Aquatic ecosystems are a large but uncertain source of greenhouse gases (GHG) to the atmosphere. Managed aquatic ecosystems may be a disproportionately large source of emissions given their co-location with human activities and the influence of artificial water level management. The Intergovernmental Panel on Climate Change (IPCC) recently published a methodology for estimating anthropogenic GHG emissions from managed aquatic ecosystems (e.g., reservoirs, canals, ditches, farm ponds) and several countries now include this source in their national GHG inventory. National GHG inventories are used to track trends in GHG emissions, monitor compliance with emission-reduction commitments under international treaties, provide an important framework for incorporating aquatic systems into climate-relevant policy discussions, and highlight the need for accurate emission estimates. In this session, we solicit presentations that address challenges and recent advances in estimating GHG emissions from managed aquatic ecosystems. We encourage contributions focusing on 1) spatial and temporal patterns in emission rates, 2) biophysical drivers of GHG production and emission, 3) models (statistical or mechanistic) for predicting aquatic GHG emissions, 4) methods for upscaling and/or downscaling emission measurements to regional and/or national scales, and 5) identification and mapping of managed aquatic ecosystems. We welcome submissions by students, early career researchers, and researchers from BIPOC, LGBTQIA+, and other marginalized identities.
Lead Organizer: Jake Beaulieu, United States Environmental Protection Agency (Beaulieu.jake@epa.gov)
Co-organizers:
Bridget Deemer, U.S. Geological Survey (bdeemer@usgs.gov)
Natalie Griffiths, Oak Ridge National Laboratory (griffithsna@ornl.gov)
Rachel Pilla, Oak Ridge National Laboratory (pillarm1@ornl.gov)
Presentations
05:30 PM
Modeling temporal patterns of greenhouse gas emissions from excavated fish ponds (8315)
Primary Presenter: Maria Camila Mejia Garcia, University of Texas Rio Grande Valley (mariacmejiag80@gmail.com)
Aquaculture is the world’s dominant source of fish production, having recently surpassed capture fisheries. Most aquaculture operations occur in freshwater environments, utilizing either excavated ponds or cage culture where mesh enclosures are deployed in existing water bodies such as reservoirs to confine culture animals. Recent studies have demonstrated that freshwater aquaculture systems are non-negligible sources of greenhouse gases (GHG) such as carbon dioxide (CO2), methane (CH4), and nitrous oxide (N2O). These emissions are temporally variable, but measurements are costly and time-consumingand there is a notable scarcity of predictive models tailored to the aquaculture sector. Drawing on temporally and spatially resolved data from aquaculture systems in Brazil, we use machine learning to model the temporal variability in CO2, CH4 and N2O fluxes from excavated ponds and cage culture systems. Through our research, we aim to elucidate drivers and patterns of temporal variability in GHG emissions from these distinct yet widespread aquaculture production systems. This could help correct datasets lacking temporally resolved measurements.
05:30 PM
METHANE EMISSION DYNAMICS IN A TROPICAL RESERVOIR POST SALVINIA MOLESTA CONTROL (8009)
Primary Presenter: Abdel Jimenez, UPRRP (abdel.jimenez1@upr.edu)
This study investigates the spatial dynamics of methane emissions from Las Curias Reservoir in Puerto Rico, following an extensive infestation and subsequent control of the invasive aquatic fern, Salvinia molesta. The intervention involved biological control through Cyrtobagous salviniae, a weevil species. Post-control, the decomposing biomass of Salvinia molesta was allowed to sink to the bottom of the reservoir, presenting a novel opportunity to examine the effect of macrophyte derived organic matter on methane production. This research employs a multifaceted methodology, encompassing floating chambers, inverted funnel traps, and comprehensive water chemistry analysis, to quantify both diffusive and ebullitive methane emissions across the reservoir during summer months. Special attention is given to areas adjacent to the dam, where significant bubbling events indicate concentrated methane release. The primary objective of this study is to elucidate the impact of Salvinia molesta decomposition on methane emissions in a tropical reservoir, thereby contributing to the understanding between invasive species management and methane emissions in tropical lentic ecosystems. The findings are expected to highlight the potential unintended consequences of invasive aquatic plant management.
