Paper Reviewed
Bao, M., Wang, J., Xu, T., Wu, H., Li, X. and Xu, J. 2019. Rising CO2 levels alter the response of the red macroalga Pyropia yezoensis under light stress. Aquaculture 501: 325-330.

Encompassing a semi-enclosed shallow basin between northern China and the Korean Peninsula, the Yellow Sea is often characterized by turbid waters that contain high levels of sediments and pollutants that are transported into the sea by rivers. Consequently, waters in this region often have less-than-optimum levels of light, which negatively impact macroalgal growth.

Pyropia yezoensis is one of the key macroalgal species inhabiting the challenging environment of the Yellow Sea, providing important economic and ecological services to the region. Given such significance, Bao et al. (2019) recently conducted an experiment to examine the interactive effects of elevated CO2 and light intensity on P. yezoensis in order to project its future growth. In doing so, they subjected samples of the red seaweed to one of three light intensity levels (low, medium or high, corresponding to irradiances of 53, 106 and 372 µmol photons m^-2 s^-1 of photosynthetically active radiation) under ambient (400 ppm) or elevated (1000 ppm) CO2 concentrations for a period of two weeks.

The results of their analysis revealed, not surprisingly, that the growth rates of P. yezoensis declined as light intensity decreased. However, they also observed that in the lowest light intensity treatment, elevated CO2 significantly enhanced the growth of this macroalgae. Consequently, Bao et al. conclude that "ocean acidification can alleviate the negative effect of low light conditions on the growth of P. yezoensis, suggesting that the primary productivity of this algae will benefit from the increase in CO2 in the future." And that is encouraging news for this and other macroalgal species that are currently growth-inhibited by low light conditions.