SEASONAL IMPACT OF THE MICROZOOPLANKTON ON PICOPLANKTON AND NANOPLANKTON GROWTH-RATES IN THE NORTHWEST MEDITERRANEAN-SEA

The effect of protozoan presence on pico- and nanoplankton growth rate s was studied during a whole seasonal cycle, together with several oth er environmental factors (such as microphytoplankton abundance, temper ature, salinity, solar irradiance and nutrients). Pico- and nanoplankt on growth rates were enhanced in the presence of protozoa inside a dia lysis bag and reached values as high as 0.08 to 0.2 h-1. At in situ co ncentrations (10(6) flagellates l-1 and 10(3) ciliates l-1), protozoa, through their excretory activity, played an important role in phytopl ankton growth. However, other environmental factors, such as allochtho nous nutrients and temperature, also have an effect on these growth ra tes.