We improve coastal ocean carbonate system estimates by assimilating glider pH and alkalinity data into a regional biogeochemical model. Joint assimilation with physical observations successfully improves pH estimates while maintaining physical estimates. A hybrid approach combining dynamical models with statistical methods produces accurate pH estimates without requiring biogeochemical models, offering an alternative solution for ocean acidification monitoring.

A dataset of phytoplankton cell counts, pigments, particulate organic carbon and optical properties enables comparison of three methods to estimate phytoplankton carbon (C_phyto) in oligotrophic waters, where uncertainties in phytoplankton productivity are still large. Two methods based on chlorophyll concentration and particulate backscattering, are scalable to global scale while cell counts reduce bias from non-algal material. This comparison clarifies uncertainties in optical C_phyto estimates.

Understanding what shapes lake water quality is vital in a changing world. We studied dissolved organic matter, a key part of water quality in lakes and the carbon cycle, to analyse its environmental drivers and make predictions, by using machine learning. Tested in lakes in Ireland and Spain, it showed good predictions, even when relying only on climate-soil data, and Julian day. This helps explain how land and climate conditions influence freshwater resources. It can be reproduced worldwide.

Island mass effect (IME) refers to elevated chlorophyll a concentrations around islands, often extending hundreds of kilometers into oligotrophic waters. Using satellite-derived nutrient and iron stress indices and in situ bio-optical data from the Tara Pacific expedition, we show that IMEs are associated with recurring iron and macronutrient enrichments, and changes in phytoplankton community composition relative to the regional background ocean.

We investigate how soil moisture influences the future land carbon sink using dedicated experiments from the latest generation of Earth system models. Our results show that soil moisture strongly reduces land carbon uptake, mainly through soil moisture–atmosphere coupling. However, models disagree on the magnitude of SM impacts. The study emphasises that improving the representation of plant water stress in models is essential to reduce uncertainties in carbon cycle projections.

Seaweeds can store carbon in the ocean, but traditional methods in food chemistry fail to measure alginate—a major organic component derived from brown algae—in seafloor mud. We developed a novel extraction method for alginate in marine sediments. This allows for high recovery rates, and we successfully used this method to quantify alginate in marine sediments from northern Japan. Our work establishes a reliable method to track alginate on the ocean floor.

We asked how organic matter pools and microbial communities vary across polygon types and soil layers in Arctic lowland tundra. Low-center polygons had lower microbial abundance, enzyme potential, and organic matter bioavailability. Organic topsoils were microbial hotspots, but thaw may also rapidly mobilize carbon from upper permafrost. Patterns consistently followed gradients in organic matter and redox conditions, offering a practical framework for scaling landscape-scale soil carbon changes.

Trees take up mercury through their leaves and enrich it in their tree-rings. We investigated tree-ring records of oak and Douglas fir in Germany reaching back ~120 years. We have found that the overall magnitude of mercury loads in trees are determined by local atmospheric Hg concentrations while changes in mercury uptake are controlled by climate. Oak and Douglas fir show different Hg records through time as a results of different adaptation strategies to high temperatures and drought.

This study examines how combining atmospheric inversion with process-based modelling can reduce discrepancies in estimates of Arctic wetland CH₄ emissions. We conducted a series of inversion experiments, each incorporating CH₄ wetland fluxes from process-based models with different CH₄ production parameterizations. Our results showed that no single parameterization captures the complexity of Arctic–Boreal emissions; instead, region-specific adjustments are needed to reduce discrepancies.

Fish otolith formation is key for understanding the incorporation of elements into biominerals. It is often assumed that the final step of biomineralization consists of inorganic precipitation as the fluid where biominerals form can hardly be sampled. Thanks to fish ear anatomy, this can be overcome with otoliths. By comparing otolith formation and inorganic precipitation, we proved that this assumption is not always true. Our findings could refine models and shed light on biomineralization.

The Arctic is warming almost four times faster than the global average, placing the numerous lakes at risk from climatic change. In lakes, ostracods (small aquatic crustaceans) can be a major contributor to the biomass and used to track climatic change through time. We characterise current environmental and habitat preferences of Arctic ostracod species to understand current, future and past change. Increasing temperature and nutrients are likely to be significant drivers of ecological change.

Salt marshes, a type of coastal wetland, store “blue” carbon. At the same time, these ecosystems can release the greenhouse gases carbon dioxide (CO₂) and methane (CH₄) via microbial decomposition of stored carbon. In this study, we studied what drives the release of CO₂ from mineral-rich salt marshes and found that the quantity and form of carbon are the most important factors. Our results improve understanding of salt marsh carbon cycling, allowing better prediction of future changes.

The atmosphere plays key roles in Earth’s biogeochemical cycles. Airborne microbes were demonstrated previously to participate in the processing of organic carbon in clouds. Using a combinaison of complementary methods, we examined here, for the first time, their potential contribution to the pool of nitrogen compounds. Airborne microorganisms interact with abundant forms of nitrogen in the air and cloud and we provide global estimates.

From a 400-year sediment record in Lake Joux, we ask how past eutrophication shapes present methane cycling. Integrating sediment and water chemistry, stable carbon isotopes, and genetic sequencing, we reveal clear depth zoning of methane-producing microbes and frequent oxygen-using methane consumers even where oxygen is not detected; both rise with nitrate and phosphate. These sediment legacies influence future methane release.

We investigated the specific plant species that act as a source of secondary fatty alcohols (SFAs) in atmospheric aerosols and their emission processes. Our study at a cool-temperate forest site suggested that SFAs in aerosols originated from conifer leaf wax and their atmospheric emission amount is primarily controlled by conifer abundance and the phenology of leaves. Our findings provide insight into estimating the global atmospheric emission flux of primary biological aerosol particles.