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    Phytoplankton Blooms at Increasing Levels of Atmospheric Carbon Dioxide: Experimental Evidence for Negative Effects on Prymnesiophytes and Positive on Small Picoeukaryotes (2017)
    Frontiers
    In:  Frontiers in Marine Science, 4 . Art.Nr. 64.
    Details
    Publication Date: 2020-02-06
    Description: Anthropogenic emissions of carbon dioxide (CO2) and the ongoing accumulation in the surface ocean together with concomitantly decreasing pH and calcium carbonate saturation states have the potential to impact phytoplankton community composition and therefore biogeochemical element cycling on a global scale. Here we report on a recent mesocosm CO2 perturbation study (Raunefjorden, Norway), with a focus on organic matter and phytoplankton dynamics. Cell numbers of three phytoplankton groups were particularly affected by increasing levels of seawater CO2 throughout the entire experiment, with the cyanobacterium Synechococcus and picoeukaryotes (prasinophytes) profiting, and the coccolithophore Emiliania huxleyi (prymnesiophyte) being negatively impacted. Combining these results with other phytoplankton community CO2 experiments into a data-set of global coverage suggests that, whenever CO2 effects are found, prymnesiophyte (especially coccolithophore) abundances are negatively affected, while the opposite holds true for small picoeukaryotes belonging to the class of prasinophytes, or the division of chlorophytes in general. Future reductions in calcium carbonate-producing coccolithophores, providing ballast which accelerates the sinking of particulate organic matter, together with increases in picoeukaryotes, an important component of the microbial loop in the euphotic zone, have the potential to impact marine export production, with feedbacks to Earth's climate system.
    Type: Article , PeerReviewed , info:eu-repo/semantics/article
    Format: text
    Format: text
    DOI: 10.3389/fmars.2017.00064
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 2
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    Marine CDOM accumulation during a coastal Arctic mesocosm experiment: No response to elevated pCO2levels (2014)
    AGU (American Geophysical Union) | Wiley
    In:  Journal of Geophysical Research: Biogeosciences, 119 (6). pp. 1216-1230.
    Details
    Publication Date: 2020-10-20
    Description: A large-scale multidisciplinary mesocosm experiment in an Arctic fjord (Kongsfjorden, Svalbard; 78°56.2′N) was used to study Arctic marine food webs and biogeochemical elements cycling at natural and elevated future carbon dioxide (CO2) levels. At the start of the experiment, marine-derived chromophoric dissolved organic matter (CDOM) dominated the CDOM pool. Thus, this experiment constituted a convenient case to study production of autochthonous CDOM, which is typically masked by high levels of CDOM of terrestrial origin in the Arctic Ocean proper. CDOM accumulated during the experiment in line with an increase in bacterial abundance; however, no response was observed to increased pCO2 levels. Changes in CDOM absorption spectral slopes indicate that bacteria were most likely responsible for the observed CDOM dynamics. Distinct absorption peaks (at ~ 330 and ~ 360 nm) were likely associated with mycosporine-like amino acids (MAAs). Due to the experimental setup, MAAs were produced in absence of ultraviolet exposure providing evidence for MAAs to be considered as multipurpose metabolites rather than simple photoprotective compounds. We showed that a small increase in CDOM during the experiment made it a major contributor to total absorption in a range of photosynthetically active radiation (PAR, 400–700 nm) and, therefore, is important for spectral light availability and may be important for photosynthesis and phytoplankton groups composition in a rapidly changing Arctic marine ecosystem.
    Type: Article , PeerReviewed , info:eu-repo/semantics/article
    Format: text
    DOI: 10.1002/2013JG002587
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 3
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    Competitive fitness of a predominant pelagic calcifier impaired by ocean acidification (2017)
    Nature Research
    In:  Nature Geoscience, 10 . pp. 19-23.
    Details
    Publication Date: 2020-06-18
    Description: Coccolithophores—single-celled calcifying phytoplankton—are an important group of marine primary producers and the dominant builders of calcium carbonate globally. Coccolithophores form extensive blooms and increase the density and sinking speed of organic matter via calcium carbonate ballasting. Thereby, they play a key role in the marine carbon cycle. Coccolithophore physiological responses to experimental ocean acidification have ranged from moderate stimulation to substantial decline in growth and calcification rates, combined with enhanced malformation of their calcite platelets. Here we report on a mesocosm experiment conducted in a Norwegian fjord in which we exposed a natural plankton community to a wide range of CO2-induced ocean acidification, to test whether these physiological responses affect the ecological success of coccolithophore populations. Under high-CO2 treatments, Emiliania huxleyi, the most abundant and productive coccolithophore species, declined in population size during the pre-bloom period and lost the ability to form blooms. As a result, particle sinking velocities declined by up to 30% and sedimented organic matter was reduced by up to 25% relative to controls. There were also strong reductions in seawater concentrations of the climate-active compound dimethylsulfide in CO2-enriched mesocosms. We conclude that ocean acidification can lower calcifying phytoplankton productivity, potentially creating a positive feedback to the climate system.
    Type: Article , PeerReviewed , info:eu-repo/semantics/article
    Format: text
    Format: text
    DOI: 10.1038/ngeo2854
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    OceanRep: Article in a Scientific Journal - peer-reviewed
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