The influence of water level on macrophyte growth and trophic interactions in eutrophic Mediterranean shallow lakes: a mesocosm experiment with and without fish

Bucak, Tuba
Saraoglu, Ece
Levi, Etie
Tavsanoglu, U. Nihan
Cakiroglu, A. Idil
Jeppesen, Erik
Beklioğlu, Meryem
1. Water-level fluctuations are typical of lakes located in the semi-arid Mediterranean region, which is characterised by warm rainy winters and hot dry summers. Ongoing climate change may exacerbate fluctuations and lead to more severe episodes of drought, so information on the effects of water level on the functioning of lake ecosystems in such regions is crucial. 2. In eutrophic Lake Eymir, Turkey, we conducted a 4-month (summer) field experiment using cylindrical 0.8-m- (low-water-level) and 1.6-m-deep (high-water-level) mesocosms (kept open to the sediment and atmosphere). Fish (tench, Tinca tinca, and bleak, Alburnus escherichii) were added to half of the mesocosms, while the rest were kept fishless. Ten shoots of Potamogeton pectinatus were transplanted to each mesocosm. 3. Sampling for physicochemical variables, chlorophyll a (chl-a), zooplankton and per cent plant volume inhabited (PVI%) by macrophytes was conducted weekly during the first 5 weeks, and subsequently biweekly. Macrophytes were harvested on the last sampling date. During the course of the experiment, the water level decreased by 0.41 +/- 0.06 m. 4. Throughout the experiment, fish affected zooplankton abundance (-), nutrient concentrations (+), chl-a (+) and water clarity (-) most strongly in the low-water-level mesocosms and the zooplankton community shifted towards dominance of small-sized forms. The fishless mesocosms had a higher zooplankton/phytoplankton ratio, suggesting higher grazing. 5. Greatest macrophyte growth was observed in the low-water-level fishless mesocosms. However, despite high nutrient concentrations and low water clarity, macrophytes were also abundant in the fish mesocosms and particularly increased following a water-level decrease from midsummer onwards. Macrophyte growth was poor in the high-water-level mesocosms, even in the fishless ones with high water clarity. This was ascribed to extensive periphyton development reducing light availability for the macrophytes. 6. Our results indicate that a reduction in water level during summer may help maintain the growth of macrophytes in Mediterranean eutrophic shallow lakes, despite a strong negative effect of fish predation on water clarity. It is therefore probable that an expected negative effect of global climate change on water clarity because of eutrophication and enhanced top-down control of fish may be, at least partly, counteracted by reduced water level, provided that physical disturbance is not severe.


The impact of climate change on a Mediterranean shallow lake: insights based on catchment and lake modelling
Coppens, Jan; Trolle, Dennis; Jeppesen, Erik; Beklioğlu, Meryem (Springer Science and Business Media LLC, 2020-05-19)
Shallow lakes in the semi-arid climate zone of the Mediterranean are sensitive to drought due to the low annual precipitation and high evaporation. Changes in precipitation and temperature as projected by climate change scenarios will have an effect on the hydrology of these shallow lakes with secondary effects on nutrient dynamics and ecological state. In this study, we used a combined modelling approach that included the catchment model Soil and Water Assessment Tool (SWAT) and the lake model PCLake to st...
The importance of allochthonous organic matter quality when investigating pulse disturbance events in freshwater lakes: a mesocosm experiment
Caldero-Pascual, Maria; Yildiz, Dilvin; Yalçın, Gülce; Metin, Melisa; Yetim, Sinem; Fiorentin, Claudia; Andersen, Mikkel Rene; Jennings, Eleanor; Jeppesen, Erik; Ger, Kemal Ali; Beklioğlu, Meryem; McCarthy, Valerie (2021-11-01)
Extreme precipitation is occurring with greater frequency and intensity as a result of climate change. Such events boost the transport of allochthonous organic matter (allo-OM) to freshwater ecosystems, yet little is known about the impacts on dissolved organic matter (DOM) quality and seston elemental stoichiometry, especially for lakes in warm climates. A mesocosm experiment located in a Turkish freshwater lake was designed to simulate a pulse event leading to increased inputs of allo-OM by examining the ...
The Influence of Land Use on Coastal Litter: An Approach to Identify Abundance and Sources in the Coastal Area of Cilician Basin, Turkey
Aydin, Carina; Guven, Olgac; Salihoğlu, Barış; Kıdeyş, Ahmet Erkan (2016-03-01)
The Cilician Basin located in the Northeastern Mediterranean is a region that is affected by a diversity of anthropogenic pressures and is further expected to suffer from negative economic, environmental and social impacts of coastal litter. To provide a baseline for litter management plans, the standing crop of coastal macro-litter was sampled on 13 beaches following MSFD guidelines. Environmental predictors characterizing beach use and potential land based litter point sources in the vicinity of the beach...
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...
The effect of cold and warm core eddies on the distribution and stoichiometry of dissolved nutrients in the northeastern Mediterranean
Yılmaz, Ayşen (1998-10-01)
The nutrient distribution and phytoplankton production in the Levantine Sea of the eastern Mediterranean are principally determined by the duration and the intensity of deep winter mixing in the quasi-permanent anticyclonic and cyclonic eddies. In the seasons of stratification, a nutrient-poor aphotic layer is formed between the euphotic zone and the nutricline; interestingly, it consistently extends down to depths of about 29.0-29.05 isopycnal surfaces, but nearly vanishes in the core of the cyclonic Rhode...
Citation Formats
T. Bucak et al., “The influence of water level on macrophyte growth and trophic interactions in eutrophic Mediterranean shallow lakes: a mesocosm experiment with and without fish,” FRESHWATER BIOLOGY, pp. 1631–1642, 2012, Accessed: 00, 2020. [Online]. Available: