Bacterial communities in the soils of the Arctic region decompose soil organic matter to CO₂ from a large carbon pool. The amount of CO₂ released is likely to increase under future climate conditions. Here, we study how temperature sensitive the growth of soil bacterial communties is for 12 sampling sites in the sub to high Arctic. We show that the optimal growth temperature varies between 23 and 34 °C and is influenced by the summer temperature.

CO₂ can be stored in the ocean via increasing alkalinity of ocean water. Alkalinity can be created via dissolution of alkaline materials, like limestone or soda. Presented research studies boundaries for increasing alkalinity in seawater. The best way to increase alkalinity was found using an equilibrated solution, for example as produced from reactors. Adding particles for dissolution into seawater on the other hand produces the risk of losing alkalinity and degassing of CO₂ to the atmosphere.

Increased spruce bark beetle outbreaks were recently seen in Sweden. When Norway spruce trees are attacked, they increase their production of VOCs, attempting to kill the beetles. We provide new insights into how the Norway spruce act when infested and found the emitted volatiles to increase up to 700 times and saw a change in compound blend. We estimate that the 2020 bark beetle outbreak in Sweden could have increased the total monoterpene emissions from the forest by more than 10 %.

We explored carbon cycling in soils in three climate zones in Chile down to a depth of 6 m, using carbon isotopes. Our results show that microbial activity several meters below the soil surface is mostly fueled by recently fixed carbon and that strong decomposition of soil organic matter only occurs in the upper decimeters of the soils. The study shows that different layers of the critical zone are tightly connected and that processes in the deep soil depend on recently fixed carbon.

The deep waters of the lower St Lawrence Estuary and gulf have, in the last decades, experienced a strong decline in their oxygen concentration. Below 65 µmol L^-1, the waters are said to be hypoxic, with dire consequences for marine life. We show that the extent of the hypoxic zone shows a seven-fold increase in the last 20 years, reaching 9400 km² in 2021. After a stable period at ~ 65 µmol L⁻¹ from 1984 to 2019, the oxygen level also suddenly decreased to ~ 35 µmol L^-1 in 2020.

The oceans are both sources and sinks for trace gases important for atmospheric chemistry and marine ecology. Here, we quantified selected trace gases (including the biological metabolites dissolved dimethyl sulfide, methanethiol and isoprene) along a 2500 km transect from the North Atlantic to the Arctic Ocean. In the context of phytoplankton and bacterial communities, our study suggests that methanethiol (rarely measured before) might substantially influence ocean–atmosphere cycling.

Gelatinous zooplankton play a key role in the ocean carbon cycle. In particular, pelagic tunicates, which feed on a wide size range of prey, produce rapidly sinking detritus. Thus, they efficiently transfer carbon from the surface to the depths. Consequently, we added these organisms to a marine biogeochemical model (PISCES-v2) and evaluated their impact on the global carbon cycle. We found that they contribute significantly to carbon export and that this contribution increases with depth.

In this study, we introduce a new method for modeling the exchange of carbon between the atmosphere and a study site located in a boreal forest in southern Finland. Our method yields more accurate results than previous approaches in this context. Accurately estimating carbon exchange is crucial for gaining a better understanding of the role of forests in regulating atmospheric carbon and addressing climate change.

Mangroves are blue carbon ecosystems known to store large amounts of organic carbon in the sediments. This study is a first attempt to apply a chronosequence (or space-for-time substitution) approach to evaluate the distribution and accumulation rate of carbon in a 30-year-old (maximum age) restored mangrove forest. Using this approach, the contribution of restored or planted mangroves to sedimentary organic carbon presents an increasing pattern with mangrove age.