Growth, photosynthesis and nutrient uptake by Grateloupia livida (Halymeniales, Rhodophyta) in response to different carbon levels

Abstract:

Grateloupia livida is a commercially important red macroalgal species. In the present study, thalli of G. livida, collected from Nan'ao Island, China, were cultured at different levels of CO₂ (c. 1000, 390 and 50 ppm) to examine the growth and physiology and how its plasticity may affect photosynthesis at different carbon levels. The pH-drift experiments showed that G. livida could reach a final pH value of 9.75. Carbonic anhydrase (CA) activity was detected potentiometrically with both thalli and homogenates of G. livida. These implied that G. livida used HCO₃⁻ as a source of inorganic carbon for photosynthesis and that this was mediated by extracellular CA activity. Thalli of G. livida grown at low CO₂ reduced the relative growth rate (RGR), both the PO₄³⁻ and NO₃⁻ uptake rates, nitrate reductase activity and photochemical activity compared with the algae grown at ambient CO₂. Moreover, the RGR and the initial slope of the rapid light curves (α) were inhibited by the high CO₂ level in the seawater. The results indicated that either raised or lowered CO₂ in culture were unfavourable environmental factors for growth and photosynthesis of G. livida.

Key Words::

• Carbon
• Grateloupia livida
• Growth
• Inorganic carbon utilization
• Nutrient uptake
• Photosynthesis

ACKNOWLEDGEMENTS

This study was supported by the National Natural Science Foundation of China (No. 41276148) and Guangdong Science and Technology Bureau (2015A020216004).