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Interpretability of negative latent heat fluxes from eddy covariance measurements in dry conditions

Porous materials are known to reversibly trap water from the air, even at low humidity. However, this behavior is poorly understood for soils. In this analysis, we test whether eddy covariance is able to measure the so-called adsorption of atmospheric water vapor by soils. We find that this flux occurs frequently during dry nights in a Mediterranean ecosystem, while EC detects downwardly directed vapor fluxes. These results can help to map moisture uptake globally.

Rates of palaeoecological change can inform ecosystem restoration

Rate-of-change records based on compositional data are ambiguous as they may rise irrespective of the underlying trajectory of ecosystems. We emphasize the importance of characterizing both the direction and the rate of palaeoecological changes in terms of key features of ecosystems rather than solely on community composition. Past accelerations of community transformation may document the potential of ecosystems to rapidly recover important ecological attributes and functions.

Distinct oxygenation modes of the Gulf of Oman over the past 43 000 years – a multi-proxy approach

We analyse benthic foraminifera, nitrogen isotopes and lipids in a sediment core from the Gulf of Oman to investigate how the oxygen minimum zone (OMZ) and bottom water (BW) oxygenation have reacted to climatic changes since 43 ka. The OMZ and BW deoxygenation was strong during the Holocene, but the OMZ was well ventilated during the LGM period. We found an unstable mode of oscillating oxygenation states, from moderately oxygenated in cold stadials to deoxygenated in warm interstadials in MIS 3.

Ideas and perspectives: Sensing energy and matter fluxes in a biota-dominated Patagonian landscape through environmental seismology – introducing the Pumalín Critical Zone Observatory

Coastal temperate rainforests, among Earth’s carbon richest biomes, are systematically underrepresented in the global network of critical zone observatories (CZOs). Introducing here a first CZO in the heart of the Patagonian rainforest, Chile, we investigate carbon sink functioning, biota-driven landscape evolution, fluxes of matter and energy, and disturbance regimes. We invite the community to join us in cross-disciplinary collaboration to advance science in this particular environment.

High-resolution spatial patterns and drivers of terrestrial ecosystem carbon dioxide, methane, and nitrous oxide fluxes in the tundra

Arctic greenhouse gas (GHG) fluxes of CO2, CH4, and N2O are important for climate feedbacks. We combined extensive in situ measurements and remote sensing data to develop machine-learning models to predict GHG fluxes at a 2 m resolution across a tundra landscape. The analysis revealed that the system was a net GHG sink and showed widespread CH4 uptake in upland vegetation types, almost surpassing the high wetland CH4 emissions at the landscape scale.

The additionality problem of ocean alkalinity enhancement

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.

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.

Responses of globally important phytoplankton species to olivine dissolution products and implications for carbon dioxide removal via ocean alkalinity enhancement

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.

Soil-biodegradable plastic films do not decompose in a lake sediment over 9 months of incubation

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.

Biomineralization of amorphous Fe-, Mn- and Si-rich mineral phases by cyanobacteria under oxic and alkaline conditions

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.

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