Fluorescence-based maximal photochemical efficiency, Fv/Fm, is widely used as an indicator to photosynthetic competence in marine systems. It has been considered a useful parameter diagnosing the nutrient stress on ph...Fluorescence-based maximal photochemical efficiency, Fv/Fm, is widely used as an indicator to photosynthetic competence in marine systems. It has been considered a useful parameter diagnosing the nutrient stress on phytoplankton photosynthesis, but many studies argue its usefulness. In the present study, we try to find a temporal relationship between Fv/Fm and nitrogen concentration, and provide a possible explanation on the controversy. We continuously measured Fv/Fm and nitrogen concentration once every 10 days from September 2003 to March 2004 at two stations in Jiaozhou Bay, northern China. It was found that Fv/ffm did not significantly correlate to synchronous nitrogen concentration, but the variation （i.e. the change between two adjacent cruises） of nitrogen concentration of the previous cruise and the variation ofFv/Fm of the current cruise were strongly correlated. This result indicates that a time lag exists between the variation of nutrient status and the subsequent Fv/Fm response. Length of the time lag seems just matched the interval of our measurements （10 days）. In the field, direct dependence of Fv/Fm on nitrogen concentration may not be found because of the lagged response of Fv/Fm to nitrogen concentration variations or physiological acclimation. Our results provide a possible way to explain the previously reported conflicting results on the relationship between Fv/Fm and nutrient status. To give a more-accurate estimate about the length of the time lag, an investigation that includes more frequent measurements is needed.展开更多
基金Supported by the Public Science and Technology Research Funds of Ocean(No.200905019)the Science Foundation of Young Scientist,SOA(No.2011129)+1 种基金the Outstanding Young & Middle Scientist of Shandong Province(No.BS2010HZ018)the Taishan Scholar Fund of Aquatic Animal Nutrition and Feed to ZHANG Limin
文摘Fluorescence-based maximal photochemical efficiency, Fv/Fm, is widely used as an indicator to photosynthetic competence in marine systems. It has been considered a useful parameter diagnosing the nutrient stress on phytoplankton photosynthesis, but many studies argue its usefulness. In the present study, we try to find a temporal relationship between Fv/Fm and nitrogen concentration, and provide a possible explanation on the controversy. We continuously measured Fv/Fm and nitrogen concentration once every 10 days from September 2003 to March 2004 at two stations in Jiaozhou Bay, northern China. It was found that Fv/ffm did not significantly correlate to synchronous nitrogen concentration, but the variation （i.e. the change between two adjacent cruises） of nitrogen concentration of the previous cruise and the variation ofFv/Fm of the current cruise were strongly correlated. This result indicates that a time lag exists between the variation of nutrient status and the subsequent Fv/Fm response. Length of the time lag seems just matched the interval of our measurements （10 days）. In the field, direct dependence of Fv/Fm on nitrogen concentration may not be found because of the lagged response of Fv/Fm to nitrogen concentration variations or physiological acclimation. Our results provide a possible way to explain the previously reported conflicting results on the relationship between Fv/Fm and nutrient status. To give a more-accurate estimate about the length of the time lag, an investigation that includes more frequent measurements is needed.
