The Mesta River (Nestos) springs from the Rila Mountains in southern Bulgaria and flows 230 km through Bulgarian and Greek territory before inflowing into the North Aegean Sea. The site covers the Bulgarian part of the river, its central point being 41 ° 45’45.36 “N and 23 ° 40’22.44” E.

In terms of the Water Framework Directive 2000/60/EC (Annex XIA) requirements, transboundary river Mesta is located in the Ecoregion 7 (Eastern Balkans), West Aegean region (BDB) with Blagoevgrad center. The river is formed by the confluence of Byala and Cherna Mesta over the town of Yakoruda, as its beginning is taken the spring of the right tributary – Bela Mesta, at an elevation of 2240 m asl. above Granchar Lake, East Rila Mountain. Some of the larger tributaries are the Dospatska, Iztok and Retizhe rivers. In Bulgaria, the Mesta River is a mountain stream with 1318 m average altitude, 129 km length and annual water discharge of 39 m3/s at the state border, having 2770 km2 of catchments area. The site is also characterized by the transfer of water quantities for various purposes in the East Aegean and Danube regions for basin management; the presence of mineral deposits and protected areas. The site includes elements of the National Ecological Network, and the catchment area falls into the territory of two national parks – Rila and Pirin.

In the middle of the last century, Mesta River was subjected of heavy pollution with organic matter from industrial origin: yeast, cellulose and cardboard production. Unfavorable ecological situation remained until 1990, when the relevant authorities banned the operation of two polluting plants. Immediate improvements of the water quality within the river system of Razlozhka-Iztok-Mesta have been registered in 1990-1991. So, the developments of the ecological status of the affected stretch of Mesta River could be defined in two large periods in terms of water quality: until 1990 – a period of heavy loading with organic matter of industrial origin and after 1990 – a period of recovery and stabilization of the ecological situation



  • Available data

 This river was selected as a model watercourse, because of the fact that its ecological status has been well studied for the last 30 years in terms of hydrology, water quality, benthic invertebrate fauna, community species and trophic structure, and other biological quality elements. The site contains non-periodic, partially systematic data for a 30 years period by the following indicators: Hydromorphological: Flow velocity, water quantities, water stands, continuity of water flow, river bed shape; Physicochemical: Temperature conditions, oxygen regime, salinity / electrical conductivity, acid-alkali reaction, biogenes, etc.; Biological: Phytobenthos, macrophytes, macrozoobenthos, fish fauna.


  • Facilities

The site does not have a field station, facilities and buildings.  For the purposes of the studies, only mobile devices for analysis, including for measuring the flow rate, of the main physicochemical indicators of the environment, biogenic and biological quality elements (phytobenthos, macrophytes, macrozoobenthos, and fauna) are used.


  • Site related research projects and on-going collaborations

Research projects:

  1. New Education and Decision Support Model for Active Behavior in Sustainable Development Based on Innovative Web Services and Qualitative Reasoning) NaturNet-REDIME (Contract GOCE-CT-2003-004074, EC 6th FP RTD)
  2. Practicability of the invertebrate community structures and fish populations parameters for ecological classification of rivers (project B-1403/MES/NSF)
  3. Development of Methods for Assessment of Minimum Water Flow Protecting the Biodiversity and Ecological Quality of the Running Waters in the Republic of Bulgaria (Project No 787-2239/1999/MOEW)
  4. Setting up the system of biological monitoring of surface water bodies in compliance with the Framework Water Directive 2000/60/EC (Project No 563/2004/MOEW/EEA).
  5. Reference & Intercallibration sites selection and Biological parameters selection relevant to the Framework Water Directive 2000/60/EC (Project No 508/2004/MOEW)
  6. Environmental quality and pressures assessment across Europe: the LTER network as an integrated and shared system for ecosystem monitoring(EnvEurope), Life+Programme – LIFE08 ENV/IT 000399
  7. WETLANET: Improving the scientific potential by building a local network of laboratories to study wetland ecosystems, their functioning, restoration and management (FP7 CSA – SUPPORT ACTION, GA 229802).
  8. FEMA: Mapping and assessment of freshwater ecosystem services in Bulgaria (September 2015-November 2016) -D-33-87 / 27.08.2015, BG03 “BIOLOGICAL DIVERSITY AND ECOSYSTEMS” PROGRAM under the Financial Mechanism of the EEA 2009-2014
  9. eLTER (European Long-Term Ecosystem and socio-ecological Research Infrastructure), Horizont H2020


On-going collaborations:

The Mesta River Research team maintains collaborations with research teams from the University of Dublin, University of Amsterdam and IFAK Magdeburg.


