Cultivation of particle-associated heterotrophic bacteria during a spring phytoplankton bloom in the North Sea

AbstractIt is generally recognized that phages are a mortality factor for their bacterial hosts. This could be particularly true in spring phytoplankton blooms, which are known to be closely followed by a highly specialized bacterial community. We hypothesized that phages modulate these dense heterotrophic bacteria successions following phytoplankton blooms. In this study, we focused on Flavobacteriia, because they are main responders during these blooms and have an important role in the degradation of polysaccharides. A cultivation-based approach was used, obtaining 44 lytic flavobacterial phages (flavophages), representing twelve new species from two viral realms. Taxonomic analysis allowed us to delineate ten new phage genera and ten new families, from which nine and four, respectively, had no previously cultivated representatives. Genomic analysis predicted various life styles and genomic replication strategies. A likely eukaryote-associated host habitat was reflected in the gene content of some of the flavophages. Detection in cellular metagenomes and by direct-plating showed that part of these phages were actively replicating in the environment during the 2018 spring bloom. Furthermore, CRISPR/Cas spacers and re-isolation during two consecutive years suggested that, at least part of the new flavophages are stable components of the microbial community in the North Sea. Together, our results indicate that these diverse flavophages have the potential to modulate their respective host populations.

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Spatiotemporal variations of fCO2 in the North Sea

Ocean Science ◽

10.5194/os-6-77-2010 ◽

2010 ◽

Vol 6 (1) ◽

pp. 77-89 ◽

Cited By ~ 36

Author(s):

A. M. Omar ◽

A. Olsen ◽

T. Johannessen ◽

M. Hoppema ◽

H. Thomas ◽

...

Keyword(s):

North Sea ◽

Surface Waters ◽

Phytoplankton Bloom ◽

Co2 Exchange ◽

Atmospheric Co2 ◽

Total Alkalinity ◽

Spatiotemporal Variations ◽

The North ◽

The North Sea ◽

Central North Sea

Abstract. Data from two Voluntary Observing Ship (VOS) (2005–2007) augmented with data subsets from ten cruises (1987–2005) were used to investigate the spatiotemporal variations of the CO2 fugacity in seawater (fCO2sw) in the North Sea at seasonal and inter-annual time scales. The observed seasonal fCO2sw variations were related to variations in sea surface temperature (SST), biology plus mixing, and air-sea CO2 exchange. Over the study period, the seasonal amplitude in fCO2sw induced by SST changes was 0.4–0.75 times those resulting from variations in biology plus mixing. Along a meridional transect, fCO2sw normally decreased northwards (−12 μatm per degree latitude), but the gradient disappeared/reversed during spring as a consequence of an enhanced seasonal amplitude of fCO2sw in southern parts of the North Sea. Along a zonal transect, a weak gradient (−0.8 μatm per degree longitude) was observed in the annual mean fCO2sw. Annually and averaged over the study area, surface waters of the North Sea were CO2 undersaturated and, thus, a sink of atmospheric CO2. However, during summer, surface waters in the region 55.5–54.5° N were CO2 supersaturated and, hence, a source for atmospheric CO2. Comparison of fCO2sw data acquired within two 1°×1° regions in the northern and southern North Sea during different years (1987, 2001, 2002, and 2005–2007) revealed large interannual variations, especially during spring and summer when year-to-year fCO2sw differences (≈160–200 μatm) approached seasonal changes (≈200–250 μatm). The springtime variations resulted from changes in magnitude and timing of the phytoplankton bloom, whereas changes in SST, wind speed and total alkalinity may have contributed to the summertime interannual fCO2sw differences. The lowest interannual variation (10–50 μatm) was observed during fall and early winter. Comparison with data reported in October 1967 suggests that the fCO2sw growth rate in the central North Sea was similar to that in the atmosphere.

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Biomass and nitrogen uptake by heterotrophic bacteria during the spring phytoplankton bloom in the North Atlantic Ocean

Deep Sea Research Part I Oceanographic Research Papers ◽

10.1016/0967-0637(94)90081-7 ◽

1994 ◽

Vol 41 (5-6) ◽

pp. 879-895 ◽

Cited By ~ 52

Author(s):

David L. Kirchman ◽

Hugh W. Ducklow ◽

James J. McCarthy ◽

Christopher Garside

Keyword(s):

Atlantic Ocean ◽

North Atlantic ◽

Nitrogen Uptake ◽

Heterotrophic Bacteria ◽

Phytoplankton Bloom ◽

North Atlantic Ocean ◽

Spring Phytoplankton Bloom ◽

The North ◽

The North Atlantic

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Spatiotemporal variations of fCO2 in the North Sea

Ocean Science Discussions ◽

10.5194/osd-6-1655-2009 ◽

2009 ◽

Vol 6 (2) ◽

pp. 1655-1686

Author(s):

A. M. Omar ◽

A. Olsen ◽

T. Johannessen ◽

M. Hoppema ◽

H. Thomas ◽

...

Keyword(s):

North Sea ◽

Surface Waters ◽

Phytoplankton Bloom ◽

Temporal Variations ◽

Co2 Exchange ◽

Atmospheric Co2 ◽

Total Alkalinity ◽

The North ◽

The North Sea ◽

Spatio Temporal

Abstract. Data from two Voluntary Observing Ship (VOS) (MS Trans Carrier and MV Nuka Arctica), acquired along one zonal and one meridional transect (2005–2007) augmented with data subsets from ten cruises (1987–2005) were used to investigate the spatio-temporal variations of the CO2 fugacity in seawater (fCO2sw) in the North Sea at seasonal and inter-annual time scales. The observed seasonal fCO2sw variations were related to variations in sea surface temperature (SST), biology plus mixing, and air-sea CO2 exchange. Over the study period, the seasonal amplitude in fCO2sw induced by SST changes was 0.4–0.75 times those resulting from variations in biology plus mixing. Along the meridional transect, fCO2sw normally decreased northwards (−12 μatm per degree latitude), but the gradient disappeared/reversed during spring as a consequence of an enhanced seasonal amplitude of fCO2sw in southern parts of the North Sea. Along the zonal transect, a weak gradient (−0.8 μatm per degree longitude) was observed in the mean annual fCO2sw. Annually and averaged over the study area, surface waters of the North Sea were CO2 undersaturated and thus a sink of atmospheric CO2 throughout the year. However, during summer, surface waters in the region 55.5–54.5° N were CO2 supersaturated and, hence, a source for atmospheric CO2. Comparison of fCO2sw data acquired within two 1°×1° regions in the northern and southern North Sea during different years (1987, 2001, 2002, and 2005–2007) revealed large interannual variations, especially during spring and summer when year-to-year fCO2sw differences (≈160–200 μatm) approached seasonal changes (≈200–250 μatm). The springtime variations resulted from changes in magnitude and timing of the phytoplankton bloom, whereas changes in SST, wind speed, and total alkalinity may have contributed to the summertime interannual fCO2sw differences. The lowest interannual variation (10–50 μatm) was observed during fall and early winter. The comparison with data reported in October 1967 suggests that the fCO2sw growth rate in the central North Sea is similar to that in the atmosphere.

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