科研之友
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摘要
This research examined the application of the maximum quantum efficiency (F (v)/F (m)) and relative electron transport rate versus irradiance curves (rETR) as a rapid, sensitive assessment of Lake Erie phytoplankton nutrient status. I evaluated the potential benefits of the variable fluorescence parameters by comparing these parameters with chemical and physiological nutrient status assays. I tested the hypothesis that F (v)/F (m) and rETR curves could diagnose nutrient status in natural lake phytoplankton and be capable of discriminating which inorganic nutrient is limited temporally and spatially. F (v)/F (m) was on average highest in the more eutrophic west basin (WB) and lowest in the more oligotrophic central basin (CB). According to the chemical and physiological indicators, P deficiency was most severe in the CB during summer stratification and N deficiency was strongest in the WB during isothermal conditions. Like F (v)/F (m), rETR at light saturation (rETR(max)) and the initial slope of the rETR versus irradiance curve (alpha) decreased as the severity of N and P deficiency increased. Amendment with N or P stimulated increased F (v)/F (m), rETR(max), and alpha in N- and P-limited samples, respectively, and abolished the photoinhibition apparent in rETR curves of nutrient-limited samples. These results supported the view that the N and P deficiency assays, and corresponding variations of variable fluorescence parameters, were valid indicators of widely variable N and P deficiency in the phytoplankton, and could be used to provide a promising tool in determining phytoplankton nutrient status. Contrary to my hopes, it did not appear that rETR-irradiance curves could discriminate between N and P deficiency. Identification of the most limiting nutrient still demanded additional information beyond the variable fluorescence measurements.
- 出版日期2014-3
