Trophic interactions of Leptodora in Lake Mendota

Abstract

Using a series of field enclosure experiments, we investigated the trophic dynamics of Leptodora kindtii in Lake Mendota. Leptodora fed on both small and large Daphnia as well as on Diaphanosoma, Conochilus, and copepod nauplii. These results were combined with field data and a computer simulation model to examine how various densities ofLeptodora might affect the densities of Daphnia and other zooplankton in Lake Mendota. Leptodora could account for all of the mortality calculated for Daphnia galeata mendotae in late June to early July. Reduced numbers minimized Leptodora's potential, however, for direct control of Daphnia earlier in the year. The simulation model demonstrated that, because the dominant planktivorous fish in the lake fed on both Leptodora and daphnids, a decrease in planktivorous fish could result in higher Daphnia mortalities due to increased predation by Leptodora. Although invertebrate predators are found in virtually all aquatic systems, their roles in shaping the community structure of lakes are poorly understood. Field researchers have seen dramatic temporal correlations between abundances of invertebrate predators and their prey (Edmondson and Litt 1982;Wright 1965). Feeding experiments with Chaoborus (Fedorenko 1975; Vanni 198 8) and Mysis relicta (Nero and Sprules 1986) confirm their potential for consuming large quantities of zooplankton. Despite this potential impact, invertebrate predators are not included in many models of aquatic food webs (Bartell et al. 1988).A research project is being conducted in Lake Mendota (Univ. Wisconsin-Madison, Center for Limnology, and the Wisconsin Dep. Nat. Resour.) to examine the potential for controlling the intensity of nuisance algal blooms by increasing the abundance of I Present address and address for reprints:

Food web consequences of size‐based predation and vertical migration of an invertebrate predator (Leptodora kindtii)

“…In previous studies, the importance of Leptodora predation has been estimated by daytime surveys of its abundance, size structure, and spatial distribution in surface layers of lakes (Lunte and Luecke 1990;Branstrator and Lehman 1991). Because of the low biomass of Leptodora in surface waters during the day (typically , 1 m 23 ), the importance of predation by Leptodora on zooplankton communities is often thought to be trivial relative to that of vertebrate planktivores (Lunte and Luecke 1990).…”

Experimental paleoecology (resurrection ecology): Chasing Van Valen's Red Queen hypothesis

“…A decrease in conspicuous herbivorous and large-bodied carnivorous cladocerans (Leptodora, Chaoborus) is a common consequence of increasing planktivorous fish densities (Lunte and Luecke 1990;McNaught 1993). Mining discharges could have facilitated the rapid initial 1920s to 1950s transition in species because the slime clays in surficial sediments were toxic to living and ephippial D. dentifera, eliminating a viable egg bank (Kerfoot et al 1999).…”

Different life-history trade-offs of twoDaphniaspecies (Cladocera, Crustacea) under natural conditions as the response to predation and competition

“…Some studies suggest that invertebrate predators may substantially regulate zooplankton communities (Dodson, 1972;Lane, 1979;Brabrand et al, 1986). Leptodora kindtii used in the study as an invertebrate predator is a common pelagic cladoceran which prefers to feed on other species of Cladocera, especially Daphnia (Karabin, 1974;Hovenkamp, 1990;Lunte and Luecke, 1990;Wojtal et al, 1999Wojtal et al, , 2008. Despite its low abundance in lakes, L. kindtii is an effectively grazing predator able to remove up to 35% of Daphnia (Hall, 1964;Wright, 1965).…”