scholarly journals Microbial food web dynamics during spring phytoplankton blooms in the naturally iron-fertilized Kerguelen area (Southern Ocean)

2014 ◽  
Vol 11 (5) ◽  
pp. 6985-7028 ◽  
Author(s):  
U. Christaki ◽  
D. Lefèvre ◽  
C. Georges ◽  
J. Colombet ◽  
P. Catala ◽  
...  
Keyword(s):  
Southern Ocean ◽  
Food Web ◽  
Bacterial Production ◽  
Microbial Food Web ◽  
Heterotrophic Nanoflagellates ◽  
Bacterial Respiration ◽  
Viral Production ◽  
Phytoplankton Blooms ◽  
Food Web Dynamics ◽  
Heterotrophic Production

Abstract. Microbial food web dynamics were determined during the onset of several spring phytoplankton blooms induced by natural iron fertilization off Kerguelen Island in the Southern Ocean (KEOPS2). The abundances of heterotrophic bacteria and heterotrophic nanoflagellates, bacterial heterotrophic production, bacterial respiration, and bacterial growth efficiency, were consistently higher in surface waters of the iron-fertilized sites than at the reference site in HNLC (high nutrient low chlorophyll) waters. The abundance of viral like particles remained unchanged, but viral production increased by a factor of 6 in iron-fertilized waters. Bacterial heterotrophic production was significantly related to heterotrophic nanoflagellate abundance and viral production across all sites, with bacterial production explaining about 70 and 85%, respectively, of the variance of each in the mixed layer (ML). Estimated rates of grazing and viral lysis, however, indicated that heterotrophic nanoflagellates accounted for a substantially higher loss of bacterial production (50%) than viruses (11%). Combining these results with rates of primary production and export determined for the study area, a budget for the flow of carbon through the microbial food web and higher levels during the early (KEOPS2) and the late phase (KEOPS1) of the Kerguelen bloom is provided.

scholarly journals Microbial food web dynamics during spring phytoplankton blooms in the naturally iron-fertilized Kerguelen area (Southern Ocean)

2014 ◽  
Vol 11 (23) ◽  
pp. 6739-6753 ◽  
Author(s):  
U. Christaki ◽  
D. Lefèvre ◽  
C. Georges ◽  
J. Colombet ◽  
P. Catala ◽  
...  
Keyword(s):  
Southern Ocean ◽  
Food Web ◽  
Bacterial Production ◽  
Trophic Levels ◽  
Microbial Food Web ◽  
Heterotrophic Nanoflagellates ◽  
Viral Production ◽  
Phytoplankton Blooms ◽  
Food Web Dynamics ◽  
Heterotrophic Production

Abstract. Microbial food web dynamics were determined during the onset of several spring phytoplankton blooms induced by natural iron fertilization off Kerguelen Island in the Southern Ocean (KEOPS2). The abundances of heterotrophic bacteria and heterotrophic nanoflagellates, bacterial heterotrophic production, bacterial respiration, and bacterial growth efficiency, were consistently higher in surface waters of the iron-fertilized sites than at the reference site in HNLC (high nutrient low chlorophyll) waters. The abundance of virus-like particles remained unchanged, but viral production increased by a factor of 6 in iron-fertilized waters. Bacterial heterotrophic production was significantly related to heterotrophic nanoflagellate abundance and viral production across all sites, with bacterial production explaining about 70 and 85%, respectively, of the variance of each in the mixed layer (ML). Estimated rates of grazing and viral lysis, however, indicated that heterotrophic nanoflagellates accounted for a substantially higher loss of bacterial production (50%) than viruses (11%). Combining these results with rates of primary production and export determined for the study area, a budget for the flow of carbon through the microbial food web and higher trophic levels during the early (KEOPS2) and the late phase (KEOPS1) of the Kerguelen bloom is provided.

scholarly journals Microbial food web dynamics in response to a Saharan dust event: results from a mesocosm study in the oligotrophic Mediterranean Sea

2014 ◽  
Vol 11 (19) ◽  
pp. 5607-5619 ◽  
Author(s):  
E. Pulido-Villena ◽  
A.-C. Baudoux ◽  
I. Obernosterer ◽  
M. Landa ◽  
J. Caparros ◽  
...  
Keyword(s):  
Food Web ◽  
Mediterranean Sea ◽  
Bacterial Abundance ◽  
Bacterial Community Composition ◽  
Saharan Dust ◽  
Microbial Food Web ◽  
Heterotrophic Nanoflagellates ◽  
Bacterial Respiration ◽  
Dust Deposition ◽  
The Impact

Abstract. The significant impact of dust deposition on heterotrophic bacterial dynamics in the surface oligotrophic ocean has recently been evidenced. Considering the central role of bacteria in the microbial loop, it is likely that dust deposition also affects the structure and the functioning of the whole microbial food web. In the frame of the DUNE project, aiming to estimate the impact of dust deposition on the oligotrophic Mediterranean Sea through mesocosm experiments, the main goal of the present paper was to assess how two successive dust deposition events affect the dynamics of the microbial food web. The first dust seeding delivered new P and N to the amended mesocosms and resulted in a pronounced stimulation of bacterial respiration. It also induced pronounced, but transient, changes in the bacterial community composition. No significant effects were observed on the abundances of viruses and heterotrophic nanoflagellates. The second dust seeding also delivered new P and N to the amended mesocosms, but the effect on the microbial food web was very different. Bacterial respiration remained constant and bacterial abundance decreased. Compositional changes following the second seeding were minor compared to the first one. The decrease in bacterial abundance coincided with an increase in virus abundance, resulting in higher virus:bacteria ratios throughout the second seeding period. Our study shows that dust deposition to the surface oligotrophic ocean may involve important modifications of the trophic links among the components of the microbial food web with presumed consequences on C and nutrient cycling.

