Daphnia diel vertical migration: implications beyond zooplankton

Abstract

Diel vertical migration (DVM) is a common behaviour of many pelagic zooplankton species. While the causes (mostly predator avoidance) and ecophysiological consequences of DVM for zooplankton have been well studied, little is known about the consequences of DVM for the pelagic food web. DVM creates a temporal and spatial grazer-free niche for edible phytoplankton, and theoretical models predict that parts of the phytoplankton community should use this niche. Conceivably, DVM could also cause nutrient transport between separated water layers. We experimentally investigated the influence of DVM of the zooplankton species, Daphnia hyalina, on the nutrient and phytoplankton dynamics of an oligotrophic lake. We used 10-m deep field enclosures with a 4-m deep, well-mixed surface layer. The enclosures contained either migrating or nonmigrating Daphnia populations; temperature was kept nearly constant across the entire enclosure depth. Our results show that DVM had significant quantitative and qualitative effects on the phytoplankton community. There was no measurable net nutrient transport between hypolimnion and epilimnion. The gelatinous green alga Planktosphaeria gelatinosa, was the dominant algal species in our experiment. Its abundance decreased in DVM treatments, and thus also influenced the total biomass and diversity of phytoplankton communities.

Has zooplankton 24 hour vertical distribution pattern in Lough Derg (Ireland) been changed over the period of ∼90 years?

“…Zooplankton distribution in Lough Derg is probably not connected with homogenous physico-chemical variables but with other environmental factors. Light, temperature and biotic interactions, such as predation, interspecific competition, food availability and feeding habits can influence and modify migration patterns (Gliwicz, Pijanowska 1988;Lampert 1989;Mavuti 1992;Loose, Dawidowicz 1994;Sakwińska, Dawidowicz 2005;Haupt et al 2009;Cohen, Forward 2009;Wojtal-Frankiewicz et al 2010). Dumont et al (1985) stressed that in the absence of strong forcing factors, such as visual predation and light damage, it would be advantageous for zooplankton not to migrate downwards during the day, allowing zooplankters to feed continuously on the phytoplankton.…”

Initial size structure of natural phytoplankton communities determines the response to Daphnia diel vertical migration

“…The submersible cages used in this study had already been successfully applied in earlier experiments Haupt et al 2009). Although predation is considered to be one of the most important causes of zooplankton DVM (Zaret, and Suffern 1976), attempts to establish a predatory dynamic by fish stocking have proven very difficult, primarily due to potential indirect effects on phytoplankton caused by nutrients excreted by enclosed fish (Schindler 1992;Vanni, and Layne 1997;Attayde, and Hansson 1999).…”

“…From this point onwards, we therefore refer to the 11 mm filtered communities as "small" communities and the 64 mm-filtered communities as "large" communities. For a detailed description of the natural summer phytoplankton community in Lake Brunnensee see Haupt et al (2009). Filtration and the filling of the enclosures began on 19 June 2007, which took approximately 48 h. The enclosures were filled haphazardly with either "small" or "large" phytoplankton.…”

“…A model developed by Petzoldt et al (2009) showed that reduced zooplankton grazing and changed nutrient recycling under DVM are important mechanisms influencing plankton dynamics. The few experiments that have been conducted to investigate the effects of zooplankton DVM on pelagic ecosystems show that it may affect phytoplankton abundance, species composition, and diversity Haupt et al 2009). …”

“…One emerging hypothesis from the post hoc analyses of experimental studies Reichwaldt et al 2004;Haupt et al 2009), is that the effects of zooplankton DVM on phytoplankton communities are species-specific, probably depending on the size of particular phytoplankton taxa and the acceptable food-size range of zooplankton. Because small phytoplankton species normally have higher growth rates than larger species (Reynolds, and Irish 1997), they may use spatial and temporal refuges created by zooplankton DVM more efficiently.…”