66
Jeffrey, 1975) can only be readily revealed by the detection of taxon-specific pigmentation
(e.g. Gieskes and Kraay, 1983a). In the following I will present a short review of the
methodology used for the measurement of chlorophylls, carotenoids, and their breakdown
products, describe how knowledge of their concentrations can be applied to unravel the
taxonomic composition of natural microalgal populations and the ecophysiological and
photophysiological properties of the various taxonomic groups, and outline how insight into
the distribution of pigments can in the future be used as an aid in the interpretation of results
obtained with the newest and most promising instruments available for the investigation of
plankton distribution and ecology: remote sensing and flow-cytometry. The more conventional
methods of pigment analysis will also be discussed, as they remain valuable in phytoplankton
biomass and productivity research, can be put to unexpected use, and are more accessible to
field workers or to those who have no means to afford the excessive technical and financial
resources needed for the sophisticated approaches just mentioned. I will start with a treatise
on the single most important pigment, chlorophyll a, and gradually expand the ideas
developed here to a discussion of other pigments: the other chlorophylls, the carotenoids, the
mycosporine-like pigments absorbing ultraviolet light, and light absorption by detrital material.
DISTRmUTION OF CHLOROPHYLL IN THE SEA: PROS AND CONS OF
DETECTION METHODS
Chlorophyll concentrations are usually measured because the pigment is considered to be
indicative of algal biomass. However, it is not the most appropriate measurement available,
as the amount per cell and the phytoplankton-to-carbon ratio is highly variable (Eppley et al.,
1977; see also Table I), depending on the physiological condition and degree of light
adaptation (Olson et al., 1990a; Olson et al., 1990b), and the state of degradation and lysis
of a population (Daley, 1973). Nevertheless, it is often a better biomass index than
conversions from cell counts based on microscopic observations (Strathmann, 1967),
especially when, as is normally the case, nano- and picoplankton (0.5 - 5.0 #Lm) are abundant.
These cells are easily overlooked, and their structure is often altered beyond recognition due
to sample treatment. This is probably the reason why in many reports the carbon:chlorophyll
ratio is unrealistically low, often less than 10. Counting particles with electronic particle
counters (e.g., Coulter Counters) is not practical; in most size classes, algal cells are usually
only a fraction of the total particle load. A solution to this problem is to count the various
components of natural phytoplankton by flow cytometry. However, only small volumes of
water can be processed. Concentration of cells before counting causes considerable
Jeffrey, 1975) can only be readily revealed by the detection of taxon-specific pigmentation
(e.g. Gieskes and Kraay, 1983a). In the following I will present a short review of the
methodology used for the measurement of chlorophylls, carotenoids, and their breakdown
products, describe how knowledge of their concentrations can be applied to unravel the
taxonomic composition of natural microalgal populations and the ecophysiological and
photophysiological properties of the various taxonomic groups, and outline how insight into
the distribution of pigments can in the future be used as an aid in the interpretation of results
obtained with the newest and most promising instruments available for the investigation of
plankton distribution and ecology: remote sensing and flow-cytometry. The more conventional
methods of pigment analysis will also be discussed, as they remain valuable in phytoplankton
biomass and productivity research, can be put to unexpected use, and are more accessible to
field workers or to those who have no means to afford the excessive technical and financial
resources needed for the sophisticated approaches just mentioned. I will start with a treatise
on the single most important pigment, chlorophyll a, and gradually expand the ideas
developed here to a discussion of other pigments: the other chlorophylls, the carotenoids, the
mycosporine-like pigments absorbing ultraviolet light, and light absorption by detrital material.
DISTRmUTION OF CHLOROPHYLL IN THE SEA: PROS AND CONS OF
DETECTION METHODS
Chlorophyll concentrations are usually measured because the pigment is considered to be
indicative of algal biomass. However, it is not the most appropriate measurement available,
as the amount per cell and the phytoplankton-to-carbon ratio is highly variable (Eppley et al.,
1977; see also Table I), depending on the physiological condition and degree of light
adaptation (Olson et al., 1990a; Olson et al., 1990b), and the state of degradation and lysis
of a population (Daley, 1973). Nevertheless, it is often a better biomass index than
conversions from cell counts based on microscopic observations (Strathmann, 1967),
especially when, as is normally the case, nano- and picoplankton (0.5 - 5.0 #Lm) are abundant.
These cells are easily overlooked, and their structure is often altered beyond recognition due
to sample treatment. This is probably the reason why in many reports the carbon:chlorophyll
ratio is unrealistically low, often less than 10. Counting particles with electronic particle
counters (e.g., Coulter Counters) is not practical; in most size classes, algal cells are usually
only a fraction of the total particle load. A solution to this problem is to count the various
components of natural phytoplankton by flow cytometry. However, only small volumes of
water can be processed. Concentration of cells before counting causes considerable