Online Version ISSN: 1314-412XVolume 5, Number 2

June 2013

2013

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English Editor

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2013

ISSN 1313 - 8820 Volume 5, Number 2June 2013

Seasonal and vertical dynamics of the water temperature and oxygen content in Kardzhali reservoir, Bulgaria

1 2I. Iliev , L. Hadjinikolova *

1Department of Biochemistry and Microbiology, Faculty of Biology, University of Plovdiv Paisii Hilendarski, 24 Tzar Assen, 4000 Plovdiv, Bulgaria2Institute of Fisheries and Aquaculture, 248 Vasil Levski , 4003 Plovdiv, Bulgaria

Abstract. The aim of the study was to determine the seasonal and vertical dynamics of water temperature and oxygen content in the aquatory of Kardzhali Reservoir, situated in the Eastern Rhodope Mountains at the altitude of 290 m. Water samples from six sampling stations, set in order to fully cover the water area near the cage farms; the aquatory free from net cages and the part near the dam wall were analyzed. In the surface layers for the period of the study, the water temperature ranges from 11.8°C to 25°C respectively in April and in July. With the increase of the air temperature in spring, the surface water layer is heated rapidly. The zone of the temperature shift (thermocline) of the stratifying lake is especially clearly observed during the months May – September

-1 -1between 5–15 meters. During the period of the study were established significant variations in the oxygen content in the water between 2.98 mg.l –13.66 mg.l -1 -1 -1(0.5 m) and 0.16 mg.l –10 mg.l (30 m). The highest average values of this parameter in vertical in the range of 10.47 mg.l were reported in April.

Keywords: monitoring,water temperature, amount of dissolved oxygen, Kardzhali reservoir

AGRICULTURAL SCIENCE AND TECHNOLOGY, VOL. 5, No 2, pp , 2013212 - 215

Introduction Material and methods

Kardzhali dam-lake is an artificial water reservoir, formed by The study was carried out in the aquatory of Kardzhali reservoir damming the waters of river Arda and it is a part of the hydro-energy for the period May 2009 – April 2010. Water samples were collected complex “Lower Arda” cascade. The Dam lake is in a region with from six sampling stations, set in order to fully cover the water area transitional to Mediterranean climate. It is situated in the boundary near the cages (three stations), the aquatory free from cages (two between the lowland hilly and foothill part of the Eastern Aegean stations), and the part near the dam wall (one station), at which point basin, passing in the horizontal line of 300 – 350 m. Due to its long is the outflow of the reservoir (Figure 1). The location of each station

in the reservoir was determined with a GPS receiver (Garmin -1Kardzhali dam is a multipurpose water body 76CSx). Water temperature and oxygen content (mg.l ) were

used for the needs of energy generation, irrigation and aquaculture. determined in-situ at every meter from the surface layer (0.5 m) to It is among the first reservoirs in the country where fish were reared the bottom layer, which, depending on the topography of the bottom in net cages, and at present there are 7 net cage farms. During of the dam and the water level in the reservoir, at the different different periods of its utilization a number of studies on the stations reach 30–60 m. The measurements were performed with a ecosystem and the quality of the water were carried out. However combined depth Oximeter type WTW Oxi 1970i.those studies were related mainly to the accumulation of heavy metals in the tissue of fish and the trophic state of the reservoir

(Veltcheva et al., 2000; Veltcheva, 1997; Traykov et al., 2003; Traykov and Boyanovsky, 2003; Traykov et al., 2005). The data related to the dynamics of some abiotic indices, such as temperature and oxygen content in the water are very limited, while at the same time these indices have a significant impact on the life of hydrobionts (Zaykov, 2006). The knowledge on these dynamics would help to evaluate the impact of organic load from the net-cage farms on water quality, especially around the farms, as the utilized area and volumes of production of the farms are constantly increasing.

The aim of the study was to determine the seasonal and vertical dynamics of water temperature and oxygen content, as limiting environmental factors influencing the processes in the aquatic environment.

retention time (over 200 days) it is categorized as lake like reservoir (Straskraba, 1998).

