GEOTRACES sessions at ASLO 2023

Dear colleagues,

We would like to draw your attention to the following GEOTRACES and GEOTRACES-related sessions at ASLO 2023, Aquatic Sciences Meeting (4-9 June 2023, Palma de Mallorca, Spain and online, https://www.aslo.org/palma-2023/).

The abstract submission deadline is 23 February 2023 (11:59 pm, Central Standard Time USA).

GEOTRACES and GEOTRACES-related sessions:

**SS033 Biogeochemical Cycling in the Caribbean Sea, the Gulf of Mexico and Beyond

Tim Conway, University of South Florida (tmconway@usf.edu)
Angela Knapp, Florida State University (anknapp@fsu.edu)
Kristen Buck, Oregon State University (kristen.buck@oregonstate.edu)
Juan Carlos Herguera, Centro de Investigación Científica y de Educación Superior de Ensenada, Baja California (herguera@cicese.mx)
Jessica Fitzsimmons, Texas A&M (jessfitz@tamu.edu)

The Caribbean and Gulf of Mexico are dynamic and interconnected marginal seas that host the complete range of marginal oceanographic environments, including coastal shelves, eutrophic coastal systems, oligotrophic open ocean waters, small anoxic basins, gradients of dust deposition, hydrocarbon seeps, and locations of hydrothermal venting and volcanic activity. Large atmospheric, riverine, submarine groundwater, and other fluxes, as well as biological productivity and export, strongly influence the biogeochemistry of nutrients and trace elements and their isotopes (TEIs) in this region, yielding a high degree of spatial and temporal variability. Further, the presence of the Mississippi River, periodic algal blooms, and pollution events (e.g. Deepwater Horizon, Piney Point, episodic nutrient discharges) make the region an ideal natural laboratory for testing biogeochemical hypotheses. At a broader scale, teleconnections between the Tropical Atlantic, Caribbean, Gulf of Mexico, the Gulf Stream, and the North Atlantic provide unique opportunities to investigate how marginal environments may serve to transform nutrient and TEI signatures prior to transport to open ocean waters. Here, we invite contributions that characterize the variability in the biogeochemistry, geochemistry, and/or physical oceanography of the Gulf of Mexico and the Caribbean, and especially the linkages between these seas and the North Atlantic Ocean. Suggested contributions may include, but are not limited to, descriptions of water column nutrient, TEI, or geochemical distributions; biogeochemical rate measurements; characterizations of molecular ecology, benthic, SGD, or other geochemical fluxes; and descriptions of circulation that impact Gulf biogeochemical dynamics. This session aims to bring together interested international investigators both to highlight new results from the Gulf and also identify areas of common interest and collaborative opportunities to help inform future planning in GEOTRACES, OCB, Global Ocean Observing Systems, and other relevant national and international programs.

**SS014 Atmospheric Supply of Soluble Trace Elements and Isotopes: Advances and Challenges

Rachel Shelley, University of East Anglia (rachel.shelley@uea.ac.uk)
Susanne Fietz, University of Stellenbosch (sfietz@sun.ac.za)
Alex Baker, University of East Anglia (alex.baker@uea.ac.uk)
Morgane Perron, CNRS – Laboratoire des sciences de l’Environnement MARin (LEMAR) (morgane.perron@utas.edu.au)

