The structure of the macroinvertebrate community (MIC) after restoration of the
Stržen riverbed was analysed. The renaturation of the double meander aims to
increase the water holding capacity of the streambed and therefore improve
ecological conditions in the area of intermittent Lake Cerknica. River
revitalisation is a disturbance, which is followed by a process of recolonisation of
the biotic community. We investigated how variability and diversity of the MIC
changed in different sections of the river (restored sites, reference sites, regulation
channel) one and two years after restoration. Hydrological factors affected our
fieldwork considerably. MI were sampled according to standard methods.
Different diversity (H', d, D) and biotic indices (EPTO, GOLD, ...) were
calculated. At the same time, physical, chemical and hydromorphological
variables were measured and substrate was monitored. Correlations between the
environmental factors and MIC's parameters were investigated using Spearman's
coefficients. 18 468 individuals belonging to 62 distinct families were detected in
the samples. In the revitalised section recolonisation of 24 families had taken place
one year after the construction works, but its diversity was lower compared to the
unrestored sites. The succession of MIC of the restored sites was interrupted by
the deepening works in the summer of 2021 while downstream MIC was affected
by sedimentation of eroded material. The diversity of MIC of all the sampling
sections decreased from 2020 to 2021, most likely due to unfavourable oxygen
and temperature conditions.
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