## 5 Microbiological Pollution
In contrast to BacHum marker, the animal associated markers (BacK for ruminant, and Pig2 Bac for pig) were of minor importance along the whole Danube River and major tributaries, except the Danube Delta, where the highest Pig2 Bac concentration (6.9 \(\times\) 10\({}^{3}\) ME/100 mL) was measured in the Sulina arm and Jantra tributary with the highest BacK concentration (2.9 \(\times\) 10\({}^{3}\) ME/100 mL) [145]. Apart from study related to JDSs, very few studies concerning microbiological pollution on the Lower Danube basin were identified. An industrial area of the Danube, near Galati town (rkm 155-158), was investigated from a microbiological point of view for a period of four months, from June to September 2010 [152]. The lowest value for total coliforms of 4.5 \(\times\) 10\({}^{2}\) MPN/mL was measured in July, while the highest value of 2 \(\times\) 10\({}^{4}\) MPN/mL in August. For faecal coliforms, the lowest pollution (4.5 \(\times\) 10\({}^{2}\) colony-forming unit (CFU)/mL) was recorded in July, while the highest value (20 \(\times\) 10\({}^{3}\) CFU/mL) in August. Maximum _E. coli_ pollution was recorded in September (6.4 \(\times\) 10\({}^{3}\) CFU/mL) [152]. A total of 32 different sites of MONITOX network were selected in the Lower Danube region and Romanian Black Sea coast for a recent study conducted in June 2019 and June-July 2020, concerning microbiological pollution in the Black Sea Basin [153]. Heterotrophic bacteria and total coliforms were used as microbiological indicators. The coliform bacteria were identified in all water samples ranging from 130 CFU/100 mL (Ostrov) and 250,000 CFU/100 mL (Calarasi/Silistra) in the Lower Danube sector and from 10 CFU/100 mL (Izmail) to 70,000 CFU/100 mL (Sfantu Gheorghe arm in the Danube Delta). The heterotrophic bacteria ranged from 155 CFU/mL (downstream Braila town) to 6080 CFU/mL (upstream Siret river) in the Lower Danube sector and from 111 CFU/mL (Black Sea, Mangalia town) to 17,000 CFU/mL (Sfantu Gheorghe arm) in the Danube Delta-Black Sea area [153]. The study enabled a comparison of microbiological contamination of surface water in the periods before (2019) and after the (2020) COVID-19 lockdown, demonstrating a decrease of bacteria load in 2020 in all the samples collected from Black Sea coast, Danube branches, Danube-Black Sea confluence, and Danube River downwards of Galati town. For these water samples, an ongoing work is carried out in the frame of the EU-funding project BSB27-MONITOX for several CECs at \"Dunarea de Jos\" University of Galati, Romania using a high-resolution mass spectrometry technique. Only a few studies on fecal pollution in the North West coast of the Black Sea were conducted in the last 10 years. Comparison between faecal and organic pollution of water samples from the Black Sea area, Romania and water samples from the Aegean Sea, Kavala, Greece were presented by [PERSON] et al. in 2020 [154]. Higher values of fecal indicators were measured in Black Sea compared with the Aegean Sea coast. Thus, total mesophilic aerobic bacteria in Black Sea area (Romania), ranged from 1.11 \(\times\) 10\({}^{2}\) to 1.70 \(\times\) 10\({}^{4}\) CFU/mL and of coliforms between 250 MPN/mL to 7000 MPN/mL. In Aegean Sea water, no coliforms were found and the number of heterotrophic bacteria was 1.50 \(\times\) 10 CFU/mL [154]. Among the study on the eastern part of the Black Sea, a recent one investigating bacterial pollution along coastal areas in Turkey, between May 2017 and February 2018, revealed a high degree of contamination in the study area [155]. Total coliform levels ranged from 1.0 \(\times\) 10\({}^{3}\) CFU/100 mL to 3.14 \(\times\) 10\({}^{8}\) CFU/100 mL. The fecal coliform levels ranged from 2.0 \(\times\) 10\({}^{2}\) CFU/100 mL to 9.04 \(\times\) 10\({}^{7}\) CFU/100 mL. Bacteriological pollution increased in all sites in summer months [155]. A comparison of the results for the seawater in Romania and Turkey is difficult due to different methods and different expressions of the results.