentage of total bacteria represented by HNA cells (%HNA, range 30–69%) decreased with increased bacterial production (range 0.15–44 ng C l−1 h−1) although this negative relation was poorly explained (log-log regression r2=0.19). The %HNA as well as the mean side scatter of this group increased significantly with depth in the meso and bathypelagic layers. Our results demonstrated that vertical stratification with regard to chlorophyll distribution above, within or below the deep chlorophyll maximum plays an important role in influencing the distribution of cells, and in the relationships between the flow cytometric parameters and environmental variables such as chlorophyll a or bacterial production. Relationships between green fluorescence and side scatter of both HNA and LNA cells depended largely on chlorophyll distribution over the water column, suggesting that the dynamic link between HNA and LNA cells differs vertically.

scholarly journals Interaction among bacterioplankton and macrophytes in shallow lakes with high macrophyte cover

2020 ◽  
Vol 82 (4) ◽  
Author(s):  
Nóra Szabó-Tugyi ◽  
Viktor R. Tóth
Keyword(s):  
Shallow Lakes ◽  
Bacterial Production ◽  
Heterotrophic Bacteria ◽  
Seasonal Pattern ◽  
Biomass Accumulation ◽  
Emergent Macrophytes ◽  
Macrophyte Growth ◽  
Macrophyte Biomass ◽  
The Relationship ◽  
Bacterioplankton Abundance

Abstract Growth of submerged and emergent macrophytes was studied together with heterotrophic bacterioplankton abundance and production in two Hungarian shallow lakes with dominant macrophyte covers. It was expected that bacterioplankton numbers and activity would have an effect on macrophyte biomass accumulation. Bacterial production and abundance showed a strong seasonal pattern with maximum in the warmest months (July, August). It was found that macrophyte biomass increased with heterotrophic bacterial production and abundance up to 5.6 µg C l− 1 h− 1 and 5.30*106 cells, respectively, while over that value was negatively associated with macrophyte growth. It was also shown that the relationship between heterotrophic bacteria and macrophytes also varied seasonally, showing a multifaceted relationship. It was demonstrated that macrophytes are not only the most significant carbon and energy source for the bacteria in shallow, macrophyte-dominated lakes, but are also competing organisms that could be supressed by excessive bacterial activity. These findings could help better understand the interaction between macrophytes and bacterioplankton, and assist wetland managers in quantifying what may be a primary cause of reed die-back.

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