24-10-2012, 11:28 AM
Relationship between the Fluorescence Lifetime of Chlorophyll ‘a’ and Primary Productivity within the Mississippi River Plume and Adjacent Shelf Region
ABSTRACT
In situ measurements of chlorophyll fluorescence intensity have been widely used to estimate phytoplankton biomass.
However, because the fluorescence quantum yield of chlorophyll a in vivo can be highly variable, measurements of
chlorophyll fluorescence intensity cannot be directly correlated with phytoplankton biomass and do not provide information
on the physiological state of the phytoplankton under study. Conversely, lifetime-based measurements of chlorophyll
fluorescence provide a framework in which photosynthetic rates of phytoplankton can be analyzed according to phytoplankton
physiology. Along with the measurement of primary production and ambient nutrient concentrations within the Mississippi
River plume in the northern Gulf of Mexico, phytoplankton fluorescence lifetimes were measured using a Fluorescence
Lifetime Phytoplankton Analyzer (developed under a NASA Small Business Innovative Research contract to Ciencia, Inc.).
Variability of fluorescence lifetimes within the plume can be used as a background from which to interpret variations in the
maximum quantum yield of photochemistry. The extent to which nutrient and effluent loading in this dynamic coastal area
affect the photosynthetic performance of phytoplankton will be presented as a function of phytoplankton fluorescence
lifetimes.
ABSTRACT
In situ measurements of chlorophyll fluorescence intensity have been widely used to estimate phytoplankton biomass.
However, because the fluorescence quantum yield of chlorophyll a in vivo can be highly variable, measurements of
chlorophyll fluorescence intensity cannot be directly correlated with phytoplankton biomass and do not provide information
on the physiological state of the phytoplankton under study. Conversely, lifetime-based measurements of chlorophyll
fluorescence provide a framework in which photosynthetic rates of phytoplankton can be analyzed according to phytoplankton
physiology. Along with the measurement of primary production and ambient nutrient concentrations within the Mississippi
River plume in the northern Gulf of Mexico, phytoplankton fluorescence lifetimes were measured using a Fluorescence
Lifetime Phytoplankton Analyzer (developed under a NASA Small Business Innovative Research contract to Ciencia, Inc.).
Variability of fluorescence lifetimes within the plume can be used as a background from which to interpret variations in the
maximum quantum yield of photochemistry. The extent to which nutrient and effluent loading in this dynamic coastal area
affect the photosynthetic performance of phytoplankton will be presented as a function of phytoplankton fluorescence
lifetimes.