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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 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. 

Biological nitrogen fixation converts inert di-nitrogen gas into bioavailable nitrogen and can be an important source of bioavailable nitrogen to organisms. This dataset synthesizes the aquatic nitrogen fixation rate measurements across inland and coastal waters. Data were derived from papers and datasets published by April 2022 and include rates measured using the acetylene reduction assay (ARA), 15N2 labeling, or the N2/Ar technique. The dataset is comprised of 4793 nitrogen fixation rates measurements from 267 studies, and is structured into four tables: 1) a reference table with sources from which data were extracted, 2) a rates table with nitrogen fixation rates that includes habitat, substrate, geographic coordinates, and method of measuring N2 fixation rates, 3) a table with supporting environmental and chemical data for a subset of the rate measurements when data were available, and 4) a data dictionary with definitions for each variable in each data table. This dataset was compiled and curated by the NSF-funded Aquatic Nitrogen Fixation Research Coordination Network (award number 2015825). 

Biological nitrogen fixation is the conversion of dinitrogen (N2) gas into bioavailable nitrogen by microorganisms with consequences for primary production, ecosystem function, and global climate. Here we present a compiled dataset of 4793 nitrogen fixation (N2-fixation) rates measured in the water column and benthos of inland and coastal systems via the acetylene reduction assay, 15N2 labeling, or N2/Ar technique. While the data are distributed across seven continents, most observations (88%) are from the northern hemisphere. 15N2 labeling accounted for 67% of water column measurements, while the acetylene reduction assay accounted for 81% of benthic N2-fixation observations. Dataset median area-, volume-, and mass-normalized N2-fixation rates are 7.1 μmol N2-N m−2 h−1, 2.3 × 10−4 μmol N2-N L−1 h−1, and 4.8 × 10−4 μmol N2-N g−1 h−1, respectively. This dataset will facilitate future efforts to study and scale N2-fixation contributions across inland and coastal aquatic environments. 

Biological nitrogen fixation is a key driver of global primary production and climate. Decades of effort have repeatedly updated nitrogen fixation estimates for terrestrial and open ocean systems, yet other aquatic systems in between have largely been ignored. Here we present an evaluation of nitrogen fixation for inland and coastal waters. We demonstrate that water column and sediment nitrogen fixation is ubiquitous across these diverse aquatic habitats, with rates ranging six orders of magnitude. We conservatively estimate that, despite accounting for less than 10% of the global surface area, inland and coastal aquatic systems fix 40 (30 to 54) teragrams of nitrogen per year, equivalent to 15% of the nitrogen fixed on land and in the open ocean. Inland systems contribute more than half of this biological nitrogen fixation. 

Biological nitrogen fixation converts inert di-nitrogen gas into bioavailable nitrogen and can be an important source of bioavailable nitrogen to organisms. This dataset synthesizes the aquatic nitrogen fixation rate measurements across inland and coastal waters. Data were derived from papers and datasets published by April 2022 and include rates measured using the acetylene reduction assay (ARA), 15N2 labeling, or the N2/Ar technique. The dataset is comprised of 4793 nitrogen fixation rates measurements from 267 studies, and is structured into four tables: 1) a reference table with sources from which data were extracted, 2) a rates table with nitrogen fixation rates that includes habitat, substrate, geographic coordinates, and method of measuring N2 fixation rates, 3) a table with supporting environmental and chemical data for a subset of the rate measurements when data were available, and 4) a data dictionary with definitions for each variable in each data table. This dataset was compiled and curated by the NSF-funded Aquatic Nitrogen Fixation Research Coordination Network (award number 2015825). 

The ocean plays a major role in controlling atmospheric carbon at decadal to millennial timescales, with benthic carbon representing the only geologic‐scale storage of oceanic carbon. Despite its importance, detailed benthic ocean observations are limited and representation of the benthic carbon cycle in ocean and Earth system models (ESMs) is mostly empirical with little prognostic capacity, which hinders our ability to properly understand the long‐term evolution of the carbon cycle and climate change‐related feedbacks. The Benthic Ecosystem and Carbon Synthesis (BECS) working group, with the support of the US Ocean Carbon & Biogeochemistry Program (OCB), identified key challenges limiting our understanding of benthic systems, opportunities to act on these challenges, and pathways to increase the representation of these systems in global modeling and observational efforts. We propose a set of priorities to advance mechanistic understanding and better quantify the importance of the benthos: (a) implementing a model intercomparison exercise with existing benthic models to support future model development, (b) data synthesis to inform both model parameterizations and future observations, (c) increased deployment of platforms and technologies in support of in situ benthic monitoring (e.g., from benchtop to field mesocosm), and (d) global coordination of a benthic observing program (“GEOSed”) to fill large regional data gaps and evaluate the mechanistic understanding of benthic processes acquired throughout the previous steps. Addressing these priorities will help inform solutions to both global and regional resource management and climate adaptation strategies. 

Abstract. In the current era of rapid climate change, accuratecharacterization of climate-relevant gas dynamics – namely production,consumption, and net emissions – is required for all biomes, especially thoseecosystems most susceptible to the impact of change. Marine environmentsinclude regions that act as net sources or sinks for numerous climate-activetrace gases including methane (CH4) and nitrous oxide (N2O). Thetemporal and spatial distributions of CH4 and N2O are controlledby the interaction of complex biogeochemical and physical processes. Toevaluate and quantify how these mechanisms affect marine CH4 andN2O cycling requires a combination of traditional scientificdisciplines including oceanography, microbiology, and numerical modeling.Fundamental to these efforts is ensuring that the datasets produced byindependent scientists are comparable and interoperable. Equally critical istransparent communication within the research community about the technicalimprovements required to increase our collective understanding of marineCH4 and N2O. A workshop sponsored by Ocean Carbon and Biogeochemistry (OCB)was organized to enhance dialogue and collaborations pertaining tomarine CH4 and N2O. Here, we summarize the outcomes from theworkshop to describe the challenges and opportunities for near-futureCH4 and N2O research in the marine environment.