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
09:00 AM
SHIFTING GLOBAL PERSPECTIVES: INSIGHTS AND APPROACHES FROM COASTAL BLUE CARBON SCIENCE (8999)
Primary Presenter: Craig Smeaton, University of St Andrews (cs244@st-andrews.ac.uk)
In the last decade Blue Carbon has transformed from an overlooked niche topic to being recognised as a core component of the global carbon cycle and key to implementing nature-based solutions to tackle climate change. Since the conception of Blue Carbon, the science has evolved from basic carbon stock assessments, to today where the biggest issue is understanding how both natural and anthropogenic disturbance impact the biogeochemical cycling in these potentially vulnerable environments. With the rapid increase in the prominence of Blue Carbon research has come many opportunities but also missteps, from these experiences other fields including limnology can benefit from the insights and lessons learned to help avoid the same issues arising. Taking the saltmarshes of the United Kingdom we will outline the critical foundational science undertaken that has led from a handful of carbon measurements a decade ago to national scale estimates of carbon stock and accumulation alongside discussing the co-development of policy with national agencies to protect and preserve carbon from natural and anthropogenic perturbations. Some of the approaches and experiences from Blue Carbon research will of course differ from those of limnology but many of the insights and lessons learned over the last decade are applicable and will place the limnology community in a better position to rapidly gain insights into elemental cycling and burial in shoreline vegetated systems and the threat of anthropogenic perturbations. In-turn, this will allow productive engagement with policymakers.
09:15 AM
09:30 AM
CHASING COASTAL CARBON: ORGANIC AND INORGANIC SOURCES AND SINKS ALONG SHIFTING FRESHWATER-MARINE GRADIENTS (9639)
Primary Presenter: John Kominoski, Florida International University (jkominos@fiu.edu)
Coastal wetlands are globally important stores of carbon (C), but rapid climate- and human-driven changes in fresh and marine water are affecting C cycling and storage capacity. The Florida Everglades is a model system to test how water management and rapid sea-level rise are changing C cycling along freshwater-to-marine gradients across diverse ecosystems that include peat and marl marshes, mangroves, and seagrass meadows. Upstream restoration of peat and marl marshes is increasing water depths and methane fluxes. Particulate organic matter nutrients increase and C decrease with water depths that elevate microbial respiration rates in marl but not peat marshes. Saltwater intrusion increases particulate organic C loss through higher electron acceptors and nutrients that prime microbial breakdown. Landscape-scale shifts in dissolved organic C concentrations and dissolved organic matter (DOM) composition illustrate how shifts in fresh and marine hydrology control sources and fluxes of C. Upstream freshwater restoration in peat drainages is mobilizing marsh C into downstream mangrove estuaries. Saltwater intrusion from sea-level rise is increasing and shifting marine and mangrove C inland in marl drainages, while upstream restoration in marl marshes is increasing humic DOM from allochthonous peat marshes. Carbonate seagrasses are net sources of atmospheric C despite being net autotrophic ecosystems. As climate and human changes continue to transform coastal ecosystems, integrated approaches that conserve and maximize C storage is critical.