водата

* e-mail: lhadjinikolova@yahoo.com

212

Figure 1. Kardzhali Dam scheme (a – general scheme ofthe reservoir, b – sampling stations in the studied areaof the dam)

a)

b)

213

absolute value for this indicator, 25.6°C, was recorded in July at Results and discussionstation 6, with variation from 22.6°C to 25°C at the other stations in the epilimnion layer.The water temperature in Kardzhali dam goes through

With the increase of the air temperature in spring, the surface significant seasonal and vertical changes. The values of the water layer is heated rapidly. This leads to a distortion of the free temperature in different parts of the reservoir, depending on season movement of water masses and initiates the formation of summer and depth of the water column are presented in Table 1. In the stratification. Heat accumulation in the surface layer is observed in surface layers for the period of the study, the water temperature April, but is weak and the process of stratification completes in May. ranges from 11.8°C to 25°C respectively in April and in July. The During this period, the surface layer (epilimnion) has a depth of zero minimum temperature at depth is measured at the station located in to 5 m and is characterized by a relatively constant temperature. proximity to the dam wall – 5.7°C in April 2010. The average During the summer months are also observed temperature temperature of the water layer varies between 8°C and 14.8°C and differences in the epilimnion itself, due to the abrupt temperature maximum values were reported in September 2009. The highest

Table 1. Values of the water temperature in Kardzhali reservoir for the period May 2009 – April 2010.

Date

21/22.05.09

28/29.07.09

9/10.09.09

17/19.11.09

13/15.04.10

21/22.05.09

28/29.07.09

9/10.09.09

17/19.11.09

13/15.04.10

21/22.05.09

28/29.07.09

9/10.09.09

17/19.11.09

13/15.04.10

21/22.05.09

28/29.07.09

9/10.09.09

17/19.11.09

13/15.04.10

21/22.05.09

28/29.07.09

9/10.09.09

17/19.11.09

13/15.04.10

21/22.05.09

28/29.07.09

9/10.09.09

17/19.11.09

13/15.04.10

21/22.05.09

28/29.07.09

9/10.09.09

17/19.11.09

13/15.04.10

20.2

25.6

22.4

13.9

12.9

18.8

24.4

21.9

13.9

11.4

13.6

18.7

21.6

13.9

9.6

8.6

11.8

13.5

13.8

7.1

7

8.2

10

12.3

6.3

7.1

10.9

6.2

12.5

11.8

9.6

7.5

6.3

6.1

5.7

20.6

24.9

21.7

13.9

11.8

19.9

24.7

21.7

13.9

10.9

12.5

19.6

21.7

13.9

9.6

8.5

11.4

13.4

13.8

7.8

6.9

8.3

9.6

12.8

6.5

6.6

7.1

7.8

21.1

22.4

22

14.1

11.3

17

24.9

22

14

10.6

13.2

19.8

22

14

9.9

9.4

11.7

12.8

13.9

8.5

7.2

8.5

9.3

12.6

6.8

6.9

7.4

7.6

11.1

6.2

6.4

6.6

6.7

7.1

5.7

20.7

24.7

21.7

14.5

11.6

20.3

24.8

21.7

14

10.8

12.8

19.6

21.7

13.9

9.7

8.7

11.6

13.4

13.8

7.8

6.9

8.3

9.4

12.5

6.4

6.7

7.1

7.8

10.9

6

20.9

25

22.1

14.1

12.7

20.8

25

22.1

13.9

10.5

13

19.8

22

13.9

9.4

8.7

11.5

13.4

13.9

7.6

6.9

8.5

11

6.7

6.7

0.5

5

10

20

30

40

60

Water depth, m1 2 3 4 5 6

Sampling station

6

214

ovariations during the day and night. of 1 C. Temperature deviations are detected only at Station 1 (the The zone of the temperature shift (thermocline) of the stratifying wall), which is probably due to the mode of operation of the reservoir,

lake is especially clearly observed during the months May – characterized by hipolimnion draining.September between 5–15 meters. Differences in temperature at During the period of the study were established significant stations were reported only for the surface water layers and are variations in the oxygen content in the water (Table 2). The highest

odetermined by the air temperature. They vary in the range of 2–3 C average values of this parameter in vertical in the range of 10.47 -1depending on the period in which sampling is made. In September mg.l were reported in April. This period is characterized by the

and November, is observed a decrease in water temperature, accumulation of heat and the start of formation of temperature accompanied by subsidence of the depth of the thermocline, which stratification, while oxygen content is almost evenly distributed in the influences the stability of stratification. The boundaries of the water column, following the curve of the temperature. The metalimnion are not clearly defined. In November is observed the percentage of saturation varies between 62 and 132% for different autumn homothermy, with vertical temperature variation in the range horizons. The high oxygen content in the water layer during the

-1Table 2. Values of the amount of dissolved oxygen (mg.l ) in Kardzhali reservoir for the period May 2009 – April 2010.

