The effect of climate change on the carbon balance between photosynthesis and respiration in planktonic and benthic microalgae

• Applicant: Professor Dr. Christian Wilhelm
• Subject Area: Oceanography
• Term: from 2015 to 2021
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 274037400

The biological process of the carbon cycle in the Antarctic Ocean is controlled by the photosynthetic activity of the planktic and benthic primary producers. The amount of fixed carbon does not only depend on the photosynthetic activity but also on the carbon losses due to respiration. Therefore, the ratio photosynthesis/respiration (rP/R) is an important parameter to predict the effect of climate change on the Antarctic ecosystem, since it was demonstrated by lab studies that this ratio is highly variable in response to environmental conditions. The quantitative changes in the rP/R of microalgae is not well studied and nothing is known about the changes in real nature. This is mainly due to methodological limitations. Photosynthesis can be assessed by 14C uptake, oxygen evolution or by fluorometric devices, a quantitative estimate of the respiration from phototrophs is still difficult. In this project we want to measure the changes in the ratio photosynthesis/respiration in species which are relevant for the antartic primary production under global change conditions (rising temperature, iron limitation). The relevance of variable ratios of rP/R is then demonstrated by comparing the daily biomass production with and without corrected respiration rates. In a second part a method will be developed to measure respiration rates without gas exchange measurements and applicably as high throughput method under field conditions. The methodology will help to improve the data set of all other projects studying primary productivity in the Antartic.

• DFG Programme: Infrastructure Priority Programmes
• Subproject of: SPP 1158: Infrastructure area - Antarctic Research with Comparative Investigations in Arctic Sea Ice Areas
• Cooperation Partner: Dr. Steffi Gäbler-Schwarz