Temporal variation in benthic macroinvertebrate community from impaired streams
2019
During the last century global population has experienced immense growth leading
to huge changes in land use planning to cope with its own sustentation. More in detail,
world population has shifted from an agriculture-based economy to an industrial society,
which has pushed the population to move from rural to urban areas. The development of
urban areas has led to changes in the physical structure of the environment (i.e. water
bodies and surrounding area) being responsible for water quality changes by diffuse and
point pollution and alterations in hydrological features such as flow magnitude and
frequency. As a consequence of the physical and chemical alterations, instream
community structure and composition has been altered and, hence, the ecological
integrity of rivers has been jeopardized.
Despite efforts to restore the natural state and functioning of the river systems
there is still a lack of knowledge on three questions that I sought to explain in this
dissertation: (i) is the variation of macroinvertebrate community inherent to the
impairment of the river or is there a natural fluctuations that guides long-term variation?;
(ii) how do rivers respond to restoration activities when biological communities may
already be adapted to such impaired conditions?; and (iii) which are the most successful
restoration measures at improving the biological condition of the river.
To answer these questions I studied impaired river systems in Canada and Italy.
Interannual variability of macroinvertebrate community from eight Canadian rivers,
representing a gradient of anthropogenic water quality pressures and variable
hydrological regimes, were studied over a period of 20 years, focusing on the relationship
between water quality, hydrologic variables and sampling features. In Italy the process of
restoration of an urban river was followed over a period of 3 years studying the
relationship between environmental variables and macroinvertebrate community,
focusing on the hydromorphological improvements.
Results of the Partial Least Square (PLS) Regressions on data from the long-term
study demonstrated that the benthic community assemblage was not driven by any of the measured environmental variables (i.e. water quality, hydrologic variables, sampling
features), while at a short-term benthic community responded to water quality and
hydrometric features, but did not show significant responses to restoration measures.
The temporal stability of the studied benthic communities to variations in environmental
and anthropogenic conditions may be reflective of the limited pool of tolerant taxa within these systems.
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