Microbial respiration in contrasting ocean provinces via high-frequency optode assays

Microbial respiration is a critical component of the marine carbon cycle, determining the proportion of fixed carbon that is subject to remineralization as opposed to being available for export to the ocean depths. Despite its importance, methodological constraints have led to an inadequate understanding of this process, especially in low-activity oligotrophic and mesopelagic regions. Here, we quantify respiration rates as low as 0.2 µmol O2 L-1 d-1 in contrasting ocean productivity provinces using oxygen optode sensors to identify size-fractionated respiration trends. In the low productivity region of the North Pacific Ocean at Station Papa, surface whole water microbial respiration was relatively stable at 1.2 µmol O2 L-1 d-1. Below the surface, there was a decoupling between respiration and bacterial production that coincided with increased phytodetritus and small phytoplankton. Size-fractionated analysis revealed that cells <5 µm were responsible for the majority of the respiration in the Pacific, both at the surface and below the mixed layer. At the North Atlantic Porcupine Abyssal Plain, surface whole water microbial respiration was higher (1.7 µmol O2 L-1 d-1) than in the Pacific and decreased by 3-fold below the euphotic zone. The Atlantic size-fraction contributions to total respiration shifted on the order of days during the evolution of a phytoplankton bloom with regular storm disturbances. The high-resolution optode method used in the Atlantic captured these significant shifts and is consistent with coinciding stain-based respiration methods and historical site estimates. This study highlights the dynamic nature of respiration across vertical, temporal, and size-fractionated factors, emphasizing the need for sensitive, high-throughput techniques to better understand ocean ecosystem metabolism

Geographical and temporal distribution of SARS-CoV-2 clades in the WHO European Region, January to June 2020

We show the distribution of SARS-CoV-2 genetic clades over time and between countries and outline potential genomic surveillance objectives. We applied three available genomic nomenclature systems for SARS-CoV-2 to all sequence data from the WHO European Region available during the COVID-19 pandemic until 10 July 2020. We highlight the importance of real-time sequencing and data dissemination in a pandemic situation. We provide a comparison of the nomenclatures and lay a foundation for future European genomic surveillance of SARS-CoV-2.Peer reviewe

The comparative role of key environmental factors in determining savanna productivity and carbon fluxes: a review, with special reference to northern Australia

Terrestrial ecosystems are highly responsive to their local environments and, as such, the rate of carbon uptake both in shorter and longer timescales and different spatial scales depends on local environmental drivers. For savannas, the key environmental drivers controlling vegetation productivity are water and nutrient availability, vapour pressure deficit (VPD), solar radiation and fire. Changes in these environmental factors can modify the carbon balance of these ecosystems. Therefore, understanding the environmental drivers responsible for the patterns (temporal and spatial) and processes (photosynthesis and respiration) has become a central goal in terrestrial carbon cycle studies. Here we have reviewed the various environmental controls on the spatial and temporal patterns on savanna carbon fluxes in northern Australia. Such studies are critical in predicting the impacts of future climate change on savanna productivity and carbon storage

Storage and Stability of Soil Organic Carbon in Aspen and Conifer Forest Soils of Northern Utah

This study compares the amount, distribution, and stability of soil organic carbon (SOC) in six paired quaking aspen (Populus tremuloides Michx) and conifer plots at three locations in northern Utah, to assess the influence of vegetation cover and other biotic and abiotic drivers on SOC storage capacity in seasonally dry environments. Aspen soils accumulated significantly more SOC in the mineral soil (0–60 cm) (92.2 ± 26.7 Mg C ha−1 vs. 66.9 ± 18.6 Mg C ha−1 under conifers), and despite thicker O horizons under conifers that contained higher amounts of SOC (11.6 ± 8.8 Mg C ha−1 under conifers vs. 1.65 ± 0.38 Mg C ha−1 in aspen), across all sites SOC storage was 25% higher under aspen. Shallow soil cores (0–15 cm) did not indicate significant differences in SOC with vegetation type. The SOC under aspen was also more stable, indicated by well-developed mollic epipedon (A horizon 38–53-cm thick vs. 5.5–34 cm under conifers), slower turnover of surficial SOC deduced from long-term laboratory incubations (67.7 ± 15.7 g CO2–C per kg C for aspen vs. 130.9 ± 41.3 g CO2–C per kg C for conifer soils), and a greater preponderance of mineral-associated SOC (55±13% in aspen vs. 41±13% in conifer). Aspen soils were generally wetter and we hypothesize that rapid litter turnover coupled with greater water supply may have caused greater downward redistribution and adsorption of dissolved organic carbon (DOC) in aspen soils