Date

21/22.05.09

28/29.07.09

9/10.09.09

17/19.11.09

13/15.04.10

21/22.05.09

28/29.07.09

9/10.09.09

17/19.11.09

13/15.04.10

21/22.05.09

28/29.07.09

9/10.09.09

17/19.11.09

13/15.04.10

21/22.05.09

28/29.07.09

9/10.09.09

17/19.11.09

13/15.04.10

21/22.05.09

28/29.07.09

9/10.09.09

17/19.11.09

13/15.04.10

21/22.05.09

28/29.07.09

9/10.09.09

17/19.11.09

13/15.04.10

21/22.05.09

28/29.07.09

9/10.09.09

17/19.11.09

13/15.04.10

8.87

4.2

4.2

6.8

14.23

9.24

3.92

3.9

6.61

12.2

8.1

2.54

3.13

6.66

10.12

5.92

1.64

0.09

5.93

10.17

6.6

1.66

0.16

5.38

9.6

2.15

2.58

9.2

14.2

13.32

11.23

10.37

10

9.77

7.66

7.57

3.58

6.221

7.34

13.2

7

3.04

5.88

7.25

11.65

7.33

1.29

5.88

7.21

11.2

7.15

1.45

3.4

7.29

10.5

7.57

1.46

4

7.76

10

7.3

1.8

6.53

9.5

8.2

4.25

2.98

6.9

13.66

9.24

3.88

2.96

6.68

12.43

7.14

1.2

2.81

6.66

11.28

7.11

2.2

3.13

6.6

10.73

7.6

2.61

4.28

3.23

10

7.4

3.18

5.51

2.82

9.85

6.67

2.68

5.48

0.1

8.74

7.55

4.85

3.98

6.85

13.21

7.25

4.85

3.92

6.47

11.75

6.77

1.57

6.8

6.4

11.1

6.5

2.88

3.4

5.94

10.42

6.91

3.35

5.43

4.45

9.79

6.57

3.44

4.64

1.26

9.51

7.98

3.78

5.75

7.1

14.05

8.16

3.72

5.56

6.82

12.17

7.26

1.3

5.18

6.59

11.35

6.97

2.43

2.84

6.56

10.48

7.23

2.44

2.89

10.2

6.7

0.5

5

10

20

30

40

60

Water depth, m1 2 3 4 5 6

Sampling station

215

spring months is largely due to the intensive development of Acknowledgementphytoplankton. Formation of temperature stratification in May is associated with lower average levels of oxygen content as low as 7.2 The study was funded by the Scientific Research Fund to

-1mg.l . In the horizontal distribution were not reported significant Ministry of Education, Youth and Science – contract DO 02-307.differences in the measured oxygen content in the water layer. In the epilimnion during July the oxygen content levels in the area around References

-1the net-cage farms (stations 2, 3, 4) vary in the range 2.6 to 3.8 mg.l . These values are lower compared to those recorded for September

-1(3.65 to 4.8 mg.l ) as well as compared to the spring and autumn levels. International review of Hydrobiology

Temperature stratification is accompanied by stratification of the oxygen curve. In late summer oxygen reaches its minimum. Proceedings of the Experimental Station of freshwater fish Plovdiv,There is a typical clearly defined metalimnion minimum, related to oxygen deficiency. Oxygen content drops sharply to values around 1

-1mg.l immediately below the epilimnion layer. In July this minimum is -1reached at a depth of about 10 m (1 – 1.2 mg.l ), and in September at

-1about 13 m (0.36 – 0.46 mg.l ). A similar trend was reported by other authors (Borovec et al., 1998; Traykov et al., 2003). This is related to periodic extinction of phytoplankton organisms, which as a result of temperature stratification remain on the border between the epi- and metalimnion and are subject to intensive decay, due to which oxygen is reduced. Similar processes were observed in other highly stratified reservoirs with high retention time (Dimitrov, 1962; Kennedy and Walker, 1990; Duras, 2001). International review of Hydrobiology, 83,

In autumn due to the decrease of surface temperatures and the 1-13.occurrence of partial water circulation, again was established equalization of the oxygen content in depth, accompanied by an increase in the percentage of saturation.

