Role of hydrology, nutrients and fish predation in determining the ecology of a system of shallow lakes

Özen, Arda
In this study, the hydrology and physical, chemical and biological variables of a shallow lake system including the Lakes Mogan and Eymir between 1997-2005 were evaluated. In Lake Eymir, a biomanipulation study was conducted between August, 1998 December, 1999. Upon biomanipulation, Lake Eymir shifted to clearwater state with submerged vegetation domination during 2000-2003. However, in 2004, the lake shifted back to algae-dominated turbid state since the buffer mechanisms provided by submerged plants were absent. In the summer of 2005, fish kills were observed due to algal bloom. However, due to increasing hydraulic residence time in the lake, internal processes became more important for nutrients. Lake Mogan faces seasonal and interannual water level fluctuations. During the low water levels experienced in 2001 and 2005, which coincided with the high hydraulic residence times, the in-lake phosphorus amount was controlled by internal processes rather than external loading. Moreover, results revealed that hydrology and submerged plants were important in the ecology of Lake Mogan. Furthermore, the relationship between the phytoplankton, zooplankton and the environment in Lakes Eymir and Mogan, which was predicted via Canonical Corresponding Analysis, revealed that nutrients and water transparency were both important for plankton communities. Both the top-down and bottom up effects were valid in Lake Eymir, while only the bottom-up effect and submerged plants were important for Lake Mogan. Finally, the present study provided a good example for the submerged plant dominated clearwater state triggered by biomanipulation, and the impact of hydrology on the ecology of shallow lakes.


Impacts of multistressors on the survival and life history traits of Daphnia Pulex
Bezirci, Gizem; Beklioğlu, Meryem; Department of Biology (2008)
As Daphnia have an important role in freshwater food webs, it is important to understand how environmental stressors affect their survival and life history traits. Daphnia pulex were first acutely exposed to a combination of NaCl salinities (0.00-10.0 g/L) and fish-exuded kairomone. The 24 and 48 hour LC50 values were 0.401 and 0.159 g/L in kairomone-absence and 1.962 and 1.007 g/L in kairomone-presence. Hence, survival decreased with increasing salinity, while the kairomone enhanced daphnid resistance to s...
Impact of alternating wet and dry periods on long-term seasonal phosphorus and nitrogen budgets of two shallow Mediterranean lakes
Coppens, Jan; ÖZEN, ARDA; Tavsanoglu, U. Nihan; Erdogan, Seyda; Levi, Eti E.; Yozgatlıgil, Ceylan; Jeppesen, Erik; Beklioğlu, Meryem (2016-09-01)
The water balance, with large seasonal and annual water level fluctuations, has a critical influence on the nitrogen and phosphorus dynamics of shallow lakes in the semi-arid climate zone. We constructed seasonal water and nutrient budgets for two connected shallow lakes, Lakes Mogan and Eymir, located in Central Anatolia, Turkey. The study period covered 20 years with alternations between dry and wet years as well as restoration efforts including sewage effluent diversion and biomanipulations in Lake Eymir...
Effect of drought and salt stresses on the gene expression levels of antioxidant enzymes in lentil (lens culinaris m.) seedlings
Aksoy, Emre; Yücel, Ayşe Meral; Department of Biology (2008)
This study was carried out for understanding of antioxidant mechanisms of lentil under abiotic stress conditions. For this aim, 14 days old lentil seedlings (Lens culinaris Medik cv. Sultan-1) were subjected to drought (20% PEG 6000), and salt (150 mM NaCl ) stress for 6, 12 and 24 hours, for 3, 5 and 7 days. PCR conditions for Mn SOD, Cu/Zn SOD, chloroplastic/mitochondrial GR, CAT and chloroplast /stromal APX antioxidant enzymes were optimized. Then, total RNA was isolated from stressed and non-stressed pl...
Water content controlled instead of suction controlled tests
Ahmadinaghadeh, Reza; Toker, Nabi Kartal; Ahmadiadli, Mohammad (2013-03-01)
Most soils that concern geotechnical engineering are in the state of partial water saturation. Current practice tries to predict engineering properties of cohesionless soils using data from tests on saturated specimens, regardless of the saturation in the field. Due to complexity of test setups and high technical requirements, unsaturated soil tests are not among the common equipment of soil mechanics laboratory. One of these problems is the existence of suction, which is a function of water content and aff...
Impacts of climatic variables on water-level variations in two shallow Eastern Mediterranean lakes
Yagbasan, Ozlem; Yazıcıgil, Hasan; Demir, Vahdettin (2017-08-01)
Variations in temperature and precipitation have direct impacts on the physical, chemical and biological characteristics of the shallow lakes. This paper examines the possible linkages between climate variables and the water levels of shallow interconnected Lakes Mogan and Eymir, located 20 km south of Ankara in Central Anatolia. The variations in the lakes' water levels during 1996-2015 are studied and the impacts of climate variables on the lake levels are assessed to address the long-term consequences. T...
Citation Formats
A. Özen, “Role of hydrology, nutrients and fish predation in determining the ecology of a system of shallow lakes,” M.S. - Master of Science, Middle East Technical University, 2006.