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

• Main Author: Bozzato, Deborah
• Other Authors: Universität Leipzig
• Format: Doctoral or Postdoctoral Thesis
• Language: English
• Published: 2019
• Subjects: Antarctic Ocean; Phytoplankton; Primary productivity; Respiration; Iron limitation; info:eu-repo/classification/ddc/570; ddc:570; Antarctic; Southern Ocean; The Antarctic; Antarc*; Antarctica
• Online Access: https://nbn-resolving.org/urn:nbn:de:bsz:15-qucosa2-367487; https://ul.qucosa.de/id/qucosa%3A36748; https://ul.qucosa.de/api/qucosa%3A36748/attachment/ATT-0/

The biological process of the carbon cycle in the Antarctic Ocean is controlled by the photosynthetic activity of the primary producers. The amount of fixed carbon does not only depend on the photosynthetic activity but also on the carbon losses due to respiration. Thus, the ratio photosynthesis to respiration (rP/R) is an important parameter to predict the effect of climate change on the Antarctic ecosystem. Indeed, the ongoing changes in climate change are influencing the dynamics of environmental conditions, which has tremendous effects on the phytoplankton community. Therefore, two ecologically relevant species from the Southern Ocean were here investigated: the diatom Chaetoceros sp. and the prymnesiophyte Phaeocystis antarctica, studying the changes in the rP/R under global climate change conditions. Three main parameters were examined i.e temperature, salinity and iron limitation. The P/R ratio was significantly affected by temperature, while salinity had only a secondary importance, although with species-specific differences. More specifically, the values were ranging from 12.3 to 7.5 for Chaetoceros sp. and from 12.4 to 2.5 for P. antarctica. The changes in this ratio were principally due to variations in respiration, rather than in photosynthesis. Chaetoceros sp. appears to be less flexible in the regulation of the extent of photoprotective mechanisms (non-photochemical quenching and alternative electrons), but its photoprotective level was generally higher than in P. antarctica. Regarding iron limitation, data were successfully collected only for Chaetoceros sp. The P/R ratio, equal to 2.8, did not change under iron limitation, with iron limited cells showing a very efficient acclimation to the lowered assimilatory metabolism by decreasing their respiratory losses.