Blidinje Lake some chemical and hydrobiological characteristics

1. Blidinje Lake some chemical and hydrobiological characteristics Anita Ivanković, Esma Velagić Habul, Dubravka Hafner and Zrinka Knezović

2. Blidinje Lake is an integral part of Nature Park “Blidinje” - founded in 1995. • District of Nature Park “Blidinje” (364 km2) includes most of the mountain massif Čvrsnica (2228 m), mountain Vran (2074 m), valley of Dugo Polje an the western part of the mountain ridge Čabulja (1500 m).

3. Blidinje Lake - largest mountain lake in Bosnia and Herzegovina • 1185 m above sea level • Very changeable area - 3,6 km2: 2,5 km2. • Mostly the lake surface water depth is on average from 30 to 70 cm. • Formation of the lake was under the influence of special factors: the devastation of forest cover and anthropogenic abyss backfilling. Nature Park “Blidinje” is under the influence of typical mountain climate.

4. The water, sampled on 5 locations on surface on coastal area, were analysed on temperature, dissolved oxygen, oxygen saturation, pH, total dissolved solid (TDS), Secchi depth, turbidity, suspended matter, conductivity, hardness, alkalinity, acidity, NO2-,NO3-, NH4+, total nitrogen (TN), SO42-, Fe, SiO2, PO43-, total phosphorous (TP), Chl a, phytoplankton and phytobenthos.

5. Blidinje Lake is shallow mountain lake with variety turbidity of water changes during a day depending on wind direction and speed. • Different locations - different micro-conditions. • It is possible to measure very different values of the same parameters on different locations.

6. The lowest water temperature (October 27th 2008.) 6°C • The highest temperature (August 4th 2008. ) 28.9 °C. • Temperature had no uniform trend in the measured periodconsidering that is very shallow lake under strong influence of air temperature and wind direction • The amount of dissolved oxygen ranged from a minimum 7.13 mgL-1(September 1st 2008.) to 11,7 mgL-1( August 16th 2008.)

7. Electrical conductivity - min 79 μScm-1, on September 15th, max 307 μScm-1,on June 29th TDS - min 39 mgL-1 on September, max 105 mgL-1 on June 15th pH is slightly alkaline average value of 8.14 and fairly uniform values throughout all period of measurement - indicate the oligotrophic status of the Blidinje Lakeand limestone lake ground

8. Nitrates showed significant fluctuations from no detected (recorded several times) to max 3.2 mgL-1 (September 15th). • Nitrites values ranged from no detected to 0.04 mgL-1 measured September 15th.. • Ammonia is also recorded and values were from no detected to 0.45 mgL-1 on September 30th. The presence of ammonia indicates recent pollution of water. That is not unexpected because the lake is used for daily supply up to 3000 sheep.

9. Transparency of the lake is extremely low, especially in the period from June to September, ranged from 10 cm to 50 cm.These values of transparency indicate eutrophic/ hipertrophic status of lake. This is not in harmony with other relevant parameters. • Turbidity - 6 FAU to on November 10th - 106 measured August 16th. The lake is exposed to strong winds influence which significantly contributes to week transparency and high turbidity. • Suspended matter ranged from 11 mgL-1 to 412 mgL-1.

10. All values of dissolved reactive phosphorous correspond to oligotrophic/mesotrophic lakes. • The highest measured values of total phosphorous correspond to eutrophic lakes (> 0.1 mgL-1). Most of the measured values of total phosphorous belong to moderate eutrophic lakes

11. Total nitrogen of no filtered samples - The lowest value was 0.56 mgL-1 measured on June 15th, while the maximum value was 3.99 mgL-1 measured on September 15th. • Total nitrogen of filtered samples - The lowest value was 0.42 mgL-1 measured on June 15th, while the maximum value was 3.71 mgL-1 measured on September 15th.

12. 2006- max 5.17 μgL-1– min0.08 μgL-1 • 2007- max 2.97 μgL-1- min 0.34 μgL-1 • 2008- max2.73 μgL-1 – min 0.24 μgL-1 • Most of the measured values of chlorophyll a during three years show oligotrophic status of the lake

13. Qualitative composition of phytoplankton Blidinje Lake • 73 species in total • on June 4th the 38 species • on June 25th were 52 species • on September 1st 22 species. • The most represented group Bacillariophyceae taxa with a total of 23 species • Dinophyta was represented with only one species of Ceratiumhirudinella detected at first and second sampling. Chroococcus limneticus, Navicula sp., Oedogonium and Staurastrum gracilis were represented at all three sampling.

14. Qualitative composition of phytobenthos Blidinje Lake • 38 species in total • 6 Cyanobacteria, • 10 Bacillariophyceae, • 4 Chlorophyceae • 10 Conjugatophyceae

16. Presence of indicator species of phytoplankton and phytobenthos in Blidinje Lake Index saprobity ranged from 1.74 to 2.38 (average 1.897) β-mesosaprobic degree II bonitet class.

17. Conclusions • The lake is shallow and exposed to wind • It has very restrictive conditions for recreation and sport except for fishing • For this mountainous area the lake has great importance and it is significant landscape that often changes colour depending of wind direction and speed • From environmental point of view, especially, hydrobiological, Blidinje Lake is unique and represents natural phenomenon