Abstract
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.
Highlights
Increasing levels of atmospheric carbon dioxide (CO2) as the result of anthropogenic burning of fossil fuels, and variations in land-use and deforestation are driving a number of environmental changes on a global scale (Ciais et al, 2013)
In accordance to CO2 manipulation, and Chla and dissolved inorganic nutrient dynamics, the experiment was sub-divided into several phases
A level of 270 μatm would suggest that a minimum of 60 μmol kg−1 of dissolved inorganic carbon had been taken up by the plankton community during a previous bloom
Summary
Increasing levels of atmospheric carbon dioxide (CO2) as the result of anthropogenic burning of fossil fuels, and variations in land-use and deforestation are driving a number of environmental changes on a global scale (Ciais et al, 2013). Increasing surface ocean temperatures have been hypothesized to lead to the shoaling of the upper mixed layer depth, changing light and nutrient availability for marine primary producers. This has the potential to impact marine primary productivity (Bopp et al, 2001; Boyd and Doney, 2002) and marine export production (Laufkötter et al, 2016). The attenuation of the organic carbon flux with depth and marine primary productivity determine the amount of atmospheric carbon locked away in the deeper ocean for timescales beyond decades (compare e.g., Buessler and Boyd, 2009; De La Rocha and Passow, 2014; Mouw et al, 2016)
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
