Trichodesmium is a keystone genus of marine cyanobacteria that is estimated to supply nearly half of the ocean’s fixed nitrogen, fuelling primary productivity and the cycling of carbon and nitrogen in the ocean. In our study we characterize Trichodesmium ecology across the western tropical South Pacific using gene and genome sequencing and geochemistry. We detected genes for phosphorus reduction, providing a mechanism for the noted importance of this organism in the ocean's phosphorus cycle.

Using satellite reflectance measurements and a machine learning algorithm, we generated a new solar-induced chlorophyll fluorescence (SIF) dataset that is closely linked to plant photosynthesis. This new dataset has higher spatial and temporal resolutions, and lower uncertainty compared to the existing satellite retrievals. We also demonstrated its application in monitoring drought and improving the understanding of the SIF–photosynthesis relationship.

The computer models we use to understand and forecast the ecosystem changes have multiple components that determine their outcomes. Due to our limited observation capacities, these components bear uncertainties that in return affect our predictions. While there are techniques for reducing these uncertainties, they are not applicable to every model due to computational and statistical barriers. This research presents a method that lowers those barriers and allows us to improve model predictions.

We developed a sensitive method to analyze the lignin composition of organic traces contained in speleothems. Lignin is a main constituent of woody plants and its composition contains information about the type of vegetation. This method offers new possibilities to reconstruct the vegetation of past millennia since it combines the advantages of lignin analysis as a highly specific vegetation biomarker with the benefits of speleothems as unique terrestrial climate archives.

Our paper provides an intensive overview of the artificial ocean iron fertilization (aOIF) experiments conducted over the last 25 years to test Martin’s hypothesis, discusses aOIF-related important unanswered open questions, suggests considerations for the design of future aOIF experiments to maximize their effectiveness, and introduces design guidelines for a future Korean Iron Fertilization Experiment in the Southern Ocean.

To determine the variability between independent measurements of dissolved methane and nitrous oxide, seawater samples were analyzed by multiple laboratories. The results revealed the influences of the different parts of the analytical process, from the initial sample collection to the calculation of the final concentrations. Recommendations are made to improve dissolved methane and nitrous oxide measurements to help preclude future analytical discrepancies between laboratories.

Primary productivity is an important factor in the functioning and structuring of the coastal ecosystem. Thus, two sediment cores from the Skagerrak (North Sea) were investigated in order to obtain a comprehensive picture of primary productivity changes during the last millennium and identify associated forcing factors (e.g. anthropogenic, climate). The cores were dated and analysed for palaeoproductivity proxies and palaeothermometers.

Carbon fixed by plants and phytoplankton through photosynthesis is ultimately stored in soils and sediments or released to the atmosphere during decomposition of dead biomass. Carbon-use efficiency is a useful metric to quantify the fate of carbon – higher efficiency means higher storage and lower release to the atmosphere. Here we summarize many definitions of carbon-use efficiency and study how this metric changes from organisms to ecosystems and from terrestrial to aquatic environments.

We tried to identify the microbes which biosynthesize a class of lipids widespread in seawater, the long chain alkyl diols (LCDs). We could not find any microorganism likely involved in the production of LCDs. The amounts of LCDs found are too high to be produced by living organisms and are likely to be part of the refractory organic matter persisting for long periods in the water column.

We apply a multivariate model evaluation to the relationship between climate, vegetation and fire in the tropics using the JSBACH land surface model and two remote-sensing data sets, with the aim to identify the potential for model improvement. The overestimation of tree cover for low precipitation and a very strong relationship between tree cover and burned area indicates opportunities in the improvement of drought effects and the impact of fire on tree cover or the adaptation of trees to fire.