Forty scientists representing various organizations from Europe, Africa, North America, and Australia are voyaging across the southern Indian Ocean from Durban, South Africa to Fremantle, Australia. This cruise is part of the international GEOTRACES program, and as such its primary focus is the study of trace elements and their isotopes. We will investigate their distributions and cycling across the transect, which crosses one of the least studied ocean regions on Earth. This includes their sources (such as the river input from the Zambezi River Delta in Mozambique), their sinks (such as burial in marine sediments), and their interactions with nutrient cycles and primary productivity. Our findings will not only provide a better understanding of this region but of global ecosystem processes.