Lagged response of phytoplanktonic photosynthetic competence to variation of nitrogen concentration in Jiaozhou Bay, China |
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Authors: | Xiang Fu Fan Li Zhenbo Lü Hongchang Zhai Boping Han |
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Institution: | 1. Shandong Provincial Key Laboratory of Restoration for Marine Ecology, Shandong Marine Fisheries Research Institute, Yantai, 264006, China 2. Second Institute of Oceanography, SOA, Hangzhou, 310012, China 3. Institute of Hydrobiology, Jinan University, Guangzhou, 510632, China
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Abstract: | Fluorescence-based maximal photochemical efficiency, F v/F m, 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 F v/F m and nitrogen concentration, and provide a possible explanation on the controversy. We continuously measured F v/F m 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 F v/F m 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 of F v/F m of the current cruise were strongly correlated. This result indicates that a time lag exists between the variation of nutrient status and the subsequent F v/F m response. Length of the time lag seems just matched the interval of our measurements (10 days). In the field, direct dependence of F v/F m on nitrogen concentration may not be found because of the lagged response of F v/F m to nitrogen concentration variations or physiological acclimation. Our results provide a possible way to explain the previously reported conflicting results on the relationship between F v/F m 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. |
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Keywords: | maximal photochemical efficiency nitrogen correlation analysis time lag phytoplankton |
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