Effect of aeration rates on growth rates and natural abundance 13C/12C ratio of Phaeodactylum tricornutum

Abstract

Studies of the photosynthetic assimilation of inorganic carbon by the diatom Phaeodactylum tricornutum showed that the aeration system has a major influence on the dissolved inorganic carbon (DIC) concentration and hence growth rates. The stable isotope ratio of 13C/12C was used as an indicator of carbon limitation. Algae from a well-aerated culture (2dm3 min-1) had a specific growth rate of 1.58 d-1, reached a cell density of 12×106 cell cm3, displayed a constant δ13C value of -23.6‰ and the inorganic carbon concentration of the growth media remained above 1.5 mol m-3. Algae from non-aerated cultures had the lowest growth rate (0.42 d-1 after 4.5 d), were able to consume DIC faster than the resupply of atmospheric CO2, and the DIC concentration reached 0.68 mol m-3 after 6.5 d of culture. The δ13C value of these algae rose to -17.83‰. Algae that were poorly aerated (0.1 dm3 min-1) had intermediate growth rates (0.72 d-1 at 4.5 d) and reduced the DIC concentration to 0.17 mol m-3 after 6.5 d. Algae grown under these conditions displayed the highest δC values, -12.3‰. Aeration (2 dm3 min-1) of a previously unaerated culture restored the DIC concentration of the culture medium to 2.0 mol m-3 and reduced the δ13C from -14.0‰ to -23.4‰. -Authors