TolerancePatterns in Stream Biofilms Link ComplexChemical Pollution to Ecological Impacts
2020
Preventing and remedying fresh waters
from chemical pollution is
a fundamental societal and scientific challenge. With other nonchemical
stressors potentially co-occurring, assessing the ecological consequences
of reducing chemical loads in the environment is arduous. In this
case study, we comparatively assessed the community structure, functions,
and tolerance of stream biofilms to micropollutant mixtures extracted
from deployed passive samplers at wastewater treatment plant effluents.
These biofilms were growing up- and downstream of one upgraded and
two nonupgraded wastewater treatment plants before being sampled for
analyses. Our results showed a substantial decrease in micropollutant
concentrations by 85%, as the result of upgrading the wastewater treatment
plant at one of the sampling sites with activated carbon filtration.
This decrease was positively correlated with a loss of community tolerance
to micropollutants and the recovery of the community structure downstream
of the effluent. On the other hand, downstream biofilms at the nonupgraded
sites displayed higher tolerance to the extracts than the upstream
biofilms. The observed higher tolerance was positively linked to micropollutant
levels both in stream water and in biofilm samples, and to shifts
in the community structure. Although more investigations of upgraded
sites are needed, our findings point toward the suitability of using
community tolerance for the retrospective assessment of the risks
posed by micropollutants, to assess community recovery, and to relate
effects to causes in complex environmental conditions.
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