404
Bienfang, 1983; Hopcroft et al., 1990). However, biologists involved in the analysis of
individual cells and particles have recently focused their interest on the smaller phytoplankton,
as for example cyanobacteria and prochlorophytes (see the review by Olson et al., this
volume). Due to technical limitations of modern instruments, the large eukaryotic cells are
currently neglected. Yet, as pointed out in a number of studies (e.g., Ryther, 1969; Goldman,
1988; Hopcroft et al., 1990; Legendre, 1990), the larger particles may dominate the export
of biogenic carbon into the deep ocean and also toward higher trophic levels. In this
perspective, Legendre and Le Fevre (this volume) developed a conceptual model which
stresses the role played by size structure in the biogeochemical cycle of carbon, including the
sequestration of carbon in deep waters and sediments, and also in the production of renewable
marine resources. Concerning the transfer of primary production to higher trophic levels,
Iverson (1990) showed that the production of carnivorous fish is directly proportional to
phytoplankton new production, which is often dominated by large cells (e.g., Michaels and
Silver, 1988). We therefore believe that a greater effort should be dedicated to studying the
large particles, on an individual basis.
A potential catch in the automatic analysis of individual cells and particles is that such
techniques are seductive. Even if flow cytometers are technologically sophisticated, they are
accessible to many researchers. These instruments are designed to count large numbers of
small particles, which is a requisite for many medical applications. In oceanography,
researchers are naturally tempted to focus on the large clusters of points corresponding to
various types of small cells, since the larger cells are virtually invisible to commercially
configured cytometers. However, the small cells may be by far less important, in the carbon
and nitrogen economy of the ocean, than the less abundant larger cells. One wonders if the
current fascination with picoplankton, which has been a virtual obsession to biological
oceanography and limnology over the last decade, is not in great part due to technological
biases, resulting in part from the increased use of flow cytometers. Of course, past emphasis
on large cells (to the virtual exclusion of anything smaller than ca. 5 ~m) was due to biases
inherent in optical microscopy, where the larger organisms are identified and counted while
the thousands of little green dots in the background remain ignored. Hopefully, a more
balanced (i.e., objective) view of the size spectrum of biogenic particles in the ocean will
emerge in the next decade, but we feel that this cannot occur unless the limitations of
automatic cell analyses are acknowledged.
Bienfang, 1983; Hopcroft et al., 1990). However, biologists involved in the analysis of
individual cells and particles have recently focused their interest on the smaller phytoplankton,
as for example cyanobacteria and prochlorophytes (see the review by Olson et al., this
volume). Due to technical limitations of modern instruments, the large eukaryotic cells are
currently neglected. Yet, as pointed out in a number of studies (e.g., Ryther, 1969; Goldman,
1988; Hopcroft et al., 1990; Legendre, 1990), the larger particles may dominate the export
of biogenic carbon into the deep ocean and also toward higher trophic levels. In this
perspective, Legendre and Le Fevre (this volume) developed a conceptual model which
stresses the role played by size structure in the biogeochemical cycle of carbon, including the
sequestration of carbon in deep waters and sediments, and also in the production of renewable
marine resources. Concerning the transfer of primary production to higher trophic levels,
Iverson (1990) showed that the production of carnivorous fish is directly proportional to
phytoplankton new production, which is often dominated by large cells (e.g., Michaels and
Silver, 1988). We therefore believe that a greater effort should be dedicated to studying the
large particles, on an individual basis.
A potential catch in the automatic analysis of individual cells and particles is that such
techniques are seductive. Even if flow cytometers are technologically sophisticated, they are
accessible to many researchers. These instruments are designed to count large numbers of
small particles, which is a requisite for many medical applications. In oceanography,
researchers are naturally tempted to focus on the large clusters of points corresponding to
various types of small cells, since the larger cells are virtually invisible to commercially
configured cytometers. However, the small cells may be by far less important, in the carbon
and nitrogen economy of the ocean, than the less abundant larger cells. One wonders if the
current fascination with picoplankton, which has been a virtual obsession to biological
oceanography and limnology over the last decade, is not in great part due to technological
biases, resulting in part from the increased use of flow cytometers. Of course, past emphasis
on large cells (to the virtual exclusion of anything smaller than ca. 5 ~m) was due to biases
inherent in optical microscopy, where the larger organisms are identified and counted while
the thousands of little green dots in the background remain ignored. Hopefully, a more
balanced (i.e., objective) view of the size spectrum of biogenic particles in the ocean will
emerge in the next decade, but we feel that this cannot occur unless the limitations of
automatic cell analyses are acknowledged.