The feasibility of Fv/Fm on judging nutrient limitation of marine algae through indoor simulation and in situ experiment

Maximum photochemical efficiency of photosystem II (Fv/Fm) has been used widely to assess the impact of environmental stressors on phytoplankton. In this study, the Fv/Fm responses of 14 kinds of typical marine algae were investigated under nitrogen (N) and phosphorus (P) limitation conditions through indoor simulation and in situ experiment. The results showed that 14 species exhibited various maximum of Fv/Fm from 0.43 to 0.72 and the sequence of different genus of algae was: Chlorophyta (0.71) > Cryptophyta (0.62) > Bacillariophyta (0.60) approximate to Chrysophyta (0.60) > Xanthophyceae (0.54) > Pyrrophyta (0.51). Fv/Fm of 12 species decreased significantly in the absence of N and P and recovered gradually after resupplying nutrients, while the other 2 species (Srippsiellla trochoidea and Prorocentrum donghaiense) seemed to be less sensitive to N and P limitation and changed little throughout the process. In addition, Fv/Fm was applied to the nutrients enrichment experiments in situ in the Yangtze River Estuary and the East China Sea shelf. It was found that Fv/Fm could be used to judge the limiting factor when the community structure remains unchanged. The results indicated that it was feasible to utilize Fv/Fm as an auxiliary probe to judge nutrient limitation on phytoplankton.