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  • 1
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    Arctic microbial community dynamics influenced by elevated CO2 levels (2013)
    Copernicus Publications (EGU)
    In:  Biogeosciences (BG), 10 (2). pp. 719-731.
    Details
    Publication Date: 2019-09-23
    Description: The Arctic Ocean ecosystem is particularly vulnerable to ocean acidification (OA) related alterations due to the relatively high CO2 solubility and low carbonate saturation states of its cold surface waters. Thus far, however, there is only little known about the consequences of OA on the base of the food web. In a mesocosm CO2-enrichment experiment (overall CO2 levels ranged from ~ 180 to 1100 μatm) in Kongsfjorden off Svalbard, we studied the consequences of OA on a natural pelagic microbial community. OA distinctly affected the composition and growth of the Arctic phytoplankton community, i.e. the picoeukaryotic photoautotrophs and to a lesser extent the nanophytoplankton thrived. A shift towards the smallest phytoplankton as a result of OA will have direct consequences for the structure and functioning of the pelagic food web and thus for the biogeochemical cycles. Besides being grazed, the dominant pico- and nanophytoplankton groups were found prone to viral lysis, thereby shunting the carbon accumulation in living organisms into the dissolved pools of organic carbon and subsequently affecting the efficiency of the biological pump in these Arctic waters.
    Type: Article , PeerReviewed , info:eu-repo/semantics/article
    Format: text
    DOI: 10.5194/bg-10-719-2013
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 2
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    Response of halocarbons to ocean acidification in the Arctic (2013)
    Copernicus Publications (EGU)
    In:  Biogeosciences (BG), 10 (4). pp. 2331-2345.
    Details
    Publication Date: 2016-07-26
    Description: The potential effect of ocean acidification (OA) on seawater halocarbons in the Arctic was investigated during a~mesocosm experiment in Spitsbergen in June–July 2010. Over a period of 5 weeks, natural phytoplankton communities in nine ~50 m3 mesocosms were studied under a range of pCO2 treatments from ~185 μatm to ~1420 μatm. In general, the response of halocarbons to pCO2 was subtle, or undetectable. A large number of significant correlations with a range of biological parameters (chlorophyll a, microbial plankton community, phytoplankton pigments) were identified, indicating a biological control on the concentrations of halocarbons within the mesocosms. The temporal dynamics of iodomethane (CH3I) alluded to active turnover of this halocarbon in the mesocosms and strong significant correlations with biological parameters suggested a biological source. However, despite a pCO2 effect on various components of the plankton community, and a strong association between CH3I and biological parameters, no effect of pCO2 was seen in CH3I. Diiodomethane (CH2I2) displayed a number of strong relationships with biological parameters. Furthermore, the concentrations, the rate of net production and the sea-to-air flux of CH2I2 showed a significant positive response to pCO2. There was no clear effect of pCO2 on bromocarbon concentrations or dynamics. However, periods of significant net loss of bromoform (CHBr3) were found to be concentration-dependent, and closely correlated with total bacteria, suggesting a degree of biological consumption of this halocarbon in Arctic waters. Although the effects of OA on halocarbon concentrations were marginal, this study provides invaluable information on the production and cycling of halocarbons in a region of the world's oceans likely to experience rapid environmental change in the coming decades.
    Type: Article , PeerReviewed , info:eu-repo/semantics/article
    Format: text
    DOI: 10.5194/bg-10-2331-2013
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 3
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    Temporal biomass dynamics of an Arctic plankton bloom in response to increasing levels of atmospheric carbon dioxide (2013)
    Copernicus Publications (EGU)
    In:  Biogeosciences (BG), 10 . pp. 161-180.
