Ocean acidification and warming caused by elevated CO2 are urgent problems facing the marine ecological environment. With the strengthening of environmental governance in China, anthropogenic inputs of terrestrial phosphorus into the coastal ocean have drastically decreased, resulting in frequent phosphorus deficiency in seawater. These environmental factors in the future may affect algal growth, photosynthesis and yield. As an important economic macroalga suitable for large-scale cultivation, Gracilariopsis lemaneiformis is also potentially affected by the coupling of ocean acidification, warming and phosphorus deficiency. In this study, G. lemaneiformis was cultured outdoors under two pCO2 levels (LC, 400 μatm; HC, 1000 μatm), two temperatures (LT, 20 ℃; HT, 24 ℃) and two phosphorus concentrations (LP, 0.1 μmol L−1; HP, 10 μmol L−1) to investigate its growth and photosynthetic performance. The results showed that LP significantly decreased the relative growth rates (RGR) and the maximum photosynthesis rate (Pm) of G. lemaneiformis both under LC and HC conditions. Under P depletion condition, the effects of warming and ocean acidification on the growth and photosynthetic performance of G. lemaneiformis showed an opposite trend, that is, HC caused a decrease in the growth, Pm, maximum relative electron transfer rate (rETRmax) and light utilization efficiency (α) from the rapid light response curve of G. lemaneiformis, and HT improved these parameters. Under LP condition, HC significantly inhibited the RGR of G. lemaneiformis in the LT group but had no significant effect on RGR in the HT group. Additionally, under LP condition, HC insignificantly affected PE and PC contents in the LT group, but significantly reduced these contents in the HT group. These findings suggest that phosphorus deficiency results in a decline in the growth of G. lemaneiformis and, under LP condition, the inhibition effect of ocean acidification on the growth of G. lemaneiformis could be mitigated by warming. This study provides scientific guidance for the field cultivation and selective breeding of G. lemaneiformis in phosphorus-deficient seawater under global climate change.
Zhou W., Wu H., Shi M., Chen Z., Wang J. & Xuet J., in press. Phosphorus deficiency regulates the growth and photophysiology responses of an economic macroalga Gracilariopsis lemaneiformis to ocean acidification and warming. Journal of Applied Phycology. Article.