Conclusions

Dynamics in temperature and the content of dissolved oxygen in the water, depending on the depth of measurement and season were established.

The zone of the temperature shift (thermocline) of the stratifying Acta Zoologica Bulgarica, lake is manifested particularly clearly in the months from May to

September between 5–15 meters. During the studied period were established significant variations in the amount of oxygen content in

-1 -1 -1 Acta Zoologica water, between 2.98 mg.l – 13.66 mg.l (0.5 m) and 0.16 mg.l –10 -1 Bulgarica, mg.l (30 m). Maximum average values of oxygen content in the

-1water (10.47 mg.l ) and minimum temperature values in depth (5.7°C) were recorded in April 2010

The studies give the possibility to determine the periods and depth zones with optimal temperature and oxygen levels for growing thermophilic species, which can be used to optimize the technological process of cage aquaculture in Kardzhali reservoir.

Borovec J, Hejzlar J and Vyhnalek V, 1998. Phosphorus Cycling in a Dimictic Reservoir-the Sec Reservoir (Czech Republic).

, Special Issue, 83, 295-302.Dimitrov M, 1962. The Benthos in “Studen kladenetz” Dam Lake.

III, 81-94.Duras J, 2001. The Klichava reservoir – water quality development between 1988-2000. In: Straskrabova. V. & Pivnicka. K. (eds.). The Klichava Reservoir – Hydrobiological and Ichthiologigal studies (1995-2000). Acta Universitatis Carolinae. Environmentalica, 15, 57-85.Kennedy R and Walker W, 1990. Reservoir nutrient dynamics. In: Thornton. K. W.. kimmel. B. and Payne. F. (eds.) Reservoir Limnology: Ecological Perspectives. Wiley. New York. 246 pp, 133-195.Straskraba M, 1998. Limnological differences between deep valley reservoirs and deep lakes.

Traykov I, Boyanovsky B, Zivkov M and Mirinchev G, 2003. Spatial heterogeneity of physical and chemical parameters in Kardjali reservoir – Effect on trophic state. In: Preprints of Proceedings. “Second International Conference Ecological Protectiton of the Planet Earth”. June 2003, Sofia p. 280-287.Traykov I and Boyanovsky B, 2003. Changes in the trophic status of the Kardjali reservoir due to water level fluctuations. Sofia University Annual Report, 95, 4, 227-230.Traykov I, Boyanovsky B, Zivkov M and Mirinchev G, 2005. Spatial heterogeneity of sediment composition and phosphorus fractions in sedimenst from the Kardjali reservoir. South-East Bulgaria. 57, 1, 95-104.Velcheva I, 1997. Research on the content of cadmium (Cd) in different organs of perch (Perca fluviatilis L.) from the artificial lakes “Kardjali'and “Studen Kladenetz” on the river Arda.

50, 43-48.Velcheva I, Kostadinova P and Popov V, 2000. Lead, Zink and Cadmium Content in Carp (Cyprinus caprio L.) Muscle Tissue from Kardzhaali Dam Lake. Proceedings of the Scientific Conference ”Ecology and Health, 2000”, House of Science and Technology, Agricultural University, Plovdiv, 319-323.Zaikov A, 2006. Aquaculture. Kabry, Sofia, 376 pp.

