ELICASeq - Elucidating lipid-carbon flux dynamics using next generation sequencing

• Applicant: Dr. Nora-Charlotte Pauli
• Subject Area: Oceanography
• Term: since 2022
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 502024352

The Southern Ocean, responsible for approximately 40 % of anthropogenic CO2 uptake, plays a crucial role in the global carbon cycle, with sinking particles, primarily phytoplankton aggregates and zooplankton faecal pellets (FP) driving carbon export to deeper waters. Lipids, comprising 10 to 30 % of carbon in phytoplankton and about 25 % in FP, are vital but poorly understood components of this carbon flux, especially given their substantial reduction with increasing depth. The DFG SPP 1158-funded project ELICA examined the lipid composition of the vertical carbon flux at the Antarctic Peninsula (AP) and South Georgia (SG) regions. We analysed the lipidome of drifting sediment traps, surface plankton communities, and krill and copepod FP, finding chloroplast lipids (glycolipids) and pigments to dominate the vertical lipid flux down to 400 m. At 100 m, lipid-carbon accounted for up to 26 % of the total organic carbon, decreasing to 20 % at 400 m, with pigments and intact polar lipids as primary components. Although FP are major carbon exporters in these regions, contributing over 60 % of total carbon flux, we observed that FP lipid composition differed markedly from surface plankton being enriched in phospholipids, while chloroplast lipids and pigments were largely degraded or digested. In this follow-up project, we aim to refine our understanding of lipid-carbon flux drivers by applying 16S and 18S metabarcoding to reveal the composition of bacteria, protists, and phytoplankton communities in water column and sediment trap samples and establish links between taxonomy and individual lipid classes, illuminating a so far unknown dimension in microbial ecology. Microscopic analyses of gel trap inserts will further characterize sinking particle types and phytoplankton remains, enhancing insights into the processes shaping lipid-carbon export in the Southern Ocean.

• DFG Programme: Infrastructure Priority Programmes
• Subproject of: SPP 1158: Infrastructure area - Antarctic Research with Comparative Investigations in Arctic Sea Ice Areas
• Co-Investigator: Professor Dr. Morten Iversen