Spatial and Temporal Patterns of Fecal Indicator Bacteria in the Surface Waters of the Golden Horn Estuary

Abstract

Objective: The Golden Horn Estuary is a semi-enclosed coastal system subjected to long-term anthropogenic pressures, including urbanization, industrial activities, and continuous domestic wastewater inputs. Despite extensive rehabilitation efforts, concerns remain regarding the current bacteriological quality of the surface waters. This study aimed to evaluate the spatial and temporal patterns of fecal indicator bacteria in the surface waters of the Golden Horn Estuary.

Materials and Methods: Surface water samples were collected monthly from three stations representing the inner (H3), middle (H2), and outer (H1) zones of the estuary between December 2023 and May 2024. Total coliforms, fecal coliforms, and intestinal enterococci were quantified using the membrane filtration method on selective media. Bacterial levels were expressed as log cfu/100 mL and assessed in relation to national and international water quality guidelines.

Results: The results demonstrated persistently elevated levels of fecal indicator bacteria throughout the study period. Clear spatial differences were observed among stations, while pronounced temporal fluctuations were evident, with higher bacterial concentrations generally recorded during the winter months. At all sampling stations, indicator bacteria levels frequently exceeded the recommended guideline limits, indicating ongoing fecal contamination within the estuary.

Conclusion: These findings indicate that, despite rehabilitation initiatives, the Golden Horn Estuary remains under continuous bacteriological pressure. The study provides updated baseline data on fecal indicator bacteria and underscores the importance of sustained monitoring to support effective coastal management and public health protection.

Keywords

• Coastal pollution
• Fecal indicator bacteria
• Golden Horn Estuary
• Membrane filtration
• Surface water quality

References

1. Alpar, B., Burak, S. & Doğan, E. (2005). Environmental and hydrological management of the Golden Horn Estuary, Istanbul. Journal of Coastal Research, 214, 646-654. https:/doi.org/10.2112/04-0154.1 google scholar
2. Altıok, H., Yüksek, A., Taş, S., Dursun, F., Ünlü, S., Çağlar, N., Aksu, A., Taşkın, Ö. S., Gürkan, Y., Öztürk, İ. D., & Adatepe, F. M. (2023). Evaluation of the pollution status after the rehabilitation works and the anthropogenic pressure factors of the Golden Horn Estuary (Sea of Marmara). Journal of the Black Sea/Mediterranean Environment, 29(1), 143–166. google scholar
3. APHA (2024). 9222 Membrane Filter Technique for Members of the Coliform Group. Standard Methods for the Examination of Water and Wastewater, 24th Edition, Washington, United States. google scholar
4. Aslan-Yılmaz, A., Okus, E. & Ovez, S. (2004). Bacteriological indicators of anthropogenic impact prior to and during the recovery of water quality in an extremely polluted estuary, Golden Horn, Turkey. Marine Pollution Bulletin, 49(11–12), 951–958. “https://doi.org/10.1016/j.marpolbul.2004.06.020”) google scholar
5. Çelik, S. & Zeki, S. (2024). Back and forth in the health of urban-front Golden Horn Estuary: Fecal indicator bacteria levels during dry and wet environmental conditions. Regional Studies in Marine Science, 78, 103730. “https://doi.org/10.1016/j.rsma.2024.103730 google scholar
6. Çiftçi Türetken, P. S. & Altuğ, G. (2016). Bacterial pollution, activity and heterotrophic diversity of the northern part of the Aegean Sea, Turkey. Environmental Monitoring and Assessment, 188, 127. (“https://doi.org/10.1007/s10661-016-5109-6”) google scholar
7. Coleman, H. M., Kanat, G. & Aydinol Turkdogan, F. I. (2009). Restoration of the Golden Horn Estuary (Haliç). Water Research, 43(20), 4989–5003. https://doi.org/10.1016/j.watres.2009.08.047 google scholar
8. Dasí, D., Camaró-Sala, M. L., González, A., García-Ferrús, M., Jiménez- Belenguer, A. I., & Castillo, M. Á. (2024). Antibiotic resistance in seawater samples from east coast of Spain. Applied Sciences, 14(5), 1965. https://doi.org/10.3390/app14051965 google scholar

