The project implementation team completed the water quality assessment report based on aquatic invertebrates. The purpose of the report was to have a detailed picture of the species composition and water quality class on Gilort River. Aquatic invertebrates are extremely effective tools in assessing water quality due to the large populations with varying degrees of tolerance to various changes in the forms of environmental pressure. They also have a relatively long life cycle and different ecological roles and are relatively easy to collect, identify and classify.

The specific objectives of the report targeted:

  • determination of identified invertebrate species at the level of species, family, order and class;
  • estimating the size and density of species populations;
  • evaluation of abiotic parameters of the inspected areas (nature of the substrate, pH, temperature, dissolved oxygen).

In order to meet the objectives of the report, two sampling campaigns were carried out, in autumn 2018 and summer 2019, collecting 25 samples of benthic invertebrates. In order to collect the samples, a total of 12 river sectors were considered, both on the main course of Gilort River (Upstream Novaci, Pociovalistea, Upstream Balcesti, Balcesti, Bengesti, Mirosloveni, Albeni 1, Albeni 2 and Stefanesti) and on 3 tributaries (Ciocadia , Galbenu and Blahnita).

A total of 103 taxa at the species or genus level were identified in the 12 samples taken in the autumn 2018 campaign, and only 92 specific or gender taxa in the 13 samples taken in the summer of 2019, probably due to increased flows from the second campaign and / or the life cycle of benthic organisms. The main taxonomic groups identified in the two years analyzed were oligochaetes, chironomids, ephemeroptera and trichoptera.

Also, the density of groups of benthic invertebrates was estimated, as number of individuals per square meter (Cimpean et al., 2011), extrapolating the data obtained from the sampling surface. The total densities calculated for the communities considered in the samples collected in autumn 2018 were generally between 1000 and 5000 individuals / sqm, except for the Mirosloveni point, where the large number of oligochaetes led to total density values that exceeded 10,000 individuals /sqm. The values of the absolute density for the benthic invertebrate communities from the stations taken in the summer of 2019 were generally between 600 and 5000 individuals / sqm, with very high values registered at the Balcesti station (over 8000 individuals / sqm). These lower total density values can be explained by the abundant rainfall characteristic of the sampling period, which resulted in increased flows at all biological sample collection points.

Gilort River water quality based on aquatic invertebrate communities

Based on the Water Framework Directive (2000/60 / EC), four biotic indices based on benthic aquatic invertebrate communities were used: the saprob index, the index based on the number of families, the EPT index (the percentage of individuals in the order Ephemeroptera , Plecoptera and Trichoptera compared to the total number of individuals in the sample) and the Extended Biotic Index (IBE).

Based on the four indices considered, the water quality of Gilort River varies between very good (category I) and poor (category IV). Sections with quality categories III and IV are recorded only for the EPT index, which refers to insect species intolerant or less tolerant of disturbances, the other indicators being all included in categories I and II (very good and good).

In many areas of the river, the bed of the riverbed is mostly made of marne. Where the EPT indicator has values in categories III and IV (mediocre or poor), this is most likely the result of erosion and sedimentation processes, but also anthropogenic interventions in the riverbed.

Referință

Cîmpean, M., Battes, K.P., Momeu, L. (2011) Hidrobiologie – Ape continentale – Ghid de lucrări practice, Presa Universitara Clujeană, Cluj Napoca, 109 p.

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