Bioconcentration, bioaccumulation, biomagnification and trophic magnification: a modelling perspective

Abstract

We present a modelling perspective on quantifying metrics of bio-uptake of organic chemicals in fish. The models can be in concentration, partition ratio, rate constant (CKk) format or fugacity, Z and D value (fZD) format that are shown to be exactly equivalent, each having it merits. For most purposes a simple, parameter-parsimonious one compartment steady-state model containing some 13 parameters is adequate for obtaining an appreciation of the uptake equilibria and kinetics for scientific and regulatory purposes. Such a model is first applied to the bioaccumulation of a series of hypothetical, non-biotransforming chemicals with log K (octanol-water partition ratio) values of 4 to 8 in 10 g fish ranging in lipid contents to deduce wet-weight and lipid normalized concentrations, bioaccumulation and biomagnification factors. The sensitivity of biomagnification factors to relative lipid contents is discussed. Second, a hypothetical 5 species linear food chain is simulated to evaluate trophic magnification factors (TMFs) showing the critical roles of K and biotransformation rate. It is shown that lipid normalization of concentrations is most insightful for less hydrophobic chemicals (log K < 5) when bio-uptake is largely controlled by respiratory intake and equilibrium (equi-fugacity) is approached. For more hydrophobic chemicals when dietary uptake kinetics dominate, wet weight concentrations and BMFs are more insightful. Finally, a preferred strategy is proposed to advance the science of bioaccumulation using a combination of well-designed ecosystem monitoring, laboratory determinations and modelling to confirm that the perceived state of the science contained in the models is consistent with observations.

Organic ultraviolet filters in nearshore waters and in the invasive lionfish (Pterois volitans) in Grenada, West Indies

“…Bioaccumulation of substances in aquatic species can be affected by sex, reproductive status, size, body lipid content, excretion, and geographical location where the sample was collected [7,19,40,41]. The octanol-water partition coefficient ( K OW ) is typically used to indicate the hydrophobicity of a substance [42,43] and the log K OW provides an estimate of the likelihood that it will disassociate from water and bioaccumulate in tissue [42]. Highly lipophilic and poorly biodegradable UV filters have a log K OW of 4–8 [7] and a log K OW value of 5 or greater is typically used to assess the potential for bioaccumulation [42].…”

Selection and application of trophic magnification factors for priority substances to normalize freshwater fish monitoring data under the European Water Framework Directive: a case study

“…Normalizing substance concentrations in fish tissues to levels of fish of a higher TL requires the knowledge of the substance-specific biomagnification properties expressed as biomagnification factor (BMF) or trophic magnification factor (TMF). BMFs are defined as the ratio of fish to diet concentrations (which may be corrected for trophic level), whereas TMFs represent the diet-weighted averaged BMFs of chemical residues across food webs [7,8] calculated from the slope of the logarithmic substance concentrations plotted against the trophic level of the investigated organisms [9]. While the BMF characterizes the increase of substance concentrations from prey to predator, the TMF integrates enrichment processes in the whole food web [10,11].…”

Using Rutilus rutilus (L.) and Perca fluviatilis (L.) as Bioindicators of the Environmental Condition and Human Health: Lake Łańskie, Poland

“…Contrary to the bioconcentration process in fish, which involves the absorption of chemicals from water through the respiratory surface and/or the skin, another process called bioaccumulation addresses all exposure routes, including food ingestion. However, like BCF, the bioaccumulation factor (BAF) in fish is the ratio of the concentration of a chemical in the organism to its concentration in water [ 5 , 6 ]. According to Zeitoun and Mehana [ 7 ], this index is used to assess the concentration of heavy metals in various fish tissues.…”