Human activities in inland waters and their catchment areas have multiple impacts on carbon cycling. Land use changes such as deforestation, expansion of agriculture and urbanization directly influence the flux of dissolved and particulate carbon from catchments to inland waters. Accompanying changes in nutrient loading alter carbon cycling through eutrophication and autochthonous production. Meanwhile, management of shoreline ecosystems and introduction of invasive species modifies the functioning of the littoral zone as a carbon filter, while fisheries directly impact carbon fluxes through biomass removal. All these activities may influence the balance between release of carbon through greenhouse gas emissions, and carbon retention via sediment accumulation. Moreover, the overarching influence of climate change affects the magnitude and timeline of the impacts of each activity. In this session we aim to bring together researchers working on these topics to present the state of the art in current understanding of modified carbon cycling in inland waters. We welcome contributions from field and experimental studies as well as catchment hydrological and biogeochemical modelling, and coupled elemental cycles. In particular, we aim to identify the controls and predictors of carbon burial in freshwater sediments, including the role of previously understudied littoral zones. Global littoral extent of inland waters is four times greater than that of the coastal ocean. Limnologists can profit from marine coastal blue carbon approaches to more rapidly gain insight on the importance of littoral extent elemental cycling and burial.
Lead Organizer: Tom Jilbert, University of Helsinki (tom.jilbert@helsinki.fi)
Co-organizers:
Roxane Maranger, University of Montreal (r.maranger@umontreal.ca)
Christopher Osburn, North Carolina State University (closburn@ncsu.edu)
Eero Asmala, Geological Survey of Finland (eero.asmala@gtk.fi)
Marie Korppoo, Finnish Environment Institute (marie.korppoo@syke.fi)
Ana Lúcia Lindroth Dauner, University of Helsinki (ana.lindrothdauner@helsinki.fi)
Presentations
06:00 PM
Using δ13C and δ15N signatures to identify carbon and nitrogen sources in the Lower Cape Fear River and Estuary, NC (8763)
Primary Presenter: Mia Carulli, University of North Carolina Wilmington (mcc2768@uncw.edu)
The Lower Cape Fear River basin spans the coastal plains of southeastern North Carolina and extends to the Atlantic Ocean. The river basin is characterized by a variety of ecosystems, with wetlands being the dominant feature. In recent years, more than half of these wetlands have been converted for agricultural and residential use, disrupting local environments and affecting waterways. In this study, δ13C and δ15N signatures were analyzed to better understand the fate, transport, and sources of carbon and nitrogen in the Lower Cape Fear River Basin and Estuary. Water samples were collected seasonally and after storm crests from eleven sites, including five along the mainstem of the Cape Fear River (from inland to the estuary mouth), one on the Black River, and one on the Northeast Cape Fear River. Additionally, two pristine control sites and two agricultural end-member sites were included. Particulate organic matter (POM) was filtered from water samples and analyzed using an isotope ratio mass spectrometer (IRMS). Results showed that δ13C signatures became heavier downstream as open ocean influence increased. One agricultural site exhibited some of the lightest signatures observed in this study, while the other displayed some of the heaviest. The control sites displayed δ13C and δ15N signatures consistent with natural baselines. After storm events, elevated water levels and runoff caused shifts in dominant carbon sources.
06:00 PM
SIMULATION OF CARBON CYCLING IN A RIVER BASIN IN FINLAND (8769)
Primary Presenter: Marie Korppoo, Finnish Environment Institute (marie.korppoo@syke.fi)
The intricate interplay between eutrophication and carbon accumulation in aquatic ecosystems remains a subject of limited understanding, posing challenges for effective river basin management. In this study, the operational, national-scale nutrient loading model, WSFS-Vemala (Vemala), simulating 67500 lakes and used for river basin management planning in Finland, was developed to include total carbon cycling in the aquatic ecosystem. Vemala v3 simulates past, present and future nutrient leaching and transport on land, as well as in rivers and lakes. A field scale model is applied for phosphorus and nitrogen terrestrial leaching from agricultural areas. The total organic carbon (TOC) and total inorganic carbon (TIC) leaching are defined by soil types and land uses. The model includes point loads, urban runoff, atmospheric deposition, and load from settlements. The lake biogeochemical model simulates total and bioavailable nutrient species and carbon. The processes affecting carbon cycling are mineralisation, photosynthesis, respiration, sedimentation and exchange of CO2 through the water-air interface. It predicts the co-impact of dissolved inorganic nitrogen and phosphate on phytoplankton growth and, therefore, on eutrophication, carbon sequestration in sediments and CO2 concentrations and emissions from lakes. Vemala v3 has been tested in the Tuusulanjärvi lake, a eutrophic lake in Southern Finland, to better understand the role of aquatic environments in carbon cycling.
