Presence or absence of picophytoplankton in the western Ross Sea during spring 1994: a matter of size definition?

The occurrence of picophytoplankton in the Ross Sea was investigated during the cruise ROSSMIZE leg 1 (November/December 1994) using epifluorescence microscopy. This study was focused on the methodological aspects dealing with size definition of picophytoplankton. The results showed that a small difference (1 µm) in the definition of the upper size limit of picophytoplankton (2.0 vs 3.0 µm) may have significant implications for the relative importance of this component in the Ross Sea ecosystem. Moreover, the lack of correlation between autotrophs 0.2±2 µm in size and larger autotrophic cells (2±3 µm) in the marginal ice zone and in the closed pack-ice zone suggests that these two components have different ecological roles that are emphasized in these environmental conditions.