Comparison of fish and phantom midge influence on cladocerans diel vertical migration in a dual basin lake |
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Authors: | A Wojtal-Frankiewicz P Frankiewicz T Jurczak J Grennan and T K McCarthy |
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Institution: | (1) Department of Applied Ecology, University of Lodz, Banacha 12/16 Str, 90-237 Lodz, Poland;(2) Department of Zoology, National University of Ireland, University Road, Galway, Ireland |
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Abstract: | Diurnal vertical migrations (DVM) behaviour of cladocerans was investigated in two mesotrophic Irish lakes connected by a
canal, characterised by interesting differences in the presence of zooplanktivorous predators. In Doon Upper, fish (mostly
juvenile perch and roach) and a little-studied phantom midge Mochlonyx fuliginosus (Chaoboridae) were found, but Doon Lower was solely inhabited by fish. As the presence of diverse predators may alter spatial
avoidance behaviour of zooplankton prey in different ways, the aim of this study was to determine whether and how two predator
types, fish and phantom midge larvae, have changed DVM pattern of cladocerans during day and night in Doon lakes. Two sampling
series of phytoplankton, zooplankton, fish, and water physical analyses were conducted on 09–10 June and 19–20 September 2007
in both lakes. In the study conducted in June, under a similar distribution of M. fuliginosus and juvenile fish in Doon Upper, a reverse migration of Daphnia
galeata was observed as a strategy allowing them to avoid both types of predators. However, in September, when M. fuliginosus lived in a 24 h refugium below the oxycline as a response to increasing predation risk posed by YOY fish penetrated the upper
strata of water during day and night, reverse migrations of D. galeata were not clear. In Doon Lower, normal migration was observed as an advantageous behavioural response against visual predators
(fish), in both large and small Cladocera species: D. galeata, Diaphanosoma branchyurum and Bosmina sp. Thus, our results indicate dissimilar migration patterns of D. galeata depending on the presence of one (Doon Lower) or two predators with different predation behaviour (Doon Upper). |
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