Ecophysiological responses of the haptophyte Phaeocystis pouchetii towards Ocean Acidification and their modulation by light

• Main Author: Großmann, Christian
• Format: Thesis
• Language: unknown
• Published: University of Bayreuth, Alfred Wegener Institute 2016
• Subjects: Arctic; Global warming; Ocean acidification
• Online Access: https://epic.awi.de/id/eprint/43082/; https://hdl.handle.net/10013/epic.49593

Anthropogenically caused emissions of the greenhouse gas carbon dioxide have led to the phenomena of Global Warming and Ocean Acidification (OA). As a result, the Arctic haptophyte Phaeocystis pouchetii will encounter elevated seawater CO2 concentrations, temperatures and irradiances as well as lower seawater pH and nutrient availability. P. pouchetii is one of the major bloom forming primary producers in the Arctic and as such of crucial importance for the Arctic ecosystem and the ocean’s carbon cycle by contributing to the process of the biological carbon pump. Aim of this study is to investigate the uncoupled effects of OA and elevated light on the physiological performance of the alga. Therefore, P. pouchetii was cultured in a matrix of 400 (present day) and 1000 μatm (OA) partial pressure of CO2 and 50 (low light: LL) and 100 μmol photons m-2 s-1 (high light: HL) light. The impact of the environmental drivers was investigated on phenomenology (growth, chlorophyll a content, particulate organic carbon and nitrogen quotas and production rates) as well as on basis of in vivo physiology (relative electron transport, net photosynthesis, respiration and CO2 uptake) using Fast Repetition Rate Fluorometry and Membrane-Inlet Mass Spectrometry. In addition, SYBR-green based Quantitative Real-Time Polymerase Chain Reaction was applied to assess the transcriptomic responses of the subunits A of photosystem I and the large subunit of ribulose-1,5-bisphosphate carboxylase/oxygenase towards OA and HL. This study revealed that P. pouchetii`s photosynthesis in general profits slightly from a shift in the ambient light from 50 to 100 μmol photons m-2 s-1 and especially profits slightly from a synergistic effect of HL and OA. Attributed to the improved photosynthesis, increased particulate organic carbon and nitrogen quotas and production rates were found manifested. For the very first time, this study provides a comprehensive dataset on the physiology of the important but under-investigated species P. pouchetii and reveled that this alga will most likely belong to the winners of Global Change.