2. Fatty Acids as Trophic and Chemical Markers
37
markers is a valuable method for studying trophodynamics and biogeochemical
cycles in aquatic ecosystems. In particular, fatty acid markers can be successfully
used to differentiate between bacterial and algal biomass or between aquatic and
terrestrial primary production. This information can then be used to elucidate the
contribution of the different carbon sources to higher trophic levels of the aquatic
food web.
Although there is no single fatty acid showing all the features of the ideal
biochemical marker, information on the distribution and trophic transference of
fatty acids with unusual structures and uncommon un saturation patters can result
in a valuable contribution to ecological studies. Among the different fatty acids
groups, the (03-PUFAs (e.g., 18:4(03, 18:5(03,20:5(03, and 22:6(03) are the most
important fatty acid markers of algal biomass. The usefulness of these (03-PUFAs
as biochemical markers is derived from their virtual absence in most bacteria and
terrestrial plants, their uneven distribution in algae, and their retention and limited
synthesis by animals.
Due to the intrinsic and environmental variability of the fatty acid composition
of closely related species of primary producers and other organisms at the bottom
of the food web, carbon sources are reflected more closely by fatty acid groups or
profiles (fatty acid signatures) rather than by single chemical compounds. Furthermore, the power of the biochemical marker approach can be enhanced by the
contribution of studies on the occurrence and distribution of other lipid and
nonlipid compounds, such as biogenic hydrocarbons (Nevenzel, 1989), sterols
(Patterson, 1991), pigments (Conte et aI., 1994; Brown and Jeffrey, 1992), and the
use of stable isotope analyses (Peterson and Fry, 1987).
Fatty acid data are sometimes analyzed to classify the samples into groups
according to certain similarities (e.g., sources of organic carbon) (Boon et aI.,
1996). In a second type of approach, the presence of individual markers is used to
infer the presence and abundance of a certain taxon. Regardless of the nature of
the approach, a salient feature of the fatty acid method is that, with little or no
modifications, it can be applied to a wide range of matrices and levels of organization, from organic matter aggregates and bacteria to mammals.
Acknowledgments. Writing of this chapter was supported in part by the appointment of G.E.N. to the Oak Ridge National Laboratory (ORNL) Research Associates Program administrated jointly by ORNL and by the Oak Ridge Institute for
Science and Education. ORNL is managed by Lockheed Martin Energy Research
Corp. for the U.S. Department of Energy under contract DE-AC05-960R22464.
H. Heras (Universidad de La Plata, Argentina) and S. M. Adams (ORNL) provided constructive comments on a previous version of this work. This chapter is
Environmental Sciences Division publication 4672.
References
Ackman, R.G.; Burgher, R.D. Cod liver oil: component fatty acids as determined by gasliquid chromatography. J. Fish. Res. Bd. Can. 21:319-326; 1964.
37
markers is a valuable method for studying trophodynamics and biogeochemical
cycles in aquatic ecosystems. In particular, fatty acid markers can be successfully
used to differentiate between bacterial and algal biomass or between aquatic and
terrestrial primary production. This information can then be used to elucidate the
contribution of the different carbon sources to higher trophic levels of the aquatic
food web.
Although there is no single fatty acid showing all the features of the ideal
biochemical marker, information on the distribution and trophic transference of
fatty acids with unusual structures and uncommon un saturation patters can result
in a valuable contribution to ecological studies. Among the different fatty acids
groups, the (03-PUFAs (e.g., 18:4(03, 18:5(03,20:5(03, and 22:6(03) are the most
important fatty acid markers of algal biomass. The usefulness of these (03-PUFAs
as biochemical markers is derived from their virtual absence in most bacteria and
terrestrial plants, their uneven distribution in algae, and their retention and limited
synthesis by animals.
Due to the intrinsic and environmental variability of the fatty acid composition
of closely related species of primary producers and other organisms at the bottom
of the food web, carbon sources are reflected more closely by fatty acid groups or
profiles (fatty acid signatures) rather than by single chemical compounds. Furthermore, the power of the biochemical marker approach can be enhanced by the
contribution of studies on the occurrence and distribution of other lipid and
nonlipid compounds, such as biogenic hydrocarbons (Nevenzel, 1989), sterols
(Patterson, 1991), pigments (Conte et aI., 1994; Brown and Jeffrey, 1992), and the
use of stable isotope analyses (Peterson and Fry, 1987).
Fatty acid data are sometimes analyzed to classify the samples into groups
according to certain similarities (e.g., sources of organic carbon) (Boon et aI.,
1996). In a second type of approach, the presence of individual markers is used to
infer the presence and abundance of a certain taxon. Regardless of the nature of
the approach, a salient feature of the fatty acid method is that, with little or no
modifications, it can be applied to a wide range of matrices and levels of organization, from organic matter aggregates and bacteria to mammals.
Acknowledgments. Writing of this chapter was supported in part by the appointment of G.E.N. to the Oak Ridge National Laboratory (ORNL) Research Associates Program administrated jointly by ORNL and by the Oak Ridge Institute for
Science and Education. ORNL is managed by Lockheed Martin Energy Research
Corp. for the U.S. Department of Energy under contract DE-AC05-960R22464.
H. Heras (Universidad de La Plata, Argentina) and S. M. Adams (ORNL) provided constructive comments on a previous version of this work. This chapter is
Environmental Sciences Division publication 4672.
References
Ackman, R.G.; Burgher, R.D. Cod liver oil: component fatty acids as determined by gasliquid chromatography. J. Fish. Res. Bd. Can. 21:319-326; 1964.