Despite our growing understanding of the global carbon cycle, scientific consensus on the drivers and mechanisms that control dissolved organic carbon (DOC) turnover in aquatic systems is lacking, hampered by the mismatch between research that approaches DOC reactivity from either intrinsic (inherent chemical properties) or extrinsic (environmental context) perspectives. Here we propose a conceptual view of DOC reactivity in w...

Freshwater reservoirs are an important source of the greenhouse gas methane (CH 4 ) to the atmosphere, but global emission estimates are poorly constrained (13.3–52.5 Tg C yr −1 ), partially due to extreme spatial variability in emission rates within and among reservoirs. Spatial heterogeneity in the availability of organic matter (OM) for biological CH 4 production by methanogenic archaea may be an important contributor to th...

Streams and river networks are increasingly recognized as significant sources for the greenhouse gas nitrous oxide (N 2 O). N 2 O is a transformation product of nitrogenous compounds in soil, sediment and water. Agricultural areas are considered a particular hotspot for emissions because of the large input of nitrogen (N) fertilizers applied on arable land. However, there is little information on N 2 O emissions from forest st...

Understanding how scale‐dependent processes regulate patterns of water chemistry remains a challenge in aquatic biogeochemistry. This study evaluated how chemical properties of streams and rivers vary with drainage size and explored mechanisms that may underlie nonlinear changes with increasing scale. To do this, we contrasted concentrations of total organic carbon (TOC) with pH and cations (Ca and Mg) from 69 catchments in no...

We quantify the allochthonous organic carbon (OC) budgets for seven north temperate lakes, using diverse information about their land cover, hydrology, and limnological characteristics. We develop a simple equilibrium model within a Bayesian framework that exploits the differences among the lakes to estimate three key rates: aerial loading (A OC ) and wetland loading (W OC ) from adjacent ecosystems and whole‐lake mineralizati...

Evasion of gaseous carbon ( C ) from streams is often poorly quantified in landscape C budgets. Even though the potential importance of the capillary network of streams as C conduits across the land–water–atmosphere interfaces is sometimes mentioned, low‐order streams are often left out of budget estimates due to being poorly characterized in terms of gas exchange and even areal surface coverage. We show that evasion of C is g...

The development of complete regional carbon (C) budgets for different biomes is an integral step in the effort to predict global response and potential feedbacks to a changing climate regime. Wetland and lake contributions to regional C cycling remain relatively uncertain despite recent research highlighting their importance. Using a combination of field surveys and tower‐based carbon dioxide (CO 2 ) flux measurements, modelin...

Based on theories of mire development and responses to a changing climate, the current role of mires as a net carbon sink has been questioned. A rigorous evaluation of the current net C‐exchange in mires requires measurements of all relevant fluxes. Estimates of annual total carbon budgets in mires are still very limited. Here, we present a full carbon budget over 2 years for a boreal minerogenic oligotrophic mire in northern...

Increasing concentrations of organic matter (OM) in surface waters have been noted over large parts of the boreal/nemoral zone in Europe and North America. This has raised questions about the causes and the likelihood of further increases. A number of drivers have been proposed, including temperature, hydrology, as well as ‐ and Cl − deposition. The data reported so far, however, have been insufficient to define the relative i...

The effect of ultraviolet radiation on the production of inorganic nitrogen, urea, and amino acids from aquatic dissolved organic matter (DOM) was investigated for waters from Hog Island Bay, a coastal lagoon in Virginia. Waters representing distinct sources of DOM to the lagoon were subjected to UV light mimicking the natural solar spectrum. Dissolved organic nitrogen concentrations did not change measurably during the 36‐h i...