Description: Research cruise SO298 with RV SONNE was sailed in the period April to June 2023 in the Equatorial Pacific Ocean (EPO) from Guayaquil (Ecuador) to Townsville (Australia), with a focus on trace element biogeochemistry and chemical oceanography but also including physical and biological oceanographic components. The research topic of the cruise was to determine in detail the distributions, sources and sinks of trace elements and their isotopes (TEIs) in the water column along a zonal section in one of the biogeochemically least studied ocean regions on earth. We aimed to investigate the biogeochemical cycling of TEIs, and their interactions with surface ocean productivity and the carbon and nitrogen cycles (incl. N2 fixation), given that some TEIs act as micronutrients. The findings will have global significance for understanding the chemical environment in which ecosystems operate. The supply pathways of TEIs to the EPO from ocean boundaries including the atmosphere (dust and rain), continents (mainly Asian rivers), sediments (on continental shelves/slopes of the Indonesian Island Arcs), and ocean crust (hydrothermalism) were investigated. The TEI transport within water masses was determined with a focus on the equatorial eastward flow of Asian shelf derived TEIs in the Equatorial Undercurrent and the deep inflow of Southern Ocean waters in the western EPO. The TEI transport assessment along the cruise track will allow a more reliable use of particular TEIs as paleo circulation proxies. The cruise is officially part of the GEOTRACES program.