macroinvertebrate species, as observed in a field study by Walters et al. (2015). Zn is
another essential metal with toxicity at high concentrations that was also found to
transfer through the food web (Farag et al. 2007) and biomagnify in the mayfly
Centroptilum triangulifer (Kim et al. 2012). While Zn concentration in mayfly larvae
was 16–19-fold higher than in the labeled contaminated periphyton used as a food
resource, Zn concentration in adults was only threefold to eightfold higher than in
diet (Kim et al. 2012). Therefore, dietary bioaccumulation dynamics in biofilm
consumers depend on the species, its growth stage, and its subsequent physiological
abilities to assimilate and/or eliminate metals.
Moreover, there may be only very limited trophic transfer for metals or metallic
nanoparticles. For example, titanium nanoparticles were fairly highly accumulated in
sediment biofilm but barely transferred from biofilms to river snails and Chinese
muddy loaches, with BMFs of just 0.01–0.02 and 0.04–0.05, respectively (Kim et al.
2016), highlighting the low degree of bioaccumulation of TiO 2 in these consumers.
Organic contaminants, and in particular persistent chemicals, are likely to be
transferred and/or biomagnified from microbial biofilms to higher trophic levels.
Concentrations of tris(2-butoxyethyl) phosphate (TBEP), a flame retardant quantified consistently across all food web compartments, were found to increase with
trophic levels (Ruhí et al. 2016). Indeed, in a Mediterranean river food web,
microbial biofilms accumulated the lowest amount of TBEP, whereas intermediate
concentrations of TBEP were found in the primary consumer Ancylus, and the
highest concentrations were found in the omnivore filter-feeding Hydropsyche and
the macroinvertebrate predator Phagocata (Ruhí et al. 2016). Similarly, concentrations of the drug carbamazepine in a stream food web including biofilms, invertebrates, and vertebrates were correlated with trophic position (Du et al. 2014). PCB
concentrations were also significantly correlated with trophic level, as described in
Walters et al. (2008, 2011), with an average BMF close to 1.6. The hydrophobicity
of PCBs (i.e., their K ow value) strongly modulates their trophic transfer and
biomagnification (Walters et al. 2008, 2011). Whereas the influence of K ow on
biomagnification varies substantially across food webs, model predictions of standardized K ow -based BMFs remain consistent with field observations (Walters et al.
2011). Like metals, some organic contaminants were also found to be biomagnified
slightly (e.g., low increase of chlorpyrifos concentrations from biofilm to snail;
Lundqvist et al. 2012) or not (e.g., diclofenac, gemfibrozil (Ruhí et al. 2016);
diphenhydramine (Du et al. 2015)) through the food web.
Exposure scenarios and environmental conditions are also likely to influence
contaminant fate through food webs. For instance, TiO 2 nanoparticles accumulated
much more in biofilm after sequential low-dose exposures than after a single highdose exposure (Kim et al. 2016). On one hand, environmental conditions may
influence contaminant uptake and dynamics in microbial biofilms and thus modulate
the amount available for further trophic transfer. On the other hand, microbial
biofilm quality as a food resource (e.g., C/N) is also likely to influence trophic
transfers of nutrients and contaminants. In addition, C/N ratio can also be modulated
by environmental factors (e.g., flow velocity; Coat et al. 2011), while dissolved
organic matter (DOM) concentrations in surrounding water can modify contaminant
140
C. Bonnineau et al.
another essential metal with toxicity at high concentrations that was also found to
transfer through the food web (Farag et al. 2007) and biomagnify in the mayfly
Centroptilum triangulifer (Kim et al. 2012). While Zn concentration in mayfly larvae
was 16–19-fold higher than in the labeled contaminated periphyton used as a food
resource, Zn concentration in adults was only threefold to eightfold higher than in
diet (Kim et al. 2012). Therefore, dietary bioaccumulation dynamics in biofilm
consumers depend on the species, its growth stage, and its subsequent physiological
abilities to assimilate and/or eliminate metals.
Moreover, there may be only very limited trophic transfer for metals or metallic
nanoparticles. For example, titanium nanoparticles were fairly highly accumulated in
sediment biofilm but barely transferred from biofilms to river snails and Chinese
muddy loaches, with BMFs of just 0.01–0.02 and 0.04–0.05, respectively (Kim et al.
2016), highlighting the low degree of bioaccumulation of TiO 2 in these consumers.
Organic contaminants, and in particular persistent chemicals, are likely to be
transferred and/or biomagnified from microbial biofilms to higher trophic levels.
Concentrations of tris(2-butoxyethyl) phosphate (TBEP), a flame retardant quantified consistently across all food web compartments, were found to increase with
trophic levels (Ruhí et al. 2016). Indeed, in a Mediterranean river food web,
microbial biofilms accumulated the lowest amount of TBEP, whereas intermediate
concentrations of TBEP were found in the primary consumer Ancylus, and the
highest concentrations were found in the omnivore filter-feeding Hydropsyche and
the macroinvertebrate predator Phagocata (Ruhí et al. 2016). Similarly, concentrations of the drug carbamazepine in a stream food web including biofilms, invertebrates, and vertebrates were correlated with trophic position (Du et al. 2014). PCB
concentrations were also significantly correlated with trophic level, as described in
Walters et al. (2008, 2011), with an average BMF close to 1.6. The hydrophobicity
of PCBs (i.e., their K ow value) strongly modulates their trophic transfer and
biomagnification (Walters et al. 2008, 2011). Whereas the influence of K ow on
biomagnification varies substantially across food webs, model predictions of standardized K ow -based BMFs remain consistent with field observations (Walters et al.
2011). Like metals, some organic contaminants were also found to be biomagnified
slightly (e.g., low increase of chlorpyrifos concentrations from biofilm to snail;
Lundqvist et al. 2012) or not (e.g., diclofenac, gemfibrozil (Ruhí et al. 2016);
diphenhydramine (Du et al. 2015)) through the food web.
Exposure scenarios and environmental conditions are also likely to influence
contaminant fate through food webs. For instance, TiO 2 nanoparticles accumulated
much more in biofilm after sequential low-dose exposures than after a single highdose exposure (Kim et al. 2016). On one hand, environmental conditions may
influence contaminant uptake and dynamics in microbial biofilms and thus modulate
the amount available for further trophic transfer. On the other hand, microbial
biofilm quality as a food resource (e.g., C/N) is also likely to influence trophic
transfers of nutrients and contaminants. In addition, C/N ratio can also be modulated
by environmental factors (e.g., flow velocity; Coat et al. 2011), while dissolved
organic matter (DOM) concentrations in surrounding water can modify contaminant
140
C. Bonnineau et al.