Phytoplankton production in Italian freshwater and marine ecosystems: State of the art and perspectives

he present work aims at evaluating the state of art of phytoplankton production research in Italy. We present a synthesis of the main results achieved in three ecosystems where primary production studies have been carried out most intensively: a large subalpine lake (Lago Maggiore, LM), a shallow marine ecosystem with strong fluvial influence (the Northern Adriatic Sea, NAS), and a coastal area of the Southern Tyrrhenian Sea (the Gulf of Naples, GoN). The present yearly production values are around 150 g C m-2 yr-1 in LM and GoN; this ranges between 80 (offshore) and 150 g C m-2 yr-1 (coast) in the NAS. The temporal and spatial variations of phytoplankton production appeared, in each ecosystem, in accordance with the trophic changes. Significant correlations between production, chlorophyll, and light were generally observed for LM and for GoN. On the contrary, these parameters were poorly correlated in the NAS, hampering the use of predictive models in this ecosystem. Discrepancies between primary production and the actual phytoplankton biomass changes were observed across trophic gradients: the largest part of the carbon that is photosynthetically produced does not seem to be transformed into new phytoplankton biomass, strongly affecting the interpretation of the production figures in the ecosystems.