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Temporal patterns of resource limitation in natural populations of rotifers

Merriman, Jodie L., Kirk, Kevin L.
Ecology 2000 v.81 no.1 pp. 141-149
Rotifera, eutrophication, herbivores, plankton, population growth, temporal variation
The availability of resources may limit consumer populations, and temporal variation in resources may facilitate the coexistence of competitors. Accurate estimates of resource availability often cannot be obtained by counting potential food items, because of difficulties in determining resource quality. Instead, resource supplementation experiments must be conducted, but few experimental studies have examined the temporal patterns of resource limitation. To determine the occurrence, intensity, and temporal variation of resource limitation in natural populations of planktonic rotifers, experiments were conducted using two species of herbivorous rotifers from a eutrophic pond, Keratella cochlearis and Synchaeta sp. The difference in population growth rates in food‐supplemented treatments relative to controls (Δr) was used as a measure of the intensity of food limitation. Rotifers were usually food limited, with Keratella and Synchaeta showing significant food limitation (Δr > 0) in 63% and 87% of the experiments, respectively. There was temporal variability in Δr on time scales of one to a few weeks, indicating rapid changes in resource availability. Synchaeta population dynamics were more closely controlled by resources than was the case for Keratella, and the intensity of food limitation was higher for Synchaeta than for Keratella, possibly due to the more specialized feeding habits of Synchaeta.