Presence of Prochlorococcus in the aphotic waters of the western Pacific Ocean
- 1State Key Laboratory of Marine Environmental Science, Xiamen University, Xiamen 361005, China
- 2Marine Laboratory, Nicholas School of the Environment, Duke University, Beaufort 28516, North Carolina, USA
- 3Physical Oceanography Laboratory, Ocean University of China, Qingdao 266100, China
- 4Institute of Oceanology, Chinese Academy of Sciences, Qingdao 266071, China
- 5State Key Laboratory of Marine Geology, Tongji University, Shanghai 200092, China
Abstract. Prochlorococcus, the smallest but most abundant marine primary producer, plays an important role in carbon cycling of the global ocean. As a phototroph, Prochlorococcus is thought to be confined to the euphotic zone, with commonly observed maximum depths of ~ 150–200 m, but here we show for the first time the substantial presence of Prochlorococcus populations in the dark ocean ("deep Prochlorococcus" hereafter). Intensive studies at the Luzon Strait in the western Pacific Ocean show that the deep Prochlorococcus populations are exported from the euphotic zone. Multiple physical processes including internal solitary waves could be responsible for the transportation. These findings reveal a novel mechanism for picoplankton carbon export other than the known mechanisms such as sinking of phytodetritus and aggregates or grazing-mediated transportation.