Recent  

We present a study linking rain, meteorology, and mountain lake phytoplankton dynamics on the base of a case study at Aydat (France) in September 2020. The air mass origin mainly influences the rain nutrient composition, which depends on the type of rain, convective or stratiform. Our results also highlighted a non-negligible presence of photosynthetic cells in rainwater. The impact of the atmospheric forcing on the lake could play a key role in phytoplankton dynamics in the temperate zone.

Peatland rewetting is known to reduce dissolved nutrients and greenhouse gases, however, short-term nutrient leaching and high CH₄ emissions shortly after rewetting are likely to occur. We investigated the rewetting of a coastal peatland with brackish water and its effects on nutrient release and greenhouse gas fluxes. Nutrient concentrations were higher in the peatland than in the adjacent bay, leading to an export. CH₄ emissions did not increase, which is in contrast to freshwater rewetting.

Soil organic carbon (SOC) that is transferred to the ocean by rivers forms a long-term sink of atmospheric CO₂ upon burial on the ocean floor. We here test if certain bacterial membrane lipids can be used to trace SOC through the monsoon-fed Godavari River basin in India. We find that these lipids trace the mobilisation and transport of SOC in the wet season, but that these lipids are not transferred far into the sea. This suggests that the burial of SOC on the sea floor is limited here.

In this study we provided a synthesis of three influential methods to quantify afforestation impact on surface temperature. Results showed that actual effect following afforestation was highly dependent on intensity of afforestation. When full afforestation is assumed, actual effect approaches potential effect. Therefore, we provided evidence that these different methods could be reconciled. And actual effect has a direct policy relevance in evaluating the climate effects of afforestation.

This work focused on the greenhouse gas emissions from alpine peatlands in response to the interactive effects of altered water table levels and nitrogen deposition. Across the two-year mesocosm experiment, N deposition showed non-linear effects on CH₄ emissions and linear effects on N₂O emissions, dependent on the water table levels. Our results implied that the projected doubling N deposition by 2050 could potentially increase emissions of methane and nitrous oxide in alpine peatlands.

Methane is a climate-relevant greenhouse gas which is emitted to the atmosphere from coastal areas such as the Baltic Sea. We measured the methane concentration in the water column of the western Kiel Bight. Methane concentrations were higher in September than in June. We found no relationship between the 2018 European Heatwave and methane concentrations. Our results show that the methane distribution in the water column is strongly affected by temporal and spatial variabilities.

Aquatic plants produce a large amount of organic matter through photosynthesis that, following seasonal decay or storms, is deposited on the seafloor. In this study, we show that plant detritus can trigger low oxygen conditions (hypoxia) in shallow coastal waters, making conditions challenging for most marine animals. We propose that the occurrence of hypoxia may be underestimated because measurements typically do not consider the region closest to the seafloor, where detritus accumulates.

This study presents the first observation of water quality changes to detect water quality degradation at Sarawak, Borneo, coastal systems using remote sensing technologies. While our findings demonstrate that the southwest coast of Sarawak is within local water quality standards, historical patterns of water quality degradation that were detected can help to alert local authorities to enhance management and monitoring strategies of coastal waters in this region.

Intensifying wildfires are increasing pyrogenic organic matter (PyOM) production and its impact on water quality. Recent work indicates that PyOM may have 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.

The effect of environmental conditions on the degree of calcification of marine phytoplankton remains unclear. This study implements a new microscopic approach to quantify the calcification of ancient coccolithophores, using North Atlantic sediments. Results show significant differences in thickness and shape factor of coccoliths for samples with minimum dissolution, providing the first evaluation of phytoplankton physiology adaptation to million-year scale variable environmental conditions.

Long-term ecological observations are key to assess, understand and predict impacts of environmental change on biotas. We present a multidisciplinary framework for such largely lacking investigations in the East Antarctic Southern Ocean, combined with case studies, experimental and modelling work. As climate change is still minor here but is projected to start soon, the timely implementation of this framework provides the unique opportunity to document its ecological impacts from the very onset.

The formation of ice is an important process in Earth’s atmosphere, biosphere and cryosphere, in particular in polar regions. Our research focus was on the influence of the sea ice diatom Fragilariopsis cylindrus and of molecules produced by it upon heterogenous ice nucleation. For that purpose, we studied the freezing of tiny droplets containing diatoms in a microfluidic device. Together with previous studies, our results suggest a common freezing behaviour of various sea ice diatoms.

We focus on the exchange of key nutrients for algae production between the Arctic and Atlantic oceans through the Fram Strait. We show that the export of dissolved silicon here is controlled by availability of nitrate which is, in turn, influenced by denitrification on Arctic shelves. We suggest that any future changes in the river inputs of silica and changes in denitrification due to climate change will impact the amount of silicon exported, with impacts to Atlantic productivity and ecology.

