405
Phytoplankton and aquatic microbial biologists often spend long, tedious hours looking down
a microscope ocular, identifying and counting organisms from natural waters. Devices capable
of automating cell counting, and discriminating amongst cell types based on simple pattern
recognition signals, potentially provide a means of reducing the tedium, increasing sample
throughput, automating and collating the output, and thereby developing a much larger data
base than could otherwise be achieved by manual, visual counting. Many of the papers in this
volume clearly show that it is technically possible to distinguish, based on cell size, shape,
and various other properties, amongst a fairly large number of cell types (e.g. papers in this
volume, Ault; DeLong; Olson et al.; Salzman et al.; Steen). Automatic analysis of individual
cells and particles has proven extremely valuable in helping to identify and enumerate new
organisms from natural waters (see Olson et al., this volume). However, the flow cytometer
is not only a counting tool. The instrument can be used to study the physiological status of
organisms as well as various transfer rates, by taking advantage of natural probes such as the
autofluorescence of chlorophyll (Owens, this volume) or of various accessory pigments
(Gieskes, this volume), or alternatively by addressing fluorochromes, i.e., staining cell
compounds such as proteins or DNA with specific fluorescent probes (e.g. DeLong in this
volume; see also Table 1 in Legendre and Yentsch, 1989). Thus, automated cell and particle
analyses is potentially a powerful tool for understanding biological processes which affect the
abundance and fate of phytoplankton and microbes in aquatic ecosystems (Azam and Smith,
this volume; Legendre and Yentsch, 1989).
In addition to techniques reviewed in the present volume, some other types of analyses, that
have been or are being used in oceanography, are also amenable to single cells or particles
(e.g. papers in this volume, Arnd-Jovin; Iturriaga). These concern in particular the elemental
composition of particles, which is of interest to geochemists. For example, Biscaye and Olsen
(1976) described the use of energy-dispersive X-ray fluorescence in conjunction with scanning
electron microscopy (SEM) to analyze metal levels on the surfaces of abiogenic and biogenic
particles. This technique is relatively standard with many scanning electron microscopes
today. A similar technique, with 5 fm spatial resolution, but much greater sensitivity, has been
developed for synchrotron radiation, and this technique has been used to study the spatial
distributions of Br, Cu, Fe, and Zn in macroalgae (Keith Jones, personal communication).
With increased luminosity, higher spatial scale resolution is achievable. Positron imaging
Phytoplankton and aquatic microbial biologists often spend long, tedious hours looking down
a microscope ocular, identifying and counting organisms from natural waters. Devices capable
of automating cell counting, and discriminating amongst cell types based on simple pattern
recognition signals, potentially provide a means of reducing the tedium, increasing sample
throughput, automating and collating the output, and thereby developing a much larger data
base than could otherwise be achieved by manual, visual counting. Many of the papers in this
volume clearly show that it is technically possible to distinguish, based on cell size, shape,
and various other properties, amongst a fairly large number of cell types (e.g. papers in this
volume, Ault; DeLong; Olson et al.; Salzman et al.; Steen). Automatic analysis of individual
cells and particles has proven extremely valuable in helping to identify and enumerate new
organisms from natural waters (see Olson et al., this volume). However, the flow cytometer
is not only a counting tool. The instrument can be used to study the physiological status of
organisms as well as various transfer rates, by taking advantage of natural probes such as the
autofluorescence of chlorophyll (Owens, this volume) or of various accessory pigments
(Gieskes, this volume), or alternatively by addressing fluorochromes, i.e., staining cell
compounds such as proteins or DNA with specific fluorescent probes (e.g. DeLong in this
volume; see also Table 1 in Legendre and Yentsch, 1989). Thus, automated cell and particle
analyses is potentially a powerful tool for understanding biological processes which affect the
abundance and fate of phytoplankton and microbes in aquatic ecosystems (Azam and Smith,
this volume; Legendre and Yentsch, 1989).
In addition to techniques reviewed in the present volume, some other types of analyses, that
have been or are being used in oceanography, are also amenable to single cells or particles
(e.g. papers in this volume, Arnd-Jovin; Iturriaga). These concern in particular the elemental
composition of particles, which is of interest to geochemists. For example, Biscaye and Olsen
(1976) described the use of energy-dispersive X-ray fluorescence in conjunction with scanning
electron microscopy (SEM) to analyze metal levels on the surfaces of abiogenic and biogenic
particles. This technique is relatively standard with many scanning electron microscopes
today. A similar technique, with 5 fm spatial resolution, but much greater sensitivity, has been
developed for synchrotron radiation, and this technique has been used to study the spatial
distributions of Br, Cu, Fe, and Zn in macroalgae (Keith Jones, personal communication).
With increased luminosity, higher spatial scale resolution is achievable. Positron imaging