Diurnal Variation in Feeding and Assimilation Rates of Planktonic Rotifers and its Possible Ecological Significance

Abstract

AbstractThough rotifers play an important role in many pelagic ecosystems, there is a lack for studies on diurnal variations in feeding behaviour. Diurnal feeding rhythms of estuarine populations of Brachionus plicatilis and Keratella cruciformis f. eichwaldi and a pond population of K. cochlearis were investigated using 14C‐Chlorella and 14C‐labelled natural bacteria populations, respectively, as a tracer food during in situ experiments. A 51Cr/14C double tracer technique was used to determine Assimilation efficiencies.All species had about two times higher feeding rates during day than during dark hours. There was a tendency for higher values during the afternoon. No trend was found regarding diurnal changes in assimilation efficiency.Diurnally segregated niches between microphagous daytime active rotifers and nighttime active crustacean populations in pelagic ecosystems are demonstrated and their ecological significance with special regard to changes in food quality and predation pressure is discussed.