  • Main references
  1. Passy-Tolar, S. & Lowe, R. 1994. Taxonomy and ultrastructure of Gomphoneismesta sp. nov. (Bacillariophyta), a new epilithic diatom from the Mesta river, Bulgaria. – J. Phycol., 30: 885-891. DOI:10.1111/j.0022-3646.1994.00885.x
  2. Passy-Tolar, S. & Lowe, R. 1995.Gomphoneismesta (Bacillariophyta). II. Morphology of the initial frustules and perizonium ultrastructure with some inferences about diatom evolution. – J. Phycol., 31: 447-456. DOI:10.1111/j.0022-3646.1995.00447.x
  3. Passy-Tolar, S., Pan, Y. & Lowe, R. 1999.Ecology of the major periphytic diatom communities from river Mesta, Bularia. – Int. Rev. Hydrobiol., 84(2): 129-174. DOI:10.1002/iroh.199900017
  4. Rusev, B. &Janeva, I. 1994.Hydrobiological and saprobiological characteristic. – In: Mihailov, G. (ed.), Current status of the anthropogenic impacts on the Bulgarian Part of the Mesta River. Final report, MOE/PHARE, Sofia, 125p.
  5. Varadinova, E. & Uzunov, Y. 2002. Recent assessment and long-term changes in the saprobiological state of the Mesta river in South-Western Bulgaria. – J. Envir. Prot. & Ecol., 3(1): 68-75.
  6. Soufi, R., E. Varadinova, Y. Uzunov. 2005. Relation of the Bulgarian Biotic Index to the standardized Indices for Water quality assessment of the river Mesta (SW Bulgaria). – Comp. rend. Acad. bulg. Sci. 57, 8: 83-86.
  7. Apostolos, A. 2005.The Ichthyofauna from the Bulgarian Sector of the Mesta River. – Acta zoological bulgarica, 57(2): 191-196.
  8. Uzunov, Y., Varadinova, E. & Soufi, R. 2005.Shifts in species diversity of the bottom invertebrates in two southwest Bulgarian rivers. – Proc. of the UNESCO-ROSTE Workshop on Regime Shifts, pp. 188-197. Varna, June, 2005
  9. Varadinova E. 2006. Composition, Dynamics and Indicator Potential of the Functional Feeding Groups of Macrozoobenthos in the Mesta River. PhD thesis, CLGE, BAS, Sofia, 230 p.
  10. Varadinova, E., Soufi, R. & Uzunov, Y. 2006.Macroinvertebrate Trophic Structure as Indicator of the Ecological Status of the River Mesta. – Proc. Int. Symp. Bioprocess systems, pp. I.33-I.43. October 24-26 2006.
  11. Ivanov, P. & Ector, L. 2006.Achnanthidiumtemniskovae sp. nov., a new diatom from the Mesta River, Bulgaria. – In: Ognjanova-Rumenova, N. & Manoylov, K. (eds), Advances in phycological studies. Festschrift in honour of Prof. Dobrina-Temniskova-Topalova, pp. 147-154.Pensoft Publishers, St. Kliment Ohridski University Press, Sofia-Moscow.
  12. Soufi, R., E. Varadinova, Y. Uzunov. 2006. Relation of the Bulgarian Biotic Index to the standardized indices for water quality assessment in Bulgaria and some biotic indices used in EC countries: investigation for the Struma river (South-Western Bulgaria). – Acta Zool. Bulg., 58, 2:265-273.
  13. Nuttle, T., P. Salles, Y. Uzunov, E. Varadinova, E. Nakova, E. Cioaca, S. Covaliov, R. Noble, A. Zitek, M. Neumann, A. Bouwer, J. Liem, A.L.R. Caldas. 2006. Navigating a Landscape of Sustainability Concepts: Towards Progressive Learning Routes within and among Qualitative Reasoning Models. – In: Tochtermann, K. and Scharl, A. (eds.) Proc. 20th Int. Conf. Informatics for Environm. Prot. (EnviroInfo 2006), Aachen, Austria, SchakerVerl. ISBN 13: 978-3-8322-5391-9, 585-586.
  14. Varadinova, E., Uzunov, Y. & Soufi, R. 2007. A New Integrated Index for Assessment of the Ecological Status of Rivers as Based on Functional Feeding Groups of the Macrozoobenthos – J. Envir. Prot. Ecol., 4(8):754-762.
  15. Bredeweg, B., P. Salles, A. Bouwer, J. Liem, T. Nuttle, , E. Cioaca, E. Nakova, R. Noble, A.L.R. Caldas, Y. Uzunov, E. Varadinova, A. Zitek. 2008. Towards a structured approach to building qualitative reasoning models and simulations; Ecological Informatics, 1, 3:1-12. DOI:10.1016/j.ecoinf.2007.02.002
