Microzooplankton grazing in a coastal embayment off Concepcion, Chile, (∼36°S) during non-upwelling conditions

The impact of grazing by natural assemblages of microzooplankton was estimated in an upwelling area (Concepcion, Chile) during the non-upwelling season in 2003 and 2004. Seawater dilution experiments using chlorophyll a (Chl a) as a tracer were used to estimate daily rates of phytoplankton growth and microzooplankton grazing. Initial Chl a concentrations ranged from 0.4 to 1.4 mg Chl a m(-3) and phytoplankton prey biomass and abundance were numerically dominated by components < 20 mu m. Phytoplankton growth and microzooplankton grazing rates were 0.19-0.25 day(-1) and 0.26-0.52 day (-1), respectively. These results suggest that microzooplankton exert a significant removal of primary production (> 100%) during the non-upwelling period.