scholarly journals Seasonal microbial food web dynamics in contrasting Southern Ocean productivity regimes

2020 ◽  
Author(s):  
Urania Christaki ◽  
Audrey Gueneugues ◽  
Yan Liu ◽  
Stéphane Blain ◽  
Philippe Catala ◽  
...  
Keyword(s):  
Southern Ocean ◽  
Food Web ◽  
Microbial Food Web ◽  
Food Web Dynamics ◽  
Ocean Productivity

scholarly journals Microbial food web dynamics in response to a Saharan dust event: results from a mesocosm study in the oligotrophic Mediterranean Sea

2014 ◽  
Vol 11 (1) ◽  
pp. 337-371 ◽  
Author(s):  
E. Pulido-Villena ◽  
A.-C. Baudoux ◽  
I. Obernosterer ◽  
M. Landa ◽  
J. Caparros ◽  
...  
Keyword(s):  
Food Web ◽  
Mediterranean Sea ◽  
Bacterial Abundance ◽  
Bacterial Community Composition ◽  
Saharan Dust ◽  
Microbial Food Web ◽  
Heterotrophic Nanoflagellates ◽  
Bacterial Respiration ◽  
Dust Deposition ◽  
The Impact

Abstract. The significant impact of dust deposition on heterotrophic bacterial dynamics in the surface oligotrophic ocean has recently been evidenced. Considering the central role of bacteria in the microbial loop, it is likely that dust deposition also affects the structure and the functioning of the whole microbial food web. In the frame of the DUNE project, aiming to estimate the impact of dust deposition on the oligotrophic Mediterranean Sea through mesocosm experiments, the main goal of the present paper was to assess how two successive dust deposition events affect the dynamics of the microbial food web. The first dust seeding delivered new P and N to the amended mesocosms and resulted in a pronounced stimulation of bacterial respiration. It also induced pronounced, but transient, changes in the bacterial community composition. No significant effects were observed on the abundances of viruses and heterotrophic nanoflagellates. The second dust seeding also delivered new P and N to the amended mesocosms but the effect on the microbial food web was very different. Bacterial respiration remained constant and bacterial abundance decreased. Compositional changes following the second seeding were minor compared to the first one. The decrease in bacterial abundance coincided with an increase in virus abundance, resulting in higher virus: bacteria ratios throughout the second seeding period. Our study shows that dust deposition to the surface oligotrophic ocean may involve important modifications of the trophic links among the components of the microbial food web with presumed consequences on C and nutrient cycling.

scholarly journals Short-term variability in microbial food web dynamics in a shallow tidal estuary

2003 ◽  
Vol 31 ◽  
pp. 145-161 ◽  
Author(s):  
A Iriarte ◽  
I Madariaga ◽  
M Revilla ◽  
A Sarobe
Keyword(s):  
Food Web ◽  
Microbial Food Web ◽  
Short Term ◽  
Tidal Estuary ◽  
Food Web Dynamics ◽  
Short Term Variability

Microbial food web structure in a naturally iron-fertilized area in the Southern Ocean (Kerguelen Plateau)

2008 ◽  
Vol 55 (5-7) ◽  
pp. 706-719 ◽  
Author(s):  
U. Christaki ◽  
I. Obernosterer ◽  
F. Van Wambeke ◽  
M. Veldhuis ◽  
N. Garcia ◽  
...  
Keyword(s):  
Southern Ocean ◽  
Food Web ◽  
Microbial Food Web ◽  
Kerguelen Plateau ◽  
Food Web Structure ◽  
Web Structure

scholarly journals Temporal variability of the microbial food web (viruses to ciliates) under the influence of the Black Sea Water inflow (N. Aegean, E. Mediterranean)

2014 ◽  
Vol 15 (4) ◽  
pp. 769 ◽  
Author(s):  
A. GIANNAKOUROU ◽  
A. TSIOLA ◽  
M. KANELLOPOULOU ◽  
I. MAGIOPOULOS ◽  
I. SIOKOU ◽  
...  
Keyword(s):  
Food Web ◽  
Black Sea ◽  
Bacterial Production ◽  
Heterotrophic Bacteria ◽  
Sea Water ◽  
Phytoplankton Bloom ◽  
Aegean Sea ◽  
Trophic Levels ◽  
Microbial Food Web ◽  
The Black Sea

Τhe entire pelagic microbial food web was studied during the winter-spring period in the frontal area of the North Aegean Sea. Abundance of viruses, heterotrophic bacteria, cyanobacteria, auto- and hetero-trophic flagellates, and ciliates, as well as bacterial production, were measured at three stations (MD1, MD2, MD3) situated along a N-S transect between the area directly influenced by the inflowing Black Sea water and the area covered by the Levantine water. Samples were collected in December 2009, and January, March, April, and May 2011. Station MD1 exhibited the highest values of abundance and integrated biomass of all microbial groups and bacterial production during all months, and MD3 the lowest. Bacteria dominated the total integrated biomass at all stations and months, followed by cyanobacteria, auto-, hetero-trophic flagellates and ciliates. On a temporal scale, the microbial food web was less important in March as all microbial parameters at all stations showed the lowest values. After the phytoplankton bloom in March, the heterotrophic part of the microbial food web (mainly) strongly increased, though the intensity of the phenomenon was diminished from North to South. Pico-sized plankton was found to be heterotrophic whereas nanoplankton was autotrophic. It seems that the influence of the Black Sea water on station MD1, permanent throughout the study period of early winter to late spring, was reflected in all microbial populations studied, and produced a more productive pelagic food web system, with potential consequences for the upper trophic levels.

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