Temperature effect on respiration and photosynthesis of the symbiont-bearing planktonic foraminifera Globigerinoides ruber, Orbulina universa, and Globigerinella siphonifera

Lombard, F., J. Erez, E. Michel, L. Labeyrie

Limnol. Oceanogr., 54(1), 2009, 210-218 | DOI: 10.4319/lo.2009.54.1.0210

ABSTRACT: Respiration and photosynthesis of the planktonic foraminifera Globigerinoides ruber, Orbulina universa, and Globigerinella siphonifera and their symbiotic algae were calculated from measured dissolved oxygen gradients using microelectrodes, using different temperatures in dark and light (250 µmol photon m-2 s-1) conditions. At one temperature (24ºC) the respiration rate increased as a power function of the foraminiferan organic carbon mass with a 0.57 ± 0.18 exponent. The effect of temperature on respiration was quantified in two ways: by normalizing the rates to the organic carbon mass and by normalizing the observed rates to a constant temperature (24ºC). This latter normalization was also used for photosynthesis. The respiration rates increase as a function of temperature for all species and can be described either with a Q10 = 3.18 (±0.27) or with an Arrhenius temperature of TA = 10,293ºK (±768ºK). Similar calculations for net photosynthesis yielded a Q10 = 2.68 (±0.36) and a TA = 8766ºK (±1203ºK), and calculations for gross photosynthesis yielded a Q10 = 2.76 (60.29) and a TA = 9026ºK (±926ºK). For the species studied, the photosynthesis : respiration ratio varied from moderate for G. siphonifera (0.58) to very high (13) for O. universa. The high ratios indicate that photosynthesis is much higher than the carbon requirements for both foraminifera and symbiont growth. This excess carbon might be the source of organic exudates.

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