Abundance and Seasonal Variations of Cladoceran and Copepod Fauna of Kesikköprü Dam Lake in Turkey

In this study, a total of 17 Cladoceran and Copepod species were identified in Kesikköprü Dam Lake (Ankara) between April 1995 and May 1996. The average individual number of copepod species was found to be 51279 Ind/m 3. The highest number of copepod species was recorded in May 1995 and the lowest in February 1996. Arctodiaptomus acutilobatus was the most abundant copepod species with an average of 18541 Ind/m 3. The average individual number of Cladoceran species was found to be 47282 Ind/m 3 . Daphnia longispina was found as the most abundant cladoceran species and its peak was observed in April 1995. The highest number of Cladoceran species was recorded in June 1995 and the lowest in January 1996.


Introduction
In the Lake ecosystems, zooplanktonic organisms, which form the second step of the food chain, are important food sources of some invertebrate animals and fishes.Also they play an important role in the water quality, eutrophication, pollution and productivity of a Lake.(Sharma 1983;Saksena 1987).The Cladocerans and Copepods are two groups of zooplankton.They have value as indicators of water quality and the structure of the biotic community (Gannon and Stemberger 1978).
Turkey is rich in freshwater sources with different ecological peculiarities.Many studies have been conducted with the purpose of identifying cladoceran and copepod species in Lakes and Dam Lakes.(Alt ı ndağ and Özkurt 1998, Ustaoğlu 1993, Ustaoğ lu 1986, Ustao ğlu et al. 2001).Also, Demir et al. (2001), showed the influence of trout cage culture on water quality, plankton and benthos in Kesikköprü Dam Lake.The aim of this study is to determine the species composition and seasonal variation of cladoceran and copepod fauna in Kesikköprü Dam Lake.

Materials and Methods
Kesikköprü Dam Lake is located in 110 km southeast of Ankara, between the Kapulukaya and Hirfanl ı Dam Lakes.lts total volume is 9500hm 3 , maximum depth 30 m, and total area 650 ha.Kesikköprü Dam Lake is 750 m above sea level and is fed by the Kızı l ı rmak River.This study was performed at five different stations of the Lake (Fig. 1).
The plankton samples were collected from each , station between April 1995-May 1996 on a monthly basis, using a 55 grn mesh size Hydro-Bios Kiel plankton net while making horizontal and vertical hauls.The zooplankton samples were immediately fıxed in 4% formaldehyde.The samples were identified according to Scourfield and Harding (1966), Smirnov (1974) and Dussart (1969).During the study period, water temperature, Secchi depth, dissolved oxygen and pH were measu red.