05:30 PM
Carbon dioxide, methane, and nitrous oxide fluxes from managed distributaries across the Rio Grande Delta (8066)
Primary Presenter: Siena Stassi, University of Texas- Rio Grande Valley (siena.stassi01@utrgv.edu)
Aquatic ecosystems are globally important emitters of greenhouse gases (GHG), with small and human-made systems exhibiting a disproportionally high contribution to emissions compared to their global coverage. The Rio Grande Delta region along the US-Mexico border harbors a unique system of abandoned channels, distributaries, and their associated ox-bows—locally known as ‘resacas’—that serve as sources of biodiversity refuge, human recreation, flood control, and irrigation. Formed by the Rio Grande’s natural flooding cycles over the past 10,000 years, resacas are now artificially sustained due to human alterations in the river’s flood cycles by dams, levees, and diversion systems. Patterns of GHG emissions from these uniquely managed natural aquatic ecosystems remain largely unexplored. To understand spatial and temporal variations in GHG emissions, we focus on biweekly sampling across three distinct resacas, each managed under different hydrologic regimes. We use portable GHG analyzers to quantify diffusive fluxes of carbon dioxide (CO2), methane (CH4), and nitrous oxide (N2O), as well as ebullitive fluxes of greenhouse gases, particularly CH4. In addition, we quantify basic limnological parameters such as dissolved oxygen, chlorophyll-a, temperature, pH, turbidity, and conductivity using a portable water quality probe. Our initial findings suggest that warmer conditions are associated with increased emissions of CO2, CH4, and N2O. Further, there are differences in GHG emission rates across the three resacas, which may be linked to different water management regimes. This research offers novel insight into the GHG dynamics of the Rio Grande Delta and their potential responses to future hydrological and temperature changes.
05:30 PM
Modelling OM sources and Processing in the La Romaine Hydroelectric Complex to Improve Attribution of Reservoir Carbon Dioxide Emissions (7892)
Primary Presenter: Camille St-Arneault, Université du Québec à Montréal (st-arneault_sergerie.camille@courrier.uqam.ca)
Although hydroelectricity has been considered a carbon-neutral energy source in the past, it is now recognized that the creation of hydroelectric reservoirs leads to GHG emissions due to land-use change caused by the impoundment of natural ecosystems. Quantifying robust carbon footprint for reservoirs requires separating emissions attributable to the reservoir, i.e., the mineralization of flooded organic carbon pools, from "natural" emissions, i.e., the degradation of DOC derived from the watershed. Here we present preliminary results of a study that reconstructs the watershed loading of DOC and its subsequent biotic and abiotic processing within three young and consecutive boreal reservoirs. This project is part of the long-term research program of the CarBBAS (Carbon Biogeochemistry in Boreal Aquatic Ecosystems) group to quantify the carbon footprint of the La Romaine hydroelectric complex in Quebec, Canada. For each reservoir we have developed a complete water balance and a full DOC mass balance using DOC concentration data from La Romaine River and dozens of tributaries within the watershed. A mechanistic model will then be used to model the DOC degradation within the reservoirs, based on the measured biological and photochemical reactivity of the incoming watershed DOC and the hydrologic residence time. The objective is to eventually subtract the resulting CO2 fluxes from the CO2 diffusive emissions that have been measured at the reservoir air/water interface, to better constrain GHG emissions that are attributable to the reservoirs.
SS08P - Advances in Estimating Greenhouse Gas Emissions from Managed Aquatic Ecosystems
Description
Time: 5:30 PM
Date: 4/6/2024
Room: Madison Ballroom D