Climatological temporal and spatial distributions of nutrients and particulate matter in the Ross Sea

•Nutrient and particulate matter climatologies show that elevated POC:chl ratios are predictable in summer in the Ross Sea.•Based on silicon removal and appearance in BSi, the role of diatoms in the Ross Sea has been underestimated.•Productivity as estimated by bio-optical models is underestimated by 80% when using constant C:chl ratios.•The likely cause for the elevated POC:chl ratios is the response of diatoms to iron limitation.