Trade-Offs in Daphnia Habitat Selection

Abstract

Abstract. Diel vertical migration (DVM) is a dynamic behavioral pattern found extensively in the world's oceans and lakes, yet the role of food and temperature distribution on DVM is still unclear. While DVM has been mostly studied in systems with surface food maxima, deep-water food maxima are quite common in lakes and oceans. In such ecosystems, optimal conditions of temperature and food are uncoupled. In a Swiss high-mountain lake (Oberer Arosasee) with a deep-water food maximum, we found that Daphnia galeata adults and juveniles exhibit DVM behavior almost throughout the year and migrated upwards, out of food-rich environments, at night. In a large indoor mesocosm experiment, we were able to show that Daphnia respond to fish-mediated cues by migrating into deeper water layers. In the presence of fish and using natural vertical food and temperature distributions in the mesocosms, we could reproduce the vertical distribution of adult Daphnia observed in the field. The indoor experiments show that food and temperature modulate the actual depth at which the animals stop migrating, whereas fish and ultraviolet radiation likely determine the timing of migration (its synchronization with dawn and dusk). Overall, our results show that the nighttime movement into the surface waters contributes to the fitness of Daphnia, given the costs and benefits associated with the trade-off between food and temperature.

Challenges and opportunities for integrating lake ecosystem modelling approaches

“…A (pseudo-) 1-or 2-D version in the horizontal would, however, increase the applicability of the model. A 2-D implementation in the x-z plane would also allow accounting for the movement of animal populations between different habitats (e.g., Vos et al 2002;Winder et al 2004).…”

Trapping migrating zooplankton

“…For example, the best layers in which to forage are frequently the most dangerous because of the presence of predators; an optimal depth selection strategy may be a diel vertical migration timed to avoid or minimize the effects of predation (Fiksen and Carlotti 1998;Han and Straskraba 1998;Tarling et al 2000). Even in the absence of significant predation risk, zooplankton should still exhibit a habitat selection pattern that optimizes growth (Kessler and Lampert 2004;Lampert et al 2003), with interactive effects of food and temperature expected in some circumstances (Kessler 2004;Winder et al 2004).…”

Vertical distribution of zooplankton in subalpine and alpine lakes: Ultraviolet radiation, fish predation, and the transparency‐gradient hypothesis

“…There are also strong interactions among environmental factors. For example, the response of Daphnia to variation in food concentrations in the water column is modified by temperature gradients (Kessler and Lampert 2004;Winder et al 2004). The relative importance of behavioral vs. pigmentation responses may also vary with taxon and latitude of a given zooplankton population (Hansson et al 2007).…”

“…These factors combine to form vertical habitat gradients in alpine lakes that influence the vertical distribution of zooplankton (Winder et al 2004). The high flux of solar radiation inhibits primary productivity near the surface of those lakes and may cause the maximal phytoplankton abundance to be located in deeper strata (Sommaruga 2001), resulting in the development of a deep-water chlorophyll maximum (DCM).…”