79
phycoerythrin is used as a nitrogen store in oligotrophic waters (Wyman et al., 1985).
However, light is the most obvious condition that influences the pigment contents of cells. The
chi a, ChI b, ChI c, fucoxanthin, violaxanthin and peridinin concentration can be changed to
enhance light absorption for photosynthesis in the aquatic environment (see Introduction),
where light is not only variable in quantity but also in quality (Fig. 2); zeaxanthin and lutein,
on the other hand, are photosynthetically incompetent (Bigidare et al., 1989) but do provide
protection against light-induced, photosensitized oxidation. Indeed, the high zeaxanthin
concentration near the tropical ocean's surface (as much zeaxanthin is found here as chI a)
suggests adaptation of the omnipresent coccoid Cyanobacteria (Waterbury et al., 1979) and
other bluegreen algae to bright light (Pearl et al., 1983; Gieskes and Kraay, 1986).
New picoplankton, new ideas on light adaptation
The scarcity in the ocean's deep chlorophyll maximum layer of violaxanthin (a
shade-adaptation pigment of green algae and abundant in Halosphaera, a representative of the
shade flora, Soumia, 1982) suggests that green algae are less prominent there than previously
thought (Jeffrey, 1976). Interestingly, the picoplanktonic Prochlorophytes commonly occurring
near the bottom of the euphotic zone of oceans (Gieskes et al., 1988; Chisholm et al., 1988;
Olson et al., 1990; Veldhuis and Kraay, 1990) seem to be better adapted to shady conditions
than green algae, which have been reported to contain relatively high amounts ChI b
in dim light (French et al., 1959; Brown and Richardson, 1968; Ramus et al., 1976;
Titlyanova et al., 1977). The Prochlorophytes do not contain normal chI a and b, but redshifted versions (Fig. 3), with an a : b ratio of 1 : 1 (Olson et al., 1990; Chisholm et al.,
1988). This enables increased absorption of blue light, the only spectral region of sunlight
irradiance available at this depth in the ocean (Wood, 1985; Glover et al., 1986, and see Fig.
2 and 11), and also in the wavelength range emitted by luminescent bacteria associated with
the decaying organic debris that tends to accumulate near the bottom of the euphotic zone of
the stratified open ocean (Sieburth, 1988).
The red-shifted chI a and b of the deep-chlorophyll-maximum's Prochlorophytes, which we
detected in Atlantic Ocean samples by TLC in 1977 (Gieskes et al., 1979; see their Fig. 2),
disappears rapidly upon transfer to shallower depths where more surface light penetrates (Fig.
12b). This also suggests that this picoplankton group is adapted to life at depth. The red shift
of about 5 nm in the absorption spectrum in acetone and ether (Fig. 3) is probably due to a
divinyl bond in the chlorophyll molecule (Goericke, pers. comm.). Bazzaz (1981) and Bazzaz
and Brereton (1982) found a divinyl chlorophyll in maize mutants with absorption and
fluorescence characteristics that resembled those of our picoplanktonic chI a. It was the only
phycoerythrin is used as a nitrogen store in oligotrophic waters (Wyman et al., 1985).
However, light is the most obvious condition that influences the pigment contents of cells. The
chi a, ChI b, ChI c, fucoxanthin, violaxanthin and peridinin concentration can be changed to
enhance light absorption for photosynthesis in the aquatic environment (see Introduction),
where light is not only variable in quantity but also in quality (Fig. 2); zeaxanthin and lutein,
on the other hand, are photosynthetically incompetent (Bigidare et al., 1989) but do provide
protection against light-induced, photosensitized oxidation. Indeed, the high zeaxanthin
concentration near the tropical ocean's surface (as much zeaxanthin is found here as chI a)
suggests adaptation of the omnipresent coccoid Cyanobacteria (Waterbury et al., 1979) and
other bluegreen algae to bright light (Pearl et al., 1983; Gieskes and Kraay, 1986).
New picoplankton, new ideas on light adaptation
The scarcity in the ocean's deep chlorophyll maximum layer of violaxanthin (a
shade-adaptation pigment of green algae and abundant in Halosphaera, a representative of the
shade flora, Soumia, 1982) suggests that green algae are less prominent there than previously
thought (Jeffrey, 1976). Interestingly, the picoplanktonic Prochlorophytes commonly occurring
near the bottom of the euphotic zone of oceans (Gieskes et al., 1988; Chisholm et al., 1988;
Olson et al., 1990; Veldhuis and Kraay, 1990) seem to be better adapted to shady conditions
than green algae, which have been reported to contain relatively high amounts ChI b
in dim light (French et al., 1959; Brown and Richardson, 1968; Ramus et al., 1976;
Titlyanova et al., 1977). The Prochlorophytes do not contain normal chI a and b, but redshifted versions (Fig. 3), with an a : b ratio of 1 : 1 (Olson et al., 1990; Chisholm et al.,
1988). This enables increased absorption of blue light, the only spectral region of sunlight
irradiance available at this depth in the ocean (Wood, 1985; Glover et al., 1986, and see Fig.
2 and 11), and also in the wavelength range emitted by luminescent bacteria associated with
the decaying organic debris that tends to accumulate near the bottom of the euphotic zone of
the stratified open ocean (Sieburth, 1988).
The red-shifted chI a and b of the deep-chlorophyll-maximum's Prochlorophytes, which we
detected in Atlantic Ocean samples by TLC in 1977 (Gieskes et al., 1979; see their Fig. 2),
disappears rapidly upon transfer to shallower depths where more surface light penetrates (Fig.
12b). This also suggests that this picoplankton group is adapted to life at depth. The red shift
of about 5 nm in the absorption spectrum in acetone and ether (Fig. 3) is probably due to a
divinyl bond in the chlorophyll molecule (Goericke, pers. comm.). Bazzaz (1981) and Bazzaz
and Brereton (1982) found a divinyl chlorophyll in maize mutants with absorption and
fluorescence characteristics that resembled those of our picoplanktonic chI a. It was the only