||Fluorescence Assessment of the Maximum Quantum Efficiency of Photosynthesis in the Western North Atlantic.
Geider, R. J. ;
Greene, R. M. ;
Kolber, Z. ;
MacIntyre, H. L. ;
Falkowski, P. G. ;
||Delaware Univ., Lewes. Coll. of Marine Studies. ;Brookhaven National Lab., Upton, NY. Oceanographic and Atmospheric Sciences Div.;Environmental Protection Agency, Narragansett, RI. Environmental Research Lab.;Department of Energy, Washington, DC.;National Science Foundation, Arlington, VA.
||DE-AC02-76CH00016, NSF-OCE89-15084; EPA/600/J-94/220 ; ERLN-X201
Plant ecology ;
Marine biology ;
Atlantic Ocean ;
Aquatic ecosystems ;
Quantum efficiency ;
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The maximum quantum efficiency (phiII) of phytoplankton photosystem II photochemistry was assessed using a pump and probe fluorometer on an offshore-onshore transect from the oligotrophic blue waters of the western Sargasso Sea to the eutrophic waters of lower Delaware Bay. Low values of the ratio of variable to maximum fluorescence (Fv/Fm) of dark adapted samples provided evidence for reduced quantum efficiences in surface waters (z = 10 m) of the Sargasso Sea. In contrast, higher values of Fv/Fm in estuarine samples indicated near maximal phiII in lower Delaware Bay, with intermediate values of Fv/Fm observed over the continental shelf. Variations of Fv/Fm in surface samples (5 or 10 m depth) were associated with changes in hydrographic features that were consistent with the hypothesis that reduced values of phiII in Sargasso Sea surface waters were due to nutrient limitation of phytoplankton photosynthetic energy conversion.