06:00 PM
EMISSION AND BURIAL POTENTIAL OF BLUE CARBON HABITATS IN FINNISH LAKES (8904)
Primary Presenter: Max Kankainen, University of Helsinki (max.kankainen@hotmail.com)
Boreal lakes represent an important long-term carbon sink and pose as major candidates for nature-based solutions to mitigate climate change through carbon sequestration. At the same time lakes are recognized as large sources of atmospheric carbon and previous studies have shown a weak linear relationship between lake sediment carbon emission and burial rate. In coastal marine environments shallow water vegetated areas, or so called “blue carbon” habitats, may sequester as much as 50% of the total global marine carbon, but have also been shown to act as sources for greenhouse gases such as methane. The carbon fluxes of equivalent blue carbon habitats in lacustrine environments remains largely unexplored. In this study we aim to quantify sediment carbon burial and remineralization rates in Finnish lakes, both in blue carbon habitats dominated by the macrophyte Phragmites australis, and deeper open water areas. Initial results suggest that shallow water vegetated areas host considerable sediment carbon stocks, although the deposits are thinner in vertical extent and of overall smaller magnitude than stocks in deep open water areas. Porewater analysis shows that upwards diffusive fluxes of TCO2, DOC and CH4 occur in both shallow and deep-water areas. Relative rates of release of these three fractions are controlled by redox conditions. Due to the short water column, blue carbon habitats emit more dissolved carbon directly into the surface water than do the sediments of deeper open water areas.
06:00 PM
Eutrophication and geochemical factors affecting carbon accumulation in boreal lake sediments (8914)
Primary Presenter: Eero Asmala, Geological Survey of Finland (eero.asmala@gtk.fi)
Boreal lakes play a crucial role in global carbon cycling, acting as significant carbon sinks. However, human activities such as nutrient enrichment can disrupt these natural processes, impacting carbon sequestration. We investigated the relationship between sediment carbon accumulation and geochemical patterns across over 200 boreal lakes in Finland. We collected sediment cores from study lakes, dated them using cesium-137, and carried out multi-element analysis. In addition to sediment geochemistry, extensive water quality monitoring data were used to identify linkages between eutrophication and sediment carbon burial. Our analysis revealed that carbon mass accumulation rate (CMAR) was strongly linked to the mass accumulation rate (MAR), with high carbon burial observed in lakes with high MAR. Lakes influenced by nutrient enrichment (eutrophication) showed lower CMAR, particularly in systems with poor ecological status. We also identified positive relationships between potentially carbon-stabilizing elements (e.g. Ca, Cu) and CMAR. On the other hand, elements associated with agricultural influence or acidic soil leaching (e.g. K, Mn, Al) were linked with relatively low CMAR. Our results suggest that carbon accumulation in sediments is closely tied to nutrient dynamics and ecological health, with eutrophic lakes demonstrating reduced carbon storage capacity. This has broader relevance for climate change mitigation strategies, particularly in boreal regions where maintaining healthy aquatic ecosystems is critical for natural carbon sinks.
06:00 PM
MODELING CARBON BIOGEOCHEMICAL CYCLING IN INTEGRATED LAKE AND RIVER NETWORKS (9423)
Primary Presenter: Veronica Slevin, University of North Carolina at Chapel Hill (vjslevin4@gmail.com)
Understanding carbon cycling across inland aquatic systems is critical because they link the land to the ocean and atmosphere. The transformation of carbon across aquatic landscapes has been studied, but few studies have considered both lakes and rivers in a network. To address this knowledge gap, a process-based model was created to evaluate the fate of carbon given different quantities, sizes, and spacing of lakes in theoretical river networks. The model has carbon inputs from both labile and recalcitrant DOC, pCO2, and POC, and returns reach and network scale equilibrium values for these pools. Our goal is to understand the effects and interactions between river-lake network structure, carbon quality, and climate (using temperature as a climate proxy) on the processing and fate of carbon moving through inland waters.
06:00 PM
Using δ13C and δ15N signatures to identify carbon and nitrogen sources in the Lower Cape Fear River and Estuary, NC (9471)
Primary Presenter: Mia Carulli, University of North Carolina Wilmington (mcc2768@uncw.edu)
The Lower Cape Fear River basin spans the coastal plains of southeastern North Carolina and extends to the Atlantic Ocean. The river basin is characterized by a variety of ecosystems, with wetlands being the dominant feature. In recent years, more than half of these wetlands have been converted for agricultural and residential use, disrupting local environments and affecting waterways. In this study, δ13C and δ15N signatures were analyzed to better understand the fate, transport, and sources of carbon and nitrogen in the Lower Cape Fear River Basin and Estuary. Water samples were collected seasonally and after storm crests from eleven sites, including five along the mainstem of the Cape Fear River (from inland to the estuary mouth), one on the Black River, and one on the Northeast Cape Fear River. Additionally, two pristine control sites and two agricultural end-member sites were included. Particulate organic matter (POM) was filtered from water samples and analyzed using an isotope ratio mass spectrometer (IRMS). Results showed that δ13C signatures became heavier downstream as open ocean influence increased. One agricultural site exhibited some of the lightest signatures observed in this study, while the other displayed some of the heaviest. The control sites displayed δ13C and δ15N signatures consistent with natural baselines. After storm events, elevated water levels and runoff caused shifts in dominant carbon sources.
SS35P - Anthropogenic perturbations of carbon cycling and accumulation in inland waters
Description
Time: 6:00 PM
Date: 29/3/2025
Room: Exhibit Hall A