Picophytoplankton contribution to phytoplankton community in the Venice Lagoon

In the framework of the researches aimed at evaluating the functional role of the different typologies of primary producers in the Lagoon of Venice (CORILA Research Programme 2004-2006, Line 312), the size distribution of the phytoplankton community has been analyzed, on a seasonally base. Emphasis has been paid on the spatial and temporal variations of autotrophic picoplankton (0.2 - 2 µm) and on its contribution to total phytoplankton biomass. Autotrophic picoplankton was mainly made up by cyanobacteria of the Synechococcus type and by small eucariotes, the larger fraction (> 3 µm) by diatoms and nanoflagellates. Picoplankton abundance (average: 15 x 106 cells dm-3) and biomass (average: 2.3 µC dm-3) indicate that this fraction represents a significant and persistent component of the phytoplankton in the Lagoon of Venice.