Algal biomarkers in surface waters around the Crozet plateau

The region around the Crozet plateau (Southern ocean) exhibits enhanced annual primary productivity, occurring during a distinct spring bloom, due to natural iron fertilisation of the macro nutrient-replete polar frontal zone. We describe differences in algal biomarker abundances and distributions, with particular emphasis on alkenones and sterols, around the Crozet plateau during an algal bloom (December 2005 to January 2006). In the centre of the bloom, diatom-derived sterols dominate, whereas alkenones are proportionally more abundant at lower productivity times or sites. This is consistent with biomarker analyses for other settings and suggests that high productivity and high nutrient, low chlorophyll (HNLC) regimes can be distinguished on the basis of algal community structure and the associated lipid biomarker assemblages.