Biomarkers
DGDG, SQDG. Le chromatogramme CCM/FID de l’extrait lipidique
apparaît specifique de chaque espèce étudiée, en particulier dans la
comparaison des teneurs relatives en MGDG et DGDG. La distribution
des acides gras polyinsaturés dans ces deux galactolipides montre des
difFérences significatives entre Gymnodmiurn mikimotoi et Gymnodinium corii.
L’acide octadécapentaénoïque (18:5 (n-3) est le principal acide gras dans
ces deux souches mais se localise principalement dans MGDG de G. corii.
Cet acide gras est moins représenté dans Heterosigma akashiwo. La teneur
relative en 18:5 (n-3) par rapport à d’autres PUFAs de structures analogues se révèle un bon critère chimique pour la caractérisation d echantillons contaminés par ces microalgues proliférant dans des conditions
environnementales comparables.
Introduction
Since the mid 1970s there has been an increasing interest in the lipid
analysis of marine microalgae. Detailed lipid analyses have revealed a
surprising diversity of chemical composition among the species. Many
new lipids have been identified which appear to have a restricted species distribution. Those that are only slowly degraded, including some
fatty acids, sterols and pigments, can be used as biological marker or
signature compounds for assessing the source of organic matter present
in various types of environmental samples (Laureillard & Saliot, 1993;
Viso & Marty, 1993; Okuyama et al., 1993; Galois et al., 1996; Ackman,
2000; Sargent, 2000). In the event of harmful algal blooms, specific
biomarkers have been suggested for indicating the presence of such
organisms in contaminated samples and also as possible tracers in the
food web (Mayzaud et al., 1976; Parrish et al., 1992; Joseph, 1993).
Moreover, certain unusual polyunsaturated fatty acids (PUFAs) and
unsaturated glycolipids have been shown to possess bioactive properties
including toxicity (Yasumoto et al., 1990; Arzul et al., 1995; Smolowitz
& Shumway, 1997; Parrish et al., 1998). By contrast, microalgae are
used in aquaculture for their nutritional value and as a source of heathpromoting (n-3) fatty acids (Murakami et al., 1992; Yongmanitchai &
Ward, 1993).
The present study focuses on the glycolipid content and fatty acid composition of toxinogenic Gymnodinium and Heterosigma strains grown
under the same culture conditions. These microalgal species are commonly encountered around Japan and in temperate Atlantic coastal
waters, in particular in thermally stratified areas including shallow
bays and the Ushant tidal front of Western Brittany (Partensky et al.,
1991; Gentien, 1998). In the Bay of Brest, blooms of the dinoflagellate
Gymnodinium mikimotoi and the Raphidophyceae Heterosigma akashiwo
have been regularly reported during summer months with large outbreaks ( > 10 6 cells/1 ) in 1985, 1987 and 1995 for G. mikimotoi (Nézan,
1996) and in 1991 and 1997 for //. akashiwo (Nézan, pers. comm.). These
dense algal proliferations were implicated in mortality of various
67
DGDG, SQDG. Le chromatogramme CCM/FID de l’extrait lipidique
apparaît specifique de chaque espèce étudiée, en particulier dans la
comparaison des teneurs relatives en MGDG et DGDG. La distribution
des acides gras polyinsaturés dans ces deux galactolipides montre des
difFérences significatives entre Gymnodmiurn mikimotoi et Gymnodinium corii.
L’acide octadécapentaénoïque (18:5 (n-3) est le principal acide gras dans
ces deux souches mais se localise principalement dans MGDG de G. corii.
Cet acide gras est moins représenté dans Heterosigma akashiwo. La teneur
relative en 18:5 (n-3) par rapport à d’autres PUFAs de structures analogues se révèle un bon critère chimique pour la caractérisation d echantillons contaminés par ces microalgues proliférant dans des conditions
environnementales comparables.
Introduction
Since the mid 1970s there has been an increasing interest in the lipid
analysis of marine microalgae. Detailed lipid analyses have revealed a
surprising diversity of chemical composition among the species. Many
new lipids have been identified which appear to have a restricted species distribution. Those that are only slowly degraded, including some
fatty acids, sterols and pigments, can be used as biological marker or
signature compounds for assessing the source of organic matter present
in various types of environmental samples (Laureillard & Saliot, 1993;
Viso & Marty, 1993; Okuyama et al., 1993; Galois et al., 1996; Ackman,
2000; Sargent, 2000). In the event of harmful algal blooms, specific
biomarkers have been suggested for indicating the presence of such
organisms in contaminated samples and also as possible tracers in the
food web (Mayzaud et al., 1976; Parrish et al., 1992; Joseph, 1993).
Moreover, certain unusual polyunsaturated fatty acids (PUFAs) and
unsaturated glycolipids have been shown to possess bioactive properties
including toxicity (Yasumoto et al., 1990; Arzul et al., 1995; Smolowitz
& Shumway, 1997; Parrish et al., 1998). By contrast, microalgae are
used in aquaculture for their nutritional value and as a source of heathpromoting (n-3) fatty acids (Murakami et al., 1992; Yongmanitchai &
Ward, 1993).
The present study focuses on the glycolipid content and fatty acid composition of toxinogenic Gymnodinium and Heterosigma strains grown
under the same culture conditions. These microalgal species are commonly encountered around Japan and in temperate Atlantic coastal
waters, in particular in thermally stratified areas including shallow
bays and the Ushant tidal front of Western Brittany (Partensky et al.,
1991; Gentien, 1998). In the Bay of Brest, blooms of the dinoflagellate
Gymnodinium mikimotoi and the Raphidophyceae Heterosigma akashiwo
have been regularly reported during summer months with large outbreaks ( > 10 6 cells/1 ) in 1985, 1987 and 1995 for G. mikimotoi (Nézan,
1996) and in 1991 and 1997 for //. akashiwo (Nézan, pers. comm.). These
dense algal proliferations were implicated in mortality of various
67