Photosynthetic adaptation strategy of Ulva prolifera floating on the sea surface to environmental changes.
For 8 consecutive years, a green tide has originated in the southern Yellow Sea and spread to the Qingdao offshore area. The causative species, Ulva prolifera, always forms a very thick thallus mat that is capable of drifting long distances over long periods. During this process, although the thalli face disturbance by complex environmental factors, they maintain high biomass and proliferation. We hypothesized that some form of photosynthetic adaptation strategy must exist to protect the thalli. Therefore, we studied the different photosynthetic response characteristics of the surface and lower layers of the floating thallus mats, and investigated the physiological and molecular-level adaptation mechanisms. The results showed that: (1) U. prolifera has strong photosynthetic capability that ensures it can gain sufficient energy to increase its biomass and adapt to long-distance migration. (2) Surface layer thalli adapt to the complex environment by dissipating excess energy via photosynthetic quantum control (energy quenching and energy redistribution between PSII/PSI) to avoid irreversible damage to the photosynthetic system. (3) Lower layer thalli increase their contents of Chlorophyll a (Chl a) and Chlorophyll b (Chl b) and decrease their Chl a/Chl b ratio to improve their ability to use light energy. (4) U. prolifera has strong photosynthetic plasticity and can adapt to frequent exchange between the surface and lower layer environments because of wave disturbance. Pigment component changes, energy quenching, and energy redistribution between PSII/PSI contribute to this photosynthetic plasticity.
College of Marine Life Science, Ocean University of China, China. Electronic address: xyzhao331@gmail.com.
Xinyu
X
Zhao
College of Marine Life Science, Ocean University of China, China. Electronic address: tangxx@ouc.edu.cn.
Xuexi
X
Tang
College of Marine Life Science, Ocean University of China, China. Electronic address: qshdzhhx@126.com.
Huanxin
H
Zhang
College of Marine Life Science, Ocean University of China, China. Electronic address: tongfeiqu@163.com.
Tongfei
T
Qu
College of Marine Life Science, Ocean University of China, China. Electronic address: ywang@ouc.edu.cn.
Ying
Y
Wang
D000222:Adaptation, Physiological / Q000528:radiation effects; D002245:Carbon Dioxide / Q000032:analysis; D002681:China; D004579:Electron Transport / Q000528:radiation effects; D018506:Gene Expression Regulation, Plant / Q000528:radiation effects; D017343:Genes, Plant; D005843:Geography; D006863:Hydrogen-Ion Concentration; D008027:Light; D009792:Oceans and Seas; D010788:Photosynthesis / Q000528:radiation effects; D045331:Photosystem I Protein Complex / Q000378:metabolism; D045332:Photosystem II Protein Complex / Q000378:metabolism; D010860:Pigments, Biological / Q000378:metabolism; D010940:Plant Proteins / Q000235:genetics / Q000378:metabolism; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D054712:Salinity; D013499:Surface Properties; D013696:Temperature; D044445:Ulva / Q000502:physiology* / Q000528:radiation effects
D045331:Photosystem I Protein Complex; D045332:Photosystem II Protein Complex; D010860:Pigments, Biological; D010940:Plant Proteins; D012333:RNA, Messenger; D002245:Carbon Dioxide
Lower layer; Photoprotection; Photosynthetic plasticity; Surface layer; Thallus mat; Ulva prolifera