SHALLOW LAKES Effect of prey type and inorganic turbidity on littoral predator–prey interactions in a shallow lake: an experimental approach Leena Nurminen • Zeynep Pekcan-Hekim • Sari Repka • Jukka Horppila Published online: 7 March 2010 Ó Springer Science+Business Media B.V. 2010 Abstract Predation often represents the prevailing process shaping aquatic ecosystems. As foraging and antipredatory behaviour frequently relate to vision, turbidity may often impair the interactions between the predator and its prey, depending on prey type and source and level of turbidity. We studied the effect of inorganic turbidity (0–30 NTU) on the effectiveness of fish feeding on two types of prey in different habitats: free-swimming cladoceran (Daphnia pulex) in open water and plant-associated cladoceran (Sida crystallina) attached to Nuphar lutea leaves. For the planktivore, we used vision-oriented perch (Perca fluviatilis) common in the littoral zone of temperate lakes. In our study, increasing inorganic turbidity did not appear to initiate any significant change in the feeding efficiency of perch on free-swimming Daphnia pulex. However, we saw a markedly differ- ent feeding efficiency when perch targeted plant- attached Sida crystallina. Our results substantiate that floating-leaved macrophytes in turbid lakes may provide a favourable habitat for plant-attached cladocerans. Keywords Inorganic turbidity  Fish predation  Plant-attached prey  Free-swimming prey  Floating-leaved vegetation Introduction In aquatic ecosystems, planktivorous fish often reg- ulate herbivorous zooplankton communities through effective predation (Carpenter et al., 1985). In order to avoid predation, among zooplankton, for instance, cladocerans display various anti-predatory responses, depending on the subject prey, predator pressure and prevailing environmental conditions (Burks et al., 2002; Nurminen et al., 2007). Free-swimming zooplankton in the water column conduct diurnal horizontal and vertical migrations by aggregating among vegetation or descending to deeper water for refuge against predation (Lauridsen et al., 1997; Burks et al., 2002; Nurminen & Horppila, 2002). Compared to free-swimming zooplankton, cladocerans having the ability to be attached to substrates may resort to slightly different predator-avoidance strategies. In addition to diurnal migratory behaviour and hiding, they can also decrease activity, and stay fixed to refuge substrata, such as macrophytes (e.g. Nurminen et al., 2005). In turbid lakes, floating- Guest editors: M. Meerhoff, M. Beklioglu, R. Burks, F. Garcı ´a- Rodrı ´guez, N. Mazzeo & B. Moss / Structure and Function of World Shallow Lakes: Proceedings from the 6th Shallow Lakes Congress, held in Punta del Este, Uruguay, 23–28 November, 2008 L. Nurminen (&)  Z. Pekcan-Hekim  S. Repka  J. Horppila Department of Biological and Environmental Sciences/ Aquatic Sciences, University of Helsinki, P.O. Box 65, 00014 Helsinki, Finland e-mail: leena.nurminen@helsinki.fi 123 Hydrobiologia (2010) 646:209–214 DOI 10.1007/s10750-010-0175-1