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 (P_m) 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, P_m, maximum relative electron transfer rate (rETR_max) 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.

_{CO 2}升高引起的海洋酸化和变暖是海洋生态环境面临的紧迫问题。随着我国环境治理的加强，人为向近海海洋输入的陆地磷大幅减少，导致海水缺磷现象频繁发生。这些环境因素未来可能会影响藻类的生长、光合作用和产量。作为适合规模化养殖的重要经济大型藻类，龙须菜也可能受到海洋酸化、变暖和缺磷耦合的潜在影响。本研究中，龙须菜在两种p CO ₂浓度（LC，400 μatm；HC，1000 μatm）、两种温度（LT，20 ℃；HT，24 ℃）和两种磷浓度（LP，0.1 μmol）下进行户外培养。 L ^-1 ; HP, 10 μmol L ^-1 ) 以研究其生长和光合性能。结果表明，在LC和HC条件下， LP均显着降低了龙须菜的相对生长速率（RGR）和最大光合速率（P _m） 。缺磷条件下，变暖和海洋酸化对龙须菜生长和光合性能的影响呈现相反的趋势，即HC导致生长、P _m、最大相对电子转移速率(rETR _max )下降。从龙须菜的快速光响应曲线中得到了光利用效率（α），HT对这些参数进行了改进。LP条件下，HC显着抑制LT组龙须菜RGR ，但对HT组龙须菜RGR无显着影响。此外，在LP条件下，HC对LT组PE和PC含量影响不显着，但显着降低HT组这些含量。这些结果表明，磷缺乏导致龙须菜生长下降，并且在LP条件下，海洋酸化对龙须菜生长的抑制作用可以通过变暖来减轻。该研究为全球气候变化背景下缺磷海水中龙须菜的田间栽培和选育提供科学指导。