Photoinhibiton of photosynthesis in marine macrophytes of the South China Sea

Photoinhlbltlon of photosynthesis was Investigated along the coast of Hainandao, an Island in the troplcal zone of the South Chlna Sea, In autumn 1990 Experiments were carned out with a portable fluorometer and an oxygen-measur~ng system constructed espec~ally for field studies The dady courses of photoinh~b~t~on of different algal species and of a seagrass were inveshgated Results showed that the highest degree of photoinhlbltion occurred between noon and afternoon In the late afternoon and in the evening photosynthet~c capacity recovered The extent of photo~nhibition depended on the turbidity of the water e g on a sunny day wth hlgh photon fluence rates (PFR) the algae were hardly photoinhib~ted when the surf and hence, the turbidity was hlgh The photosynthet~c capac~ty depended exclusively on the PFR and did not underlie any circadian rhythms in the photo synthehc activity Different species show different sensitiv~ties at comparable hght condltlons, reflecting the importance of photoinhtbition for the algal zonatlon pattern in the llttoral