Tracing dissolved organic matter availability across an East-to-West gradient in the subtropical Atlantic

durch Helmke Hepach

Mittwoch 17.12.2025, 13:15 → 14:30 Europe/Berlin

8A-002 - Hörsaal Ostufer / Lecture Hall East (GEOMAR - Standort Ostufer / GEOMAR - East Shore)

Abstract:

The subtropical Atlantic Ocean is characterized by a strong gradient in biological activity from the East, where nutrient rich water from coastal upwelling and aerosol dust deposition from the African continent lead to enhanced organic matter production, to the West where autotrophic and heterotrophic activity decline due to limited substrate availability. Yet, DOC concentrations remain surprisingly high within the western subtropical Atlantic. This has been hypothesized to be a result of nutrient limitation, inhibiting DOC uptake. Here, we present data from the SO287-CONNECT cruise from Gran Canaria, Spain to Guayaquil, Equador onboard the RV Sonne in December 2021 and January 2022. During this time, atmospheric nutrient input was negligible. Primary production was comparably low and declined even further towards the subtropical Gyre and further West, still, we verify relatively high DOC concentrations in the Western subtropical Atlantic. We investigate the availability of the present dissolved organic matter for carbon cycling and influencing factors of DOM gradients. The results of this study provide insight into projected declining NPP rates in the future in the subtropical ocean.