SS3.18 Habitat Coupling in Lakes
Date: Thursday, June 13, 2002
Time: 10:15:00 AM
Location: Esquimalt
 
BurksRL, Rhodes College, Memphis, USA, burksr@rhodes.edu
Haines, A, C, University of Notre Dame, Notre Dame, USA, andrew.c.haines.4@nd.edu
Lodge, D, M, University of Notre Dame, Notre Dame, USA, david.m.lodge.1@nd.edu
 
DO LITTORAL AND PELAGIC ZONES ‘SMELL’ DIFFERENT? DAPHNID BEHAVIORAL RESPONSES TO CHEMICAL CUES FROM WHOLE LAKE ZONES, MACROPHYTES, AND PREDATORS
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Diel horizontal migration (DHM) is a predator-avoidance strategy that links pelagic and littoral zones as Daphnia (an important zooplankter) seek refuge in macrophytes from pelagic fishes. However, in laboratory experiments, daphnids avoid macrophytes in the absence of fish, perhaps due to the chemical environment of either the macrophyte or associated predatory invertebrates. To identify important cues for DHM, we examined daphnid behavior in the presence of chemical cues from pelagic and littoral zones of 4 lakes (differing in predation pressure) and from macrophytes, fish, and dragonflies. We measured daphnid movement within a 3-m horizontal tube where chemical cues were introduced in one or both ends. Daphnids migrated away from pelagic water from all 4 lakes. When forced to choose between pelagic and littoral water, daphnids migrated toward littoral water. Daphnids moved toward macrophytes when fish occurred but otherwise avoided macrophytes, even when dragonflies occurred. These results suggest that chemical cues differ between whole lake zones, that cues from both macrophytes and predators influence DHM, and that daphnids avoid vegetated zones when not under risk of predation from pelagic fishes.