## 3 Results
### Macrozoobenthos Diversity and Habitats Type  
Over the course of the three-year study period, 58 taxa in total were identified from the study region (Supplementary Material Table S3). These taxa belong to 16 major taxonomic groups, as follows: Cnidaria (4), Platyhelminthes (2), Nemerteta (3), Polychaeta (19), Gastropoda (3), Bivalvia (12), Thoronida (1), Cirripedia (1), Amphipoda (6), Cumacea (1) and Decapoda (4). Polychaetes and bivalves made up 53% of the total diversity, followed by crustaceans and the other groups. Out of the species collected, two [_Pitar rudis_ ([PERSON], 1795) and _Licocarcinus navigator_ ([PERSON], 1794)] are currently listed in the Order No. 488/2020 regarding the approval of the list of endangered marine species of the Romanian Black Sea coast in order to protect and conserve them [51]. Dominant species included deposit-feeding oligochaetes and polychaetes (_Melinna palmata_, _Heteronastus filiformis_), suspension-feeding mollusks (_Abra nitida_, _Spisula subtruncata_, _Pitar rudis_) and small crustaceans (_Microdeutopus vesiculatus_, _Perioculodes longinanus_, _Ibinoe elisae_). The higher species richness (25-30) was observed in the stations MN209/VIII-25 and MN207/06-40 and lower (11) in MN207/02-25, MN207/03-20, and MN207/03-25 (Supplementary Material Table S1). [PERSON]'s index (d) varied from 1.23 to 3.09 with an average value of 2.01. The Shannon index (H\({}^{\prime}\)) also ranged from 0.70 to 2.13 with an average value of 1.59 (Supplementary Material Table S1). All three diversity indices showed a decline in diversity in areas with traces of trawling identified by geophysical methods (Supplementary Material Table S1 and Figure 6). As in the case of diversity, the values of abundance (indv.m\({}^{-2}\)) and biomass (g.m\({}^{-2}\)) varied from one station to another, a fact illustrated by the similarity indices of the analyzed populations and the dendrogram of the ordering of these stations according to the degree of similarity of macrozoobenthic populations (Figures 6 and 7). The abundance of macrozoobenthic populations varied from 1048 indv.m\({}^{-2}\) to 11,824 indv.m\({}^{-2}\) with an average value of 3254 indv.m\({}^{-2}\), and the biomass from 11.2 g.m\({}^{-2}\) to 1191 g.m\({}^{-2}\) (Supplementary Material Table S1). The spatial distribution of the abundances showed that the highest density was recorded in the SW area of ROSCI0066, namely in the station where no traces of trawling were highlighted (Figure 6). Based on the presence of ecosystem engineers, their coverage, and the kind of substrate, three benthic habitats were identified. According to the SIMPER analysis, there were 32% to 51% similarities between the macrozoobenthic communities at various locations. All of the sampling stations were classified into three categories that correspond to benthic habitats based on similarity values. The ANOSIM of community structure revealed that the three groups' overall community dissimilarity was greater than 69% (global test; R = 0.63, \(p\) = 0.001) (Table 1). \begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**Groups** & **R** & **Significance Level \%** & **Possible** & **Actual** & **Number \(\geq\) Observed** \\  & **Statistic** & **Significance Level \%** & **Permutations** & **Permutations** & **Number \(\geq\) Observed** \\ \hline A, B & 0.667 & 2.9 & 35 & 35 & 1 \\ A, C & 0.893 & 0.1 & 715 & 715 & 1 \\ B, C & 0.385 & 2.2 & 715 & 715 & 16 \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Tests for differences between unordered habitat groups (_Pairwise Tests_). Figure 6: Contour maps showing the variation in the number of macrozoobenthic taxa (**A**), their mean density, M-AMBI*(n) index (**B**) and trawling marks (**A,B**) in ROSCI0066, based on samples collected between 2019 and 2020. The Whitaker index of association-based shade-plot analysis revealed the species with comparable patterns of abundance throughout the samples (Figure 7).