Impact of deoxygenation and warming on global marine species in the 21st century Biogeosciences DOI 10.5194/bg-20-2425-2023 14 July 2023 Ocean temperature and oxygen shape marine habitats together with species’ characteristics. We calculated the impacts of projected 21st-century warming and oxygen loss on the contemporary habitat volume of 47 marine species and described the drivers of these impacts. Most species lose less than 5 % of their habitat at 2 ◦C of global warming, but some species incur losses 2–3 times greater than that. We also calculate which species may be most vulnerable to climate change and why this is the case. Read more
Quantifying land carbon cycle feedbacks under negative CO2 emissions Biogeosciences DOI 10.5194/bg-20-2283-2023 10 July 2023 We propose a new method to quantify carbon cycle feedbacks under negative CO2 emissions. Our method isolates the lagged carbon cycle response to preceding positive emissions from the response to negative emissions. Our findings suggest that feedback parameters calculated with the novel approach are larger than those calculated with the conventional approach whereby carbon cycle inertia is not corrected for, with implications for the effectiveness of carbon dioxide removal in reducing CO2 levels. Read more
Hyperspectral imaging sediment core scanning tracks high-resolution Holocene variations in (an)oxygenic phototrophic communities at Lake Cadagno, Swiss Alps Biogeosciences DOI 10.5194/bg-20-2221-2023 30 June 2023 This study shows, for the first time, that hyperspectral imaging can detect bacteriochlorophyll pigments produced by green sulfur bacteria in sediment cores. We tested our method on cores from Lake Cadagno, Switzerland, and were able to reconstruct high-resolution variations in the abundance of green and purple sulfur bacteria over the past 12 700 years. Climate conditions, flood events, and land use had major impacts on the lake’s biogeochemical conditions over short and long timescales. Read more
The Volyn biota (Ukraine) – indications of 1.5 Gyr old eukaryotes in 3D preservation, a spotlight on the “boring billion” Biogeosciences DOI 10.5194/bg-20-1901-2023 16 June 2023 This research describes the occurrence of Precambrian fossils, with exceptionally well preserved morphology in 3D. These microfossils reach a size of millimeters (possibly up to centimeters) and thus indicate the presence of multicellular eukaryotes. Many of them are filamentous, but other types were also found. These fossils lived in a depth of several hundred meters and thus provide good evidence of a continental the deep biosphere, from a time generally considered as the “boring billion”. Read more
Reconstructing ocean carbon storage with CMIP6 Earth system models and synthetic Argo observations Biogeosciences DOI 10.5194/bg-20-1671-2023 19 May 2023 We present a new method for reconstructing ocean carbon using climate models and temperature and salinity observations. To test this method, we reconstruct modelled carbon using synthetic observations consistent with current sampling programmes. Sensitivity tests show skill in reconstructing carbon trends and variability within the upper 2000 m. Our results indicate that this method can be used for a new global estimate for ocean carbon content. Read more
Particulate organic matter in the Lena River and its delta: from the permafrost catchment to the Arctic Ocean Biogeosciences DOI 10.5194/bg-20-1423-2023 28 April 2023 Arctic warming accelerates permafrost thaw and release of terrestrial organic matter (OM) via rivers to the Arctic Ocean. We compared particulate organic carbon (POC), total suspended matter, and C isotopes (δ13C and Δ14C of POC) in the Lena delta and Lena River along a ∼1600 km transect. We show that the Lena delta, as an interface between the Lena River and the Arctic Ocean, plays a crucial role in determining the qualitative and quantitative composition of OM discharged into the Arctic Ocean. Read more
Reconciling the paradox of soil organic carbon erosion by water Biogeosciences DOI 10.5194/bg-20-635-2023 31 March 2023 The direction and magnitude of the net erosion-induced land–atmosphere C exchange have been the topic of a big scientific debate for more than a decade now. Many have assumed that erosion leads to a loss of soil carbon to the atmosphere, whereas others have shown that erosion ultimately leads to a carbon sink. Here, we show that the soil carbon erosion source–sink paradox is reconciled when the broad range of temporal and spatial scales at which the underlying processes operate are considered. Read more
Nitrous oxide (N2O) synthesis by the freshwater cyanobacterium Microcystis aeruginosa Biogeosciences DOI 10.5194/bg-20-687-2023 27 March 2023 We show, for the first time, that pure cultures of the cyanobacterium Microcystis aeruginosa can synthesize the potent greenhouse gas N2O using nitrite as substrate. Our findings have broad environmental implications because M. aeruginosa is globally found in freshwater ecosystems and is often the dominant species found in algae blooms. Further research is now needed to determine the occurrence and significance of N2O emissions from ecosystems rich with M. aeruginosa. Read more
The dispersal of fluvially discharged and marine, shelf-produced particulate organic matter in the northern Gulf of Mexico Biogeosciences DOI 10.5194/bg-20-663-2023 24 March 2023 Terrestrial organic matter (TerrOM) is transported to the ocean by rivers, where its burial can potentially form a long-term carbon sink. This burial is dependent on the type and characteristics of the TerrOM. We used bulk sediment properties, biomarkers, and palynology to identify the dispersal patterns of plant-derived, soil–microbial, and marine OM in the northern Gulf of Mexico and show that plant-derived OM is transported further into the coastal zone than soil and marine-produced TerrOM. Read more
The influence of elevated CO2 and soil depth on rhizosphere activity and nutrient availability in a mature Eucalyptus woodland Biogeosciences DOI 10.5194/bg-20-505-2023 17 March 2023 Elevated CO2 in the atmosphere increases forest biomass productivity when growth is not limited by soil nutrients. This study explores how mature trees stimulate soil availability of nitrogen and phosphorus with free-air carbon dioxide enrichment after 5 years of fumigation. We found that both nutrient availability and processes feeding available pools increased in the rhizosphere, and phosphorus increased at depth. This appears to not be by decomposition but by faster recycling of nutrients. Read more