Approximately 50% of primary production occurs in the oceans. Iron (Fe), and other trace elements (TEs), are essential micronutrients as primary producers require Fe for carbon (C), nitrogen (N) and phosphorus (P) acquisition. However, in vast areas of the ocean, marine production is limited by insufficient Fe availability or by the scarcity of a combination of two or more micronutrient TEs. Therefore, the availability of TEs, particularly Fe, exerts a fundamental control on marine biological activity, from bacterial and primary productivity of phytoplankton through to the fisheries which ultimately depend on them. Micronutrient TEs thereby support marine ecosystem services and CO 2 sequestration in most ocean basins and over various timescales. Atmospheric deposition provides an external source of TEs to the surface ocean. Large deposition events can relieve micronutrient (co-)limitation through the partial dissolution of TEs from aerosols. However, large deposition events are sporadic and currently poorly understood. This presents a challenge for predicting how ocean ecosystems will respond to changes in soluble TE fluxes in the future. Therefore, it is vital that models are able to represent and reproduce current and past TE distributions in the ocean in order to improve predictive capabilities. A further challenge is understanding how the different chemical compositions and atmospheric processing of natural and anthropogenic particles impacts TE solubility following deposition to seawater and, thus, the ability of biota to assimilate the TEs. Although mineral dust is proportionally the largest source of aerosol TEs to the global ocean, anthropogenic and wildfire aerosols have a greater ability to dissolve in seawater. This results in the liberation of a larger fraction of bioaccessible TEs, due to several factors. Following aerosol deposition, new resource competition among primary producers can alter community structure and dynamics, which influences the capacity of the ocean to sequester CO 2 , fix nitrogen and produce biological gases which readily form cloud condensation nuclei. All three features exert crucial climate feedbacks. The degree to which autotrophs or heterotrophs are stimulated or suppressed by atmospheric deposition depends on the physicochemical form in which atmospheric TEs are delivered to seawater and on the initial nutrient status of the water. Again, highlighting the need for a more integrated understanding of biogeochemical cycling including the atmospheric component. In this session, we would like to invite submissions from novel experimental and modelling work on TE biogeochemistry at the air-sea interface. Presentations addressing key research questions including the controls on dissolution and/or uptake of aerosol TEs, as well as modelling estimates of aerosol TE deposition fluxes in the present, past, or future are welcomed. Studies focusing on the Southern Hemisphere and other historically under-studied oceanic regions are particularly encouraged. This session has broad applicability to different research communities, e.g., climate change, human health, fisheries, and paleoclimate. As such, we welcome cross-disciplinary submissions which address questions about the flux of TEs across the air-sea interface and the associated impact on marine ecosystems.

**SSO38 Trace Metal and Macronutrient Behaviour in Large Rivers and Estuaries 

Adrienne Hollister, Jacobs University Bremen (a.hollister@jacobs-university.de)
Hannah Whitby, University of Liverpool (hannah.whitby@liverpool.ac.uk)
Rebecca Zitoun, GEOMAR Helmholtz Centre for Oceanographic Research (rzitoun@geomar.de)
Juan Santos-Echeandía, Spanish Institute for Oceanography (juan.santos@ieo.csic.es)

Rivers are a major source of trace metals, macronutrients and organic matter to the global oceans. Processes such as colloidal flocculation, particle adsorption-desorption and biological activity influence the concentrations and speciation of trace metals and nutrients during estuarine mixing, and therefore their overall behaviour and flux to the ocean. Major rivers such as the Amazon are becoming increasingly vulnerable to anthropogenic impacts, including land use change, hydroelectric dams, metal pollution (e.g. from mining), plastic pollution (relevant as metal vectors), and agricultural runoff. These and other anthropogenic impacts to a river’s catchment area can lead to potentially toxic concentrations of metals (e.g. Cu, Zn, Pt, Hg, Pb, Fe), or of macronutrients leading to eutrophication. In addition, climate change is projected to cause both increased droughts and flooding, resulting in changes in river flow and chemical output. These changes may have a drastic effect on trace metal and nutrient sources, cycling, transport, fluxes, reactivity and sinks at the land-ocean interface. As climate and land use changes amplify, it is essential to establish a baseline for riverine trace metal and nutrient concentrations and fluxes to the ocean and sediments, and to understand how these parameters may change with changing environmental conditions. Generally, this session aims to evaluate the behaviour, fluxes, sources and sinks of trace elements and their isotopes (TEI) as well as macronutrients (N, P, Si) from major rivers to the ocean. Contributions focused on observational, experimental, and modelling approaches regarding metal- and nutrient cycling, their chemical and biological transformation and distribution in rivers and estuaries are welcome.

Posters, presentations and hybrid presentations are welcome. 

To submit an abstract please follow the instructions available here:
https://www.aslo.org/palma-2023/abstract-preparation-guide/

An updated list of GEOTRACES relevant sessions at ASLO 2023 will be available at: https://www.geotraces.org/event/aslo-2023-aquatic-science-meeting/

If you wish your session to be included in this list, please send an e-mail to ipo@geotraces.org

Best regards,
GEOTRACES IPO