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The manuscript should be structured as follows: Title, Names of authors and affiliation address, Abstract, List of keywords, Introduction, Material and methods,Results, Discussion, Conclusion, Acknowledgements (if any), References, Tables, Figures.The title needs to be as concise and informative about the nature of research. It should be written with small letter /bold, 14/ without any abbreviations. Names and affiliation of authorsThe names of the authors should be presented from the initials of first names followed by the family names. The complete address and name of the institution should be stated next. The affiliation of authors are designated by different signs. For the author who is going to be corresponding by the editorial board and readers, an E-mail address and telephone number should be presented as footnote on the first page. Corresponding author is indicated with *. Abstract should be not more than 350 words. It should be clearly stated what new findings have been made in the course of research. Abbreviations and references to authors are inadmissible in the summary. It should be understandable without having read the paper and should be in one paragraph. Keywords: Up to maximum of 5 keywords should be selected not repeating the title but giving the essence of study. The introduction must answer the following questions: What is known and what is new on the studied issue? What necessitated the research problem, described in the paper? What is your hypothesis and goal ?Material and methods: The objects of research, organization of experiments, chemical analyses, statistical and other methods and conditions applied for the experiments should be described in detail. A criterion of sufficient information is to be

possible for others to repeat the experi-ment in order to verify results.Results are presented in understandable tables and figures, accompanied by the statistical parameters needed for the evaluation. Data from tables and figures should not be repeated in the text.Tables should be as simple and as few as possible. Each table should have its own explanatory title and to be typed on a separate page. They should be outside the main body of the text and an indication should be given where it should be inserted.Figures should be sharp with good contrast and rendition. Graphic materials should be preferred. Photographs to be appropriate for printing. Illustrations are supplied in colour as an exception after special agreement with the editorial board and possible payment of extra costs. The figures are to be each in a single file and their location should be given within the text. Discussion: The objective of this section is to indicate the scientific significance of the study. By comparing the results and conclusions of other scientists the contribution of the study for expanding or modifying existing knowledge is pointed out clearly and convincingly to the reader.Conclusion: The most important conse- quences for the science and practice resulting from the conducted research should be summarized in a few sentences. The conclusions shouldn't be numbered and no new paragraphs be used. Contributions are the core of conclusions. References:In the text, references should be cited as follows: single author: Sandberg (2002); two authors: Andersson and Georges (2004); more than two authors: Andersson et al.(2003). When several references are cited simultaneously, they should be ranked by chronological order e.g.: (Sandberg, 2002; Andersson et al., 2003; Andersson and Georges, 2004).References are arranged alphabetically by the name of the first author. If an author is cited more than once, first his individual publications are given ranked by year, then come publications with one co-author, two co-authors, etc. The names of authors, article and journal titles in the Cyrillic or alphabet different from Latin, should be transliterated into Latin and article titles should be translated into English. The original language of articles and books translated into English is indicated in

parenthesis after the bibliographic reference (Bulgarian = Bg, Russian = Ru, Serbian = Sr, if in the Cyrillic, Mongolian = Мо, Greek = Gr, Georgian = Geor., Japanese = Jа, Chinese = Ch, Arabic = Аr, etc.)The following order in the reference list is recommended:Journal articles: Author(s) surname and initials, year. Title. Full title of the journal, volume, pages. Example:Simm G, Lewis RM, Grundy B and Dingwall WS, 2002. Responses to selection for lean growth in sheep. Animal Science, 74, 39-50Books: Author(s) surname and initials, year. Title. Edition, name of publisher, place of publication. Example: Oldenbroek JK, 1999. Genebanks and the conservation of farm animal genetic resources, Second edition. DLO Institute for Animal Science and Heal th, Netherlands.Book chapter or conference proceedings: Author(s) surname and initials, year. Title. In: Title of the book or of the proceedings followed by the editor(s), volume, pages. Name of publisher, place of publication. Example: Mauff G, Pulverer G, Operkuch W, Hummel K and Hidden C, 1995. C3-variants and diverse phenotypes of unconverted and converted C3. In: Provides of the Biological Fluids (ed. H. Peters), vol. 22, 143-165, Pergamon Press. Oxford, UK.Todorov N and Mitev J, 1995. Effect of level of feeding during dry period, and body condition score on reproductive perfor-

thmance in dairy cows,IX International Conference on Production Diseases in Farm Animals, Sept.11 – 14, Berlin, Germany, p. 302 (Abstr.).Thesis:Penkov D, 2008. Estimation of metabolic energy and true digestibility of amino acids of some feeds in experiments with muscus duck (Carina moshata, L). Thesis for DSc. Agrarian University, Plovdiv, 314 pp.

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Volume 5, Number 2June 2013