Conveners: Maeve C. Lohan, University of Plymouth, firstname.lastname@example.org; Sylvia G. Sander, University of Otago, email@example.com; Kristen N. Buck, Bermuda Institute of Ocean Sciences, firstname.lastname@example.org
The bioactive trace metals iron, copper, cobalt, nickel, zinc and cadmium are essential micronutrients for marine phytoplankton and exert a major influence on the global carbon cycle. Complexation of these metals by organic ligands may enhance or reduce bioavailability depending upon the metal-ligand complex formed. Yet we know little about the composition, sources and cycling of metal-binding ligands, which is hindering further advances in the field of trace metal biogeochemistry. An active SCOR Working Group (WG 139) ‘Organic Ligands- A Key Control on Trace Metal Cycling in the Ocean’ fosters the multidisciplinary collaboration of trace metal biogeochemists, organic geochemists and biogeochemical modelers in order to advance this field. This session is a community wide forum to highlight recent accomplishments in metal-binding ligand characterization and approaches for assessing ligand composition, sources and impacts on trace metal cycling in the aquatic environment, and to discuss future efforts in this field. We welcome abstracts related to metal- binding ligands from throughout the multidisciplinary field of oceanography.
Nitrogen is one of the most biologically important elements on earth and is often the nutrient limiting primary production in aquatic systems. While a great deal is known about the fate and functions of dissolved inorganic nitrogen (DIN) in aquatic systems, relatively little is known about the sources, sinks, cycling or composition of dissolved organic nitrogen (DON). This is surprising as DON often exceeds DIN concentrations, representing up to 85% of total dissolved nitrogen pool. DON was once believed to be primarily refractory due to its relatively high and stable concentrations. We now know that DON is a chemically complex mixture with fractions of the DON pool being extremely labile. The development of new analytical techniques has changed the way we think about DON, its functions in aquatic systems, and its roles in the global nitrogen cycle. The focus of this session is to highlight our current knowledge of the sources, sinks, cycling, and composition of DON across aquatic environments. We encourage entries from freshwater, brackish, marine, and atmospheric systems including chemical, biological and physical investigations to foster cross-disciplinary discussions. We specifically encourage studies using state-of-the-art analytical techniques to investigate DON production, cycling, composition, bioavailability and transport at all scales.
This session focuses upon current and developing understanding of sources, sinks, and chemistry of chromophoric dissolved organic matter (CDOM), and the power of CDOM as an interpretive prism through which the cycling of the greater DOM pool can be resolved. CDOM is increasingly recognized as a significant component of and useful tracer for dissolved organic matter (DOM). Thus, understanding the processes that govern the spatial and temporal distributions of different pools of CDOM and fluorescent DOM (FDOM) is of importance to a comprehensive understanding of global CDOM and DOM cycles. Consequently, the distributions, production, transport and fate of CDOM are being charted throughout the oceans. Terrestrial-sources and photochemical-sinks for CDOM have long been recognized. Yet, recent research highlights the production of bio-refractory, photo-labile CDOM in the deep ocean and that CDOM and FDOM can serve as tracers of labile and refractory DOC pools. Coupling of advanced analytical techniques, such as high resolution mass spectrometry, with CDOM and FDOM datasets is revealing the molecular character of DOM’s optical signatures. Presentations detailing ocean CDOM production, photochemistry and chemical composition are welcome.
Conveners: Jutta Niggemann, Max Planck Research Group for Marine Geochemistry, email@example.com; Aron Stubbins, Skidaway Institute of Oceanography, firstname.lastname@example.org; Thorsten Dittmar, Max Planck Research Group for Marine Geochemistry, email@example.com
Dissolved organic matter (DOM) is the main carbon and energy source for heterotrophic microorganisms in aquatic systems. The microbial community shapes DOM composition (and vice versa), leaving behind a characteristic molecular imprint in DOM. Abiotic environmental factors like solar irradiation, interactions with solids or hydrothermal heating cause substantial changes in the molecular DOM composition. Emerging analytical techniques provide molecular information on DOM composition and microbial communities in unsurpassed detail, allowing for a molecular-level understanding of biotic and abiotic processing of DOM. This session aims at bringing together different fields of DOM research. Integrative studies linking molecular DOM characteristics to microbiological and abiotic transformation are of particular interest.
