Campaign Summary Report - Mission Microbiomes from Cape Town (2022-05-03) to Walvis Bay (2022-05-31) on board AtlantECO flagship SV Tara

The objective of this leg was to study the microbiome of Benguela upwelling region. We focussed on both the southern and northern regions, with a specific focus on oxygen minimum zones and the nutrient budget. It is well known that the productivity resulting from upwelling regions produce large algae blooms, however very little is known about how the resident microbiome helps or hinders this. Our strategy was therefore to sample inshore, on shelf and just off shelf in the form of transects up the South African and Namibian coast so we could capture freshly upwelled waters (inshore), modified upwelled waters (shelf) and more nutrient depleted waters (offshore) so we can try to understand how the microbial loop adapts during these different stages. We were also interested in aerial transport especially from the Namib desert, and how (or if at all) this influences algal productivity. Finally, we introduced a few extra biogeochemical protocols that measured nutrient uptake (microbes + algae) as well as nutrient transformation rates at depth. This is in part due to a nutrient deficiency in the South African upwelling that we are trying to further understand. Our South African station included the use of a McLane pump at depth where there was no oxygen so we could capture the microbial community composition in situ without any contamination of oxygen. We also measured N₂O, a highly concentrated greenhouse gas, that we know is being produced in our south African stations. This data will help to parameterize a model of the Benguela so we may predict future scenarios in the region with more accuracy.