GLORIA

GEOMAR Library Ocean Research Information Access

X
feed icon rss

Your email was sent successfully. Check your inbox.

An error occurred while sending the email. Please try again.

Proceed reservation?

Export
Filter
  • Frontiers  (17)
  • ASLO (Association for the Sciences of Limnology and Oceanography)  (2)
  • 2020-2024  (19)
  • 1
    facet.materialart.
    Unknown
    The Calcium Carbonate Shell of Emiliania huxleyi Provides Limited Protection Against Viral Infection (2020)
    Frontiers
    Details
    Publication Date: 2023-02-08
    Description: Coccolithophores are an important group of marine phytoplankton which cover themselves with the coccosphere – a shell composed of numerous calcium carbonate (CaCO3) platelets. Despite more than a century of coccolithophore research, it remains speculative why coccolithophores calcify. Resolving this question is essential to assess the competitive fitness of coccolithophores in the future ocean where changes in calcification are expected. Here, we used the Emiliania huxleyi – Emiliania huxleyi Virus 86 host-virus model system to test the hypothesis that the coccosphere serves as a physical barrier reducing viral infection. Therefore, we removed the coccosphere from living E. huxleyi cells and compared the infection progress relative to calcified cells in a series of 6 experiments under different growth conditions. We found that the coccosphere does not constitute an effective physical barrier against viral penetration, since non-growing calcified cells were susceptible to viral infection and lysis (growth stopped by light limitation). However, we also found that protection against the virus may depend on the daily growth cycle. E. huxleyi reached higher peak abundances when decalcified cells were allowed to rebuild their coccosphere before entering cell division phase and being exposed to the virus, thereby suggesting that rates of viral infection could be reduced by the coccosphere during the critical phase in the cell cycle. However, the benefit of this potential protection is arguably of limited ecological significance since the concentrations of both, calcified and decalcified E. huxleyi approached similar values until the end of the bloom. We conclude that the coccosphere provides at best a limited protection against infection with the EhV86.
    Type: Article , PeerReviewed
    Format: text
    Format: image
    Location Call Number Limitation Availability
    BibTip Others were also interested in ...
    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 2
    facet.materialart.
    Unknown
    Metabolic Responses of Subtropical Microplankton After a Simulated Deep-Water Upwelling Event Suggest a Possible Dominance of Mixotrophy Under Increasing CO2 Levels (2020)
    Frontiers
    Details
    Publication Date: 2023-02-08
    Description: In the autumn of 2014, nine large mesocosms were deployed in the oligotrophic subtropical North-Atlantic coastal waters off Gran Canaria (Spain). Their deployment was designed to address the acidification effects of CO2 levels from 400 to 1,400 mu atm, on a plankton community experiencing upwelling of nutrient-rich deep water. Among other parameters, chlorophyll a (chl-a), potential respiration (Phi), and biomass in terms of particulate protein (B) were measured in the microplankton community (0.7-50.0 mu m) during an oligotrophic phase (Phase I), a phytoplankton-bloom phase (Phase II), and a post-bloom phase (Phase III). Here, we explore the use of the Phi/chl-a ratio in monitoring shifts in the microplankton community composition and its metabolism. Phi/chl-a values below 2.5 mu L O-2 h(-1) (mu g chl-a)(-1) indicated a community dominated by photoautotrophs. When Phi/chl-a ranged higher, between 2.5 and 7.0 mu L O-2 h(-1) (pg chl-a)(-1) , it indicated a mixed community of phytoplankton, microzooplankton and heterotrophic prokaryotes. When Phi/chl-a rose above 7.0 mu L O-2 h(-1) (mu g chl-a)(-1), it indicated a community where microzooplankton proliferated (〉10.0 mu L O-2 h(-1) (mu g chl-a)(-1)), because heterotrophic dinoflagellates bloomed. The first derivative of B, as a function of time (dB/dt), indicates the rate of protein build-up when positive and the rate of protein loss, when negative. It revealed that the maximum increase in particulate protein (biomass) occurred between 1 and 2 days before the chl-a peak. A day after this peak, the trough revealed the maximum net biomass loss. This analysis did not detect significant changes in particulate protein, neither in Phase I nor in Phase III. Integral analysis of Phi/chl-a and B, over the duration of each phase, for each mesocosm, reflected a positive relationship between 4) and pCO(2) during Phase II [alpha = 230.10-5 mu L O-2 h(-1) L-1 (patm CO2)(-1) (phase-day)(-1), R-2 = 0.30] and between chl-a and pCO(2) during Phase III [alpha = 100.10(-5) Ag chl-a L-1 (mu atmCO(2))(-1) (phase-day)(-1), R-2 = 0.84]. At the end of Phase II, a harmful algal species (HAS), Vicicitus globosus, bloomed in the high pCO(2) mesocosms. In these mesocosms, microzooplankton did not proliferate, and chl-a retention time in the water column increased. In these V globosus-disrupted communities, the (Phi/chl-a ratio [4.1 +/- 1.5 /mu L O-2 h(-1) (mu g chl-a)(-1)] was more similar to the Phi/chl-a ratio in a mixed plankton community than to a photoautotroph-dominated one.
