Methane seep carbonates preserve information about the history of methane seepage and of the fauna inhabiting these ecosystems. For this information to be useful, a reliable determination of the carbonates’ stratigraphic ages is required, but this is not always available. Here we investigate the using strontium isotope stratigraphy to date fossil methane seep carbonates via detailed petrographic and geochemical investigation of the different carbonate phases in biostratigraphically well-dated seep carbonates of Paleozoic, Mesozoic, and Cenozoic age. The best results are obtained from banded, botryoidal rim cements from carbonate phases showing a weak or no cathodoluminescence signal, an oxygen isotope signature close to that of seawater, and the lowest Mn concentrations. We then applied the method to a presumably late Jurassic seep carbonate from the Great Valley Group in California. Strontium isotope ratios of the least diagenetically altered carbonate phases indicate a Tithonian (late Jurassic) age for this seep site, which is in conflict with a recent study that suggested the absence of Jurassic strata from the Great Valley Group.

Freshwater microbes play a crucial role in the global carbon cycle. Anthropogenic stressors that lead to changes in these microbial communities are likely to have profound consequences for freshwater ecosystems. Using field data from the coordinated sampling of 617 lakes, ponds, rivers, and streams by citizen scientists, we observed linkages between microbial community composition, light and chemical pollution, and greenhouse gas concentration. All sampled water bodies were net emitters of CO₂, with higher concentrations in running waters, and increasing concentrations at higher latitudes. Light pollution occurred at 75% of sites, was higher in urban areas and along rivers, and had a measurable effect on the microbial alpha diversity. Genetic elements suggestive of chemical stress and antimicrobial resistances (IntI1, blaOX₅₈) were found in 85% of sites, and were also more prevalent in urban streams and rivers. Light pollution and CO₂ were significantly related to microbial community composition, with CO₂ inversely related to microbial phototrophy. Results of synchronous nationwide sampling indicate that pollution-driven alterations to the freshwater microbiome lead to changes in CO₂ production in natural waters and highlight the vulnerability of running waters to anthropogenic stressors.

Crop fields are cultivated across continuities of soil, topography, and local climate that drive biological processes and nutrient cycling at the landscape scale; yet land management and agricultural research are often performed at the field scale, potentially neglecting the context of the surrounding landscape. Adding to this complexity is the overlap of ecosystems and their biogeochemical legacies, as a patchwork of crops fields, natural grasslands, and forests develops across the landscape. Furthermore, as new technologies and policies are introduced, management practices change, including fertilization strategies, which further alter biological productivity and nutrient cycling. All of these environmental, biological, and historical legacies are potentially recorded in the isotopic signal of plant, soil, and sediment organic matter across the landscape. We mapped over 1500 plant, soil, and sediment isotopic values and generated an isotopic landscape (isoscape) over a 40‐km²agricultural site inNEGermany. We observed distinct patterns in the isotopic composition of organic matter sampled from the landscape that clearly reflect the landscape complexity. C₃crop intrinsic water‐use efficiency reflected a precipitation gradient, while native forest and grassland plant species did not, suggesting that native plants are more adapted to predominant climatic conditions. δ¹³C_soilpatterns reflected both the long‐term input of plant organic matter, which was affected by the local climate conditions, and the repeated cultivation of corn. Soil organic matter¹⁵N isotopic values also revealed spatial differences in fertilization regimes. Forest fragments, in which the nitrogen cycle was relatively open, were more water‐use efficient. Sediments from small water bodies received substantial inputs from surrounding field vegetation but were also affected by seasonal drying. These isotopic maps can be used to visualize large spatial heterogeneity and complexity, and they are a powerful means to interpret past and current trends in agricultural landscapes.