MEPS 130:125-134 (1996)  -  doi:10.3354/meps130125

We studied the feeding behavior of the surface-deposit feeder Saccoglossus kowalevskii under oscillatory flows in the laboratory. Low oscillatory flow (peak speed = 10 cm s^-1) without associated sediment transport had no effect on egestion rates in comparison to no-flow conditions. Moderate flows (peak speed = 15 and 17.5 cm s^-1) with incipient sediment transport caused an increase in egestion rates of 35 to 100% relative to low-flow rates. High flow (peak speed = 25 cm s^-1) with bulk sediment transport caused a decrease in egestion rates to one-third the low-flow rates. When compared to a functional response curve previously determined for S. kowalevskii, our data show that under high flow S. kowalevskii does not feed at rates predicted by the available food resources (as measured by chlorophyll a concentration). Under moderate flow, S. kowalevskii is stimulated to feed at higher rates than predicted by the available food resources. And under low flow, S. kowalevskii appears to be un-affected by flow and continues feeding at rates predicted by the available food resources. Flow and the associated sediment flux thus lead to an envelope of egestion rates about the no-flow functional response, indicating that the feeding behavior of S. kowalevskii is a function both of available food resources and flow regime. Laboratory still-water functional responses and simple feeding models are thus inadequate. Accurate extrapolation and prediction require that flow and sediment flux parameters be incorporated in feeding models.

Saccoglossus kowalevskii . Deposit feeder . Oscillatory flow