Coastal waters are impacted by a range of natural and anthropogenic factors, which superimpose on effects of increasing atmospheric CO2, resulting in dynamically changing seawater carbonate chemistry. Research on influences of dynamic pH/pCO2 on marine ecosystem is still in its infancy, although effects of ocean acidification have been extensively studied. In the present study, we manipulated the culturing pH/pCO2 to investigate physiological performance and fatty acid (FA) composition of two coastal diatoms Skeletonema costatum and Thalassiosira weissflogii in both steady and fluctuating pH/pCO2 regimes. Generally, seawater acidification and pH variability showed neutral or positive effects on specific growth rate, chlorophyll a, and biogenic silica contents of two species. Elevated pCO2 inhibited net photosynthetic rate by 27 % and enhanced mitochondrial respiration rate of S. costatum by 36 % in the steady pH regime, while these rates were unaltered by elevated pCO2 in the fluctuating regime. Elevated pCO2 leaded to 21 % lower saturated FA and twofold increase in polyunsaturated FA proportions of T. weissflogii. Our results indicate that costal acidification could affect primary production in a different way from ocean acidification. Together with the altered nutritional quality of prey for higher trophic levels, coastal acidification might have far-reaching consequence for marine ecosystem functioning.
Shang Y., Qiu J., Weng Y., Wang X., Zhang D., Zhou Y., Xu J. & Li F., 2024. Effects of pH/pCO2 fluctuation on photosynthesis and fatty acid composition of two marine diatoms, with reference to consequence of coastal acidification. EGUsphere. Article.