    Details
    Publication Date: 2019-09-23
    Description: Ocean acidification and carbonation, driven by anthropogenic emissions of carbon dioxide (CO2), have been shown to affect a variety of marine organisms and are likely to change ecosystem functioning. High latitudes, especially the Arctic, will be the first to encounter profound changes in carbonate chemistry speciation at a large scale, namely the under-saturation of surface waters with respect to aragonite, a calcium carbonate polymorph produced by several organisms in this region. During a CO2 perturbation study in 2010, in the framework of the EU-funded project EPOCA, the temporal dynamics of a plankton bloom was followed in nine mesocosms, manipulated for CO2 levels ranging initially from about 185 to 1420 μatm. Dissolved inorganic nutrients were added halfway through the experiment. Autotrophic biomass, as identified by chlorophyll a standing stocks (Chl a), peaked three times in all mesocosms. However, while absolute Chl a concentrations were similar in all mesocosms during the first phase of the experiment, higher autotrophic biomass was measured at high in comparison to low CO2 during the second phase, right after dissolved inorganic nutrient addition. This trend then reversed in the third phase. There were several statistically significant CO2 effects on a variety of parameters measured in certain phases, such as nutrient utilization, standing stocks of particulate organic matter, and phytoplankton species composition. Interestingly, CO2 effects developed slowly but steadily, becoming more and more statistically significant with time. The observed CO2 related shifts in nutrient flow into different phytoplankton groups (mainly diatoms, dinoflagellates, prasinophytes and haptophytes) could have consequences for future organic matter flow to higher trophic levels and export production, with consequences for ecosystem productivity and atmospheric CO2.
    Type: Article , PeerReviewed , info:eu-repo/semantics/article
    Format: text
    DOI: 10.5194/bg-10-161-2013
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 4
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    Effect of CO2 enrichment on bacterial metabolism in an Arctic fjord (2013)
    Copernicus Publications (EGU)
    In:  Biogeosciences (BG), 10 (5). pp. 3285-3296.
    Details
    Publication Date: 2019-09-23
    Description: he anthropogenic increase of carbon dioxide (CO2) alters the seawater carbonate chemistry, with a decline of pH and an increase in the partial pressure of CO2 (pCO2). Although bacteria play a major role in carbon cycling, little is known about the impact of rising pCO2 on bacterial carbon metabolism, especially for natural bacterial communities. In this study, we investigated the effect of rising pCO2 on bacterial production (BP), bacterial respiration (BR) and bacterial carbon metabolism during a mesocosm experiment performed in Kongsfjorden (Svalbard) in 2010. Nine mesocosms with pCO2 levels ranging from ca. 180 to 1400 μatm were deployed in the fjord and monitored for 30 days. Generally BP gradually decreased in all mesocosms in an initial phase, showed a large (3.6-fold average) but temporary increase on day 10, and increased slightly after inorganic nutrient addition. Over the wide range of pCO2 investigated, the patterns in BP and growth rate of bulk and free-living communities were generally similar over time. However, BP of the bulk community significantly decreased with increasing pCO2 after nutrient addition (day 14). In addition, increasing pCO2 enhanced the leucine to thymidine (Leu : TdR) ratio at the end of experiment, suggesting that pCO2 may alter the growth balance of bacteria. Stepwise multiple regression analysis suggests that multiple factors, including pCO2, explained the changes of BP, growth rate and Leu : TdR ratio at the end of the experiment. In contrast to BP, no clear trend and effect of changes of pCO2 was observed for BR, bacterial carbon demand and bacterial growth efficiency. Overall, the results suggest that changes in pCO2 potentially influence bacterial production, growth rate and growth balance rather than the conversion of dissolved organic matter into CO2.
    Type: Article , PeerReviewed , info:eu-repo/semantics/article
    Format: text
    DOI: 10.5194/bg-10-3285-2013
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 5
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    Nutrient limitation driven dynamics of amino acids and fatty acids in coastal phytoplankton (2019)
    ASLO (Association for the Sciences of Limnology and Oceanography) | Wiley
    In:  Limnology and Oceanography, 64 (1). pp. 302-316.
    Details
    Publication Date: 2022-01-31
    Description: Coastal seas like the North Sea have been subject to major changes in nutrient inputs over the last decades, resulting in shifts of limiting nutrients for phytoplankton communities. Here, we investigated the seasonal and spatial distribution and synthesis patterns of individual amino acids and distinct fatty acid groups and show how these were affected by different nutrient limitations in natural coastal phytoplankton communities. Nitrogen limited communities exhibited substantially slower synthesis of essential amino acids compared to synthesis of nonessential amino acids. In short‐term nutrient addition experiments, this trend was reversed immediately after N addition to levels found under not limiting conditions. On the contrary, phosphorus limited communities showed no such shift in amino acids. Both N and P limitation induced a shift from structural to storage fatty acids with a concurrent decrease in the synthesis of poly‐unsaturated fatty acids. Reversed effects in fatty acid synthesis after N or P addition were only apparent after 72 h, when they could be found in both fatty acid biosynthesis and concentrations. The different strategies of qualitative and quantitative regulation of different biomolecule synthesis under nutrient scarcity may have far‐reaching consequences for the phytoplankton's nutritional value. Higher trophic levels may have to cope with the loss of essential amino acids and poly‐unsaturated fatty acids in nutrient limited phytoplankton, which could induce changes in the structure of food webs.