9. European Parliament & Council of the European Union. (2006). Directive 2006/7/EC of the European Parliament and of the Council of 15 February 2006 concerning the management of bathing water quality and repealing Directive 76/160/EEC. Official Journal of the European Union, L64, 37–51. google scholar
10. Field, K. G. & Samadpour, M. (2007). Fecal source tracking, the indicator paradigm, and managing water quality. Water Research, 41(6), 3517-3538. https://doi.org/10.1016/j.watres.2007.06.056 google scholar
11. Haley, B. M., Sun, Y., Jagai, J. S., Leibler, J. H., Fulweiler, R., Ashmore, J., Wellenius, G. A. & Heiger-Bernays, W. (2024). Association between combined sewer overflow events and gastrointestinal illness in Massachusetts municipalities with and without river-sourced drinking water, 2014–2019. Environmental Health Perspectives, 132(5), 57008. https://doi.org/10.1289/EHP14213. google scholar
12. Holcomb, D. A. & Stewart J. R. (2020). Microbial indicators of fecal pollution: Recent progress and challenges in assessing water quality. Current Environmental Health Reports, 7(3), 311-324. https://doi.org/10.1007/s40572-020-00278-1. google scholar
13. Kalkan, S. & Altuğ, G. (2015). Bio-indicator bacteria & environmental variables of the coastal zones: The example of the Güllük Bay, Aegean Sea, Turkey. Marine Pollution Bulletin, 95(1), 380-4. https://doi.org/10.1016/j.marpolbul.2015.04.017. google scholar
14. Karabaş, N., Taş, S., Ergüven, G. Ö. & Bayhan, H. (2018). A research on coliform bacteria in the Golden Horn Estuary (Sea of Marmara, Turkey). Desalination and Water Treatment, 115, 199–206.https://doi.org/10.5004/dwt.2018.22497 google scholar
15. Larsson, D. G. J., & Flach, C. F. (2022). Antibiotic resistance in the environment. Nature Reviews Microbiology, 20(5), 257-269. google scholar
16. Li, E., Saleem, F., Edge, T. A. & Schellhorn, H. E. (2021). Biological indicators for fecal pollution detection and source tracking: A review. Processes, 9(11), 2058. https://doi.org/10.3390/pr9112058 google scholar
17. Mallin, M. A., Williams, K. E., Esham, E. C. & Lowe, P. R. (2000). Effect of human development on bacteriological water quality in coastal watersheds. Ecological Applications, 10(4), 1047–1056.https://doi.org/10.1890/1051-0761(2000)010%5b1047:EOHDOB%5d2.0.CO">https://doi.org/10.1890/1051-0761(2000)010%5b1047:EOHDOB%5d2.0.CO;2″, )[https://doi.org/10.1890/1051- 0761(2000)010[1047:EOHDOB]2.0.CO;2] google scholar
18. Republic of Türkiye Ministry of Environment and Urbanization. (2019). Regulation on Bathing Water Quality. Official Gazette of the Republic of Türkiye, No. 30845, 26 July 2019. google scholar
19. Rodrigues, C. & Cunha, M. Â. (2017). Assessment of the microbiological quality of recreational waters: indicators and methods. Euro- Mediterranean Journal for Environmental Integration, 2, 25. https://doi.org/10.1007/s41207-017-0035-8″) google scholar
20. Semin, S., Tas, S., & Dursun, F. (2023). Spatial–temporal variability of phytoplankton community and potentially harmful species in the Golden Horn Estuary (Sea of Marmara, Türkiye). Journal of the Marine Biological Association of the United Kingdom, 103, e56. https://doi.org/10.1017/S0025315423000449 google scholar
21. Sur, H., Okus, E., Sarikaya, H. Z., Altiok, H., Eroglu, V. & Ozturk, I. (2002). Rehabilitation and water quality monitoring in the Golden Horn. Water Science and Technology, 46(8), 29–36. https://doi.org/10.2166/wst.2002.0138 google scholar
22. Tas, S. (2019). Microalgal blooms in a eutrophic estuary (Golden Horn, Sea of Marmara) following a remediation effort. Botanica Marina, 62(6), 537-547. https://doi.org/10.1515/bot-2019-0035 google scholar
23. Tuholske, C., Halpern, B. S., Blasco, G., Villasenor, J. C., Frazier, M. & Caylor, K. (2021). Mapping global inputs and impacts from of human sewage in coastal ecosystems. PLOS ONE, 16(11), e0258898. https://doi.org/10.1371/journal.pone.0258898. google scholar
24. WHO (2003). Guidelines for safe recreational water environments. Volume 1: Coastal and fresh waters. World Health Organization, Geneva. google scholar
25. Wild, T., Fuchs, G. & Davis, M. K. (2024). Sitting in our own soup? Combined sewers, climate change and nature-based solutions for urban water management in Berlin. Nature-Based Solutions, 5, 100113. https://doi.org/10.1016/j.nbsj.2024.100113 google scholar
26. Zeki, S., Aslan, A, Burak, S. & Rose, J. B. (2021). Occurrence of a human‐associated microbial source tracking marker and its relationship with faecal indicator bacteria in an urban estuary. Letters in Applied Microbiology, 72(2), 167–177. https://doi.org/10.1111/lam.13405 google scholar