The additionality problem of ocean alkalinity enhancement Biogeosciences DOI 10.5194/bg-21-261-2024 8 January 2024 Ocean alkalinity enhancement (OAE) is a widely considered marine carbon dioxide removal method. OAE aims to accelerate chemical rock weathering, which is a natural process that slowly sequesters atmospheric carbon dioxide. This study shows that the addition of anthropogenic alkalinity via OAE can reduce the natural release of alkalinity and, therefore, reduce the efficiency of OAE for climate mitigation. However, the additionality problem could be mitigated via a variety of activities. Read more
Reviews and syntheses: expanding the global coverage of gross primary production and net community production measurements using Biogeochemical-Argo floats Biogeosciences DOI 10.5194/bg-21-13-2024 27 December 2023 This paper provides an overview of the capacity to expand the global coverage of marine primary production estimates using autonomous ocean-going instruments, called Biogeochemical-Argo floats. We review existing approaches to quantifying primary production using floats, provide examples of the current implementation of the methods, and offer insights into how they can be better exploited. This paper is timely, given the ongoing expansion of the Biogeochemical-Argo array. Read more
Responses of globally important phytoplankton species to olivine dissolution products and implications for carbon dioxide removal via ocean alkalinity enhancement Biogeosciences DOI 10.5194/bg-20-4669-2023 22 November 2023 Applications of the mineral olivine are a promising means to capture carbon dioxide via coastal enhanced weathering, but little is known about the impacts on important marine phytoplankton. We examined the effects of olivine dissolution products on species from three major phytoplankton groups: diatoms, coccolithophores, and cyanobacteria. Growth and productivity were generally either unaffected or stimulated, suggesting the effects of olivine on key phytoplankton are negligible or positive. Read more
Soil-biodegradable plastic films do not decompose in a lake sediment over 9 months of incubation Biogeosciences DOI 10.5194/bg-20-4213-2023 9 October 2023 Agriculture relies heavily on plastic mulch films, which may be transported to aquatic environments. We investigated the breakdown of soil-biodegradable agricultural mulch films in lake sediments. After 40 weeks, films were intact, and no significant CO2 or CH4 was produced from the biodegradable mulch films. We conclude that the mulch films we used have a low biodegradability in lake sediments. The sediment lacks the microbes needed to break down the biodegradable plastics that were used here. Read more
Biomineralization of amorphous Fe-, Mn- and Si-rich mineral phases by cyanobacteria under oxic and alkaline conditions Biogeosciences DOI 10.5194/bg-20-4183-2023 4 October 2023 Iron and manganese are poorly soluble in oxic and alkaline solutions but much more soluble under anoxic conditions. As a result, authigenic minerals rich in Fe and/or Mn have been viewed as diagnostic of anoxic conditions. However, here we reveal a new case of biomineralization by specific cyanobacteria, forming abundant Fe(III)- and Mn(IV)-rich amorphous phases under oxic conditions in an alkaline lake. This might be an overlooked biotic contribution to the scavenging of Fe from water columns. Read more
Methane emissions due to reservoir flushing: a significant emission pathway? Biogeosciences DOI 10.5194/bg-20-4057-2023 25 September 2023 Based on a large dataset of seasonally resolved methane (CH4) pore water concentrations in a reservoir’s sediment, we assess the significance of CH4 emissions due to reservoir flushing. In the studied reservoir, CH4 emissions caused by one flushing operation can represent 7 %–14 % of the annual CH4 emissions and depend on the timing of the flushing operation. In reservoirs with high sediment loadings, regular flushing may substantially contribute to the overall CH4 emissions. Read more
Element ∕ Ca ratios in Nodosariida (Foraminifera) and their potential application for paleoenvironmental reconstructions Biogeosciences DOI 10.5194/bg-20-4043-2023 22 September 2023 We analyzed Mg / Ca and other El / Ca (Na / Ca, B / Ca, Sr / Ca and Ba / Ca) in Nodosariata. Their calcite chemistry is markedly different to that of the other calcifying orders of foraminifera. We show a relation between the species average Mg / Ca and its sensitivity to changes in temperature. Differences were reflected in both the Mg incorporation and the sensitivities of Mg / Ca to temperature. Read more
High-resolution data reveal a surge of biomass loss from temperate and Atlantic pine forests, contextualizing the 2022 fire season distinctiveness in France Biogeosciences DOI 10.5194/bg-20-3803-2023 13 September 2023 This study analyses the ecological impact of the 2022 summer fire season in France by using high-resolution satellite data. The total biomass loss was 2.553 Mt, equivalent to a 17 % increase of the average natural mortality of all French forests. While Mediterranean forests had a lower biomass loss, there was a drastic increase in burned area and biomass loss over the Atlantic pine forests and temperate forests. This result revisits the distinctiveness of the 2022 fire season. Read more
Potential bioavailability of representative pyrogenic organic matter compounds in comparison to natural dissolved organic matter pools Biogeosciences DOI 10.5194/bg-20-3449-2023 14 August 2023 Intensifying wildfires are increasing pyrogenic organic matter (PyOM) production and its impact on water quality. Recent work indicates that PyOM may have a greater impact on aquatic biogeochemistry than previously assumed, driven by higher bioavailability. We provide a full assessment of the potential bioavailability of PyOM across its chemical spectrum. We indicate that PyOM can be actively transformed within the river corridor and, therefore, may be a growing source of riverine C emissions. Read more
All about nitrite: exploring nitrite sources and sinks in the eastern tropical North Pacific oxygen minimum zone Biogeosciences DOI 10.5194/bg-20-2499-2023 24 July 2023 Nitrogen (N) is essential for life; thus, its availability plays a key role in determining marine productivity. Using incubations of seawater spiked with a rare form of N measurable on a mass spectrometer, we quantified microbial pathways that determine marine N availability. The results show that pathways that recycle N have higher rates than those that result in its loss from biomass and present new evidence for anaerobic nitrite oxidation, a process long thought to be strictly aerobic. Read more