organic compounds are metabolized by unique enzymes contained in bacteria.
Metabolites, used as energy, are produced by anaerobic bacteria, which are incorporated into cell mass, and/or are changed into nontoxic biological wastes, in the
process of dissimilation (Rehm and Reed 1999). Hydrophytes, fungi, and bacteria
use water soluble organic compound as a carbon or energy source. The bacteria
Nitrosomonas converts ammonium to nitrates.
The use of biological treatment methods driven by microbial communities is
increasing worldwide as a means of remedying anthropogenic pollution (Bond and
Lovely 2003). Passive treatment in constructed wetlands is one such technique that
is applied to handle a wide range of pollutants such as metals, organic substances,
and nutrients. In particular, actions taken to decrease nitrogen transport to downstream recipients have led to increasing numbers of constructed wetlands in agricultural areas in Europe and North America. The efficiency with which individual
wetlands remove nitrogen (mainly through denitrification) varies greatly and has
been associated with, e.g., incoming nitrogen load and amount of available carbon
(Fleischer et al. 1994; Weisner et al. 1994). It is probable that the functioning of
these ecosystems is influenced by the composition and diversity of bacterial communities that are present (Bell et al. 2005). Nevertheless, in that context, few studies
of the performance of constructed wetlands have examined the denitrifying bacteria,
which constitute an integral part of the nitrogen removal process. Information is
lacking about the composition and activity of the denitrifying bacterial community
(Philippot and Hallin 2005) and its link to the DE nitrification rate in wetlands (Rich
and Myrold 2004), although there is evidence that bacterial community composition
does affect the DE nitrification in both terrestrial and aquatic ecosystems (Wallenstein et al. 2006). Thus, knowledge regarding the composition of denitrifying
bacterial communities and the parameters influencing them may prove useful in
improving nitrogen removal in constructed wetlands.
Theories about the distribution of bacterial communities include the idea that
environmental parameters shape the community composition (Martiny et al. 2006;
Shade et al. 2008). The denitrifying bacterial community requires the availability of
organic carbon and an anaerobic environment in order to reduce nitrate, although
there are also other parameters that may influence the community structure and
thereby also the DE nitrification rate. In wetlands, it has been shown that the
structure and/or function of microbial communities can be affected by several
different environmental parameters, including the macrophyte community composition (Weisner et al. 1994), pH and hydraulic loads (Beisner et al. 2006), nitrate and
nitrate loads (Horner-Devine et al. 2003), and habitat size (Reche et al. 2005).
Recently developed molecular methods have enabled characterization of bacterial
communities and assessments of the relative importance of the multiple interacting
drivers that structure these communities in different ecosystems. The analysis of the
eubacteria 16S rRNA gene (rDNA) can provide a broad description of the bacterial
community composition in a habitat (Dahllöf 2002) and studies of several habitats
are available in the literature for comparison (e.g., Langenheder and Prosser 2008).
The functional diversity represented by the denitrifying bacterial community phylogeny may not relate to the taxonomical diversity indicated by the 16S rDNA
6 Constructed Wetlands: A Clean-Green Technology for Degradation and. . .
151
Metabolites, used as energy, are produced by anaerobic bacteria, which are incorporated into cell mass, and/or are changed into nontoxic biological wastes, in the
process of dissimilation (Rehm and Reed 1999). Hydrophytes, fungi, and bacteria
use water soluble organic compound as a carbon or energy source. The bacteria
Nitrosomonas converts ammonium to nitrates.
The use of biological treatment methods driven by microbial communities is
increasing worldwide as a means of remedying anthropogenic pollution (Bond and
Lovely 2003). Passive treatment in constructed wetlands is one such technique that
is applied to handle a wide range of pollutants such as metals, organic substances,
and nutrients. In particular, actions taken to decrease nitrogen transport to downstream recipients have led to increasing numbers of constructed wetlands in agricultural areas in Europe and North America. The efficiency with which individual
wetlands remove nitrogen (mainly through denitrification) varies greatly and has
been associated with, e.g., incoming nitrogen load and amount of available carbon
(Fleischer et al. 1994; Weisner et al. 1994). It is probable that the functioning of
these ecosystems is influenced by the composition and diversity of bacterial communities that are present (Bell et al. 2005). Nevertheless, in that context, few studies
of the performance of constructed wetlands have examined the denitrifying bacteria,
which constitute an integral part of the nitrogen removal process. Information is
lacking about the composition and activity of the denitrifying bacterial community
(Philippot and Hallin 2005) and its link to the DE nitrification rate in wetlands (Rich
and Myrold 2004), although there is evidence that bacterial community composition
does affect the DE nitrification in both terrestrial and aquatic ecosystems (Wallenstein et al. 2006). Thus, knowledge regarding the composition of denitrifying
bacterial communities and the parameters influencing them may prove useful in
improving nitrogen removal in constructed wetlands.
Theories about the distribution of bacterial communities include the idea that
environmental parameters shape the community composition (Martiny et al. 2006;
Shade et al. 2008). The denitrifying bacterial community requires the availability of
organic carbon and an anaerobic environment in order to reduce nitrate, although
there are also other parameters that may influence the community structure and
thereby also the DE nitrification rate. In wetlands, it has been shown that the
structure and/or function of microbial communities can be affected by several
different environmental parameters, including the macrophyte community composition (Weisner et al. 1994), pH and hydraulic loads (Beisner et al. 2006), nitrate and
nitrate loads (Horner-Devine et al. 2003), and habitat size (Reche et al. 2005).
Recently developed molecular methods have enabled characterization of bacterial
communities and assessments of the relative importance of the multiple interacting
drivers that structure these communities in different ecosystems. The analysis of the
eubacteria 16S rRNA gene (rDNA) can provide a broad description of the bacterial
community composition in a habitat (Dahllöf 2002) and studies of several habitats
are available in the literature for comparison (e.g., Langenheder and Prosser 2008).
The functional diversity represented by the denitrifying bacterial community phylogeny may not relate to the taxonomical diversity indicated by the 16S rDNA
6 Constructed Wetlands: A Clean-Green Technology for Degradation and. . .
151