In aquatic ecosystems, the production of nitrous oxide (N2O), an important greenhouse gas, was until recently mostly ascribed to the activity of nitrifiers and denitrifiers. Recent research has revealed that a range of other organisms are also capable of producing N2O, but quantifying their contribution has remained challenging. Plouviez et al. present a novel approach based on the stable nitrogen and oxygen isotope composition of N2O, combined with the intramolecular distribution of 15N ("site preference"). They found that various microalgae grown in darkness present distinct stable isotope patterns, which paves the way for improving our ability to distinguish the contribution of different microbial groups to N2O production in aquatic ecosystems.

This study presents a novel view on water vapour dynamics and the role it plays for atmospheric composition and transport mechanisms.

The study analyzed lake sediments from the southwest Maya lowlands to track past land use and population size. The authors found that over 3,300 years, land use was highly variable, with more fire and maize agriculture earlier (3500-2000 BP) with a denser population but less burning in a later period (1600-1000 BP). Surprisingly, their hydrogen isotope data showed no strong signature of drought locally, suggesting that climate in that area remained relatively stable. Therefore, the authors argue that collapse or population decline in the southwest Maya lowlands was likely driven more by social, political, or regional factors than by local drought.

This paper reports the alarming increase in wildfires in the Amazon rainforest during the severe 2023/2024 drought leading to an increase in large-scale forest degradation. It is highly relevant as the fire-driven forest degradation impacted also intact forests and released large amounts of carbon dioxide to the atmosphere pushing the Amazon rainforest closer to a potential tipping point.

The ocean plays a key role in the global carbon cycle and its carbon sink strength is critical for removing atmospheric carbon dioxide and stabilizing global climate. This oceanic carbon sink strength is difficult to measure and models provide estimates that differ from one another. Terhaar combines multiple modeling approaches using composite model-based averages and fully coupled Earth System Models to take advantages of the benefits of both, and in doing so derives a similar sink strength to existing estimates but with reduced uncertainty.

Ecosystems are, in many ways, changing more rapidly than they have in the past. Rapid past ecological changes can provide critical insight into how to best understand ecosystem function to improve ecological restoration, but a historic focus on community composition in the paleoecological literature can obscure the causes of these changes, making mechanisms unclear. The authors demonstrate a path forward using pollen and diatom records from a lake in the Italian Alps to construct a narrative of terrestrial and aquatic ecosystem changes that combines well-established vegetation changes with rapid changes to water management changes to explore how rapidly the ecosystem responds to perturbations, and how aquatic function has been restored after pollution events. Doing so provides new insight into how to use the paleoecological record to understand restoration success and the time scales upon which ecosystem changes occur.