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"autofluorescence" and have become a routine component of the multiparameter flow
cytometric analyses of laboratory and field phytoplankton samples (Cullen et al., 1988).
Using flow cytometry, separation of photosynthetic cells from heterotrophic organisms and
detrital materials is routinely achieved. Flow cytometry has the ability to distinguish between
individual species or groups of related species within a single sample (Olson et al., 1989b).
The ability to detect both chI and phycoerythrin fluorescence with flow cytometry has been
instrumental in demonstrating the ubiquitous distribution of marine Synechococcus species and
their contribution to algal biomass and productivity (Olson et al., 1988, 1989a). Fluorescence
and particle size data were also central to the recent identification of free-living marine
prochlorophytes (Chisholm et al., 1988).
In addition to these taxonomic considerations, fluorescence analyses from flow cytometry
measurements have also been used to evaluate the photosynthetic physiology of algal
populations in laboratory and field studies. Sosik et al. (1989) investigated the relationship
between flow cytometric fluorescence signals and pigment composition between species and
with adaptation to various light conditions. Perry and Porter (1989) demonstrated the
relationship between fluorescence per cell measured by flow cytometry and the effective
cellular absorption cross-section. Several field studies have shown changes in fluorescence
per cell that appear to be linked to light adaptation (Olson et al., 1989a; Demers et al., 1989;
Campbell et al., 1989).
All of the fluorescence techniques described in previous sections, which may be used for
estimating photosynthetic capacity or· physiological state, rely on quantifying relative
fluorescence yields by scaling of fluorescence data either between measurements on a single
sample or between samples. With dilute algal suspensions or algae concentrated on filters,
fluorescence scaling presents minor but correctable problems in instruments with a fixed
excitation and detection geometry. Internal normalization to Fo and Fm fluorescence levels
using the light doubling and modulated excitation techniques provides the most unambiguous
scaling of data. Unfortunately, these scaling procedures are not easily applied to flow
cytometric analyses in which individual cells are entrained in a rapidly flowing medium. Thus
there is considerable uncertainty as to the nature and interpretation of fluorescence signals
measured in flow cytometry (Neale et al., 1989). Several problems must be addressed.
"autofluorescence" and have become a routine component of the multiparameter flow
cytometric analyses of laboratory and field phytoplankton samples (Cullen et al., 1988).
Using flow cytometry, separation of photosynthetic cells from heterotrophic organisms and
detrital materials is routinely achieved. Flow cytometry has the ability to distinguish between
individual species or groups of related species within a single sample (Olson et al., 1989b).
The ability to detect both chI and phycoerythrin fluorescence with flow cytometry has been
instrumental in demonstrating the ubiquitous distribution of marine Synechococcus species and
their contribution to algal biomass and productivity (Olson et al., 1988, 1989a). Fluorescence
and particle size data were also central to the recent identification of free-living marine
prochlorophytes (Chisholm et al., 1988).
In addition to these taxonomic considerations, fluorescence analyses from flow cytometry
measurements have also been used to evaluate the photosynthetic physiology of algal
populations in laboratory and field studies. Sosik et al. (1989) investigated the relationship
between flow cytometric fluorescence signals and pigment composition between species and
with adaptation to various light conditions. Perry and Porter (1989) demonstrated the
relationship between fluorescence per cell measured by flow cytometry and the effective
cellular absorption cross-section. Several field studies have shown changes in fluorescence
per cell that appear to be linked to light adaptation (Olson et al., 1989a; Demers et al., 1989;
Campbell et al., 1989).
All of the fluorescence techniques described in previous sections, which may be used for
estimating photosynthetic capacity or· physiological state, rely on quantifying relative
fluorescence yields by scaling of fluorescence data either between measurements on a single
sample or between samples. With dilute algal suspensions or algae concentrated on filters,
fluorescence scaling presents minor but correctable problems in instruments with a fixed
excitation and detection geometry. Internal normalization to Fo and Fm fluorescence levels
using the light doubling and modulated excitation techniques provides the most unambiguous
scaling of data. Unfortunately, these scaling procedures are not easily applied to flow
cytometric analyses in which individual cells are entrained in a rapidly flowing medium. Thus
there is considerable uncertainty as to the nature and interpretation of fluorescence signals
measured in flow cytometry (Neale et al., 1989). Several problems must be addressed.