## 1 Introduction
They are responsible for the organic matter's biodegradation. Fecal and non-fecal coliforms, or total coliforms, are frequently utilized as markers of the overall bacteriological indicators of surface-waters. Total coliforms offer information about the rate of organic contamination and fecal coliforms are useful indicators for assessing fecal contamination and the potential presence of pathogens [13]. Using culture methods, ref. [14] showed that a high concentration of heterotrophic bacteria in the water makes it difficult to determine the presence of fecal coliforms. In these conditions, the evaluation of the total coliforms can serve as an indicator of water pollution. In the 1990s, the issue of pharmaceutical residues in water gained attention. Following numerous published reports, only in 2013, three pharmaceutical substances ended high up on the watch list of Directive 39/2013 within the Water Framework (diclofenac, 17-\(\beta\)-estradiol, 17-\(\alpha\)-ethinylestradiol). Starting with Directive 2013/39/EU [15] to current Decision 2022/1307 [16], the Watch List mechanism established in 2013 by EU Directive was intended to improve the available information on the occurrence of substances of greatest concern. In the context of the great number of reports regarding the occurrence of the contaminants of emerging concern (CECs) in the environment and the continuous updating of the regulation in the field of water policy [15; 16; 17; 18; 19; 20], there is a need for constant monitoring of these contaminants in the water environment [21; 22; 23; 24; 25; 26; 27]. A better knowledge of pollutants' occurrence will help to derive prioritization strategy and development of environmental quality standards. The Danube River is among the world's top 10 rivers considered at risk [1]. As the second largest catchment region in Europe, the Danube River Basin was subjected to numerous monitoring campaigns along the entire river length, either within the Joint Danube Surveys (JDS), coordinated by the International Commission for the Protection of Danube River (ICPDR) [28; 29; 30; 31; 32], or individual surveys conducted on shorter sectors [10; 12; 23; 33; 34]. The Joint Danube Survey JDS4 included 51 sampling sites in 13 countries across the Danube River Basin [31], out of which in Romania only 7 sampling sites have been surveyed. The MONITOX project, supported by the EC through the Joint Operational Programme Black Sea Basin 2014-2020 [35], has established a complex network of 32 sampling points on Romanian territory along the Danube River, Danube Delta and up to the Black Sea littoral, starting from Ostrov/Silistra at Romania-Bulgaria border (Figure 1), in order to assess the quality of surface water from a physico-chemical, chemical, and microbiological point of view. The Black Sea was also selected due to the semi-enclosed sea character, the size of the hydrographical basin, and its hydrobiological features which make the Black Sea a unique ecosystem, extremely sensitive and exposed to organic and inorganic threats [36]. Due to the limited information reported in literature, a total of 30 CECs--including pharmaceuticals, azolic pesticides, synthetic hormones, and endocrine disruptors--were selected for monitoring in the present study, performed within the MONITOX program using liquid chromatography-tandem high resolution mass spectrometry (LC-HRMS/MS). The selection of emerging organic contaminants was based on several criteria: (i) ecotoxicological potential; (ii) inclusion on the watch list of the last Decision in the Water Framework; (iii) compounds not routinely monitored; (iv) contaminants which had been previously detected in the Danube River. Besides the selected CECs, the surface water physico-chemical parameters (9 metals, 7 nutrient compounds) and two microbiological indicators were investigated in the fluvial, deltaic, and marine environments belonging to the connected system Danube River-Danube Delta-Black Sea in SE part of Romania.