including pH and temperature, were also shown to be important drivers of metal
accumulation in sediments (Lin and Chen 1998; Saeedi et al. 2011; Li et al. 2013), in
which the sorption, release, and transport of metals are important processes influencing the chemical quality of water bodies (Tao et al. 2005; Fan et al. 2007).
After sorption to sediments and leaf litter material, organic contaminants can be
partially or totally biodegraded by the attached microbial communities. Thus, two
species of aquatic hyphomycetes (Heliscus lugdunensis, Clavariopsis aquatica)
typically associated with submerged leaf litter were found to biotransform
1-naphthol (Augustin et al. 2006) or technical nonylphenol (Sole et al. 2008).
Recently, leaf-associated communities from sites downstream of agricultural areas
were shown to exhibit a greater potential to degrade the maize herbicide nicosulfuron
compared to those from upstream communities, and this was partly explained by the
pre-exposure history of these communities to the contaminant (Carles et al. 2017). In
these microbial communities, Carles et al. (2018) isolated an ascomycete fungus
(Plectosphaerella cucumerina AR1) capable of transforming nicosulfuron into its
two major metabolites (2-amino-4,6-dimethoxypyrimidine and 2-(aminosulfonyl)N,N-dimethyl-3-pyridinecarboxamide) in the presence of glucose. Microbial
biofilms from river sediments have also been shown to degrade nonylphenol
(Wang et al. 2014) and the herbicides diuron (Pesce et al. 2009) and isoproturon
(Trinh et al. 2012), among others.
3.3 Contaminant Distribution in Different Kinds of Biofilms
and Potential Contribution to Trophic Transfer
in Aquatic Ecosystems
Periphytic, sediment, and leaf litter biofilms can all act as both sink and source of
contaminants for the aquatic ecosystem. Only a few studies have set out to investigate in situ the relationship between contaminant concentrations in periphytic
biofilms and in sediments in contaminated rivers, and the focus has been exclusively
on metals (Farag et al. 1998, 2007; Holding et al. 2003; Kohušová et al. 2011;
Ancion et al. 2013). Conceptually, any sound assessment of contaminant
bioaccumulation in microbial biofilms and its consequences on trophic transfers of
contaminants in aquatic ecosystems needs to account for the ecological dynamics
affecting each type of aquatic biofilm. Periphytic biofilms follow a several-stage life
cycle from colonization and co-adhesion to final detachment (due to biological
mechanisms and/or physical constraints), and so contaminant bioaccumulation in
these microbial communities can be viewed as transient. Bioaccumulation of contaminants on leaf litter is also transient (according to the leaf litter decay rates) and
seasonally specific as it depends on the availability of plant litter (e.g., litter fall
peaks in autumn in temperate rivers). In sediments, contaminants are accumulated in
microbial biofilms attached to sediment but also complexed with inert material. The
specific bioaccumulation of microbial biofilms in this accumulation cannot be,
Role of Biofilms in Contaminant Bioaccumulation and Trophic Transfer in Aquatic. . .
135
accumulation in sediments (Lin and Chen 1998; Saeedi et al. 2011; Li et al. 2013), in
which the sorption, release, and transport of metals are important processes influencing the chemical quality of water bodies (Tao et al. 2005; Fan et al. 2007).
After sorption to sediments and leaf litter material, organic contaminants can be
partially or totally biodegraded by the attached microbial communities. Thus, two
species of aquatic hyphomycetes (Heliscus lugdunensis, Clavariopsis aquatica)
typically associated with submerged leaf litter were found to biotransform
1-naphthol (Augustin et al. 2006) or technical nonylphenol (Sole et al. 2008).
Recently, leaf-associated communities from sites downstream of agricultural areas
were shown to exhibit a greater potential to degrade the maize herbicide nicosulfuron
compared to those from upstream communities, and this was partly explained by the
pre-exposure history of these communities to the contaminant (Carles et al. 2017). In
these microbial communities, Carles et al. (2018) isolated an ascomycete fungus
(Plectosphaerella cucumerina AR1) capable of transforming nicosulfuron into its
two major metabolites (2-amino-4,6-dimethoxypyrimidine and 2-(aminosulfonyl)N,N-dimethyl-3-pyridinecarboxamide) in the presence of glucose. Microbial
biofilms from river sediments have also been shown to degrade nonylphenol
(Wang et al. 2014) and the herbicides diuron (Pesce et al. 2009) and isoproturon
(Trinh et al. 2012), among others.
3.3 Contaminant Distribution in Different Kinds of Biofilms
and Potential Contribution to Trophic Transfer
in Aquatic Ecosystems
Periphytic, sediment, and leaf litter biofilms can all act as both sink and source of
contaminants for the aquatic ecosystem. Only a few studies have set out to investigate in situ the relationship between contaminant concentrations in periphytic
biofilms and in sediments in contaminated rivers, and the focus has been exclusively
on metals (Farag et al. 1998, 2007; Holding et al. 2003; Kohušová et al. 2011;
Ancion et al. 2013). Conceptually, any sound assessment of contaminant
bioaccumulation in microbial biofilms and its consequences on trophic transfers of
contaminants in aquatic ecosystems needs to account for the ecological dynamics
affecting each type of aquatic biofilm. Periphytic biofilms follow a several-stage life
cycle from colonization and co-adhesion to final detachment (due to biological
mechanisms and/or physical constraints), and so contaminant bioaccumulation in
these microbial communities can be viewed as transient. Bioaccumulation of contaminants on leaf litter is also transient (according to the leaf litter decay rates) and
seasonally specific as it depends on the availability of plant litter (e.g., litter fall
peaks in autumn in temperate rivers). In sediments, contaminants are accumulated in
microbial biofilms attached to sediment but also complexed with inert material. The
specific bioaccumulation of microbial biofilms in this accumulation cannot be,
Role of Biofilms in Contaminant Bioaccumulation and Trophic Transfer in Aquatic. . .
135