Eutrophication-induced phosphorus limitation in the Mississippi River plume: Evidence from fast repetition rate fluorometry uri icon

abstract

  • We assessed nutrient limitation in the Mississippi River plume and Louisiana continental shelf during the summer of 2002 (0408 July). We measured nutrient concentrations, alkaline phosphatase (AP) activities, chlorophyll a (Chl a) concentrations, and four fast repetition rate fluorescence (FRRF) parameters: the maximum quantum yield of photochemistry in photosystem II (PSII), Fv:Fm; the functional absorption cross section for PSII, PSII; the time for photosynthetic electron transport on the acceptor side of PSII, Qa; and the connectivity factor, p, in 24hlong nutrient addition bioassays near the Mississippi River delta. Low phosphorus (P) concentrations, elevated inorganic nitrogentophosphorus ratios, high AP activities, and Chl a increases in response to P additions in the bioassays all indicated phosphorus limitation that was confirmed by the response of FRRF parameters. This is the first study to use FRRF to confirm results from basic oceanographic methods to demonstrate phosphorus limitation in a marine setting. Fv:Fm and p responded positively to phosphorus addition, while PSII and Qa decreased in the same treatments. When nitrate alone was added, none of the measured parameters differed significantly from the control. We therefore suggest that FRRF can be used to rapidly detect phosphorus limitation in marine ecosystems.

published proceedings

  • LIMNOLOGY AND OCEANOGRAPHY

author list (cited authors)

  • Sylvan, J. B., Quigg, A., Tozzi, S., & Ammerman, J. W.

citation count

  • 65

complete list of authors

  • Sylvan, JB||Quigg, A||Tozzi, S||Ammerman, JW

publication date

  • November 2007

publisher