IIM-CSIC and UVigo describe how ocean acidification affects marine phytoplankton
Details of the research are published in the journal Limnology and Oceanography. The study describes how ocean acidification affects the photosynthetic system and photoprotection of these small photosynthetic beings.
Santiago de Compostela, Monday, February 20, 2023. A research team from the Higher Council for Scientific Research (CSIC) and the Mariña Research Center in The University of Vigo (CIM-UVIGO) has studied, under laboratory conditions, the physiological regulation of the constituent pigments of the plankton photosynthetic machinery in the face of ocean acidification parallel to the increase in atmospheric CO2.
“The results, which we report through an article published in the journal Limnology and Oceanography, contribute to the knowledge of the physiological regulation of the photosynthetic apparatus and the photoprotective capacity of marine phytoplankton in the future CO2 scenarios to which global change leads", explains Cristina Sobrino, professor at UVIGO and principal investigator of the Stress@2 project "Downregulation of phytoplankton metabolism in a world of high CO2: Consequences for resistance to abiotic and biotic factors”, project within the framework of which the study was developed.
The research, carried out by the groups Photobiology and Phytoplankton Toxinology (Instituto de Investigaciones Mariñas-CSIC) and Biological Oceanography of the Faculty of Marine Sciences (UVIGO) focused on the response of the photosynthetic apparatus of three species of marine microalgae to ocean acidification, monitoring its pigment content and its ability to protect itself from light. As model organisms, the study was undertaken with two diatoms (Thalassiosira pseudonana and Skeletonema costatum) and a coccolithophore (Emiliania huxleyi).
“Phytoplankton, although it accounts for barely 1% of the biomass of photosynthetic organisms, is responsible for half of the planet's primary production and for fixing 50% of atmospheric CO2 . For this reason, the study of possible modifications in the components of their photosynthetic systems in the face of the increase in atmospheric CO2 (and therefore ocean acidification) is especially relevant”, highlights José Luis Garrido, lead scientist of the Mariñas Research Institute of the CSIC.
“Diatoms make up 40% of phytoplankton species, have a silicic exoskeleton and are especially relevant in coastal waters. The cells of the coccolithophores, on the contrary, are covered with small calcareous plates and have an extraordinary biogeochemical importance due to their influence on the climate and on the precipitation of CaCO3 in the ocean”, they explain from the CSIC and UVIGO.
The research reveals that, at the CO2 concentrations expected by the end of the century, the metabolism of phytoplankton is down-regulated or relaxed and, consequently, there is a decrease in the concentration of metabolic components (for example, the pigments of the photosynthetic apparatus) as well as a decrease in general enzymatic activity. However, the final net balance assumes an increase in production rates and biomass.
“This translates, in short, into greater efficiency on the part of the cell by optimizing the available resources” points out Paulo Alcaraz-Rocha, the first author of the work. "However, not everything is so good, since this down regulation or relaxation of metabolism will leave the cell more susceptible to damage related to UV radiation or high light intensities," he clarifies.
“It is also observed that specific environmental disturbances can reverse this relaxation, significantly activating metabolism and even leading to pigmentary content and photoprotection capacities that may be greater under high CO2 conditions. Statistical analysis of the different responses observed in the study finally allows us to discover which pigments can potentially act as indicators of ocean acidification.”