The grazing rate of planktonic copepods

Abstract

The filtering rate of four species of marine planktonic copepods was measured by estimating the rate at which they consumed cultures of Chlamydomonas.The filtering rate was independent of the concentration of the food organism and it is concluded that the copepods were acting as filter feeders.The filtering rates were much greater than those reported by Fuller & Clarke (1936) and Fuller (1937), but agreed with those reported by Harvey (1937).Some evidence was obtained that grazing was restricted to some only of the 24 hr., most probably to the hours of darkness.The filtering rates were approximately proportional to the square of the linear dimensions of the copepod.The purely mechanical selection suggested by Fuller (1937) to account for differences in filtering rates obtained with different species of diatoms cannot account for all the differences which have been observed.It is probable that the copepods could obtain sufficient particulate food in the sea by filtering a daily volume of water corresponding to the filtering rates found.