Seasonal Evaluation of Microbial Quality of Water Resources Feeding İğneada Floodplain Forests

Background/aim: The İğneada Floodplain Forests represent one of the largest forest-marsh ecosystems in Türkiye, hosting significant biodiversity. However, increasing tourism investments, camping activities, and seasonal population growth in the region pose potential pressure on the water resources feeding this ecosystem. This study aimed to determine the fecal pollution levels of the basins and sub-basins feeding the İğneada Floodplain Forests using microbiological culture methods and to identify the pollution sources (human or animal) using molecular microbial source tracking (MST) via detection of host-specific Bacteroidales 16S rRNA genes. Materials and methods: Water samples were collected seasonally in 2021 and 2022 from 18 stations across the Bulanık, Çavuşköprü, and Efendi stream basins. Microbiological quality was assessed using membrane filtration and pour plate methods. For molecular analysis, qPCR was performed using universal (BacUni), human-specific (HF183, Bachum), and ruminant-specific (BacCow, BacR) markers. The relationships between microbial data, physicochemical parameters, and climatic factors were evaluated statistically using PCA, K-means clustering, and Spearman correlation analyses. Results: Microbiological analyses revealed high levels of fecal pollution, particularly in the Bulanık Creek (Station 9B) and Çavuşköprü Creek (Station 12Ç), which were identified as outliers with extreme pollution loads. A strong positive correlation was found between human-specific molecular markers and fecal indicator bacteria (Spearman r>0.8; p<0.001), indicating a predominance of human-induced pollution. While seasonal temperature increases correlated with Clostridia and total colony counts, anthropogenic factors were found to be more dominant than climatic factors in driving fecal pollution. Conclusion: The water resources feeding the İğneada Floodplain Forests are under significant anthropogenic pressure, primarily from human-origin fecal contamination. The findings underscore the urgent need for management strategies to mitigate pollution and ensure the sustainability of this critical wetland ecosystem.