Conveners: John Lehrter, EPA Gulf Ecology Division, firstname.lastname@example.org; Katja Fennel, Dalhousie University, email@example.com; Wally Fulweiler, Boston University, firstname.lastname@example.org; Roxane Maranger, University of Montreal, email@example.com
Human impacts to aquatic ecosystems often manifest at the sediment-water interface. Local and regional scale issues such as eutrophication, sedimentation and resuspension of inorganic and organic particles, toxic pollution, and over-fishing can have dramatic effects on benthic biological communities (ranging from microbial organisms to mega fauna) and induce feedbacks to the water column by altering biogeochemical processes. Recently, there is increasing awareness of compounding effects by global scale phenomena such as rising sea surface temperatures and ocean acidification. However, despite advancements in the theory, observation, and modeling of communities and biogeochemical processes at the sediment-water interface that have occurred over the last several decades, many regulating mechanisms are still poorly characterized. Hence, our ability to accurately predict and mitigate the impacts of human activities is hindered. This session invites investigators to present and discuss recent observational or modeling studies that add to our understanding of processes at the sediment-water interface. Presentations that integrate or synthesize across multiple spatial and temporal scales or levels of functional organization, genes to ecosystems, are encouraged. Non-research presentations that provide environmental policy perspectives and challenges, which may inform knowledge gaps and research needs, are also encouraged.
Conveners: Lasse Riemann, University of Copenhagen, Denmark, firstname.lastname@example.org; Jonathan P. Zehr, University of California, USA, email@example.com; Julie LaRoche, Dalhousie University, Canada, firstname.lastname@example.org
Nitrogen cycling in marine waters is largely mediated by microbes. Bacteria or Archaea transform organic and inorganic nitrogen into bioavailable nutrients supporting productivity at local and global scales. Despite being essential for carbon biogeochemistry, many aspects of the marine nitrogen cycle remain poorly constrained and understood. Magnitudes of sources and sinks of nitrogen have been intensively debated throughout the last decade without reaching consensus. Recent discoveries of new organisms and pathways relevant for the oceanic nitrogen cycle along with developments of new applications of tracer techniques, molecular biology, and ‘omics’ have provided important new insights. In future endeavors to understand the marine nitrogen cycle it will be essential to examine the diversity and composition of microbial assemblages responsible for nitrogen transformations and, in particular, identify rates of activity for key microbes. In turn, this will promote the identification of environmental drivers important for the cycling of nitrogen, and facilitate establishment of couplings between key organisms, functional genes, and process rates. The session goal is to promote exchange among researchers from various fields to integrate data on biogeochemistry and process rates with the molecular ecology of microbes to facilitate understanding, modeling, and ultimately, prediction of nitrogen transformations in the sea.
Emerging contaminants such as pharmaceuticals, flame retardants, natural plant products, and pesticides have been documented to be present at low levels in many aquatic environments worldwide. This session will involve presentations that describe the variation in the presence and distribution of these chemicals in the aquatic environment, and the impact different emerging contaminants may have on aquatic organisms, communities and ecosystems.
Catchments from the Arctic to the Tropics are readily defined ecological units linking land to the ocean, and as such represent a logical spatial scale for monitoring and studying organic matter (OM) processing. The geochemical composition of rivers draining watersheds represents an integrated signal of all processes occurring within the catchment, and therefore is impacted by climate and land-use change, as well as seasonal cycles that are frequently missed due to snapshot sampling. We solicit contributions that consider molecular to watershed scale processes with respect to understanding OM dynamics. Research utilizing biomarkers, natural abundance and radiocarbon isotopes (including compound specific), spectrophotometric techniques (e.g. absorbance, fluorescence), advanced mass spectrometry (e.g. FT-ICR MS), NMR and other characterization and isolation techniques to understand OM dynamics and reactivity (e.g. photo and biolability) are encouraged. Studies utilizing these analyses to examine OM processing and how it is changing in river basins due to land use (e.g. deforestation, urbanization) and climate change (e.g. permafrost thaw, rainforest to savanna), as well as time series studies are especially encouraged to contribute to the session. We also solicit studies bringing together a broad range of geochemical techniques to further our understanding of OM at the land-ocean interface.
Conveners: Andreas Brand, Eawag, Surface Water Group, email@example.com; Joerg Lewandowski, IGB Berlin -Ecohydrology group, firstname.lastname@example.org; Gunnar Nuetzmann, IGB Berlin -Ecohydrology group, email@example.com; Christof Meile, Department of Marine Sciences, University of Georgia; firstname.lastname@example.org
Porewater advection is critical for the understanding of early diagenesis in many aquatic settings. Some of these processes such as wave-induced porewater advection and the pumping activity of animals such as Arenicola marina have been closely investigated in marine environments. In addition, recent studies suggest that porewater advection is also a key process in limnic sediments. For example, tube dwelling fauna can induce porewater advection in the sediment surrounding their burrows due to their pumping activity, and porewater advection can become the dominant transport mechanism in sediments close to the thermocline in lakes with intense seiche activity. Furthermore, groundwater discharge can be the dominant transport mechanism in the open water – sediment – groundwater discharge transition zone. Since sediments are typically highly reactive, the turnover rates of organic carbon, nutrients, oxygen and other electron acceptors are tightly coupled to the transport processes which govern the supply of chemical compounds. In this session we aim to discuss novel approaches ranging from experimental investigations in the laboratory and in situ at various scales to numerical studies which investigate the impact of advection on biogeochemistry.
