Grazing by a Dominant Rotifer Conochilus unicornis Rousselet in a Mountain lake: In Situ Measurements with Synthetic Microspheres
Grazing rates of zooplankton were analysed in the summer of 1999 in Yellow Belly Lake, an oligotrophic system in the SawtoothMountains of Idaho (U.S.A.). The colonial rotifer Conochilus unicornis was a dominant species in the epilimnion, with densities reaching 20 colonies l−1 (ca. 400 ind. l−1). Clearance rates were measured with an in situ Haney Grazing chamber and synthetic microspheres 5, 9 and 23μm in diameter. At epilimnetic temperatures of around 14 ◦C, mean clearance rates for 5μm particles ranged from 30 to 65 μl ind.−1 h −1. Clearance rates were 2–9 times higher on the 5μm spheres than on the 9 μm spheres, and C. unicornis almost never fed on the 23 μm spheres. Grazing rates did not change over the diel cycle. Clearance rates declined more than 10-fold as temperatures declined from 14 ◦C in the epilimnion to 7 ◦C in the metalimnion. In the epilimnion, grazing by C. unicornis was more important than grazing by crustaceans in the community, at least on particles ≤9μm. The results show the importance of grazing by rotifers in lakes, and the significance of spatial variations that influence grazing rates.
Armengol, X., L. Boronat, A. Camacho and W.A. Wurtsbaugh. 2001. Grazing by a dominant rotifer Conochilus unicornis Rousselet in a mountain lake: in situ measurements with synthetic microspheres. Hydrobiolgia 446/447:107-114.