Four-month mesocosm experiment from June 1st to September 25th, 2009, was conducted
to determine the effect of water level dierence in combination with fish predation
pressure, on submerged macrophyte development, in an eutrophic shallow lake.
Effect of water level fluctuation was simulated by placing enclosures to the different
water depths that included 0.8 m, 1.6 m and 2.3 m on Lake Eymir. These enclosures
having a cylindirical shape and 1.2 m diameter, were open to sediment and
atmosphere interaction. The highest water level mesocosms were cancelled after fifth
sampling due to rapture in the bags, hence this thesis does not include the results of 2.3
m. At each depth, half of the enclosures were stocked with planktivo-omnivorous fish
(Tinca tinca, Alburnus spp.) which are natural fauna of Lake Eymir. Before stocking
of fish, ten shoots of Potamageton pectinatus were added to all of the enclosures in
order to observe submerged macrophyte development.
Sampling for physico-chemical parameters, zooplankton, chlorophyll a, PVI% and periphyton was conducted weekly for the first five weeks, last six samplings were
done biweekly. Macrophyte harvesting for dry weight estimation was done at the end
of the experiment. Throughout the experiment water level decreased 0.41 ± / 0.06 m in
each enclosures.
Water level was so critical for macrophyte development that no significant macrophyte
growth was observed in enclosures located at 1.6 m (HW). However, fish predation
did not prevent the growth of macrophyte in enclosures located at 0.8 m (LW)
but it was important in HW enclosure for affecting water clarity. Fish predation
affected chlorophyll a, zooplankton and nutrient concentrations and the effect was
mostly pronounced at LW enclosures. They had high chlorophyll a and nutrient concentrations
but it did not repress macrophyte growth as in temperate lakes. Despite
high water clarity in HW fishless enclosures, very low macrophyte biomass may be
attributed to enhanced periphyton development. Zooplankton community shifted to
small sized ones under fish predation while fishless enclosures had higher zooplankton
/phytoplankton ratio for each depth. Hence, regarding these results it can be stated
that decrease in water level can compensate the negative effects of fish predation on
macrophyte growth in warm Mediterranean lakes.
| Identifer | oai:union.ndltd.org:METU/oai:etd.lib.metu.edu.tr:http://etd.lib.metu.edu.tr/upload/12612995/index.pdf |
| Date | 01 February 2011 |
| Creators | Tuba, Bucak |
| Contributors | Beklioglu Yerli, Meryem |
| Publisher | METU |
| Source Sets | Middle East Technical Univ. |
| Language | English |
| Detected Language | English |
| Type | M.S. Thesis |
| Format | text/pdf |
| Rights | To liberate the content for METU campus |
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