Effects of increased CO2 and temperature on the growth of diatoms in laboratory

Abstract

We examined the combined impacts of future increases of CO2 and temperature on the growth of four marine diatoms (Skeletonema costatum, Chaetoceros debilis, Chaetoceros didymus, Thalassiosira nordenskioeldii). The four strains were incubated under four different conditions: present (pCO2: 400 ppm, temperature: 20°C), acidification (pCO2: 1000 ppm, temperature: 20°C), global warming (pCO2: 400 ppm, temperature: 25°C), and greenhouse (pCO2: 1000 ppm, temperature: 25°C) conditions. With incubation at higher temperatures, growth of S. costatum was suppressed, while C. debilis showed enhanced growth. Both C. didymus and T. nordenskioldii showed similar growth rates under current and elevated temperature. None of the four species appeared affected intheir cell growth by elevated CO2 concentrations. Chaetoceros spp. showed an increase of pH per unit fluorescence under elevated CO2 concentrations, but no difference in pH from that under current conditions was observed for either S. costatum or T. nordenskioeldii, implying that Chaetoceros spp. can take up more CO2 in the future climate conditions. Our results of cell growth and pH change per unit fluorescence suggest that both C. debilis and C. didymus are better adapted to future oceanic conditions of rising water temperature and CO2 than are S. costatumand T. nordenskioeldii.d under four different conditions: present (pCO2: 400 ppm, temperature: 20°C), acidification (pCO2: 1000 ppm, temperature: 20°C), global warming (pCO2: 400 ppm, temperature: 25°C), and greenhouse (pCO2: 1000 ppm, temperature: 25°C) conditions. With incubation at higher temperatures, growth of S. costatum was suppressed, while C. debilis showed enhanced growth. Both C. didymus and T. nordenskioldii showed similar growth rates under current and elevated temperature. None of the four species appeared affected intheir cell growth by elevated CO2 concentrations. Chaetoceros spp. showed an increase of pH per unit fluorescence under elevated CO2 concentrations, but no difference in pH from that under current conditions was observed for either S. costatum or T. nordenskioeldii, implying that Chaetoceros spp. can take up more CO2 in the future climate conditions. Our results of cell growth and pH change per unit fluorescence suggest that both C. debilis and C. didymus are better adapted to future oceanic conditions of rising water temperature and CO2 than are S. costatumand T. nordenskioeldii.