    Type: Article , PeerReviewed
    Format: text
    Format: text
    DOI: 10.1002/lno.11040
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 6
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    Virus production in phosphorus-limited Micromonas pusilla stimulated by a supply of naturally low concentrations of different phosphorus sources, far into the lytic cycle (2016)
    Oxford University Press
    Details
    Publication Date: 2016-07-13
    Description: Earlier studies show that the proliferation of phytoplankton viruses can be inhibited by depletion of soluble reactive phosphorus (SRP; orthophosphate). In natural marine waters, phytoplankton phosphorus (P) availability is, however, largely determined by the supply rate of SRP (e.g. through remineralization) and potentially by the source of P as well (i.e. the utilization of soluble non-reactive P; SNP). Here we show how a steady low supply of P (mimicking natural P recycling) to virally infected P-limited Micromonas pusilla stimulates virus proliferation. Independent of the degree of P limitation prior to infection (0.32 and 0.97μ max chemostat cultures), SRP supply resulted in 2-fold higher viral burst sizes (viruses lysed per host cell) as compared with no addition (P starvation). Delaying these spikes during the infection cycle showed that the added SRP was utilized for extra M. pusilla virus (MpV) production far into the lytic cycle (18 h post-infection). Moreover, P-limited M. pusilla utilized several SNP compounds with high efficiency and with the same extent of burst size stimulation as for SRP. Finally, addition of virus-free MpV lysate (representing a complex SNP mixture) to newly infected cells enhanced MpV production, implicating host-associated alkaline phosphatase activity, and highlighting its important role in oligotrophic environments.
    Print ISSN: 0168-6496
    Electronic ISSN: 1574-6941
    Topics: Biology
    Published by Oxford University Press
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  • 7
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    Genome sequence of P. globosa virus PgV-16T [Microbiology] (2013)
    National Academy of Sciences
    Details
    Publication Date: 2013-06-26
    Description: Large dsDNA viruses are involved in the population control of many globally distributed species of eukaryotic phytoplankton and have a prominent role in bloom termination. The genus Phaeocystis (Haptophyta, Prymnesiophyceae) includes several high-biomass-forming phytoplankton species, such as Phaeocystis globosa, the blooms of which occur mostly in the coastal zone of...
    Print ISSN: 0027-8424
    Electronic ISSN: 1091-6490
    Topics: Biology , Medicine , Natural Sciences in General
    Published by National Academy of Sciences
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  • 8
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    Elevated CO2 and Phosphate Limitation Favor Micromonas pusilla through Stimulated Growth and Reduced Viral Impact [Environmental Microbiology] (2014)
    The American Society for Microbiology (ASM)
    Details
    Publication Date: 2014-04-26
    Description: Growth and viral infection of the marine picoeukaryote Micromonas pusilla was studied under a future-ocean scenario of elevated partial CO 2 (pCO 2 ; 750 μatm versus the present-day 370 μatm) and simultaneous limitation of phosphorus (P). Independent of the pCO 2 level, the ratios of M. pusilla cellular carbon (C) to nitrogen (N), C:P and N:P, increased with increasing P stress. Furthermore, in the P-limited chemostats at growth rates of 0.32 and 0.97 of the maximum growth rate (μ max ), the supply of elevated pCO 2 led to an additional rise in cellular C:N and C:P ratios, as well as a 1.4-fold increase in M. pusilla abundance. Viral lysis was not affected by pCO 2 , but P limitation led to a 150% prolongation of the latent period (6 to 12 h) and an 80% reduction in viral burst sizes (63 viruses per cell) compared to P-replete conditions (4 to 8 h latent period and burst size of 320). Growth at 0.32 μ max further prolonged the latent period by another 150% (12 to 18 h). Thus, enhanced P stress due to climate change-induced strengthened vertical stratification can be expected to lead to reduced and delayed virus production in picoeukaryotes. This effect is tempered, but likely not counteracted, by the increase in cell abundance under elevated pCO 2 . Although the influence of potential P-limitation-relieving factors, such as the uptake of organic P and P utilization during infection, is unclear, our current results suggest that when P limitation prevails in future oceans, picoeukaryotes and grazing will be favored over larger-sized phytoplankton and viral lysis, with increased matter and nutrient flow to higher trophic levels.
