D-glucuronic, D-galacturonic, and mannuronic acids) was found to facilitate the
sorption of various cationic metals (e.g., Pb
2+ , Cu
2+ ) (Flemming 1995). Sorption
of organic contaminants is partly driven by hydrophobic interactions, and so octanolwater partition coefficient (K ow ) is often used to estimate the sorption capacity of
organic contaminants in microbial biofilms. However, other types of interactions
also occur (e.g., ionic, electrostatic, etc.) and thus need to be considered.
Microbial biofilms influence contaminant fate in aquatic ecosystems through their
contribution to biotransformation processes and trophic transfers. Indeed, both
phototrophic and heterotrophic biofilms are foundational to aquatic food webs.
Phototrophic biofilms generate biomass from light energy and carbon dioxide, thus
providing organic substrates and oxygen (Roeselers et al. 2008), while heterotrophic
biofilms are able to decompose various organic materials and thus play a key role in
nutrient fluxes in aquatic ecosystems (Romani and Sabater 2001; Battin et al. 2003).
Accordingly, while periphytic biofilms are at the base of “green” food webs
supported by primary production (Danger et al. 2008; Zou et al. 2016), biofilms
formed on organic substrates play a functionally pivotal role in “brown” food webs
based on allochthonous organic matter decomposition (Hall and Meyer 1998). The
spatial proximity between autotrophic and heterotrophic microorganisms also drives
carbon and nutrient cycling within periphytic biofilms where autotrophic biomass
and activity can stimulate the development and activity of heterotrophic microbial
communities (Romani et al. 2004). This same pattern has been observed in detritusbased food webs where primary production can stimulate leaf litter decomposition
by microbial heterotrophs (Danger et al. 2013). In aquatic environments, “green”
and “brown” food webs thus tend to connect through complex interactions (Zou
et al. 2016). Biofilm assemblages play a key role in interconnecting between these
“green” and “brown” food webs that are foundational to ecosystem functioning
(Krumins et al. 2013; Zou et al. 2016) (Fig. 3). Whatever the substrate and food web
involved, these biofilm assemblages are consumed by various microbial predators
(e.g., amoeba, ciliate, rotifers; Neury-Ormanni et al. 2016) and meso-/macrofauna
(Alvarez and Peckarsky 2005; Guasch et al. 2016) or fish (Schneck et al. 2013),
which means that contaminants bioaccumulated in microbial biofilms are likely to be
transferred to higher trophic levels in the food web (Singh et al. 2006).
During the last decade, research on the role of microbial biofilms in contaminant
fate and transfer has mainly focused on metal accumulation in periphytic biofilms
(e.g., Ancion et al. 2010; Fabure et al. 2015; Pesce et al. 2018) and on the
degradation of organic contaminants in sediments (e.g., Pesce et al. 2009, 2013;
Trinh et al. 2012). Nevertheless, recent studies have highlighted the potential role of
periphytic and leaf litter biofilms in organic contaminant accumulation and trophic
transfer (e.g., Kohušová et al. 2011; Ruhí et al. 2016). Furthermore, the daughter
directive 2008/105/EU of the Water Framework Directive and Guidance Document
No. 25 both recognize the importance of monitoring and preserving the sediment
compartment to preserve aquatic ecosystems (European Commission 2010). However, scarce few studies have focused on contaminant accumulation in sediment
microbial communities.
Scientific literature on contaminant bioaccumulation in microbial biofilms remain
dispersed, insofar as most of the studies available are focusing on one type of
Role of Biofilms in Contaminant Bioaccumulation and Trophic Transfer in Aquatic. . .
119
sorption of various cationic metals (e.g., Pb
2+ , Cu
2+ ) (Flemming 1995). Sorption
of organic contaminants is partly driven by hydrophobic interactions, and so octanolwater partition coefficient (K ow ) is often used to estimate the sorption capacity of
organic contaminants in microbial biofilms. However, other types of interactions
also occur (e.g., ionic, electrostatic, etc.) and thus need to be considered.
Microbial biofilms influence contaminant fate in aquatic ecosystems through their
contribution to biotransformation processes and trophic transfers. Indeed, both
phototrophic and heterotrophic biofilms are foundational to aquatic food webs.
Phototrophic biofilms generate biomass from light energy and carbon dioxide, thus
providing organic substrates and oxygen (Roeselers et al. 2008), while heterotrophic
biofilms are able to decompose various organic materials and thus play a key role in
nutrient fluxes in aquatic ecosystems (Romani and Sabater 2001; Battin et al. 2003).
Accordingly, while periphytic biofilms are at the base of “green” food webs
supported by primary production (Danger et al. 2008; Zou et al. 2016), biofilms
formed on organic substrates play a functionally pivotal role in “brown” food webs
based on allochthonous organic matter decomposition (Hall and Meyer 1998). The
spatial proximity between autotrophic and heterotrophic microorganisms also drives
carbon and nutrient cycling within periphytic biofilms where autotrophic biomass
and activity can stimulate the development and activity of heterotrophic microbial
communities (Romani et al. 2004). This same pattern has been observed in detritusbased food webs where primary production can stimulate leaf litter decomposition
by microbial heterotrophs (Danger et al. 2013). In aquatic environments, “green”
and “brown” food webs thus tend to connect through complex interactions (Zou
et al. 2016). Biofilm assemblages play a key role in interconnecting between these
“green” and “brown” food webs that are foundational to ecosystem functioning
(Krumins et al. 2013; Zou et al. 2016) (Fig. 3). Whatever the substrate and food web
involved, these biofilm assemblages are consumed by various microbial predators
(e.g., amoeba, ciliate, rotifers; Neury-Ormanni et al. 2016) and meso-/macrofauna
(Alvarez and Peckarsky 2005; Guasch et al. 2016) or fish (Schneck et al. 2013),
which means that contaminants bioaccumulated in microbial biofilms are likely to be
transferred to higher trophic levels in the food web (Singh et al. 2006).
During the last decade, research on the role of microbial biofilms in contaminant
fate and transfer has mainly focused on metal accumulation in periphytic biofilms
(e.g., Ancion et al. 2010; Fabure et al. 2015; Pesce et al. 2018) and on the
degradation of organic contaminants in sediments (e.g., Pesce et al. 2009, 2013;
Trinh et al. 2012). Nevertheless, recent studies have highlighted the potential role of
periphytic and leaf litter biofilms in organic contaminant accumulation and trophic
transfer (e.g., Kohušová et al. 2011; Ruhí et al. 2016). Furthermore, the daughter
directive 2008/105/EU of the Water Framework Directive and Guidance Document
No. 25 both recognize the importance of monitoring and preserving the sediment
compartment to preserve aquatic ecosystems (European Commission 2010). However, scarce few studies have focused on contaminant accumulation in sediment
microbial communities.
Scientific literature on contaminant bioaccumulation in microbial biofilms remain
dispersed, insofar as most of the studies available are focusing on one type of
Role of Biofilms in Contaminant Bioaccumulation and Trophic Transfer in Aquatic. . .
119