Impact of turbulence and turbidity on the grazing rate of the rotiferBrachionus calyciflorus(Pallas)

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Abstract

The impact of turbulence and turbidity on Brachionus calyciflorus grazing rate was determined in short feeding periods (10 min), using labelled Chlorella pyrenoïdosa. The response to water motion of B. calyciflorus depends on it physiological state: the grazing rate of recently fed amictic females stomach green (with one or two eggs) is significantly reduced in agitated environments compared with non-agitated environments. In contrast, the grazing rate of starved amictic females is not reduced by water motion, whatever its velocity (V1=0.18 m s-1 and V2=0.22 m s-1). In the presence of suspended particles (3-6-μm silica beads), a larger reduction in grazing rate is observed in agitated water at any water velocity (V1=0.18 m s-1 or V2=0.22 m s-1), than in stagnant water. A synergy between turbulence and turbidity is unfavourable to feeding of rotifers.

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