09:45 AM
Changes in Composition of Particulate and Dissolved Organic Matter in the Negro River Under Different Climate Change Scenarios (9151)
Primary Presenter: Giovana Bataglion, Federal University of Amazonas (giovanabataglion@ufam.edu.br)
The increase in temperature and CO2 levels can cause changes in natural organic matter (NOM) due to disturbances in both productivity and microbial activity. In the Amazon region, despite the crucial role of aquatic ecosystems as sources and sinks of carbon, NOM remains poorly explored at the molecular level. This study aimed to characterize particulate organic matter (POM) and dissolved organic matter (DOM) fractions using GC-MS and FT-ICR MS, respectively, to assess the effects of a progressive increase in temperature and CO2 concentration over 28 days. Water from the Negro River (Brazil) was incubated in microcosms simulating climate change scenarios projected by the IPCC: control (ambient temperature and CO2 levels), mild (+1.5°C and 200 ppm), moderate (+2.5°C and 400 ppm), and drastic (+4.5°C and 850 ppm). During incubation, aliquots of water were taken from the microcosms and subjected to filtration using 0.7 µm glass fiber filter. The particulate fraction underwent liquid-liquid extraction, while the dissolved fraction was subjected to solid-phase extraction (Strata-X, 1 g). The initial results showed various chemical classes in POM samples, particularly n-alkanes, and fatty alcohols and acids, while in the DOM extracts, oxygenated formulae such as O1-20, NO1-20, and SO1-20, were observed. For both POM and DOM fractions, the results revealed that exposure time was a more significant factor in changing composition than temperature and CO2 concentration, with the most pronounced changes observed after 2 days of incubation.
10:00 AM
SEDIMENT CARBON SEQUESTRATION IN VEGETATED AREAS OF FINNISH LAKES: FIRST RESULTS FROM THE BLUE LAKES PROJECT (8827)
Primary Presenter: Ana Lúcia Lindroth Dauner, University of Helsinki (ana.lindrothdauner@helsinki.fi)
Aquatic vegetated ecosystems play an important role in global carbon sequestration. Although coastal marine environments have been relatively more studied in the past decades, vegetated shorelines in freshwater ecosystems can also bury significant amounts of carbon. This is especially relevant in boreal landscapes, which often show high densities of small, shallow lakes. In Finland, for example, it has been suggested that lakes may host nationally significant carbon stocks. Given this context, one goal of the Blue Lakes project is to understand drivers of sedimentary carbon burial along vegetated shorelines of boreal lakes. We took sediment cores from three large lakes in Finland with sites chosen based on previous satellite data of macrophyte presence. At each site, sediment cores were sampled in a transect through macrophyte zones, from the landside towards the waterside. Sedimentary carbon stocks (mass of carbon per area) showed a large spatial variability regarding lakes, zones and type of vegetation. However, grain size was the most significant parameter explaining variability in the magnitude of large C stocks. Sites dominated by silts and with large C stocks were found in sheltered embayments, regardless of proximity to rivers, density of vegetation or slope of the shoreline, implying a strong control of exposure on C accumulation. Refining C stock estimates according to the shoreline exposure degree will allow to more precise upscaling when combining these data with macrophyte vegetation surface area coverage in Finnish lakes.
10:15 AM
Land use as a key driver of increased organic carbon burial in boreal lakes (8903)
Primary Presenter: Tuomas Junna, Geological Survey of Finland (tuomas.junna@gtk.fi)
The abundant lakes in the boreal region are an active zone for cycling of organic carbon, functioning as simultaneous sources and sinks of atmospheric carbon dioxide. While previous studies have documented increased carbon loading and accelerated carbon accumulation to inland waters, the catchment level drivers of this increase remain ambiguous. Using caesium-137 dating and C-N analysis, we calculated the post year 1986 carbon accumulation rates from lake sediment cores collected from 213 individual lakes in boreal Finland. The linkages between carbon accumulation rates, lake morphometry and catchment land use were statistically investigated. We show that modern sediment carbon accumulation rates in boreal lakes are significantly higher than over the Holocene epoch, mainly due to increased terrestrial OC inputs. Extensive ditch excavation enhances the delivery of terrestrial OC to lakes, which has resulted in elevated carbon accumulation in lakes with high percentage of ditched area in their catchment. Recalcitrant terrestrial carbon from forested and peatland areas is buried more effectively, whereas increased soil erosion and enhanced mineralization of labile OC from agricultural runoff reduces the relative burial of terrestrial OC.
SS35A - Anthropogenic perturbations of carbon cycling and accumulation in inland waters
Description
Time: 9:00 AM
Date: 28/3/2025
Room: W206B