Environmental Engineering Reference
In-Depth Information
reduce their exposure time to toxicants by escaping from adverse situations. Both
periphyton and phytoplankton can also be used to run PICT approaches in lake
ecosystems, as shown by Nyström et al. (
2002
) and Bérard et al. (
2003
), who
assessed the toxic effects of Irgarol 1051 and/or atrazine on microalgal communities
in Lake Geneva
3.3
Recovery Studies
In only a few, more recently performed studies have researchers examined recovery
processes of phototrophic communities, following herbicide exposure under natural
river contamination conditions (Dorigo et al.
2010a, b
; Morin et al.
2010
; Rotter
et al.
2011
). The authors of these four studies have attempted to characterize the
dynamics of recovery of periphytic communities transplanted from herbicide-
contaminated sites to “nonpolluted” reference sites. The recovery processes were
evaluated for changes in community structure (biomass, distribution of algal
classes), diversity (diatom taxonomic composition, 18S PCR-DGGE band patterns)
and tolerance capacities, using PICT-approaches for the most predominant herbi-
cide in the studied rivers (i.e., diuron in Dorigo et al.
2010a, b
and prometryn in
Rotter et al.
2011
). The results indicated a high recovery potential for periphytic
communities. Evidence supported the view that communities recovered, at least
partially, in structural, diversity, and functional attributes, after a few weeks within
reference sites. Accordingly, Dorigo et al. (
2010a, b
) and Rotter et al. (
2011
) empha-
sized that the use of bioilm recovery capacity could potentially be a suitable man-
agement tool for analysis of recovery processes in freshwater ecosystems, especially
when using the PICT-concept. However, Morin et al. (
2010
) emphasized that immi-
gration and emigration of algal species certainly takes place in such transplantation
experiments. Therefore, the observed trajectories of recovery were probably
assisted by such species migration, rather than resulting only from the new expo-
sure conditions at transplantation sites.
4
Potential Future Areas for Research
Among many future areas of research, three main promising ones have been
identiied:
•
Improvement of exposure characterization, and improved measurement of
bioavailable contaminant concentrations
Improvement or diversiication of effects characterization from individual to the
•
community level
Assessment of environmental restoration and ecological trajectories after removal
•
of toxic pressure
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