Other Mesozooplankton Groups
(^) Filtering-rate determinations for euphausiids, also important in the planktonic
economy, are fewer. One by McClatchie (1985) shows a different approach to the
measurement. He used a spherical 250-liter flow-through chamber with a magnetic
stirring bar at the bottom. Diatom culture was added to the inflow in pulses, mixed
through the chamber quickly, and then diluted away at a rate measured from
chlorophyll fluorescence. The increase in apparent rate of dilution with Thysanoessa
raschii present was the basis for determining their ingestion rate, and thus water-
clearance rate, F. The euphausiid ingestion rate closely tracked (Fig. 7.8a) the diatom
concentration through four-fold pulses, which implied a constant F = 15.4 ml krill−1 h
−1. The functional response curve (Fig. 7.8b), then, increases linearly over the range