147
This is of interest because the theoretical approach can be considerably simplified in such a
case.
Another point is worth noting and refers to the links which may exist between the real and
the imaginary parts of the index. Inasmuch as absorbing substances in living organisms are
more or less correlated to the total carbon content, n' and n could be related. Such a
"chemical" link cannot be tight because the pigment-to-carbon ratio is not stable; it exists only
as a first approximation, useful for interspecific algae comparison. A "physical" and exact
relationship results from the anomalous dispersion phenomenon. The Ketteler - Helmoltz
theory predicts that, as soon as n' departs from zero (inside an absorption band), n is affected,
being depressed and then enhanced on both sides of the absorption band (see for instance Fig.
13 and comments in Morel and Bricaud, 1987). For algal cells with several pigments and the
resulting intricate absorption bands, the n '(A) spectrum exhibits complicated patterns. In
response, the n(A) spectrum is also featured around a "mean" value related, as said before,
to the carbon content. This is part of the complexity when modeling the optical properties of
phytoplankters (see Bricaud and Morel, 1986; Stramski et at., 1988).
Size distribution of marine parlicles
It has long been thought that the population of particles, even if widely distributed with
respect to size, is nevertheless more or less centered around an "average" size. Many studies
were devoted to determining this supposedly existing average size and its possible change with
location and depth. From microscopic observations, however, Gordon (1970) concluded that
the size frequency distribution is continuous and monotonic, with an almost exponential
increase of the number of particles for decreasing sizes. Thus the concept of an average size
appeared to be meaningless, as necessarily "close to the smallest observable size" (Sheldon
et ai., 1972). Meanwhile, electronic sizing and counting techniques (Coulter counter) provided
a new insight into the size spectrum over a wide range of diameters, between 3 and 100 tLm
(Sheldon and Parsons, 1966). The steeply ascending slope toward the smaller particles proved
to be the general rule, even though some relative maxima or dominance of certain sizes, due
to the occurence of particular planktonic species, were often found to be superimposed over
the general trend.
This is of interest because the theoretical approach can be considerably simplified in such a
case.
Another point is worth noting and refers to the links which may exist between the real and
the imaginary parts of the index. Inasmuch as absorbing substances in living organisms are
more or less correlated to the total carbon content, n' and n could be related. Such a
"chemical" link cannot be tight because the pigment-to-carbon ratio is not stable; it exists only
as a first approximation, useful for interspecific algae comparison. A "physical" and exact
relationship results from the anomalous dispersion phenomenon. The Ketteler - Helmoltz
theory predicts that, as soon as n' departs from zero (inside an absorption band), n is affected,
being depressed and then enhanced on both sides of the absorption band (see for instance Fig.
13 and comments in Morel and Bricaud, 1987). For algal cells with several pigments and the
resulting intricate absorption bands, the n '(A) spectrum exhibits complicated patterns. In
response, the n(A) spectrum is also featured around a "mean" value related, as said before,
to the carbon content. This is part of the complexity when modeling the optical properties of
phytoplankters (see Bricaud and Morel, 1986; Stramski et at., 1988).
Size distribution of marine parlicles
It has long been thought that the population of particles, even if widely distributed with
respect to size, is nevertheless more or less centered around an "average" size. Many studies
were devoted to determining this supposedly existing average size and its possible change with
location and depth. From microscopic observations, however, Gordon (1970) concluded that
the size frequency distribution is continuous and monotonic, with an almost exponential
increase of the number of particles for decreasing sizes. Thus the concept of an average size
appeared to be meaningless, as necessarily "close to the smallest observable size" (Sheldon
et ai., 1972). Meanwhile, electronic sizing and counting techniques (Coulter counter) provided
a new insight into the size spectrum over a wide range of diameters, between 3 and 100 tLm
(Sheldon and Parsons, 1966). The steeply ascending slope toward the smaller particles proved
to be the general rule, even though some relative maxima or dominance of certain sizes, due
to the occurence of particular planktonic species, were often found to be superimposed over
the general trend.