Temporal variation of seston biomarkers within the Humboldt Current System off northern Chile (21°S): first simultaneous records on fatty acids,n-alkanes and glycerol-dialkyl-glycerol-tetraethers (GDGT)

Abstract

Proportions and concentrations of seston fatty acids, n-alkanes and glycerol dialkyl glycerol tetraethers (GDGTs) were used to assess potential differences in the phytoplankton composition and food quality in the Humboldt Current System (winter 2006, summer 2007 and winter 2007) in surface, oxycline, intermediate and bottom water layers. The zone below the intermediate depth was poorer in fatty acids (minimum 15 – maximum 117 µg fatty acids L−1) than the upper water layers (minimum 36 – maximum 210 µg fatty acids L−1), which were richer in saturated fatty acids (SAFA, up to 80%), but had a similar proportion of bacterial markers (13:0.15 iso/anteiso, 15:0, and 17:0 sum up to 67%). Isoprenoid GDGTs showed the presence of archaea in the different water layers. All the water layers also showed long chained fatty acids (22:0, 24:1 and 26:0), which can be considered to be of terrestrial origin. The n-alkanes were used to confirm this potential terrestrial origin through the Carbon Preference Index (CPI), which...