A comparative study of the sensitivity of F v/F m to phosphorus limitation on four marine algae

We studied the effects of nitrogen (N) and phosphorus (P) supply on F (v)/F (m) (maximal quantum yield of photosystem II) in the algae Chaetoceros debilis, Dicrateria inornata, Platymonas subcordiformis and Heterosigma akashiwo to determine the sensitivity of F (v)/F (m) to P-limitation of the four species. Obvious decrease of F (v)/F (m) value was monitored in periods of P-depletion, the decrease showing different magnitudes among algal species. A more clear decrease of F (v)/F (m) in Platymonas subcordiformis and Heterosigma akashiwo was observed, compared with that in Chaetoceros debilis and Dicrateria inornata. After the re-supply of P, the index F (v)/F (m) of the four species all recovered quickly in 24 h. Cell division was maintained and chlorophyll content continued to increase until the end of the experiment in Platymonas subcordiformis and Heterosigma akashiwo, while in Chaetoceros debilis and Dicrateria inornata, the division stopped in the later period when the growth of organisms came into the stationary phase. The most obvious respond of chlorophyll content to P-additions was observed in Heterosigma akashiwo culture in 24 h. The sensitivity of F (v)/F (m) to nutrient limitations is different among algal species, and much should be done to improve the application of this index.