Particle retention efficiencies of an herbivorous copepod, Acartia clausi (adult and copepodite stages): Effects on grazing1

Abstract

From measurements of the distances between setules (mesh size) on the maxilla of Acartia clausi, a spectrum of filtration efficiencies for small particles has been established. The slope of the spectrum decreases from young stages (copepodite I) to adults. The average size of particle that can be collected increases slightly from 3 µ in CI to 7 µ in adult stages, whereas the size for which the efficiency is 100% increases sharply from 5 µ to 12 µ. Two experiments were done to show the reality of the spectrum of filtration efficiency. A model of growth of particles and grazing by copepods, using the initial experimental conditions and the efficiency spectrum, was used to simulate the evolution of particles in the two experiments. The fit of the model to the experimental data is good for experiment I (dark) and the first 4 days of experiment II (natural daylight). The results of experiment II show that processes other than grazing become important in a long term experiment.