The theory of domains of attraction (alternative ‘stable’ states) allows the integration of variability, discontinuities and persistence in ecosystem dynamics. This thesis investigates the potential for alternative domains of attraction in a zooplankton community. Two alternative states have been proposed for the zooplankton community of small fishless, oligotrophic, mountain lakes. In the ‘competition state’, Daphnia (Cladocera) outcompete solitary rotifers and impede predator recruitment. This state is persistent and resilient to disturbance. In the ‘predator state’, predation by Chaoborus (Diptera) on both prey types alters community dynamics to favor rotifers over Daphnia. Persistence of the predator state requires reduced prey competition and enhanced young predator recruitment in summer, and predator survival in high densities over the winter.

Field experiments were carried out in large enclosures. Daphnia density reductions and predator additions in the spring were used to generate the predator state and test its persistence. Lake and enclosure communities were monitored for three consecutive years using an adaptive sampling concept where sampling interval varied based on system dynamics rather than the calendar. In the first year, predator recruitment in enclosures was enhanced and the new Chaoborus cohorts survived overwinter in high densities. However, developmental delays prior to the winter prevented persistence of the predator state over several generations. Enhanced predator densities in the spring, as well as cold temperature, delayed Daphnia population onset and increase. This released solitary rotifer populations to feed young predator recruits in early summer. Nonetheless, in the highest predator treatments, both prey types remained depleted till late summer which resulted in delayed predator development. Therefore, the predator state was a transient state that persisted for, at most, two generations. Nevertheless, the predator state persisted between seasons: an example of an extended transient state in zooplankton community dynamics.

Cold water can delay the onset of the predator reproductive phase and delay recruitment of young Chaoborus. Laboratory experiments showed that although C. americanus larvae pupated at a temperature as low as 5°C, pupae did not metamorphose into adults (ecdysis) below 9°C. Surprisingly, half of C. trivittatus pupae were able to complete ecdysis even at 5°C. Cold temperature in spring can impede predator state persistence, depending on the Chaoborus species present in the community.

A threshold was present in the zooplankton community dynamics but under oligotrophy, this community could not sustain two domains of attraction. Thresholds in dynamics do not always lead to alternative domains of attraction but can also lead to transient states and extended (lasting more than one season) transient states. Distinguishing between different dynamic behavior is important to determine if natural disturbances and human interventions will lead to temporary or permanent changes in ecosystem dynamics.