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| Site name: | Varna lake -Bay | Country: | Bulgaria | GIG Region: | Black Sea |
|---|---|---|---|---|---|
| GIG Type: | TW | Site code: | ---- | Altitude(m a.s.l.): | 0 |
| Area (km²): | 17 | Max depth (m): | 19 | Mixing regime: | ---- |
| Alkalinity (m eq/l): | ---- | Retention time (yr): | ---- | Chlorophyll a (µg/l): | ---- |
| Total phosphorus (µg/l): | ---- | Eutrophication status: | 3-High | Hydromorphological status: | low |
Description
It is situated in south-western direction from the city of Varna, the lake is the largest by volume and deepest liman along the Black Sea coast, divided from the sea by a 2 km-wide strip of sand and having an area of 17 km2, maximal depth 19 m, and a volume of 166 million m3.
The two canals connecting the lake to Varna bay increased the exchange of water through slow currents between the two water basins. Those changes however have not influenced beneficially the total flow - approximately 4 times its volume per year.
Vertical distribution of oxygen and H2S, along with temperature conditions and pollutant substances determine the character of the abiotic environment of the Varna Lake. With the coming of the summer months bottom layers under 4-5m start emitting hydrogen sulphide due to decaying processes and intense thermal stratification. The hypoxic and anoxic phenomena lead to mass mortalities of fish and crustaceans.
However, positive trend in the inter-annual variations of the dissolved oxygen content in the lake has been lately observed with a marked improvement of water quality in summer months compared to historical records.
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