  16. Uzunov, Y., Varadinova, E., Yaneva, I., Kumanski, K. & Stoichev, S. 2008. Long-term changes of the bottom invertebrate fauna of the Mesta River in Southwest Bulgaria – Ann. Univ. “St. Kl. Ohridski”.
  17. Vidinova Y, I. Botev, V. Tyufekchieva, T. Nedyalkova, I. Yaneva, B. Zadnepolsli, E. Varadinova.2008. Results of rapid hydrobiological monitoring of watersheds from the East- and West Aegean Sea River Basin Districts in Bulgaria – Acta Zool. Bulg., 2:233-242, ISSN: 0324-0770.
  18. Varadinova, E., Y. Vidinova, V. Tyufekchieva, I. Yaneva. 2008. Trophic structure of macrozoobenthos as measure of water bodies ecological state assessment, Journal of Balkan Ecology, 11, 3, 297-308, ISBN ISSN 1311-0527
  19. Varadinova, Е. R. Soufi, M. Kerakova, Y. Uzunov. 2010. Ecological State Assessment of the Transboundary Mesta River (South-West Bulgaria), Hydrology Conference 2010, The Changing Physical and Social Environment: Hydrologic Impacts and Feedbacks, October 11 – 13, 2010, San Diego, CA, USA.
  20. Кerakova M. 2010.Actual assessment of the ecological status of the Bulgarian part of the Mesta River. – MSc Thesis, Biological Faculty of the University of Sofia, 77 p. (In Bulgarian).
  21. Uzunov, Y, E. Varadinova, I. Yaneva, S. Stoichev, Y. Vidinova, K. Kumanski. 2011. Long-term changes of the bottom invertebrate fauna of the Mesta River in southwestern Bulgaria, Annual de l’universite de Sofia „St. Kliment Ohridski“ Faculte de Biologie Livre 1 – Zoologie,99: 33-52, ISSN 0204-9929
  22. Varadinova, E., M. Kerakova, R. Soufi, M. Aleksandrova, S. Stoichev, Y. Vidinova, V. Tyufekchieva, Y. Uzunov. 2013. Bottom invertebrate communities (the macrozoobenthos): Key biological quality element for ecological classification of the Mesta River basin. – In: (Y. Uzunov, L. Pehlivanov, B. Georgiev, E.Varadinova (eds.). Mesta River: Biological quality elements & Ecological status, Professor Marin Drinov Academic Publishing house, 61-97, ISBN 978-954-322-689-4
  23. Varadinova, E., M. Kerakova, Y. Uzunov. 2013. Mesta River: The trophic structure of the macrozoobenthos. – In: (Y. Uzunov, L. Pehlivanov, B. Georgiev, E. Varadinova (eds.). Mesta River: Biological quality elements & Ecological status, Professor Marin Drinov Academic Publishing house, 97-123, ISBN 978-954-322-689-4
  24. Pehlivanov,L.,A. Apostolou, E. Varadinova, M. Pavlova, M. Vassilev, B. Velkov, M. Kerakova. 2013. Recent Fish Fauna of the Mesta River Basin: Composition, Distribution, and Ecological Quality Assessment. – In: Uzunov, Y. et al. (Eds.). Mesta River: Biological Quality Elements and Ecological State. Sofia, Prof. Marin Drinov Academic Publ. House: 123-132.
  25. Uzunov, Y., L. Pehlivanov, B.B. Georgiev, E. Varadinova (Eds.) 2013. Mesta River: Biological Quality Elements and Ecological State. Sofia, Prof. Marin Drinov Academic Publ. House, vi+136 pp. ISBN 978-954-322-689-4
  26. Кerakova, M., Y. Uzunov, E. Varadinova. 2017. Comparison of Trophic Structure of the Benthic Macroinvertebrates in Three Bulgarian Riverine Water Bodies – Turkish Journal of Zoology, 41:267-277. DOI: 10.3906/zoo-1510-62
  27. Varadinova, Е. & M. Kerakova 2018.Trophic Structure of the Riverine Macroinvertebrates in Type-specific Reference Conditions – Acta zoological bulgarica, Sppl. 12, 101-108.


Responsible Institution:

Institute of Biodiversity and Ecosystem Research, Bulgarian Academy of Sciences

Address: 2 Gagarin Street, 1113 Sofia, BULGARIA

Phone: +359 2 871 71 95 / +359 2 871 91 38

Fax: +359 2 870 54 98




Site coordinator:

Assoc. prof. Emilia Varadinova, PhD

Phone: +359 888 994 507