Synergism between elevated pCO2 and temperature on the Antarctic sea ice diatom Nitzschia lecointei

[摘要] Polar oceans are particularly susceptible to ocean acidification and warming.Diatoms play a significant role in sea ice biogeochemistry and provide animportant food source to grazers in ice-covered oceans, especially duringearly spring. However, the ecophysiology of ice-living organisms has receivedlittle attention in terms of ocean acidification. In this study, thesynergism between temperature and partial pressure of CO₂ (pCO₂)was investigated in relationship to the optimal growth temperature of theAntarctic sea ice diatom Nitzschia lecointei. Diatoms were kept incultures at controlled levels of pCO₂ (∼390 and∼960 μatm) and temperature (−1.8 and 2.5 °C) for14 days. Synergism between temperature and pCO₂ was detected in growthrate and acyl lipid fatty acid (FA) content. Optimal growth rate was observedaround 5 °C in a separate experiment. Carbon enrichment onlypromoted (6%) growth rate closer to the optimal growth, but not at thecontrol temperature (−1.8 °C). At −1.8 °C and at∼960 μatm pCO₂, the total FA content was reducedrelative to the ∼390 μatm treatment, although no differencebetween pCO₂ treatments was observed at 2.5 °C. A largeproportion (97%) of the total FAs comprised on average ofpolyunsaturated fatty acids (PUFA) at −1.8 °C. Cellular PUFAcontent was reduced at ∼960 relative to ∼390 μatmpCO₂. Effects of carbon enrichment may be different depending on oceanwarming scenario or season, e.g. reduced cellular FA content in response toelevated CO₂ at low temperatures only, reflected as reduced food qualityfor higher trophic levels. Synergy between warming and acidification may beparticularly important in polar areas since a narrow thermal window generallylimits cold-water organisms.

[学科分类] 地球化学与岩石