Flow through the feeding structures of suspension feeding zooplankton: a physical model approach

Abstract

Simple multi-filament models of suspension feeding zooplankton feeding structures were constructed and the flow through and around the models was described. The fraction of water passing the filter depends on filament diameter, interfilament spacing and the number of filaments. Within a realistic range of Reynolds' numbers (Re) only a fraction of the head on water stream passed through the filters. The significance of morphological characteristics was also investigated for a biological more relevant 90° sweep. Spreading the filaments apart caused a significant increase in leakage compared with parallel filaments and, by introducing side branches the models acted as slightly leaky sieves. The leakage can change from 20-30% to almost 100% when Re increased from 0.1 to 1. Leakage depends on the orientation of the side branches indicating the importance of asymmetric drag during water processing at low Re. The observations are discussed in the context of the morphology and movements of feeding structures of ciliary feeding benthic larvae and of setal feeding copepods. The usefulness of physical models as a supplement to direct observations on zooplankton and mathematical models is emphasized.