METEOR M187

Phytoplankton are the base of marine food webs and sequester atmospheric carbon. Previous research in the Southeast Atlantic has shown that phytoplankton growth is limited by a sequence of nutrients, including ‘colimitation’ of phytoplankton growth by multiple nutrients at the same time. However, the causative mechanisms of this are poorly constrained. On M187 we will trace upwelled ocean filaments as they are advected away from the Namibian coast towards the South Atlantic Gyre. We will investigate the evolution of key physical, chemical and biological factors as the filaments are transported offshore and age. We will achieve this by combining (i) Lagrangian tracking of upwelling filaments using deployed drifters as they move offshore, and (ii) a high-resolution transect from upwelling sites to the subtropical gyre. We will investigate in detail how the amounts, forms and sources of nutrients, microbial diversity, and nutrient limitation changes in filaments. The proposed activities will shed light on key mechanisms establishing the major oceanic nutrient limitation provinces, so that they can be included in models used to predict the impacts of climate change.