371
Coccolithophores have been receiving increased attention of late because their coccoliths can
drastically alter water reflectance properties during blooms (Holligan et al. 1983; Ackleson
et al. 1988), and the production of dimethyl sulfide by these cells may be important in
affecting weather patterns (Charlson et al. 1987). Furthermore, their CaC03 precipitating
capabilities could be an important consideration in the global carbon budget. Flow cytometric
analysis could greatly facilitate the study of their ecology.
Optics
Particles play an important role in determining the bulk optical properties of seawater, and
measurements of the optical properties of individual particles by flow cytometry are of
obvious value in this context (Ackleson and Robins 1990). Progress has been made in
interpreting flow cytometric measurements of both chlorophyll fluorescence and light
scattering by phytoplankton cells with this in mind.
Fluorescence: Chlorophyll fluorescence measurements of bulk water samples are widely used
in biological oceanography for studying phytoplankton biomass and physiology. The unique
place of flow cytometry in the suite of in vivo fluorescence techniques is now being
appreciated (Cullen et al. 1988), and a biophysical framework within which we can interpret
these measurements of individual cells is being constructed (Neale et al. 1989; see chapter by
T. Owens, this volume). Because fluorescence is highly dependent on instrument
characteristics such as time scale and excitation light intensity, and since flow cytometers used
in oceanography vary widely in these characteristics, empirical evaluation of flow cytometric
fluorescence signals has been a necessary first step.
Sosik et al. (1989) analyzed flow cytometric fluorescence measurements from three species
of phytoplankton and found that variations in fluorescence/chlorophyll a could be accounted
for by considering the accessory pigments absorbing the light in each species (Fig. 12). The
dinoflagellate in this study (Amphidinium carteri) contained more accessory pigments per
chlorophyll a than either of the other species examined (a diatom and a coccolithophore), so
that more of the excitation light was absorbed and passed on to chlorophyll a, which then
fluoresced. We also suggested that pigment ratios could account for differences in results
Coccolithophores have been receiving increased attention of late because their coccoliths can
drastically alter water reflectance properties during blooms (Holligan et al. 1983; Ackleson
et al. 1988), and the production of dimethyl sulfide by these cells may be important in
affecting weather patterns (Charlson et al. 1987). Furthermore, their CaC03 precipitating
capabilities could be an important consideration in the global carbon budget. Flow cytometric
analysis could greatly facilitate the study of their ecology.
Optics
Particles play an important role in determining the bulk optical properties of seawater, and
measurements of the optical properties of individual particles by flow cytometry are of
obvious value in this context (Ackleson and Robins 1990). Progress has been made in
interpreting flow cytometric measurements of both chlorophyll fluorescence and light
scattering by phytoplankton cells with this in mind.
Fluorescence: Chlorophyll fluorescence measurements of bulk water samples are widely used
in biological oceanography for studying phytoplankton biomass and physiology. The unique
place of flow cytometry in the suite of in vivo fluorescence techniques is now being
appreciated (Cullen et al. 1988), and a biophysical framework within which we can interpret
these measurements of individual cells is being constructed (Neale et al. 1989; see chapter by
T. Owens, this volume). Because fluorescence is highly dependent on instrument
characteristics such as time scale and excitation light intensity, and since flow cytometers used
in oceanography vary widely in these characteristics, empirical evaluation of flow cytometric
fluorescence signals has been a necessary first step.
Sosik et al. (1989) analyzed flow cytometric fluorescence measurements from three species
of phytoplankton and found that variations in fluorescence/chlorophyll a could be accounted
for by considering the accessory pigments absorbing the light in each species (Fig. 12). The
dinoflagellate in this study (Amphidinium carteri) contained more accessory pigments per
chlorophyll a than either of the other species examined (a diatom and a coccolithophore), so
that more of the excitation light was absorbed and passed on to chlorophyll a, which then
fluoresced. We also suggested that pigment ratios could account for differences in results