142
specifically the abundance of phytoplankton, were the source of most of the variations they
had detected in the optical properties of oceanic waters. This is now well established and
substantiated by useful relationships between bulk optical and biological parameters,
empirically derived from numerous field experiments (see e.g. Morel and Prieur, 1977; Smith
and Baker, 1978; Gordon et al., 1988; Morel, 1988) as now used in the interpretation of
ocean color data.
Analytical Optics was developed to increase the understanding and to separately assess the
optical influences of each particular component of the oceanic system. Among the various
particles present in this system, priority was naturally given to algal cells. Their
photosynthetic performance relies on their absorptive capabilities and they also can be isolated
and grown in axenic cultures for detailed experiments. In the fundamental study of
photosynthesis, physiologists and biophysicists were often far advanced in this bio-optical
research (see e.g. Rabinowitch and Govindjee, 1969) and marine biologists subsequently
benefited from this experience. Optical (in vitro) techniques were developed for the study of
absorption, scattering and fluorescence by various phytoplankters in relation to their pigment
content and composition. Due to these spectrophometric measurements, the knowledge of the
optical properties at the level of individual cells is considerable in phototrophic and
heterotrophic organisms. With the introduction of flow-cytometric methods, a new technique
became available with unprecedented capabilities in terms of the number of processed particles
and of detectable parameters. Cell analysis and discrimination rest on their optical properties,
eapecially light scattering in different directions and auto- or induced fluorescence. A
meaningful interpretation of the optical signatures as well as improvements in this technique
still require a continuous effort in optical research.
The present paper is organized as follows: the physical characteristics of a cell or of a
population of particles (refractive index, typical size, or size distribution) which rule their
optical behavior are examined and the necessary optical parameters are introduced (Part 2).
In Part 3, the relevant theories to be operated when interpreting or trying to predict the optical
properties of individual cells or particles are briefly reviewed (a more detailed presentation
was previously given in Morel and Bricaud, 1986). Their applicability is demonstrated by
using some examples selected from among the phototrophic and heterotrophic organisms. The
specifically the abundance of phytoplankton, were the source of most of the variations they
had detected in the optical properties of oceanic waters. This is now well established and
substantiated by useful relationships between bulk optical and biological parameters,
empirically derived from numerous field experiments (see e.g. Morel and Prieur, 1977; Smith
and Baker, 1978; Gordon et al., 1988; Morel, 1988) as now used in the interpretation of
ocean color data.
Analytical Optics was developed to increase the understanding and to separately assess the
optical influences of each particular component of the oceanic system. Among the various
particles present in this system, priority was naturally given to algal cells. Their
photosynthetic performance relies on their absorptive capabilities and they also can be isolated
and grown in axenic cultures for detailed experiments. In the fundamental study of
photosynthesis, physiologists and biophysicists were often far advanced in this bio-optical
research (see e.g. Rabinowitch and Govindjee, 1969) and marine biologists subsequently
benefited from this experience. Optical (in vitro) techniques were developed for the study of
absorption, scattering and fluorescence by various phytoplankters in relation to their pigment
content and composition. Due to these spectrophometric measurements, the knowledge of the
optical properties at the level of individual cells is considerable in phototrophic and
heterotrophic organisms. With the introduction of flow-cytometric methods, a new technique
became available with unprecedented capabilities in terms of the number of processed particles
and of detectable parameters. Cell analysis and discrimination rest on their optical properties,
eapecially light scattering in different directions and auto- or induced fluorescence. A
meaningful interpretation of the optical signatures as well as improvements in this technique
still require a continuous effort in optical research.
The present paper is organized as follows: the physical characteristics of a cell or of a
population of particles (refractive index, typical size, or size distribution) which rule their
optical behavior are examined and the necessary optical parameters are introduced (Part 2).
In Part 3, the relevant theories to be operated when interpreting or trying to predict the optical
properties of individual cells or particles are briefly reviewed (a more detailed presentation
was previously given in Morel and Bricaud, 1986). Their applicability is demonstrated by
using some examples selected from among the phototrophic and heterotrophic organisms. The