Site name/location:
Lake Balaton LTER Site, Tihany, Hungary

Principal contact:
Dr. Lajos Vörös, director
Balaton Limnological Research Institute of the Hungarian Academy of Sciences
H-8237 Tihany, PO.Box 35.
Tel: 36 87-448-244; Fax: 36 87-448-006
E-mail: vorosl@tres.blki.hu

Location:
46°42’-47°04’ N, 17°15’-18°10’ E; 104,8 m above sea level (Adriatic)

Site description:
Lake Balaton was formed mainly by tectonic forces about 10,000 years ago. Prior to the opening of Sió-canal in 1863, its water level was 3 m higher and its surface was about one and half times larger than that the present. With its surface area of 593 km2, Lake Balaton is the largest lake in Central Europe, but its mean depth is only 3.2 m. The main inflow, the Zala River, empties into the southwestern end of the lake, while the Sió-canal drains the water from the eastern basin into the River Danube. The lake is covered by ice in winter. In summer the average water temperature is 23o C. The strong waves swirl up much sediments, rendering the transparency low. The major ions of the water are Ca2+, Mg2+ and HCO3-. The pH is 8.4, rising to higher values during intensive primary production. Oxygen deficiency is formed only temporarily in the western part of the lake in calm summer periods with algal blooms. The distribution of macrophytes is restricted by strong waves to a relatively narrow belt. Only 3 per cent of the lake surface is covered by reeds, and even less by submerged macrophytes. The major primary producers are phytoplankton. Zooplankton is not abundant. Zoobenthos represents an important food for the fish. The annual commercial fish catch is 1200 tons. The southern shore of the lake consists of sandy beach, while on the northern shore there are mountains of volcanic origin with old ruins on their tops and vineyards on their slopes. The picturesque landscape and the water ideal for swimming and other water sports attract 2 million tourists annually. The sewage discharge from rapidly developing towns in the watershed, the growing use of fertilizers in agriculture and large animal farms increased the nutrient loading to the lake in the last decades. A rapid eutrophication became apparent by increased production and biomass of phytoplankton. Blooms of blue-green algae are frequent in the most polluted western part of the lake. A eutrophication control program has been formulated, based on intensive scientific research. Most of the municipal sewage is now diverted from recreational areas. Phosphorus removal was introduced at other sewage treatment plants. A reservoir was constructed to retain the nutrients carried by the Zala River. Pollution due to liquid manure was reduced. A soil protection program is in progress.

Research history:
The first large scale research program (1891-1918) resulted in a series of monographs on the geology, geography, meteorology, hydrology, zoology and botany of Lake Balaton and its surroundings. In 1927 the Balaton Limnological Research Institute of the Hungarian Academy of Sciences has been established on the shore of the Lake. Water chemists, microbiologists, algologists, botanists, zoologists and ichthyologists deal here with the ecology of the lake. From 1927 to 1977 most of the work of the Institute was published in Annal.Biol.Tihany. Recently the papers appear in international journals. For a review of the last 17 years see: Salánki J. and Nemcsók J. (Eds): The results of Lake Balaton Research 1981-1997.
The present staff consists of 28 scientists.

The main fields of research are:
- Eutrophication processes of Lake Balaton
- Feeding, population dynamics and production of aquatic invertebrates
- Biological role and dynamics of fish populations
- Monitoring lake pollution
- Mechanisms of the biological effects of heavy metals and organic pollutants.

Data sets:
- Meteorological and hydrological data are available for the whole Century.
- Fortnightly monitoring of water chemistry (pH, main ions, TOC, BOD, P and N forms etc) at 12 stations started in 1975.
- Quantitative fitoplankton monitoring at monthly or fortnightly intervals started in 1945 in the Eastern-basin of the lake, and in 1965 in the whole lake. The cell numbers of the different species are computer stored. This data base contains more than 100.000 data.
- Zooplankton was monitored in a similar way.
- Fish yields are recorded since 1905.
- Less data are available from the benthic and littoral invertebrates
- The distribution of macrophytes was studied already in the last century, but more quantitative data were obtained in the last decades.
- Data on watershed development (urbanization, tourism, water use, sewage treatment, land use, fertiliser application) are also collected.

Access to site:
by car from Budapest (140 km),
by train from Budapest to Balatonfüred (132 km) and by bus from Balatonfüred to Tihany (9 km).

Housing available:
The Institute has a guest house with 15 rooms and 2 appartements. For visitors accompanied by family double room flats are also available. The Institute has a 2 ha lakeshore park.

Research facilities:
research vessel, motor boats, collecting devices, aquaria, chemical laboratory, isotop laboratory, mass spectrometer laboratory, morphological laboratory with electron microscope, algological laboratory with culturing devices, zoological laboratory with physiological equipments, ichthyological laboratory, library.