“…The observed spatiotemporal differences in the relative importance of Phaeocystis and diatoms in the SO are thought to be largely controlled by differences in light and iron levels, but the relative importance of the different bottom-up factors appears to vary depending on the time and location of the sampling (Arrigo et al, 1998(Arrigo et al, , 1999Goffart et al, 2000;Sedwick et al, 2000;Garcia et al, 2009;Tang et al, 2009;Mills et al, 2010;Feng et al, 2010;Smith et al, 2011Smith et al, , 2014. Concurrently, while available models agree with the observations on the general importance of light and iron levels, differences in the dominant bottom-up factors controlling the distribution of Phaeocystis at high SO latitudes across models are possibly a result of differences in how this phytoplankton type is parametrized (Tagliabue and Arrigo, 2005;Pasquer et al, 2005;Wang and Moore, 2011;Le Quéré et al, 2016;Kaufman et al, 2017;Losa et al, 2019). In this context, whether the model explicitly represents both Phaeocystis life stages (Pasquer et al, 2005;Kaufman et al, 2017;Losa et al, 2019) or only the colonial stage (Wang and Moore, 2011;Le Quéré et al, 2016) is key as single cells are known to have lower iron requirements than Phaeocystis colonies (Veldhuis et al, 1991).…”