Elevated temperature relieves phosphorus limitation of marine unicellular diazotrophic cyanobacteria
Lixia Deng, Shunyan Cheung, Chang‐Keun Kang, Kailin Liu, Xiaomin Xia, Hongbin Liu
Abstract
Abstract The warming ocean is expected to be more phosphorus (P) limited due to increasing stratification. P is a major limiting nutrient of marine diazotrophs, while the interactive effect of temperature elevation and P limitation on marine unicellular diazotrophs is unknown. Here, we examined the physiology of a major unicellular diazotroph, Crocosphaera watsonii , grown under P‐limited and P‐replete conditions at 25°C, 28°C, and 31°C. Growth, N 2 , and CO 2 fixation rates of C. watsonii increased with temperature under P limitation, and growth rates were similar between P‐limited and P‐replete treatments at 31°C. At high temperature, the P use efficiencies for N 2 and CO 2 fixation under P limitation were more than twice higher than under P‐replete conditions. Expression of genes involved in P acquisition, intracellular recycling, and substitution in C. watsonii was upregulated at higher temperature under P limitation. These results suggest that P limitation in C. watsonii was relieved with elevated temperature through various temperature‐dependent economic strategies on P metabolism. Through meta‐analysis of a field data set using general additive model, we found that C. watsonii abundance was correlated mainly with temperature and phosphate, and predicted to increase significantly with further warming.