Ann. Limnol. - Int. J. Lim.
Volume 48, Number 1, 2012
|Page(s)||113 - 123|
|Published online||20 March 2012|
Consecutive earthquakes temporarily restructured the zooplankton community in an Alpine Lake
1 National Institute of Biology, Večna pot 111, 1000 Ljubljana, Slovenia
2 Faculty of Environmental Sciences, University of Nova Gorica, Vipavska 13, 5000 Nova Gorica, Slovenia
3 Anton Melik Geographical Institute, ZRC SAZU, Gosposka ulica 13, 1000 Ljubljana, Slovenia
4 Department of Biology, State University of Ghent, K.L. Ledeganckstraat 35, 9000 Ghent, Belgium
* Corresponding author: Henri.Dumont@UGent.be
Accepted: 18 October 2011
Two consecutive earthquakes temporary changed a zooplankton community in a high-mountain Lake Krn (altitude 1383 m a.s.l.). It was dominated by the eurytherm copepod, Cyclops vicinus, until 1998, when the first earthquake hit the lake (EMS=5.6). After the earthquake, the population of C. vicinus collapsed and the thermophilic cladoceran, Ceriodaphnia quadrangula, took over. After the second earthquake in 2004 (EMS=4.0), C. vicinus became untraceable. In 2008, few copepods reappeared and by 2010 they became the sole dominant again. Only Secchi-disc depth showed a statistically significant increase over time, while Ntot, Ptot and temperature showed an increasing trend, yet the relationship was insignificant. To compare multi-parameter properties of the water column, the studied period was divided into Period 1 (before the first earthquake), Period 2 (between earthquakes) and Period 3 (after the second earthquake). A Hotteling T2 test confirmed a statistically significant difference between Periods 1 and 2 & 3 (P<0.01), but not between Periods 2 and 3 (P>0.1). During simple laboratory experiment, specimens of C. vicinus were covered with a thin layer of sediment, to mimic the earthquake's effect on their survival. A hypothesis was that the timing of both earthquakes had been crucial for decimation of C. vicinus population as they re-suspended sediment with hibernating copepodites. As these became subsequently buried they were deprived of a re-activation signal and exposed prolonged anoxic conditions there. C. quadrangula temporary filled the void left by the copepod, which needed 6 years to regain its dominance.
Key words: Competition / earthquake / high-mountain lake / invasion / zooplankton community
© EDP Sciences, 2012
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