## 3 Results
### Macrozoobenthos  
In 2018-2020, the total taxa composition of the riverine macrozoobenthos of the Lower Dniester covering all two sites of investigation (Maiaky and Palanca) consisted of 108 species from 44 families. Species number varied from 1 to 18 per sampling area of 0.025 m\({}^{2}\) and up to 40 species in the drag-samplings (Table 3). The most diverse taxa were Diptera (23), Gastropoda (22), Oligochaeta (18), and Crustacea (11); species numbers in the other groups did not exceeded 5. The most frequent taxa were _Aulodrilus pluriseta_ ([PERSON], 1906), _Branchiura sowerbyi_ [PERSON], 1893, Corixiidae Gen. sp., _Dreissena polymorpha_ ([PERSON], 1771), _Eseriana esperi_ ([PERSON], 1823), _Katumysis warpachowskyi_ [PERSON], 1877, _Limmodrillus_ spp., _Limnomysis benedeni_ [PERSON], 1882, _Lithoglyplus naticoides_ ([PERSON], 1828), _Polypedilum_ (_Uleysipedilum_) _convictum_ ([PERSON], 1856), _Psammoryctides barhatus_ ([PERSON], 1861), _Tubifex tubifex_ ([PERSON], 1774), _Viviparus ater_ ([PERSON] and [PERSON], 1832), _Viviparus contetcus_ ([PERSON], 1813), and _Viviparus viviparus_ ([PERSON], 1758). Sensitive Ephemeroptera, Pecoptera, and Trichoptera (EPT) taxa were found accidently in dredge samples within the Palanca sampling points: 3 October 2018 _Enomus tenellus_ ([PERSON], 1842) 28 October 2019, _Mystacides longicornis_ ([PERSON], 1758), Polycentropodidae, 22 October 2020-_Agraylea_ sp. All of listed EPT species had low number (1-80 ind./sample) and did not influence the total abundance of the bottom community. _Branchiura sowerbyi_, an alien warm water species from Asia, was present in all biotopes such as silt, sand, and aquatic vegetation. Previously, it was known mainly from the Danube region and was rare in Dniester (Serbia, 1983; [PERSON], 1983; [PERSON], 1983). Other invasive species, known for the Dniester basin such as _Ferrissia californica_ ([PERSON], 1863), _Macrobrachium nipponense_ ([PERSON], 1849), _Physella acuta_ ([PERSON], 1805), _Dreissena rostriformis bugensis_ [PERSON], 1897, _Potamopyrgus antipodarum_ ([PERSON], 1853) were not a significant element of the fauna in terms of general abundance or biomass. \begin{table}
\begin{tabular}{c c c c c} \hline \hline \multirow{2}{*}{**Biotic Characteristics**} & \multicolumn{3}{c}{**1949–1951**} & \multicolumn{3}{c}{**2018–2020**} \\ \cline{2-5}  & **Average \(\pm\) SE** & **Range** & **Average \(\pm\) SE** & **Range** \\ \hline Abundance, ind. m\({}^{-2}\) & 3914 \(\pm\) 828 & 1463–6432 & 14,528 \(\pm\) 3552 & 107–58,764 \\ Biomass, g m\({}^{-2}\) & 29 \(\pm\) 9 & 7.27–56 & 799 \(\pm\) 230 & 0.76–3411 \\ Number of Taxa & 11 \(\pm\) 3 & 3–21 & 8 \(\pm\) 1 & 1–40 \\ Shannon Index & 0.81 \(\pm\) 0.16 & 0.22–1.25 & 1.28 \(\pm\) 0.08 & 0.1–1.85 \\ Saprobic Index (Zelinka \& Marvan) & 2.14\(\pm\)0.09 & 1.9-2.32 & 2.25 \(\pm\) 0.06 & 1.94–3.27 \\ Romania Saprobic Index & 2.28 \(\pm\) 0.11 & 1.98–2.5 & 2.2 \(\pm\) 0.06 & 1.96–3.08 \\ BMWP Score & 19 \(\pm\) 6 & 8–47 & 14 \(\pm\) 1 & 1–32 \\ BMWP N taxa & 5 \(\pm\) 1 & 2–10 & 4 \(\pm\) 1 & 1–7 \\ Average BMWP score per Taxon & 4.1 \(\pm\) 0.15 & 3.75–4.7 & 3.43 \(\pm\) 0.18 & 1–4.57 \\ DSFI Diversity Groups & — & 0–1 & — & 0–3 \\ DSFI & — & — & — & — \\ BBI & 3.5 \(\pm\) 0.24 & 3–4 & 3.9 \(\pm\) 0.11 & 3–5 \\ Potamon Type Index & 3.45 \(\pm\) 0.58 & 1.87–5 & 3.05 \(\pm\) 0.19 & 1.67–5 \\ Functional Feeding Groups & & & & \\ \% Grazers and scrapers & 20.02 \(\pm\) 11.03 & 0–68.18 & 11.53 \(\pm\) 2.46 & 0–47.41 \\ \% Miners & & & 1.29 \(\pm\) 0.75 & 0–15.82 \\ \% Shredders & & & 0.73 \(\pm\) 0.36 & 0–7.71 \\ \% Gatherers/Collectors & 34.91 \(\pm\) 15.29 & 3.05–95.04 & 47.92 \(\pm\) 6.9 & 0–92.4 \\ \% Active filter feeders & 20.71 \(\pm\) 12.2 & 0–77.88 & 7.29 \(\pm\) 1.83 & 0–40 \\ \% Passive filter feeders & 3.42 \(\pm\) 3.39 & 0–20.36 & 1.03 \(\pm\) 1.02 & 0–22.37 \\ \hline \hline \end{tabular}
\end{table} 
Table 3: Benthic community state of the Lower Dniester within natural flow [3; 9] and modern periods, calculated using with Asterics 4.04.