Inferred influence of nutrient availability on the relationship between Sun-induced chlorophyll fluorescence and incident irradiance in the Bering Sea
This study examines variability in the relationship between Sun-induced chlorophyllfluorescence and incident solar irradiance as a potential diagnostic of the nutritional statusof phytoplankton. The study site is the Bering Sea, where two optical drifters werecaught for more than 100 days in an anti...
| Published in: | Journal of Geophysical Research |
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| Main Authors: | , , , |
| Format: | Article in Journal/Newspaper |
| Language: | English |
| Published: |
Amer Geophysical Union
2008
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| Subjects: | |
| Online Access: | https://doi.org/10.1029/2007JC004355 http://ecite.utas.edu.au/108989 |
| Summary: | This study examines variability in the relationship between Sun-induced chlorophyllfluorescence and incident solar irradiance as a potential diagnostic of the nutritional statusof phytoplankton. The study site is the Bering Sea, where two optical drifters werecaught for more than 100 days in an anticyclonic eddy, while two others provided datafrom adjacent waters. Estimates of fluorescence emission normalized to the absorption oflight by pigments were analyzed as a function of irradiance to describe variability ofthe quantum yield of fluorescence. Yields in bright sunlight and under lower light variedby a factor of 5 or more on the scale of days to weeks. For the one drifter that remained inthe high-velocity region of the eddy, there was a lagged correlation between the eddyrotation period and fluorescence parameters, with higher fluorescence yields in both lowand high irradiance associated with slower rotation. Since nutrient input to the photiczone may increase with increasing shear of the eddy flow, this is consistent with theestablished suggestion that Sun-induced fluorescence increases with nutrient stress inphytoplankton. Independent measurements of variable fluorescence (Fv/Fm, an indicatorof photosynthetic efficiency) further support this interpretation. However, modeling showsthat the established hypothesis of competition between photosynthesis and fluorescencefor absorbed photons (i.e., photochemical quenching), with high fluorescence yieldsreflecting photosynthetic debility, does not apply near the sea surface, wherephotosynthesis is saturated, and dissipation of excess absorbed radiation bynonphotochemical quenching is the dominant influence on fluorescence yield. |
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