Variability in Diatom Abundance and Diversity Determined by Sea Ice Dynamics

High primary production in the Southern Ocean has frequently been linked to sea ice dynamics, particularly to the timing and location of spring retreat. We show in this study that diatoms correlate with average primary production as well as to its spatial and temporal variability such as the abundance and diversity of diatoms are the main drivers of primary production at the sea ice edge of western Antarctic Peninsula continental shelf. Flagellate abundance and diversity, particularly that of cryptophytes, the second most abundant phytoplankton taxon in the region, are not correlated with primary production in space or time, such that this group’s abundance alternates with that of diatom. Given that as much as 80% of the variability of primary production can be explained by the variability of diatom abundance it is reasonable to expect a relationship between sea ice retreat and diatoms. On average, when sea ice retreat occurs later in the season, diatom abundance also increases, with late sea ice retreat correlating with higher diatoms. There is a spatial dependence though, where late retreat is correlated with increased production on the entire wAP shelf and in coastal regions, but no or low influence in slope waters. Not only environmental factors should be considered: large, chain-forming diatoms with high Carbon:Chlorophyll a ratio are able to fix more inorganic carbon, indicating that biological characteristics of diatoms and cell size are also responsible for their high productivity.