Relatively little is known about the role of turbulence in a predator - prey system where the
predator is a passive, pelagic forager. The Campanulariid hydroid Clytia gracilis (Cnidaria,
Hydrozoa) is unusual because it occurs as planktonic colonies and is reported to forage passively
in the water column on Georges Bank, Massachusetts, USA. In this study we investigated the role
of various turbulence conditions on the feeding rate of C. gracilis colonies in laboratory
experiments. We found a positive relationship between turbulence velocities and feeding rates up
to a turbulent energy dissipation rate of ca 1 cm2 s-3. Beyond this threshold feeding rate decreased
slightly, indicating a dome-shaped relationship. Additionally, a negative relationship was found
between feeding efficiency and hydroid colony size under lower turbulent velocities, but this
trend was not significant under higher turbulence regimes.