    Type: Article , PeerReviewed
    Format: text
    Format: other
    Location Call Number Limitation Availability
    BibTip Others were also interested in ...
    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 3
    facet.materialart.
    Unknown
    The Possession of Coccoliths Fails to Deter Microzooplankton Grazers (2020)
    Frontiers
    Details
    Publication Date: 2023-02-08
    Description: Phytoplankton play a central role in the regulation of global carbon and nutrient cycles, forming the basis of the marine food webs. A group of biogeochemically important phytoplankton, the coccolithophores, produce calcium carbonate scales that have been hypothesized to deter or reduce grazing by microzooplankton. Here, a meta-analysis of mesocosm-based experiments demonstrates that calcification of the cosmopolitan coccolithophore, Emiliania huxleyi, fails to deter microzooplankton grazing. The median grazing to growth ratio for E. huxleyi (0.56 ± 0.40) was not significantly different among non-calcified nano- or picoeukaryotes (0.71 ± 0.31 and 0.55 ± 0.34, respectively). Additionally, the environmental concentration of E. huxleyi did not drive preferential grazing of non-calcified groups. These results strongly suggest that the possession of coccoliths does not provide E. huxleyi effective protection from microzooplankton grazing. Such indiscriminate consumption has implications for the dissolution and fate of CaCO3 in the ocean, and the evolution of coccoliths.
    Type: Article , PeerReviewed , info:eu-repo/semantics/article
    Format: text
    Format: text
    Location Call Number Limitation Availability
    BibTip Others were also interested in ...
    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 4
    facet.materialart.
    Unknown
    Influence of the calcium carbonate shell of coccolithophores on ingestion and growth of a dinoflagellate predator (2021)
    Frontiers
    Details
    Publication Date: 2024-02-07
    Description: Coccolithophores are an important group of ~200 marine phytoplankton species which cover themselves with a calcium carbonate shell called “coccosphere”. Coccolithophores are ecologically and biogeochemically important but the reason why they calcify remains elusive. One key function may be that the coccosphere offers protection against microzooplankton predation, which is one of the main causes of phytoplankton death in the ocean. Here, we investigated the effect of the coccosphere on ingestion and growth of the heterotrophic dinoflagellate Oxyrrhis marina. Calcified and decalcified cells of the coccolithophore species Emiliania huxleyi, Pleurochrysis carterae, and Gephyrocapsa oceanica were offered separately to the predator as well as in an initial ~1:1 mixture. The decrease of the prey concentrations and predator abundances were monitored over a period of 48-72 hours. We found that O. marina did not actively select against calcified cells, but rather showed a size selective feeding behavior. Thus, the coccosphere does not provide a direct protection against grazing by O. marina. However, O. marina showed slower growth when calcified coccolithophores were fed. This could be due to reduced digestion rates of calcified cells and/or increased swimming efforts when ballasted with heavy calcium carbonate. Furthermore, we show that the coccosphere reduces the ingestion capacity simply by occupying much of the intracellular space of the predator. We speculate that the slower growth of the grazer when feeding on calcified cells is of limited benefit to the coccolithophore population because other co-occurring phytoplankton species within the community that do not invest energy in the formation of a calcite shell could also benefit from the reduced growth of the predators. Altogether, these new insights constitute a step forward in our understanding of the ecological relevance of calcification in coccolithophores.
