26
G.E. Napolitano
PUFA, including 16:2m4, 16:2ffi6, 16:3ffi3, 16:3m4, 16:4ffil, and 16:4ffi3, can be
abundant in the lipids of green algae and diatoms (Cranwell et ai., 1990; Wood,
1974; Kates and Volcani, 1966). Linoleic acid (I8:2ffi6) is important in green
algae (Napolitano et aI., 1994; Nichols, 1965) and in a number of cyanobacteria,
including species of Spirulina. Nostoc. Synechococcus. Aphonocaspa, Oscillatoria. Lyngbia. and Anabaena (Petkov and Fumadzieva, 1993; Kenyon, 1972;
Holton et aI., 1968; Nichols et ai., 1968). Linoleic acid is a minor constituent of
the lipids of diatoms and dinotlagellates. ex-Linolenic acid (I8:3ffi3) is a major
component in the lipids of most green algae and some cyanobacteria (Ahlgren et
aI., 1992) and also accounts for 40% of the total fatty acids of the freshwater
heterotrophic Cryptophyceae (Chylomonas paramecium) (Beach et aI., 1970).
Two PUFA, 18:4ffi3 and the unusual 18:5ffi3, complete the series of potentially
useful C 18 PUFA markers. High proportions of 18:4ffi3 can occur in certain
strains of green and cyanobacteria. Nevertheless, this fatty acid is a major component of the lipids of most species of dinotlagellates examined so far (Ahlgren et
aI., 1992). The existence of 18:5ffi3 was revealed less than two decades ago in the
lipids of marine dinotlagellates (Joseph, 1977; Ackman et aI., 1974), and its
occurrence was later extended to other marine algal classes (Napolitano et al.,
1988; Volkman et aI., 1981). The distribution of 18:5ffi3 in the freshwater environment seems to be much more restricted and unpredictable than in the ocean.
Bourdier and Amblard (1988, 1987) reported 18:5ffi3 among the major fatty acids
in the lipids of phytoplankton during a bloom in Lake Pavin (up to 12% of the total
fatty acids), when the dinotlagellate Peridinium willei dominated. However, fatty
acids of a spring bloom dominated by the dinotlagellate Peridinopsis penardii
showed that 18:5ffi3 comprised only 0.0 I % of the total fatty acids (Napolitano et
ai., 1995).
C20 and C22 PUFA are typically absent in freshwater green algae (Pohl and
Zurheide, 1982; Nichols, 1965) and cyanobacteria (Ahlgren et aI., 1992; Murata et
aI., 1992; Ahlgren et aI., 1990). Eicosapentaenoic acid (20:5ffi3) is the prominent
PUFA in virtually all species of diatoms so far studied (Napolitano et aI., 1994;
Sicko-Goad, 1988; Kates and Volcani, 1966). Docosahexaenoic acid (22:6ffi3) is
normally a minor fatty acid in diatoms (Napolitano et aI., 1994) (Table 2.1) but
can be a dominant constituent in the lipids of dinotlagellates (Napolitano et aI.,
1995) and some species of the small group of freshwater Chrysophyceae (Ahlgren
et aI., 1992).
Very-long-chain fatty acids (VLCF; carbon chain length between 24-30) are
normally omitted in most analyses, assuming that there is nothing of importance
beyond 24: I. VLCF may represent a substantial fraction of the total lipids in
several green algae, including Botryococcus braunii. Chlorella kessleri. and Eu[(lena gracilis (Rezanka, 1989), and they constitute a potential group of biochemical markers. Nevertheless, because terrestrial sources of VLCF may predominate
in freshwater environments (see below), algal sources should be identified on the
basis of characteristic fatty acid profi les and not by the presence of a few fatty acid
components.
G.E. Napolitano
PUFA, including 16:2m4, 16:2ffi6, 16:3ffi3, 16:3m4, 16:4ffil, and 16:4ffi3, can be
abundant in the lipids of green algae and diatoms (Cranwell et ai., 1990; Wood,
1974; Kates and Volcani, 1966). Linoleic acid (I8:2ffi6) is important in green
algae (Napolitano et aI., 1994; Nichols, 1965) and in a number of cyanobacteria,
including species of Spirulina. Nostoc. Synechococcus. Aphonocaspa, Oscillatoria. Lyngbia. and Anabaena (Petkov and Fumadzieva, 1993; Kenyon, 1972;
Holton et aI., 1968; Nichols et ai., 1968). Linoleic acid is a minor constituent of
the lipids of diatoms and dinotlagellates. ex-Linolenic acid (I8:3ffi3) is a major
component in the lipids of most green algae and some cyanobacteria (Ahlgren et
aI., 1992) and also accounts for 40% of the total fatty acids of the freshwater
heterotrophic Cryptophyceae (Chylomonas paramecium) (Beach et aI., 1970).
Two PUFA, 18:4ffi3 and the unusual 18:5ffi3, complete the series of potentially
useful C 18 PUFA markers. High proportions of 18:4ffi3 can occur in certain
strains of green and cyanobacteria. Nevertheless, this fatty acid is a major component of the lipids of most species of dinotlagellates examined so far (Ahlgren et
aI., 1992). The existence of 18:5ffi3 was revealed less than two decades ago in the
lipids of marine dinotlagellates (Joseph, 1977; Ackman et aI., 1974), and its
occurrence was later extended to other marine algal classes (Napolitano et al.,
1988; Volkman et aI., 1981). The distribution of 18:5ffi3 in the freshwater environment seems to be much more restricted and unpredictable than in the ocean.
Bourdier and Amblard (1988, 1987) reported 18:5ffi3 among the major fatty acids
in the lipids of phytoplankton during a bloom in Lake Pavin (up to 12% of the total
fatty acids), when the dinotlagellate Peridinium willei dominated. However, fatty
acids of a spring bloom dominated by the dinotlagellate Peridinopsis penardii
showed that 18:5ffi3 comprised only 0.0 I % of the total fatty acids (Napolitano et
ai., 1995).
C20 and C22 PUFA are typically absent in freshwater green algae (Pohl and
Zurheide, 1982; Nichols, 1965) and cyanobacteria (Ahlgren et aI., 1992; Murata et
aI., 1992; Ahlgren et aI., 1990). Eicosapentaenoic acid (20:5ffi3) is the prominent
PUFA in virtually all species of diatoms so far studied (Napolitano et aI., 1994;
Sicko-Goad, 1988; Kates and Volcani, 1966). Docosahexaenoic acid (22:6ffi3) is
normally a minor fatty acid in diatoms (Napolitano et aI., 1994) (Table 2.1) but
can be a dominant constituent in the lipids of dinotlagellates (Napolitano et aI.,
1995) and some species of the small group of freshwater Chrysophyceae (Ahlgren
et aI., 1992).
Very-long-chain fatty acids (VLCF; carbon chain length between 24-30) are
normally omitted in most analyses, assuming that there is nothing of importance
beyond 24: I. VLCF may represent a substantial fraction of the total lipids in
several green algae, including Botryococcus braunii. Chlorella kessleri. and Eu[(lena gracilis (Rezanka, 1989), and they constitute a potential group of biochemical markers. Nevertheless, because terrestrial sources of VLCF may predominate
in freshwater environments (see below), algal sources should be identified on the
basis of characteristic fatty acid profi les and not by the presence of a few fatty acid
components.