Combined effects of inorganic carbon and light on iPhaeocystis globosa/i Scherffel (Prymnesiophyceae)

摘要

Phaeocystis globosa (Prymnesiophyceae) is an ecologically dominating phytoplankton species inmany areas around the world. It plays an important role in both the globalsulfur and carbon cycles, by the production of dimethylsulfide (DMS) and thedrawdown of inorganic carbon. Phaeocystis globosa has a polymorphic life cycle and isconsidered to be a harmful algal bloom (HAB) forming species. All theseaspects make this an interesting species to study the effects of increasingcarbon dioxide (CO₂) concentrations, due to anthropogenic carbonemissions.Here, the combined effects of three different dissolved carbon dioxideconcentrations (CO_2(aq)) (low: 4 μmol kg?1, intermediate: 6–10 μmol kg?1 and high CO_2(aq): 21–24 μmol kg−1)and two different light intensities (low light, suboptimal: 80 μmolphotons m?2 s−1 and high light, light saturated: 240 μmolphotons m?2 s−1) are reported.The experiments demonstrated that the specific growth rate of P. globosa in the highlight cultures decreased with increasing CO_2(aq) from 1.4 to 1.1 d?1 in the low and high CO₂ cultures, respectively. Concurrently,the photosynthetic efficiency (F_V/F_M) increased with increasingCO_2(aq) from 0.56 to 0.66. The different light conditions affectedphotosynthetic efficiency and cellular chlorophyll a concentrations, both ofwhich were lower in the high light cultures as compared to the low lightcultures. These results suggest that in future inorganic carbonenriched oceans, P. globosa will become less competitive and feedback mechanisms toglobal change may decrease in strength.