Vertical water column resource partitioning by a ciliated protozoan population under stratified conditions in the northern Adriatic

Abstract

The vertical distribution of the ciliated protozoan stock, potential prey and potential predators were repeatedly sampled over two diurnal cycles at an eutrophic site off the Po River delta during summer when the water column was strongly stratified. A subsurface ciliated protozoan maximum (SCPM) was associated with a subsurface nanoplankton chlorophyll maximum (SCM), which was located below the pycnocline at the nutricline. A subsurface oxygen maximum indicated that the SCM resulted from in situ growth. The associated SCPM appeared to result from the interaction of two primary factors: (i) the availability of a high prey biomass (i.e. nanoplankton) and (ii) low grazing pressure from potential predators (i.e. macrozooplankton). © 1990 Oxford University Press.