Temporal biomass dynamics of an Arctic plankton bloom in response to increasing levels of atmospheric carbon dioxide

[摘要] Ocean acidification and carbonation, driven by anthropogenic emissions ofcarbon dioxide (CO₂), have been shown to affect a variety of marineorganisms and are likely to change ecosystem functioning. High latitudes,especially the Arctic, will be the first to encounter profound changes incarbonate chemistry speciation at a large scale, namely the under-saturationof surface waters with respect to aragonite, a calcium carbonate polymorphproduced by several organisms in this region. During a CO₂ perturbationstudy in Kongsfjorden on the west coast ofSpitsbergen (Norway), inthe framework of theEU-funded project EPOCA, the temporaldynamics of a plankton bloom was followed in nine mesocosms, manipulated forCO₂ 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 absoluteChl a concentrations were similar in all mesocosms during the firstphase of the experiment, higher autotrophic biomass was measured as high incomparison to low CO₂ during the second phase, right after dissolvedinorganic nutrient addition. This trend then reversed in the third phase.There were several statistically significant CO₂ effects on a variety ofparameters measured in certain phases, such as nutrient utilization, standingstocks of particulate organic matter, and phytoplankton species composition.Interestingly, CO₂ effects developed slowly but steadily, becoming moreand more statistically significant with time. The observed CO₂-relatedshifts in nutrient flow into different phytoplankton groups (mainlydinoflagellates, prasinophytes and haptophytes) could have consequences forfuture organic matter flow to higher trophic levels and export production,with consequences for ecosystem productivity and atmospheric CO₂.

[学科分类] 地球化学与岩石