    Type: Article , PeerReviewed
    Format: text
    Format: archive
    Location Call Number Limitation Availability
    BibTip Others were also interested in ...
    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 5
    facet.materialart.
    Unknown
    Ocean Acidification Alters the Predator – Prey Relationship Between Hydrozoa and Fish Larvae (2022)
    Frontiers
    Details
    Publication Date: 2024-02-07
    Description: Anthropogenic CO2 emissions cause a drop in seawater pH and shift the inorganic carbon speciation. Collectively, the term ocean acidification (OA) summarizes these changes. Few studies have examined OA effects on predatory plankton, e.g. Hydrozoa and fish larvae as well as their interaction in complex natural communities. Because Hydrozoa can seriously compete with and prey on other higher-level predators such as fish, changes in their abundances may have significant consequences for marine food webs and ecosystem services. To investigate the interaction between Hydrozoa and fish larvae influenced by OA, we enclosed a natural plankton community in Raunefjord, Norway, for 53 days in eight ≈ 58 m³ pelagic mesocosms. CO2 levels in four mesocosms were increased to ≈ 2000 µatm pCO2, whereas the other four served as untreated controls. We studied OA-induced changes at the top of the food web by following ≈2000 larvae of Atlantic herring (Clupea harengus) hatched inside each mesocosm during the first week of the experiment, and a Hydrozoa population that had already established inside the mesocosms. Under OA, we detected 20% higher abundance of hydromedusae staged jellyfish, but 25% lower biomass. At the same time, survival rates of Atlantic herring larvae were higher under OA (control pCO2: 0.1%, high pCO2: 1.7%) in the final phase of the study. These results indicate that a decrease in predation pressure shortly after hatch likely shaped higher herring larvae survival, when hydromedusae abundance was lower in the OA treatment compared to control conditions. We conclude that indirect food-web mediated OA effects drove the observed changes in the Hydrozoa – fish relationship, based on significant changes in the phyto-, micro-, and mesoplankton community under high pCO2. Ultimately, the observed immediate consequences of these changes for fish larvae survival and the balance of the Hydrozoa – fish larvae predator – prey relationship has important implications for the functioning of oceanic food webs.
    Type: Article , PeerReviewed , info:eu-repo/semantics/article
    Format: text
    Format: archive
    Location Call Number Limitation Availability
    BibTip Others were also interested in ...
    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 6
    facet.materialart.
    Unknown
    The importance of the dissolved organic matter pool for the carbon sequestration potential of artificial upwelling (2022)
    Frontiers
    Details
    Publication Date: 2024-02-07
    Description: In the face of climate change there is a need to reduce atmospheric CO2 concentrations. Artificial upwelling of nutrient-rich deep waters has been proposed as a method to enhance the biological carbon pump in oligotrophic oceanic regions in order to increase carbon sequestration. Here we examine the effect of different artificial upwelling intensities and modes (single pulse versus recurring pulses) on the dynamics of the dissolved organic matter pool (DOM). We introduced nutrient-rich deep water to large scale mesocosms (~44 m3) in the oligotrophic subtropical North Atlantic and found that artificial upwelling strongly increased DOM concentrations and changed its characteristics. The magnitude of the observed changes was related to the upwelling intensity: more intense treatments led to higher accumulation of dissolved organic carbon (〉70 μM of excess DOC over ambient waters for the most intense) and to comparatively stronger changes in DOM characteristics (increased proportions of chromophoric DOM (CDOM) and humic-like fluorescent DOM), suggesting a transformation of the DOM pool at the molecular level. Moreover, the single upwelling pulse resulted in higher CDOM quantities with higher molecular weight than the recurring upwelling mode. Together, our results indicate that under artificial upwelling, large DOM pools may accumulate in the surface ocean without being remineralized in the short-term. Possible reasons for this persistence could be a combination of the molecular diversification of DOM due to microbial reworking, nutrient limitation and reduced metabolic capabilities of the prokaryotic communities within the mesocosms. Our study demonstrates the importance of the DOC pool when assessing the carbon sequestration potential of artificial upwelling.
