In this study, the factors influencing zooplankton community structure in Turkish
shallow lakes were elucidated with four main approaches: (i) space-for-time
substitution for shallow lakes using snap-shot sampling in 31 lakes along a latitudinal
gradient / (ii) in-situ mesocosm experiments in eleven lakes along a latitudinal
gradient using three sets of artificial plants systems / (iii)&lsquo / Habitat Choice&rsquo / laboratory
experiments mimicking a &lsquo / shallow littoral&rsquo / zone with plants and a &lsquo / deeper pelagic&rsquo / zone with sediments testing the response of Daphnia magna to predation cues / and
(iv) long-term monitoring data (1997-2011) from two interconnected lakes.
Snap-shot and long-term monitoring showed that eutrophication has a strong
influence on the zooplankton community via increased fish predation, nutrient
loading and salinization. Here too the zooplankton community shifted towards a
smaller sized profile, especially in lakes located at lower latitudes. Moreover, The
laboratory and in-situ mesocosm experiments revealed that under predation risk
Daphnia preferred to hide near sediment instead of using submerged plants as a
refuge. Accordingly, in-situ mesocosm experiments revealed a predation pressure
induced size structure shift towards small-medium sized zooplankton and calanoid
copepods.
The long-term monitored lakes experienced (i) drought-induced water level drop,
leading to increased salinity and eutrophication, and consequent anoxic conditions
and fish kill / as well as (ii) biomanipulation in the downstream. Both conditions
resulted in major reduction in the top-down control of fish and ultimate
predomination by large sized Daphnia spp.
Nevertheless, the excessive exploitation of lakes and ongoing warming entail Turkish
shallow lakes to become more eutrophic, making this study indicative for the
Mediterranean region.
| Identifer | oai:union.ndltd.org:METU/oai:etd.lib.metu.edu.tr:http://etd.lib.metu.edu.tr/upload/12615354/index.pdf |
| Date | 01 January 2013 |
| Creators | Yazgan Tavsanoglu, Ulku Nihan |
| Contributors | Beklioglu Yerli, Meryem |
| Publisher | METU |
| Source Sets | Middle East Technical Univ. |
| Language | English |
| Detected Language | English |
| Type | Ph.D. Thesis |
| Format | text/pdf |
| Rights | Access forbidden for 1 year |
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