however, distinguished from the total accumulation in sediments because of
methodological difficulties in discriminating the biotic from the abiotic fraction of
sediments. Nevertheless, due to both physicochemical and biological characteristics,
sediments can store contaminants for much longer, and can thus be viewed as a more
stable compartment, even if disruptions (flood events, changes in pH or redox
potential, etc.) can trigger releases.
By taking up contaminants from the surface water, microbial biofilms help to
“clean” the water. But they can only completely degrade a few organic contaminants
(the in situ efficiency of this kind of process being still unknown), and so the
remaining bulk of accumulated contaminants (and/or their metabolites) will be either
resuspended in the water column in a dissolved or complexed form (e.g., following
biofilm detachment or sediment mobilization) or get transferred to higher trophic
levels.
4 Contaminant Transfer from Microbial Biofilms Through
Food Webs
In freshwater ecosystems, microbial biofilms are an important food resource (in both
the green and brown food webs; Fig. 3), even if potentially contaminated by metals
or organic contaminants. Microcosm and field studies conducted to investigate the
role and importance of these biofilm communities in contaminant trophic transfer
have revealed important differences in terms of contaminant fate through food webs.
4.1 Current Approaches Used to Follow Contaminants
Through Food Webs
Microcosm experiments are commonly used to reproduce simple food webs under
controlled conditions in order to limit any confounding factors likely to influence the
bioaccumulation process (e.g., temperature, nutrients, pH, ionic composition) and
explore the fate of the contaminants. These microcosm experiments typically consist
in exposing animals to a food source, namely, a single (often algal) microorganism
species or natural biofilms, spiked with a contaminant. For instance, simplified food
chains, i.e., from primary producers to consumers such as crustaceans, insects,
bivalves, and more rarely fish, have been reproduced in microcosm experiments to
determine the trophic transfer of metals or metallic nanoparticles (Croteau et al.
2005; Conley et al. 2009; Komjarova and Blust 2009; Prokes et al. 2012; Golding
et al. 2013; Kim et al. 2016). These microcosm studies usually contaminate the food
resource in an independent spiking process before introducing it into the microcosm.
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C. Bonnineau et al.
methodological difficulties in discriminating the biotic from the abiotic fraction of
sediments. Nevertheless, due to both physicochemical and biological characteristics,
sediments can store contaminants for much longer, and can thus be viewed as a more
stable compartment, even if disruptions (flood events, changes in pH or redox
potential, etc.) can trigger releases.
By taking up contaminants from the surface water, microbial biofilms help to
“clean” the water. But they can only completely degrade a few organic contaminants
(the in situ efficiency of this kind of process being still unknown), and so the
remaining bulk of accumulated contaminants (and/or their metabolites) will be either
resuspended in the water column in a dissolved or complexed form (e.g., following
biofilm detachment or sediment mobilization) or get transferred to higher trophic
levels.
4 Contaminant Transfer from Microbial Biofilms Through
Food Webs
In freshwater ecosystems, microbial biofilms are an important food resource (in both
the green and brown food webs; Fig. 3), even if potentially contaminated by metals
or organic contaminants. Microcosm and field studies conducted to investigate the
role and importance of these biofilm communities in contaminant trophic transfer
have revealed important differences in terms of contaminant fate through food webs.
4.1 Current Approaches Used to Follow Contaminants
Through Food Webs
Microcosm experiments are commonly used to reproduce simple food webs under
controlled conditions in order to limit any confounding factors likely to influence the
bioaccumulation process (e.g., temperature, nutrients, pH, ionic composition) and
explore the fate of the contaminants. These microcosm experiments typically consist
in exposing animals to a food source, namely, a single (often algal) microorganism
species or natural biofilms, spiked with a contaminant. For instance, simplified food
chains, i.e., from primary producers to consumers such as crustaceans, insects,
bivalves, and more rarely fish, have been reproduced in microcosm experiments to
determine the trophic transfer of metals or metallic nanoparticles (Croteau et al.
2005; Conley et al. 2009; Komjarova and Blust 2009; Prokes et al. 2012; Golding
et al. 2013; Kim et al. 2016). These microcosm studies usually contaminate the food
resource in an independent spiking process before introducing it into the microcosm.
136
C. Bonnineau et al.