    Type: Article , PeerReviewed , info:eu-repo/semantics/article
    Format: text
    Format: text
    Location Call Number Limitation Availability
    BibTip Others were also interested in ...
    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 7
    facet.materialart.
    Unknown
    Response of plankton community respiration under variable simulated upwelling events (2022)
    Frontiers
    Details
    Publication Date: 2024-02-07
    Description: Climate change is expected to alter the intensity and frequency of upwelling in high productive coastal regions, thus impacting nutrient fluxes, primary productivity and consequently carbon cycling. However, it is unknown how these changes will impact the planktonic (phytoplankton and bacteria) community structure, which affects community respiration (CR) and hence the carbon available for sequestration or transfer to upper trophic levels. Here we present results from a 37-day mesocosm experiment where we examined the response of CR to nutrient additions by simulating upwelling events at different intensities (low, medium, high and extreme) and modes (singular and recurring additions). We also analysed the potential contribution of different plankton size classes and functional groups to CR. The trend in accumulated CR with respect to nutrient fertilisation (total nitrogen added during the experiment) was linear in the two modes. Microplankton (mostly diatoms) and nanoplankton (small flagellates) dominated under extreme upwelling intensities and high CR in both singular and recurring upwelling modes, explaining 〉65% of the observed variability in CR. In contrast, prokaryotic picoplankton (heterotrophic bacteria and autotrophic cyanobacteria) explained 〈43% of the variance in CR under the rest of the upwelling intensities and modes tested. Changes in planktonic community structure, while modulating CR variability, would regulate the metabolic balance of the ecosystem, shifting it towards net-heterotrophy when the community is dominated by small heterotrophs and to net-autotrophy when large autotrophs prevail; although depending on the mode in which nutrients are supplied to the system. This shift in the dominance of planktonic organism will hence affect not only CR but also carbon sequestration in upwelling regions
    Type: Article , PeerReviewed , info:eu-repo/semantics/article
    Format: text
    Location Call Number Limitation Availability
    BibTip Others were also interested in ...
    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 8
    facet.materialart.
    Unknown
    Counteracting effects of nutrient composition (Si:N) on export flux under artificial upwelling (2023)
    Frontiers
    Details
    Publication Date: 2024-02-07
    Description: To keep global warming below 1.5 °C, technologies that remove carbon from the atmosphere will be needed. Ocean artificial upwelling of nutrient-rich water stimulates primary productivity and could enhance the biological carbon pump for natural CO2 removal. Its potential may depend on the Si availability in the upwelled water, which regulates the abundance of diatoms that are key carbon exporters. In a mesocosm experiment, we tested the effect of nutrient composition (Si relative to N) in artificially upwelled waters on export quantity and quality in a subtropical oligotrophic environment. Upwelling led to a doubling of exported particulate matter and increased C:N ratios to well beyond Redfield (9.5 to 11.1). High Si availability stimulated this carbon over-consumption further, resulting in a temporary ~5-fold increase in POC export and ~30% increase in C:N ratios compared to Si-scarce upwelling. Whilst the biogenic Si ballast of the export flux increased more than 3.5-fold over the Si:N gradient, these heavier particles did not sink faster. On the contrary, sinking velocity decreased considerably under high Si:N, most likely due to reduced particle size. Respiration rates remained similar across all treatments indicating that biogenic Si did not protect particles against microbial degradation. Si availability thus influenced key processes of the biological carbon pump in counteracting ways by increasing the export magnitude and associated C:N ratios but decreasing the efficiency of carbon transfer to depth. These opposing effects need to be considered when evaluating the potential of artificial upwelling as negative emission technology.
    Type: Article , PeerReviewed
    Format: text
    Format: text
    Location Call Number Limitation Availability
    BibTip Others were also interested in ...
    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 9
    facet.materialart.
