Dissolved organic matter plays a critical role in aquatic biogeochemical cycles, fuels microbial metabolism, and stores as much carbon as the atmospheric carbon reservoir. Because the reactivity and fate of dissolved organic matter is largely controlled by its chemical composition, a wide range of analytical approaches including ultra-high resolution mass spectrometry, nuclear magnetic resonance spectroscopy, natural abundance isotopic analyses, and fluorescence spectroscopy, have been employed to trace its sources and transformations along the land–ocean continuum. Applying these approaches to environmental samples requires overcoming significant logistical challenges, including high salinity, sample volatility and degradation, and low organic carbon concentrations. In addition, each method captures only a subset of the total dissolved organic matter pool. As a result of these challenges and others, our understanding of the environmental role of dissolved organic matter within aquatic biogeochemistry remains limited.
In this session, we welcome studies that integrate various analytical approaches to characterize the composition and/or fate of dissolved organic matter along the land–ocean continuum. We also welcome contributions focused on novel techniques for isolating, concentrating, and purifying organic matter prior to analysis. We hope that by highlighting analytical advances made throughout the aquatic continuum across salinity and organic carbon concentration gradients, the insights gained may inform future efforts as a community to characterize dissolved organic matter in a changing environment. Submissions by students and early career researchers, and researchers from BIPOC, LGBTQIA+, and other underrepresented identities are highly encouraged.
Lead Organizer: Jennifer Bowen, Stanford University (bowen.jenniferc@gmail.com)
Co-organizers:
Benjamin Granzow, Scripps Institution of Oceanography (bgranzow@ucsd.edu)
Margot White, ETH Zurich (margot.white@eaps.ethz.ch)
Presentations
04:30 PM
The labile organic sulfur pool: characterization, quantification, and distribution in the surface ocean (9216)
Tutorial/Invited: Invited
Primary Presenter: Bryndan Durham, University of Florida (b.durham@ufl.edu)
Marine organic matter has historically been thought of in terms of its carbon, nitrogen, and phosphorus content, yet we now recognize sulfur as a fundamental component of phytoplankton stoichiometry with one sulfur atom assimilated into biomass for every 95 atoms of carbon (C124N16P1S1.3). This stoichiometry indicates a large global inventory of labile organic sulfur in marine phytoplankton (~28 Tg S). As organic sulfur metabolites travel through the ocean's organic matter reservoir attached to carbon backbones, their transformation represents a link between marine carbon and sulfur cycles. Yet, many labile organic sulfur compounds present in the ocean remain uncharacterized. Here, we leverage methods that identify sulfur-containing compounds through isotopic patterns to explore environmental metabolomic data through the lens of organic sulfur cycling. For a subset of chemically identified sulfur metabolites, we track their abundance and distributions and their potential metabolic links between phytoplankton producers and associated bacterial consumers. Exploring data from the North Pacific, North Atlantic, and Gulf of Mexico provides a means to assess organic sulfur inventories and distributions across a range of ocean biomes. Enhanced resolution of microbial sulfur metabolites improves our ability to decipher sulfur-based microbial metabolic networks that influence ocean biogeochemical cycles.
04:45 PM
Importance of land-based sampling in marine dissolved organic matter research (9147)
Primary Presenter: Lisa Schellenberg, Royal Netherlands Institute for Sea Research (lisa.schellenberg@nioz.nl)
Many traditional conservation approaches treat marine and terrestrial ecosystems separately, failing to account for the interconnection between land and sea. Pollutants enter marine environments through surface runoff (e.g. from intense rainfalls) and subsurface groundwater discharge, affecting coastal ecosystems. Research highlights that anthropogenic pollutants (e.g. pharmaceuticals, pesticides or human metabolites) are of growing concern due to their potential cumulative and unnoticed effects on aquatic organisms. In this study we are joining fluorescence spectroscopy and untargeted metabolomics (LC-MS/MS) of dissolved organic matter, to assess the influx of pollutants from land on nearshore reef systems, in regards to seasonal rainfall events. By integrating both land-based and coastal water samples we can identify pollutants of terrestrial origin as some substances are naturally occurring in one system that might be identified as potential pollutants in another. Field data showed significant seasonal variability in anthropogenically derived pollutants, with increased abundance linked to higher precipitation, mainly from human metabolites and personal care products. Pollutant levels in the wet season of 2022 were more than 3.6 times higher than in the dry season of 2022 or wet season of 2021, corresponding to rainfall more than double that of 2021. This study recommends taking samples along the land-sea continuum and highlights rain events derived pollution of coastal waters with potential detrimental impact on coral reefs.
05:00 PM
Unraveling the Chemical Complexities and Implications of Macroalgae-derived DOM on Reefs using Untargeted Mass Spectrometry and Chemoinformatics Strategies (8944)
Primary Presenter: Lydia Davis, University of North Carolina Wilmington (davisla@uncw.edu)
In many parts of the world, corals are declining due to warming oceans, pathogens, and acidification due to climate change. Macroalgae and sponges are rapidly superseding coral populations as dominant members of reef communities. Macroalgae are key primary producers in marine ecosystems and are established producers of dissolved organic matter (DOM) while sponges are well-known consumers of DOM. As macroalgae and sponges continue to thrive, it is important to understand how metabolites of dominant macroalgae influence reef communities and how sponges may respond to the availability of algal metabolites. Untargeted high-resolution tandem mass spectrometry and chemoinformatic analyses such as MS/MS library searching, chemical class prediction, molecular networking, and data mining are emerging as new tools to investigate the chemical complexity of marine DOM. These approaches were utilized to evaluate the chemical profile of macroalgae-derived DOC using predominant species collected from waters off the coast of southeastern North Carolina. As a follow-on study, field work was completed using Padina sp. collected near Key West, FL, USA. For these experiments, algal exudate was sampled and then fed to the sponges, Xestospongia muta and Agelas wiedenmayeri in a series of laboratory experiments. Collectively, these experiments unveiled the unique chemical fingerprint of macroalgae-derived DOM and its influence on reef sponges, shedding light on the effects of a changing climate on these communities.
05:15 PM
DOM cycling on coral reefs: Assessing the impacts of macroalgae and emergent sponges on DOM composition (8939)
Primary Presenter: Wendy Strangman, UNC Wilmington (strangmanw@uncw.edu)
Sponges now dominate Caribbean reefs after decades of declines of reef-building corals. Unlike most benthic reef organisms, sponges are ecosystem engineers that filter huge volumes of seawater, turning-over the water-column and transforming seawater chemistry. Interestingly, the most common species of emergent (large, non-cryptic) sponges on Caribbean reefs range from those having a high abundance of microbial symbionts in their tissues (HMA) to those with low microbial abundance (LMA) and we have demonstrated that these two categories of emergent sponges had variable effects on DOM composition. While the quantity of DOM in seawater commonly assessed, little is known about the finer-scale composition of the DOM that is processed by sponges. In tandem, abundances of macroalgae and cyanobacteria are increasing on coral reefs and many species have been shown to generate large amounts DOM. Using a suite of complimentary approaches, including new derivatization techniques, targeted analyses, untargeted metabolomics, and both on-reef and controlled laboratory experiments, we are beginning to generate a more detailed characterization of ambient and algal-derived DOM components in seawater and the effect of sponge processing. Results highlighting specific changes between algal species on DOM production and between HMA and LMA sponges on DOM composition will be presented.
05:30 PM
SS41B - Advancing the chemical and isotopic characterization of dissolved organic matter across the land–ocean aquatic continuum
Description
Time: 4:30 PM
Date: 31/3/2025
Room: W201CD