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P.F. Landrum and S.w. Fisher
9.9. Conclusions
Lipids are the dominant force in determining organic contaminant accumulation
in aquatic organisms. Lipid normalization eliminates most variability between
species in bioconcentration studies and is, thus, useful in making predictions
about bioconcentration from physical parameters such as log Kow. Normalizing
contaminant loads to lipid levels is also helpful in cases in which the contaminant
must leave a lipid compartment and negotiate an intermediate aqueous phase
before final deposition in a second lipid compartment (e.g., bioaccumulation and
trophic transfer). Evidence varies as to whether total lipids or the abundance of
specific lipid subclasses are the most relevant referent, but it is clear that lipid
normalization will significantly reduce variation for comparing contaminant loads
between species. This is an area that should be studied further.
Studies of the relationships between lipids and contaminant accumulation have
led to new insights on obviously important but seldom studied phenomena. The
role of lipids, for instance, in producing membrane narcosis is pivotal, and its
study may elucidate important details of the mechanism for narcosis and how
toxins can affect lipid levels, resulting in alterations in energy (lipid) stores and
perhaps membrane function. In addition, lipid metabolism appears to account for
biomagnification in which contaminants appear to accumulate in predators
against a concentration gradient. Finally, study of lipid mobilization and deposition in reproduction may help to define the ability of contaminants to move into
filial generations during reproduction; it may also provide insight into the sorts of
toxin-induced biological effects that can be expected in contaminated offspring.
In short, our ability to predict the movement of organic contaminants in aquatic
systems and to project the effects of that contamination depends on an understanding of the importance of lipids. Because these are the key elements of risk assessment, our ability to conduct accurate assessments may reasonably be seen to
depend on our knowledge of lipids and their dynamics.
Acknowledgments. We thank Duane Gossiaux for his help in generating the
graphics for Figure 9.1. This chapter is GLERL contribution 1024.
References
Arts, M.T.; Headley, J.Y.; Peru, K.M. Persistence of herbicide residues in Gammarus
lacustris (Crustacea: Amphipoda) in prairie wetlands. Environ. Toxico!. Chern. 15:481488; 1996.
Arts, M.T.; Ferguson. M.E.; Glozier. N.E.; Robarts, R.D.; Donald, D.B. Spatial and temporal variability in lipid dynamics of common amphipods: assessing the potential for
uptake of lipophilic contaminants. Ecotoxicology 4:91-113; 1995.
Axelman. J.; Broman. D.; Naf. c.; Pettersen, H. Compound dependence of the relationship
log Kow and log BCF L . Environ. Sci. Pollut. Res. 2:33-36; 1995.
Banerjee, S.; Baughman, G.L. Bioconcentration factors and lipid solubility. Environ. Sci.
Techno!. 25:536-539; 1991.
P.F. Landrum and S.w. Fisher
9.9. Conclusions
Lipids are the dominant force in determining organic contaminant accumulation
in aquatic organisms. Lipid normalization eliminates most variability between
species in bioconcentration studies and is, thus, useful in making predictions
about bioconcentration from physical parameters such as log Kow. Normalizing
contaminant loads to lipid levels is also helpful in cases in which the contaminant
must leave a lipid compartment and negotiate an intermediate aqueous phase
before final deposition in a second lipid compartment (e.g., bioaccumulation and
trophic transfer). Evidence varies as to whether total lipids or the abundance of
specific lipid subclasses are the most relevant referent, but it is clear that lipid
normalization will significantly reduce variation for comparing contaminant loads
between species. This is an area that should be studied further.
Studies of the relationships between lipids and contaminant accumulation have
led to new insights on obviously important but seldom studied phenomena. The
role of lipids, for instance, in producing membrane narcosis is pivotal, and its
study may elucidate important details of the mechanism for narcosis and how
toxins can affect lipid levels, resulting in alterations in energy (lipid) stores and
perhaps membrane function. In addition, lipid metabolism appears to account for
biomagnification in which contaminants appear to accumulate in predators
against a concentration gradient. Finally, study of lipid mobilization and deposition in reproduction may help to define the ability of contaminants to move into
filial generations during reproduction; it may also provide insight into the sorts of
toxin-induced biological effects that can be expected in contaminated offspring.
In short, our ability to predict the movement of organic contaminants in aquatic
systems and to project the effects of that contamination depends on an understanding of the importance of lipids. Because these are the key elements of risk assessment, our ability to conduct accurate assessments may reasonably be seen to
depend on our knowledge of lipids and their dynamics.
Acknowledgments. We thank Duane Gossiaux for his help in generating the
graphics for Figure 9.1. This chapter is GLERL contribution 1024.
References
Arts, M.T.; Headley, J.Y.; Peru, K.M. Persistence of herbicide residues in Gammarus
lacustris (Crustacea: Amphipoda) in prairie wetlands. Environ. Toxico!. Chern. 15:481488; 1996.
Arts, M.T.; Ferguson. M.E.; Glozier. N.E.; Robarts, R.D.; Donald, D.B. Spatial and temporal variability in lipid dynamics of common amphipods: assessing the potential for
uptake of lipophilic contaminants. Ecotoxicology 4:91-113; 1995.
Axelman. J.; Broman. D.; Naf. c.; Pettersen, H. Compound dependence of the relationship
log Kow and log BCF L . Environ. Sci. Pollut. Res. 2:33-36; 1995.
Banerjee, S.; Baughman, G.L. Bioconcentration factors and lipid solubility. Environ. Sci.
Techno!. 25:536-539; 1991.