    Unknown
    Microzooplankton communities and their grazing of phytoplankton under artificial upwelling in the oligotrophic ocean (2023)
    Frontiers
    Details
    Publication Date: 2024-02-07
    Description: Ocean artificial upwelling has been suggested to boost primary production and increase harvestable resources such as fish. Yet, for this ecosystem-based approach to work, an effective energy transfer up the food web is required. Here, we studied the trophic role of microzooplankton under artificial upwelling via biomass and community composition as well as grazing rates on phytoplankton. Using mesocosms in the oligotrophic ocean, we supplied nutrient-rich deep water at varying intensities (low to high) and addition modes (a Singular large pulse or smaller Recurring pulses). Deep-water fertilization created a diatom-dominated bloom that scaled with the amount of inorganic nutrients added, but also Synechococcus -like cells, picoeukaryotes and nanophytoplankton increased in abundance with added nutrients. After 30 days, towards the end of the experiment, coccolithophores bloomed under recurring upwelling of high intensity. Across all upwelling scenarios, the microzooplankton community was dominated by ciliates, dinoflagellates (mixo- and heterotrophic) and radiolarians. Under the highest upwelling intensity, the average grazing rates of Synechococcus -like cells, picoeukaryotes and nanophytoplankton by microzooplankton were 0.35 d -1 ± 0.18 (SD), 0.09 d -1 ± 0.12 (SD), and 0.11 d -1 ± 0.13 (SD), respectively. There was little temporal variation in grazing of nanophytoplankton but grazing of Synechococcus -like cells and picoeukaryotes were more variable. There were positive correlations between abundance of these groups and grazing rates, suggesting a response in the microzooplankton community to prey availability. The average phytoplankton to microzooplankton ratio (biovolume) increased with added deep water, and this increase was highest in the Singular treatment, reaching ~30 (m 3 m -3 ), whereas the phytoplankton to total zooplankton biomass ratio (weight) increased from ~1 under low upwelling to ~6 (g g -1 ) in the highest upwelling but without a difference between the Singular and the Recurring mode. Several smaller, recurring upwelling events increased the importance of microzooplankton compared with one large pulse of deep water. Our results demonstrate that microzooplankton would be an important component for trophic transfer if artificial upwelling would be carried out at scale in the oligotrophic ocean.
    Type: Article , PeerReviewed , info:eu-repo/semantics/article
    Format: text
    Format: other
    Format: image
    Format: image
    Format: image
    Format: image
    Format: image
    Location Call Number Limitation Availability
    BibTip Others were also interested in ...
    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 10
    facet.materialart.
    Unknown
    Extreme Levels of Ocean Acidification Restructure the Plankton Community and Biogeochemistry of a Temperate Coastal Ecosystem: A Mesocosm Study (2021)
    Frontiers
    Details
    Publication Date: 2024-02-07
    Description: The oceans’ uptake of anthropogenic carbon dioxide (CO2) decreases seawater pH and alters the inorganic carbon speciation – summarized in the term ocean acidification (OA). Already today, coastal regions experience episodic pH events during which surface layer pH drops below values projected for the surface ocean at the end of the century. Future OA is expected to further enhance the intensity of these coastal extreme pH events. To evaluate the influence of such episodic OA events in coastal regions, we deployed eight pelagic mesocosms for 53 days in Raunefjord, Norway, and enclosed 56–61 m3 of local seawater containing a natural plankton community under nutrient limited post-bloom conditions. Four mesocosms were enriched with CO2 to simulate extreme pCO2 levels of 1978 – 2069 μatm while the other four served as untreated controls. Here, we present results from multivariate analyses on OA-induced changes in the phyto-, micro-, and mesozooplankton community structure. Pronounced differences in the plankton community emerged early in the experiment, and were amplified by enhanced top-down control throughout the study period. The plankton groups responding most profoundly to high CO2 conditions were cyanobacteria (negative), chlorophyceae (negative), auto- and heterotrophic microzooplankton (negative), and a variety of mesozooplanktonic taxa, including copepoda (mixed), appendicularia (positive), hydrozoa (positive), fish larvae (positive), and gastropoda (negative). The restructuring of the community coincided with significant changes in the concentration and elemental stoichiometry of particulate organic matter. Results imply that extreme CO2 events can lead to a substantial reorganization of the planktonic food web, affecting multiple trophic levels from phytoplankton to primary and secondary consumers.
    Type: Article , PeerReviewed
    Format: text
    Format: text
    Format: text
    Location Call Number Limitation Availability
    BibTip Others were also interested in ...
    OceanRep: Article in a Scientific Journal - peer-reviewed
Close ⊗
This website uses cookies and the analysis tool Matomo. More information can be found here...