The impact of tropical cyclones on Asian forest was assessed by starting the analysis from the observed storm tracks rather than the observed damage. We demonstrate here that a larger proportion of tropical cyclones making landfall in East Asia’s mid latitudes result in increased leaf growth two months later. The finding of a common increase in forest growth following the passage of tropical cyclones is novel and calls for refining the present-day vision of cyclones as agents of destruction.

In this work we present an alternative machine learning approach to model the exchange of carbon between the atmosphere and the study site, located in a boreal forest in Southern Finland. The suggested method produces more accurate results than another which has been widely used previously in this context. Accurate estimations of the exchange of carbon are needed for better understanding of the role of forests in regulating atmospheric carbon and climate change.

Since phytoplankton (small, drifting photosynthetic organisms) drift with ocean currents, biomass accumulation rates should be evaluated in a Lagrangian (observer moves with a fluid parcel) as opposed to Eulerian (observer is stationary) framework. Here we use profiling floats and surface drifters combined with satellite data to analyze time and length scales of chlorophyll concentrations (a proxy for biomass) and of velocity to quantify how phytoplankton variability is related to water motion.

Trace gas air-sea exchange exerts an important control on air quality and climate, especially in the Southern Ocean (SO). Almost all of the measurements there are skewed to summer, but it is essential to expand our measurement database over greater temporal and spatial scales. Therefore, we report measured concentrations of dimethylsulphide (DMS, and related sulphur compounds) and isoprene in the Atlantic sector of the SO. The observations of isoprene are the first in the winter in the SO.

In this study, we present observations of lateral and vertical carbon fluxes from a permafrost-affected study site in the Russian Arctic. From this dataset we estimate the net ecosystem carbon balance for this study site. We show that lateral carbon export has a low impact on the net ecosystem carbon balance during the complete study period (3 months). Nevertheless, our results also show that lateral carbon export can exceed vertical carbon uptake at the beginning of the growing season.

The Neodymium (Nd) is one of the most useful tracers to fingerprint water mass provenance. However, the use of Nd is hampered by the lack of adequate quantification of the external sources. Here, we present the first simulation of dissolved Nd concentration and Nd isotopic composition in the Mediterranean Sea using a high-resolution model. We aims to better understand how the various external sources affect the Nd cycle, and particularly assess how it is impacted by atmospheric inputs.

With regard to global warming, an understanding of past temperature changes is becoming increasingly important. Branched glycerol dialkyl glycerol tetraethers (brGDGTs) are membrane lipids used globally to reconstruct lake water temperatures. In the Bale Mountain lakes, we find a unique composition of brGDGT isomers. We present a modified local calibration and a new high altitude temperature reconstruction from the Horn of Africa spanning the last 12500 years.

Thermal stratification in rivers has increased, often with negative ecological effects. We implemented vertical water sampling both seasonally and diurnally and then calculated three stratification indices in the Nakdong River after intensive river channel modification. The results suggest that the river has summer stratification, which is involved in amplifying cyanobacterial bloom intensity.

Tidal salt marshes soils emit greenhouse gases, as well as sulfur-based gases, which play roles in global climate, but are not well studied since they are difficult to measure in wet soils. We found that traditional methods of measuring these gases worked well for carbon dioxide, but less so for methane, nitrous oxide, carbon disulfide, and dimethylsulfide. The unpredictability of these gases complicates scientists’ ability to accurate calculate gas budgets for scientific and policy purposes.

We generated high-resolution records of carbonate accumulation rate from Miocene to Quaternary in the tropical Atlantic Ocean to characterise the variability in pelagic carbonate production during warm climate. It follows orbital cycles, responding to local changes in tropical conditions as well as to long-term shifts in climate and ocean chemistry. These changes were sufficiently large to play a role in the carbon cycle and global climate evolution.

Drought legacies on ecosystem carbon fluxes are challenging to detect in observation. We developed an approach to quantify drought legacies on gross primary productivity (GPP) using eddy-covariance (EC) data. To the best of our knowledge, this is the first time drought legacies on ecosystem carbon fluxes in observation are found using EC data. The GPP reduction due to drought legacy effects is of comparable magnitude to the concurrent effects, which confirms the importance of legacy effects.

Soils will likely get warmer in the future and this can increase the release of carbon dioxide (CO₂) into the atmosphere. As microbes can take up soil CO₂ and prevent further escape into the atmosphere, this study compares the rate of uptake and release of CO₂ at two different temperatures. With warming, the rate of CO₂ uptake increases less than the rate of release, indicating that the capacity to modulate soil CO₂ release into the atmosphere will decrease under future warming.

Quantifying the feedback from the decomposition of thawing permafrost soils is crucial to establish adequate climate warming mitigation scenarios. Past efforts have focused on abiotic (chemistry, moisture, temperature) and to some extent microbial drivers of decomposition, but not biotic drivers such as soil fauna. We added soil fauna (collembola Folsomia candida) to permafrost, which did not affect bacterial communities, but increased CO₂ production (+12 %) which we suggest is due to priming.