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Abstract Ponds influence global carbon (C) cycling due to high rates of organic C (OC) burial and carbon dioxide (CO₂) and methane (CH₄) emissions. Here, we quantified OC burial rates and CO₂and CH₄concentrations and fluxes in two ponds that were similar in size and gross primary production, but differed in depth and dominant primary producers. The deeper (3.9 m) Texas Hollow Pond was phytoplankton dominated with stronger and longer (143 d) stratification compared to the shallower (2.7 m) macrophyte‐dominated Mud Pond (85 d). Both ponds exhibited high CO₂and CH₄emissions and high OC burial, yet C pathways differed. Strong stratification in Texas Hollow Pond led to anoxic bottom waters, benthic CO₂and CH₄accumulation, and limited OC decomposition, whereas Mud Pond remained oxygenated with similar gas concentrations across the water column. Texas Hollow Pond had 2.6 times higher CO₂emissions than Mud Pond, perhaps related to greater wetland C inputs in Texas Hollow. Despite similar diffusive CH₄emissions between ponds, the weakly stratified Mud Pond had twice as much CH₄ebullition, likely due to warmer waters and macrophyte‐derived OC fueling methanogenesis. In summary, slight differences in depth and light attenuation can regulate stratification, plant communities, oxygen availability, and C processing in ponds. Given that ponds are hotspots for C cycling and are sensitive to climate‐driven changes in stratification, understanding the mechanisms behind C processing is critical for local management and predicting global C budgets. 

Abstract Ponds, wetlands, and shallow lakes (collectively “shallow waterbodies”) are among the most biogeochemically active freshwater ecosystems. Measurements of gross primary production (GPP), respiration (R), and net ecosystem production (NEP) are rare in shallow waterbodies compared to larger and deeper lakes, which can bias our understanding of lentic ecosystem processes. In this study, we calculated GPP, R, and NEP in 26 small, shallow waterbodies across temperate North America and Europe. We observed high rates of GPP (mean 8.4 g O₂ m⁻³ d⁻¹) and R (mean −9.1 g O₂ m⁻³ d⁻¹), while NEP varied from net heterotrophic to autotrophic. Metabolism rates were affected by depth and aquatic vegetation cover, and the shallowest waterbodies had the highest GPP, R, and the most variable NEP. The shallow waterbodies from this study had considerably higher metabolism rates compared to deeper lakes, stressing the importance of these systems as highly productive biogeochemical hotspots. 

Abstract Inland waters play a major role in global greenhouse gas (GHG) budgets. The smallest of these systems (i.e., ponds) have a particularly large—but poorly constrained—emissions footprint at the global scale. Much of this uncertainty is due to a poor understanding of temporal variability in emissions. Here, we conducted high‐resolution temporal sampling to quantify GHG exchange between four temperate constructed ponds and the atmosphere on an annual basis. We show these ponds are a net source of GHGs to the atmosphere (564.4 g CO₂‐eq m⁻² yr⁻¹), driven by highly temporally variable diffusive methane (CH₄) emissions. Diffusive CH₄release to the atmosphere was twice as high during periods when the ponds had a stratified water column than when it was mixed. Ebullitive CH₄release was also higher during stratification. Building ponds to favor mixed conditions thus presents an opportunity to minimize the global GHG footprint of future pond construction. 

{"Abstract":["Ponds play an important role in global carbon (C) cycling due to high, but\n variable, C burial rates and emissions of carbon dioxide (CO2) and methane\n (CH4) to the atmosphere. Here, we sampled two ponds of similar size, but\n with contrasting stratification and dominant types of primary producers.\n We quantified organic C (OC) burial rates and CO2 and CH4 concentrations\n and fluxes. The dataset includes data on thermal mixing, water chemistry,\n carbon burial, CO2 and CH4 concentrations, and ebullitive CH4 fluxes."],"Methods":["See the associated manuscript in Limnology &\n Oceanography"],"TechnicalInfo":["This readme.txt file was generated on 08-31-2024 by Meredith Holgerson\n GENERAL INFORMATION 1. Dataset Title: Mixing and Carbon Processing in Two\n Natural Ponds 2. Author Information\\ Principal Investigator Contact\n Information\\ Name: Meredith Holgerson\\ Institution: Cornell University\\\n Email:\n [meredith.holgerson@cornell.edu](mailto:meredith.holgerson@cornell.edu) 3.\n Field data collection occurred in 2021 and 2022 DATA & FILE OVERVIEW\n 1. File List: (1) 1_TemperatureSensorData.xlsx: Temperature sensor data\n with three tabs, one for each pond and a ReadMe (2)\n 2_Sonde_Nutrients_Chla.xlsx: Sonde, nutrients, and chlorophyll data, each\n with their own tab, and a ReadMe (3) 3_SedimentData.xlsx: Sediment data\n with three tabs, including loss-on-ignition for each pond (2 tabs), carbon\n burial for both ponds together (1 tab), and a ReadMe (4)\n 4_GreenhouseGasData.xlsx: Greenhouse gas data with four tabs, one each for\n water GHG concentrations, air GHG concentrations, ebullitive fluxes, and a\n ReadMe 2. Relationship between files: All files were used in analysis 3.\n "NA" in cells refer to data that are not available\n METHODOLOGICAL INFORMATION 1. Description of methods used for data\n compilation: Please see associated manuscript 2. Methods for processing\n the data: Please see associated manuscript DATA-SPECIFIC INFORMATION:\n Please see the "README" files in each of the Excel documents"]}