Rotifer populations in plankton communities: Energetics and life history strategies

Abstract

Rotifers play an important role in many freshwater plankton communities. The populations are controlled from ‘bottom-up’ depending on different food quantities and qualities. As threshold food levels for rotifers are higher than for cladocerans they are often outcompeted when food concentrations are lowered by the clearance activity of cladocerans. Rotifers also are controlled from ‘top-down’ by predators, especially by copepods, by instars ofChaoborus and by predatory rotifers. Mechanical interference by daphnids is considered here as a special case of ‘predation’. Different defense mechanisms are discussed. At the cost of higher food concentrations (high Ks-food levels) rotifers may exhibit high maximum growth rates (rmax) and short times for their population development. This ability increases with rotifer body size. Within this taxonomic unity, therefore, different life history strategies have developed. These strategies may be characterized by the rmax/Ks-model presented.