title: Contrasting Photophysiological Characteristics of Phytoplankton Assemblages in the Northern South China Sea.
abstract: The growth of phytoplankton and thus marine primary productivity depend on photophysiological performance of phytoplankton cells that respond to changing environmental conditions. The South China Sea (SCS) is the largest marginal sea of the western Pacific and plays important roles in modulating regional climate and carbon budget. However, little has been documented on photophysiological characteristics of phytoplankton in the SCS. For the first time, we investigated photophysiological characteristics of phytoplankton assemblages in the northern South China Sea (NSCS) using a real-time in-situ active chlorophyll a fluorometry, covering 4.0 × 105 km2. The functional absorption cross section of photosystem II (PSII) in darkness (σPSII) or under ambient light (σPSII') (A2 quanta-1) increased from the surface to deeper waters at all the stations during the survey period (29 July to 23 August 2012). While the maximum (Fv/Fm, measured in darkness) or effective (Fq'/Fm', measured under ambient light) photochemical efficiency of PSII appeared to increase with increasing depth at most stations, it showed inverse relationship with depth in river plume areas. The functional absorption cross section of PSII changes could be attributed to light-adapted genotypic feature due to niche-partition and the alteration of photochemical efficiency of PSII could be attributed to photo-acclimation. The chlorophyll a fluorometry can be taken as an analog to estimate primary productivity, since areas of higher photochemical efficiency of PSII coincided with those of higher primary productivity reported previously in the NSCS.
authors.affiliation: State Key Laboratory of Marine Environmental Science, Xiamen University, Xiamen 361005, China.
authors.forename: Peng
authors.initials: P
authors.lastname: Jin
authors.affiliation: State Key Laboratory of Marine Environmental Science, Xiamen University, Xiamen 361005, China.
authors.forename: Guang
authors.initials: G
authors.lastname: Gao
authors.affiliation: State Key Laboratory of Marine Environmental Science, Xiamen University, Xiamen 361005, China.
authors.forename: Xin
authors.initials: X
authors.lastname: Liu
authors.affiliation: State Key Laboratory of Marine Environmental Science, Xiamen University, Xiamen 361005, China.
authors.forename: Futian
authors.initials: F
authors.lastname: Li
authors.affiliation: State Key Laboratory of Marine Environmental Science, Xiamen University, Xiamen 361005, China.
authors.forename: Shanying
authors.initials: S
authors.lastname: Tong
authors.affiliation: State Key Laboratory of Marine Environmental Science, Xiamen University, Xiamen 361005, China.
authors.forename: Jiancheng
authors.initials: J
authors.lastname: Ding
authors.affiliation: Marine Biology Institute, Shantou University, Shantou, Guangdong 515063, China.
authors.forename: Zhihai
authors.initials: Z
authors.lastname: Zhong
authors.affiliation: State Key Laboratory of Marine Environmental Science, Xiamen University, Xiamen 361005, China.
authors.forename: Nana
authors.initials: N
authors.lastname: Liu
authors.affiliation: State Key Laboratory of Marine Environmental Science, Xiamen University, Xiamen 361005, China.
authors.forename: Kunshan
authors.initials: K
authors.lastname: Gao
mesh_terms: D002138:Calibration; D002681:China; D002734:Chlorophyll / Q000502:physiology; D000077194:Chlorophyll A; D002980:Climate; D004583:Electrons; D005838:Genotype; D005843:Geography; D009792:Oceans and Seas; D055668:Photochemical Processes; D010788:Photosynthesis; D045332:Photosystem II Protein Complex / Q000502:physiology; D010839:Phytoplankton / Q000502:physiology*
chemical_list: D045332:Photosystem II Protein Complex; D002734:Chlorophyll; D000077194:Chlorophyll A