    Print ISSN: 0099-2240
    Electronic ISSN: 1098-5336
    Topics: Biology
    Published by The American Society for Microbiology (ASM)
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  • 9
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    Counting Viruses and Bacteria in Photosynthetic Microbial Mats [Methods] (2015)
    The American Society for Microbiology (ASM)
    Details
    Publication Date: 2015-02-28
    Description: Viral abundances in benthic environments are the highest found in aquatic systems. Photosynthetic microbial mats represent benthic environments with high microbial activity and possibly high viral densities, yet viral abundances have not been examined in such systems. Existing extraction procedures typically used in benthic viral ecology were applied to the complex matrix of microbial mats but were found to inefficiently extract viruses. Here, we present a method for extraction and quantification of viruses from photosynthetic microbial mats using epifluorescence microscopy (EFM) and flow cytometry (FCM). A combination of EDTA addition, probe sonication, and enzyme treatment applied to a glutaraldehyde-fixed sample resulted in a substantially higher viral (5- to 33-fold) extraction efficiency and reduced background noise compared to previously published methods. Using this method, it was found that in general, intertidal photosynthetic microbial mats harbor very high viral abundances (2.8 x 10 10 ± 0.3 x 10 10 g –1 ) compared with benthic habitats (10 7 to 10 9 g –1 ). This procedure also showed 4.5- and 4-fold-increased efficacies of extraction of viruses and bacteria, respectively, from intertidal sediments, allowing a single method to be used for the microbial mat and underlying sediment.
    Print ISSN: 0099-2240
    Electronic ISSN: 1098-5336
    Topics: Biology
    Published by The American Society for Microbiology (ASM)
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  • 10
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    Regional Variation in Lytic and Lysogenic Viral Infection in the Southern Ocean and Its Contribution to Biogeochemical Cycling [Geomicrobiology] (2012)
    The American Society for Microbiology (ASM)
    Details
    Publication Date: 2012-08-25
    Description: Lytic and lysogenic viral infection was investigated throughout the Southern Ocean at sites spanning the sub-Antarctic zone, the Antarctic Circumpolar Current, and an Antarctic continental sea. Higher lytic virus activity was recorded in the more productive sub-Antarctic zone than in the iron-limited waters of the Antarctic Circumpolar Current during two transects. Reduced lytic viral activity in the Antarctic Circumpolar Current was combined with a shift toward lysogenic infection, probably resulting from the lower concentration of potential prokaryotic hosts. Superimposed on this variation, lytic viral production was lower in a transect completed in the Drake Passage in autumn (1.8 x 10 8 to 1.5 x 10 9 liter –1 day –1 ) than over the Greenwich Meridian during summer (5.1 x 10 8 to 2.0 x 10 10 cells liter –1 day –1 ), indicating that viral activity is linked to the overall seasonal fluctuations in biotic activity. Interestingly, while prokaryotic abundance was lowest in the coastal Weddell Sea, levels of bacterial and lytic viral production (4.3 x 10 8 to 1.7 x 10 10 cells liter –1 day –1 ) in this area were similar to those of the other zones. This may explain the weak relationship between the distribution of prokaryotes and chlorophyll in the Weddell Sea, as a high turnover of prokaryotic biomass may have been stimulated by the availability of substrates in the form of viral lysate. With estimated carbon and iron releases of 0.02 to 7.5 μg liter –1 day –1 and 1.5 to 175.7 pg liter –1 day –1 , respectively, viral activity in the Southern Ocean is shown to be a major contributor to satisfying the elemental requirements of microbes, notably prokaryotes in the Weddell Sea and phytoplankton in the sub-Antarctic zone.
    Print ISSN: 0099-2240
    Electronic ISSN: 1098-5336
    Topics: Biology
    Published by The American Society for Microbiology (ASM)
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