GEOTRACES at Ocean Sciences 2026

*OB020 – Multi-tracer approaches to understanding and quantifying marine biogeochemical processes
Friday, 27 February 2026, 8h30 – 15h30 (local time), Hall 3, Coral Cove (SEC)
Poster session on Thursday, 26 February 2026

Co-conveners
William M Landing, Florida State University
Hélène Planquette, IUEM Institut Universitaire Européen de la Mer, LEMAR, CNRS
Anne Leal, Lamont Doherty Earth Observatory at Columbia University

Description
There is a long history on the use of multiple tracers to investigate and quantify biogeochemical processes in the oceans, from the use of carbon, nutrient and trace element stoichiometries to demonstrate uptake and regeneration processes, to studies of the microbial impacts on trace element speciation and distributions, to the coupling of natural radionuclide cycling with particle chemistry to quantify fluxes, among many others. Our understanding of the rates and mechanisms of trace element and isotope (TEI) input, biogeochemical cycling, and removal is improved by multi-tracer data from basin-wide research cruises, data from more focused process studies, and synthesis and modeling of these data. In addition to contributions in these topical areas, we particularly encourage submissions that integrate multiple tracers or isotope systems to provide constraints on biogeochemical processes in the oceans and that highlight the benefits of multi-proxy approaches.

*CB002 – Coastal, Shelf, and Island Mass Effects on Trace Element Biogeochemistry in the Ocean
Wednesday, 25 February 2026, 8h30 – 10h00 (local time), Hall 4, eLightning Theater 2 (SEC)
Poster session on Wednesday, 25 February 2026

Co-conveners
David González-Santana, IOCAG Universidad de Las Palmas de Gran Canaria
Aridane G. González, IOCAG. Universidad de Las Palmas de Gran Canaria
Emilie Le Roy, IUEM Institut Universitaire Européen de la Mer
Gabriel Dulaquais, IUEM Institut Universitaire Européen de la Mer

Description
The marine biogeochemical cycles of trace elements, their stable isotopes compositions and organic binding ligands are affected by the island mass effects. With terrigenous, shelf and even glaciogenic inputs, islands are natural laboratories for studying the importance of lateral fluxes of trace elements, their impact on the physico-chemical processes and associated biological responses. This session aims to bring together researchers from diverse fields to discuss the latest findings on the biogeochemical processes occurring in the ocean and related to the island and shelf effects, from the coast to the open ocean. The aim is to improve our knowledge, identify biogeochemical impacts, and characterise physico-chemical speciation of metals and redox chemistry. We welcome research studies and experiments focusing on processes affecting trace metal chemistry, the nutrient cycle and organic ligands.

*HE004 – Mercury in Polar Waters: Sources, Transformations, and Bioaccumulation in Food Webs
Poster session: Tuesday, 24 February 2026, 16:00 – 18:00 (local time), Hall 4 (Poster Hall) (SEC)

Co-conveners
Emily Seelen, University of Alaska Fairbanks
Marissa Despins, University of California Santa Cruz
Stephen Kohler, Norwegian University of Science and Technology
Marissa Despins, University of California Santa Cruz

Description
High latitude environments are undergoing profound changes driven by climate warming. The impact of this change–sea ice loss, permafrost thaw, and shifting ocean circulation–is expected to alter the concentration and distribution of mercury (Hg) in polar marine waters. While models indicate that Hg concentrations will rise in the Arctic under current emission climate scenarios, the processes influencing Hg mobility and speciation remain poorly understood, especially in the Antarctic, where data is even more limited. To accurately model the fate of Hg in a warming climate and risk for human exposure, it is imperative that we understand the mechanisms governing Hg cycling, particularly methylation and demethylation pathways, which still remain elusive. This session invites contributions that explore the biogeochemical cycling of Hg in both the Arctic and Antarctic, with a focus on the release and delivery of Hg species to coastal zones, processes that influence Hg transformations, and bioaccumulation in marine food webs. Interdisciplinary perspectives that incorporate Indigenous knowledge and community-based monitoring are also encouraged, as are studies addressing the vulnerability of subsistence-dependent communities to changing Hg exposure.

*OB026 – Revising Ocean Silicon Cycle: Pathways, Stoichiometry and Climate-Carbon Feedback in the Anthropocene
Poster session: Monday, 23 February 2026

Co-conveners
Diksha Sharma
Haimanti Biswas, CSIR-National Institute of Oceanography
Damien Cardinal, Sorbonne Université
Shaily Rahman, University of Colorado Boulder

Description
Silicon (Si), the second most abundant element in Earth’s crust, is an essential nutrient for marine organisms (phytoplankton, sponges, radiolarians) and plays crucial roles in marine carbon cycling and ecosystems and, atmospheric CO2 inventory. The ocean receives Si from different sources, including continental erosion (riverine and groundwater discharge, glacial meltwaters…), sedimentary recycling (reverse weathering, diagenesis…), hydrothermal input, and atmospheric deposition. However, anthropogenic activities significantly alter Si supply to the ocean: damming restricts the riverine input of Si, while climate-induced ocean stratification limits vertical mixing, curtailing Si supply to surface waters. Contrarily, increasing nitrogen (N) and phosphorus (P) inputs to the coastal areas are disrupting the Redfieldian Si:N:P stoichiometry, causing a regional shift from siliceous to non-siliceous species, impacting carbon export and trophic dynamics. Understanding how climate-driven changes—such as enhanced weathering, glacial melt, dust input, and deep-sea geochemical processes—reshape the marine Si cycle is critical for predicting shifts in elemental cycling, phytoplankton community structure, and carbon storage. This interdisciplinary session explores evolving Si fluxes across ocean’s interfaces and their biogeochemical impacts, encouraging studies using isotopic tracers, omics, satellite products, and coupled Earth system models, to identify hidden fluxes, feedbacks, and vulnerabilities in the Si cycle under changing oceanic state.

*TH33B – BioGeoSCAPES: Querying the Ocean’s Microbial Life Support System
Town Hall event: Wednesday, 25 February 2026

Description:
Earth’s life support system is underpinned by the activity of marine microbes that mediate biogeochemical cycles. BioGeoSCAPES is a community-led international effort that aims to address fundamental gaps in the mechanistic understanding of how the ocean ensemble of microbes and their  biochemical reactions shape nutrient biogeochemical cycles and are in turn influenced by these cycles. BioGeoSCAPES involves multiple scales of study, combining integrated biological and chemical sampling with analytical techniques, computational biology and ocean modelling. The resulting scientific efforts will deliver a coordinated and improved understanding of the structure and function of our planet’s oceans.

The town hall will report on: 1) Progress in developing the BioGeoSCAPES Science Plan, including the science themes and international implementation strategy. 2) Upcoming webinars, workshops and BioGeosSCAPES-related research activities and 3) Education and training activities, including the launch of two cohorts of a BioGeoSCAPES ECR Fellows program; upcoming, webinars, workshops and plans for a summer school. The town hall will disseminate information, build community engagement, and gather feedback on BioGeoSCAPES progress and plans. The target audience includes marine microbiologists, biogeochemists, physiologists, trace metal chemists, organic geochemists, and global, regional and process-based modellers, including those using machine learning and bioinformatics.