Impact of water level fluctuations and fish on macroinvertebrate community and periphyton growth in shallow lakes - a mesocosm approach

Saraoğlu, Ece
A mesocosm experiment was conducted in Lake Eymir between June – September 2009 in order to elucidate the effects of water level changes and fish predation on periphyton growth and macroinvertebrates in semi-arid shallow lakes. Twenty four cylindrical enclosures, each with 1.2 m diameter, open to lake bottom and atmosphere, were placed at three different depths, i.e. 0.8 m (low water level, LW), 1.6 m (high water level, HW) and 2.3 m (however, data regarding the enclosures at 2.3 m were excluded in this study due to complications after fifth sampling) to simulate water level fluctuations. At each water level, four replicates were stocked with omnivorous–planktivorous fish (Tinca tinca and Alburnus escherichii) and the other four replicates were left fishless to observe the effect of fish predation. Ten shoots of submerged macrophytes (Potamogeton pectinatus) were planted and six polyethylene strips were hung in the water column in each enclosure to monitor macrophyte and periphyton growth. The mesocosms were sampled for physical, chemical and biological parameters weekly in the first month and fortnightly thereafter. Benthic macroinvertebrate samples were taken before the start, in the middle and at the end of the experiment with Kajak corer. Macrophytes were harvested after the last sampling for determination of dry weight, epiphyton, and the associated macroinvertebrates. All macroinvertebrate samples were sieved through 212 μm mesh size before identification and counting. Over the course of the experiment, an average of 0.46 ± 0.03 m water level decrease in the mesocosms triggered submerged macrophyte growth in all LW enclosures, overriding the negative effects of fish predation. The results indicate that while fish predation pressure had negative influences on macroinvertebrate communities in terms of both abundance and richness, structural complexity created by dense vegetation in the LW mesocosms weakened the top-down effect of fish on macroinvertebrates by acting as a refuge in this semi-arid shallow lake.


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Citation Formats
E. Saraoğlu, “Impact of water level fluctuations and fish on macroinvertebrate community and periphyton growth in shallow lakes - a mesocosm approach,” M.S. - Master of Science, Middle East Technical University, 2012.