Conveners:Stephane Blain, Universite Pierre et Marie Curie, email@example.com; Queguiner, Universite d'Aix-Marseille, firstname.lastname@example.org; Strass, Alfred Wegener Institute for Polar and Marine Research, Volker.email@example.com; Dieter Wolf-Gladrow, Alfred Wegener Institute for Polar and Marine Research, Dieter.Wolf-Gladrow@awi.de
In the macronutrient-rich waters of the Southern Ocean, the biological pump of CO2 is likely controlled by the supply and bioavailability of iron. Through diverse interactions, iron limitation causes co-limitations principally by the light regime or by silicon. These processes are themselves modulated by the biological couplings in the food webs, and iron availability drives the functional structure and the biodiversity within the Southern Ocean ecosystems. Iron impacts the coupling between the different biogeochemical cycles with feedbacks on climate or on the productivity of adjacent ocean basins, possibly affecting the global carbon cycle. Resolving this complex multi-faceted story requires a large international effort which is underway. This session aims to bring together the most recent findings on the following issues: the impact of iron supply on carbon sequestration and atmospheric CO2 drawdown, the interaction between iron availability and the structure, biodiversity, and functioning of pelagic ecosystems, the identification of iron sources and transport pathways, the transformations of iron mediated by biotic or abiotic processes, and the coupling/decoupling between iron and major nutrient biogeochemical cycles. We invite submissions addressing any of these topics, either obtained from the most recent field studies (such as KEOPS2, or Eddy Pump), modeling studies or re-analysis of relevant previous observations.
Quantifying carbon fluxes in freshwater aquatic ecosystems provides insights into basin wide ecological and geochemical processes, and is critical to understanding past, present, and projected changes throughout the basin. Inland aquatic systems process carbon rapidly and need to be considered in order to accurately estimate net ecosystem production on large scales. Development of aquatic carbon flux estimates at large spatial scales (catchment, regional and global) is an area of active research in the aquatic biogeochemical community. Greater knowledge of the processes driving carbon fluxes as well as spatial and temporal variability in these estimates has been gained. This session will focus on large-scale carbon flux estimates in inland and coastal aquatic ecosystems. We encourage contributions focusing on carbon in any form (inorganic, organic, dissolved, particulate, gaseous) and which cover spatial scales ranging from catchments to continental scale and beyond.
The international GEOTRACES program is a multi-nation and multi-year effort to determine the concentration and speciation of trace elements and select isotopes in the world’s major ocean basins and some marginal seas at high vertical and horizontal resolution, reminiscent of the GEOSECS program. This program’s goal is “to improve the understanding of biogeochemical cycles and large-scale distribution of trace elements and their isotopes in the marine environment.” ( www.geotraces.org). To date, 35 “GEOTRACES compliant” section and process cruises have been completed and many more are planned. For this session, we invite investigators to share their findings from any GEOTRACES cruise including those related to dissolved and particulate trace elements, isotopes, nutrients and dissolved gases as well as atmospheric analyses. We also welcome presentations describing intercalibration, data management and modeling efforts related to GEOTRACES process and section studies.
Conveners: Hannelore Waska, Max Planck Institute for Marine Microbiology, firstname.lastname@example.org; Thomas Riedel, Technische Universität Braunschweig, email@example.com; Andrea Koschinsky, Jacobs University Bremen, firstname.lastname@example.org
Cycling of trace elements (TE) such as Fe, Cu and many others is strongly coupled to the presence and quality of dissolved organic matter (DOM) in aquatic systems. DOM may increase water solubility of some TE through formation of complexes and/or colloids, while hydrolyzing metals may cause coagulation and subsequent immobilization of DOM. These interactions strongly influence the bioavailability of trace metals as micronutrients and their toxicity, as well as the availability of DOM as a microbial energy source. Investigations of metal-DOM interactions in aquatic environments are often hampered by the high complexity of DOM and its possible interactions with different metals. In this session, we invite contributions from (i) recent advancements in the field of metal-DOM analytics, (ii) new insights into processes and pathways of metal-DOM interactions, and (iii) impacts of metal-DOM associations on trace metal bioavailability for bacterial and algal primary productivity in marine as well as limnic environments.
The remineralization rate of organic matter is determined by interactions between chemical structure and the metabolic capabilities of the heterotrophic community. The well- established size-reactivity continuum posits that particulate and high-molecular-weight dissolved organic matter is on average more reactive than smaller molecules, however the mechanisms driving the relationship between molecular size and reactivity remain poorly understood. Understanding the pathways by which specific macromolecules (e.g. specific polysaccharides or proteins) or randomly-structured polymers (e.g. lignin and humic substances) are remineralized is a particular challenge, since determining the structure of these macromolecules is often difficult. This session will combine research on the chemical structure and physical associations of organic macromolecules in aquatic environments with research on the biological mechanisms by which they are degraded.