The contribution of microbial communities in polymetallic nodules to thediversity of the deep-sea microbiome of the Peru Basin (4130–4198 mdepth) Biogeosciences DOI 10.5194/bg-17-3203-2020 7 July 2020 Industrial-scale mining of deep-sea polymetallic nodules will remove nodules in large areas of the sea floor. We describe community composition of microbes associated with nodules of the Peru Basin. Our results show that nodules provide a unique ecological niche, playing an important role in shaping the diversity of the benthic deep-sea microbiome and potentially in element fluxes. We believe that our findings are highly relevant to expanding our knowledge of the impact associated with mining. Read more
Is there warming in the pipeline? A multi-model analysis of the Zero Emissions Commitment from CO2 Biogeosciences DOI 10.5194/bg-17-2987-2020 25 June 2020 The Zero Emissions Commitment (ZEC) is the change in global temperature expected to occur following the complete cessation of CO 2 emissions. Here we use 18 climate models to assess the value of ZEC. For our experiment we find that ZEC 50 years after emissions cease is between −0.36 to +0.29 °C. The most likely value of ZEC is assessed to be close to zero. However, substantial continued warming for decades or centuries following cessation of CO 2 emission cannot be ruled out. Read more
Summarizing the state of the terrestrial biosphere in few dimensions Biogeosciences DOI 10.5194/bg-17-2397-2020 19 May 2020 To closely monitor the state of our planet, we require systems that can monitor the observation of many different properties at the same time. We create indicators that resemble the behavior of many different simultaneous observations. We apply the method to create indicators representing the Earth’s biosphere. The indicators show a productivity gradient and a water gradient. The resulting indicators can detect a large number of changes and extremes in the Earth system. Read more
Authigenic formation of Ca–Mg carbonates in the shallow alkaline LakeNeusiedl, Austria Biogeosciences DOI 10.5194/bg-17-2085-2020 29 April 2020 Dolomite (CaMg(CO 3 ) 2 ) is supersaturated in many aquatic settings (e.g., seawater) on modern Earth but does not precipitate directly from the fluid, a fact known as the dolomite problem. The widely acknowledged concept of dolomite precipitation involves microbial extracellular polymeric substances (EPSs) and anoxic conditions as important drivers. In contrast, results from Lake Neusiedl support an alternative concept of Ca–Mg carbonate precipitation under aerobic and alkaline conditions. Read more
Scaling carbon fluxes from eddy covariance sites to globe: synthesis andevaluation of the FLUXCOM approach Biogeosciences DOI 10.5194/bg-17-1343-2020 26 March 2020 We test the approach of producing global gridded carbon fluxes based on combining machine learning with local measurements, remote sensing and climate data. We show that we can reproduce seasonal variations in carbon assimilated by plants via photosynthesis and in ecosystem net carbon balance. The ecosystem’s mean carbon balance and carbon flux trends require cautious interpretation. The analysis paves the way for future improvements of the data-driven assessment of carbon fluxes. FLUXCOM approach">Read more
No nitrogen fixation in the Bay of Bengal? Biogeosciences DOI 10.5194/bg-17-851-2020 27 February 2020 Oxygen minimum zones (OMZs) are ocean areas severely depleted in oxygen as a result of physical, chemical, and biological processes. Biologically, organic material is produced in the sea surface and exported to deeper waters, where it respires. In the Bay of Bengal (BoB), an OMZ is present, but there are traces of oxygen left. Our study now suggests that this is because one key process, nitrogen fixation, is absent in the BoB, thus preventing primary production and consecutive respiration. Read more
Dimensions of marine phytoplankton diversity Biogeosciences DOI 10.5194/bg-17-609-2020 18 February 2020 Phytoplankton are an essential component of the marine food web and earth’s carbon cycle. We use observations, ecological theory and a unique trait-based ecosystem model to explain controls on patterns of marine phytoplankton biodiversity. We find that different dimensions of diversity (size classes, biogeochemical functional groups, thermal norms) are controlled by a disparate combination of mechanisms. This may explain why previous studies of phytoplankton diversity had conflicting results. Read more
Microbial community composition and abundance after millennia of submarine permafrost warming Biogeosciences DOI 10.5194/bg-16-3941-2019 8 November 2019 Permafrost temperatures increased substantially at a global scale, potentially altering microbial assemblages involved in carbon mobilization before permafrost thaws. We used Arctic Shelf submarine permafrost as a natural laboratory to investigate the microbial response to long-term permafrost warming. Our work shows that millennia after permafrost warming by > 10 °C, microbial community composition and population size reflect the paleoenvironment rather than a direct effect through warming. Read more
Physical constraints for respiration in microbial hotspots in soil and their importance for denitrification Biogeosciences DOI 10.5194/bg-16-3665-2019 27 September 2019 A combination of gas chromatography and X-ray CT reveals the microscale processes that govern soil respiration. Aerobic and anaerobic respiration in microbial hotspots depends not only on the quality and quantity of soil organic matter, but also on the spatial distribution of hotspots. Denitrification kinetics are mainly governed by hotspot architecture due to local competition for oxygen during growth. Cumulative behavior is mainly governed by water saturation due to the overall supply with O2. Read more
Ideas and perspectives: is shale gas a major driver of recent increase in global atmospheric methane? Biogeosciences DOI 10.5194/bg-16-3033-2019 14 August 2019 Atmospheric methane has risen rapidly since 2008 and has become more depleted in 13C, in contrast to the trend towards more 13C enrichment in the late 20th century. Many have used this isotopic evidence to infer an increased biogenic source. Here I analyze the 13C trend with the consideration that methane from shale gas is somewhat depleted in 13C compared to other fossil fuels. I conclude that shale gas may be responsible for a third of the global increase from all sources. Read more