Dissolved free amino acids and polyamines are two major dissolved organic nitrogen sources for marine bacterioplankton in the northern slope of the South China Sea. - Liu, Qian; Lu, Ye; Xu, Jun; Zhu, Zhuo-Yi; Yuan, Yeping; Ma, Wen-Chao; Qian, Yurong; Wang, Chun-Sheng; Xu, Xue-Wei (Biogeochemistry, 2022)