Results
The temperature of Kesikköprü Dam Lake varied from 4 to 24 °C, Secchi depth 5.5 to 12 m, dissolved oxygen 8.0 to 12 mg/I and pH 7.2 to 8.6 (Table 1).During the research period, Cladocera are represented by 9 species and the Copepoda by 8 species in the Kesikköprü Dam Lake.(Fischer, 1848) Arctodiaptomus acutilobatus (Wierzejski, 1887) Acanthodiaptomus denticomis (Wierzejski, 1857) Nitocra hibemica Brady, 1880 The average individual number of all copepod species in the Dam Lake was found to be 51,279 Ind/m 3 .Specieswise percentages were as follows: Eucyclops serrulatus was found at all stations and was the second most abundant species, with an average of 6329 Ind/m 3 and 12.75%.The highest number of this species was recorded in May 1995 with 19825 Ind/m 3 , and the lowest in August 1995 with 1314 Ind/m 3 Cyclops abyssorum was found at all stations except station Il and is the 3 rd most abundant species with an average of 5750 Ind/m 3 and 11.59%.The peak in this species was observed in October 1995 with 17198 Ind/m 3 a n d t h e l o w e s t n u m b e r i n J u l y 1 9 9 5 w i t h 1 3 1 4 I n d / m 3 .Nitocra hibemica was found at I., Il. and V. stations.It has an abundance of 5189 Ind/m 3 and 10.46%.The highest number of this species was recorded in May 1995 with 10589 Ind/m 3 and lowest in October 1995, February 1996 with 3503 Ind/m3 .Megacyclops viridis was mostly found at all stations except station IV.It has an abundance of 4423 Ind/m3 and 8.91%.The highest number was observed in April with 12341 Ind/m 3 and the lowest in February 1996 with 1314 Ind/m3 .Acanthodiaptomus denticomis was observed at all stations with 3987 Ind/m 3 and 8.04%.The highest number (18034 Ind/m 3) was determined in October 1995 and the lowest (876 Ind/m 3) in September, December 1995 .Diacyclops bicuspidatus was found at all stations except station V. with 2731 Ind/m 3 and 5.50%.The peak (10112 Ind/m 3) was observed in May 1996 and the lowest number (1314 Ind/m 3) was found in February 1996.Cyclops vicinus was recorded at all stations except station III.lts individual number and percentage were 2670 Ind/m3 and 5.38% respectively.The highest number (17198 Ind/m3 ) was observed in April 1996 and the lowest in June 1995 (1752 Ind/m 3).
In Kesikköprü dam lake, the average individual number of all cladoceran species was found to be 47282 Ind/m3 .Species-wise percentages were as follows; Daphnia longispina 23.52%, Daphnia pulex 21.36%, Diaphanosoma lacustris 14.14%, Daphnia magna 13.43%, Chydorus sphaericus 8.29%, Bosmina longirostris 8.08%, Monospilus dispar 5.04c/o, Disparalona rostrata 3.17% and Macrothrix laticomis 2.96%.Specimens were found most abundant at station IV (mean: 61320 Ind/m 3) and the least at station III (mean: 33468 Ind/m 3).The highest number of cladoceran species (86080 Indim') was recorded in June 1995 and the lowest number (8758 Ind/m 3) in January 1996.Peaks were observed in spring (May, June) and autumn (September, October), But the population density decreased in winter (January, February) and in summer (July, August).Among the cladoceran species; Daphnia longispina, (the most abundant species), was found at all stations except station II.Its peak was observed in April 1995.The lowest number was recorded in January 1996 .Daphnia pulex was found at al! stations and was the second most abundant species, with an average of 9964 Ind/m 3 and 21.36%.The highest number of this species was recorded in June 1995 with 16773 Ind/m 3 , and the lowest in December 1995 with 2627 Ind/m 3 .Diaphanosoma lacustris was found at all stations and it is the 3 rd most abundant species with an average of 6599 Ind/m 3 , and 14.14%.The peak in this species was observed in October 1995 with 18538 Ind/m 3 a n d t h e l o w e s t n u m b e r i n F e b r u a r y 1 9 9 6 w i t h 1 3 1 4 I n d / m 3 .Daphnia magna was also found at all stations except station III.Its peak was observed in May 1996 with 15844 Ind/m 3 .The lowest number of this species was recorded in December with 2627 Ind/m 3 .Chydorus sphaericus was found at all stations with an average of 4218 Ind/m 3 and 8.29%.The peak in this species was observed in June 1995 with 15884 Ind/m3 and the lowest number in August 1995 with 876 Ind/m 3.During the study, Bosmina longirostris was found only at stations II and V. Its peak was determined in May 1996 with 13217 Ind/m 3 and the lowest number in November 1995 and February 1996 with 1314 Ind/m 3 .Monospilus dispar was also found at all stations except station I.It has an average of 2352 Ind/m 3 and 5.04%.Peak was observed in October 1995.The lowest number was recorded in December 1995.Disparalona rostrata was determined to have an abundance of 1477 Ind/m 3 and 3.17%.The highest number was observed in June 1995 with 4406 Ind/m3 and the lowest in December 1995 with 1314 Ind/m 3.
The last species, Macrothrix laticomis, was observed at all stations but low numbers.It has an abundance of 1381 Ind/m3 and 2.96%.The highest number of this species was recorded in April 1996 with 6635 Ind/m 3 and lowest in January 1996 with 1314 Ind/m 3 .was the second abundant cladoceran species, observed in 11 months of the research period.But, in this study, Chydorus sphaericus was found as the fifth dominant species.Cyclops vicinus was the dominant species of the Kunduzlar Dam Lake (11.94%) and Cyclops vicinus was again common species of Çatören Dam Lake (16.99%) (Alt ı ndağ and Özkurt 1998).This species was found throughout the sampling period in both Dam Lakes.In present study, in contrast Cyclops vicinus was found in the lowest numbers during the study period (2670 Ind/m 3 and 5.38%).In Karamuk Lake, Acanthodiaptomus denticomis was the common copepod species and its individual number (in summer and autumn) was recorded very high (Emir and Demirsoy, 1996).Similarly, in present study, the same copepod species reached at the highest density in summer, autumn and spring seasons.Daphnia pulex, D. longispina and D. magna were generally common species which found in Turkish Lakes and reservoirs.These species were nearly found at all stations and all months.Gündüz (1987), recorded the Daphnia longispina in Karam ı k and Hoyran Lakes.Also he found Daphnia magna, D. longispina and D. galeata in the Bafra Bal ı k Lake.Kesikköprü Dam Lake is an oligotrophic lake because of the high oxygen concentration and Secchi depth in all seasons.This study will be a resource for future studies in Kesikköprü Dam Lake.

Conclusion
In Kesikköprü Dam Lake, Cladocera and copepoda biomass exhibited two peaks.Generally, peaks were observed in spring (April, May, June) and autumn (September, October).In contrast, the population density decreased in winter (January, February) and in summer (July, August).