Award: OCE-1657944

GEOTRACES is a global scientific effort to better understand the chemical composition of the world?s oceans and its potential for change. The goal of GEOTRACES is to determine the distributions of rare ?trace? elements and their isotopes in the ocean. While they are low in concentration, many of these trace elements are also important for marine life. For instance, phytoplankton, the tiny plants at the base of ocean food webs, need iron to grow. Everything from tiny fish to giant whales in turn rely on phytoplankton, and therefore on the availability of iron in the ocean. Understanding the distributions of trace elements such as iron will increase the understanding of processes that shape their distributions and also the organisms that depend on these elements. Until quite recently, these elements could not be measured at a global scale, but GEOTRACES has enabled this global effort and is making the data freely available. This project, based on a 2-month research cruise in the Pacific Ocean between Alaska and Tahiti (code named ?GP15?), was an important mission for U.S. GEOTRACES. This expedition allowed us to sample a large variety of ocean ecosystems and examine the influence of continental margin fluxes, atmospheric dust deposition, and the emission of fluids from deep sea hydrothermal vent systems. It was the first meridional section of the U.S. GEOTRACES program, and indeed, this transect allowed us to explore virtually all of the processes and fluxes known to introduce trace elements to the ocean. This project also provided baseline measurements of trace elements in the Clarion-Clipperton fracture zone, where large-scale deep sea mining is planned. The effect of mining activities on trace elements in the water column is one that is highly uncertain and could be uniquely assessed by the GEOTRACES community and the data collected during this project. This expedition supported a large variety of individual science projects to study the chemical and biological interactions of trace elements, and the objectives of this project were to coordinate, manage, and facilitate the success of those projects and the overall mission by suppling core data and samples, as well as overseeing quality control and submission of the data to publicly available databases. The project concluded with an in-person and hybrid data synthesis meeting that we expect to result in a variety of high quality research papers. Last Modified: 11/29/2022 Submitted by: Karen L Casciotti