Climate change scenarios predict that atmospheric CO2 concentrations will have doubled by the end of this century. Rising CO2 concentrations reduce the pH in lakes and oceans, and could affect the species composition of phytoplankton in these aquatic ecosystems. Phytoplankton species utilize CO2 for photosynthesis, accounting for almost 50% of the world?s carbon fixation. Yet, despite the global significance of these organisms, theory capable of predicting changes in phytoplankton species composition in response to rising CO2 is still in its infancy. Besides CO2, phytoplankton can use bicarbonate as inorganic carbon source. In this project we aim at a better understanding of competition for inorganic carbon between phytoplankton species. The major challenge is that competition for inorganic carbon seems conceptually and experimentally more complex than competition for other limiting resources. Uptake of inorganic carbon triggers a chain of chemical reactions, increasing the pH and shifting the relative availability of CO2 and bicarbonate. We will develop new competition models, which focus on dynamic changes in carbon chemistry and pH during the time course of competition. The model predictions will be tested in monoculture and competition experiments. These experiments will be carried out in advanced chemostats, with full control of CO2, temperature, light, and nutrient conditions. Furthermore, we will develop molecular and computational tools to study adaptive changes in carbon uptake strategies of different species during competition. This research will improve prediction of the impacts of rising CO2 concentrations on the primary production, pH, and species composition of aquatic ecosystems.

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Photosynthetic pigments are responsible for light harvesting, and therefore play a key role in the struggle for light in aquatic and terrestrial plant communities. Many but not all photosynthetic pigments are rich in nitrogen. The costs and benefits of nitrogen investments into different pigments are likely to depend on the environmental conditions. The key objective of this study is to understand how nitrogen and light limitation will modify strategic investments in different photosynthetic pigments, and how this will affect plant community structure and diversity. As a study system I will use phytoplankton species because their habitats vary widely in nitrogen availability and underwater light spectrum, which is exploited by photosynthetic pigments in a variety of colours and nitrogen requirements. I will develop a mathematical model that describes the dynamics of phytoplankton competition in the light spectrum, with investments in different pigments depending upon nutrient and light availability. The model will be calibrated on monoculture data obtained from chemostat experiments. Next, the model predictions will be tested in competition experiments in chemostats and plankton towers. Finally, the model will be used to predict the global distribution of the major taxonomic groups of marine phytoplankton based on global data of ocean colour and nitrogen concentration. These predictions will be tested using hyperspectral remote sensing to detect distribution patterns of phytoplankton groups with different optical properties. This multi-faceted and mechanistic approach will contribute to a better understanding of different allocation strategies in phototrophic organisms, and of the interactive effects of nitrogen and light limitation on phytoplankton communities.

As more than 80% of the chemical products produced in the world are monomers (and their precursors) and polymers, materials such as plastics will play a central role in the transition to a sustainable chemical industry. Today, about 325 million tons of plastics (and about 400 million tons of the monomers from which they are made) are annually produced in the world. As plastic volumes have been growing annually by 4-6% per year during the last decades and as this growth is expected to continue to at least 2050, the plastic production volumes are expected to triple in the period 2016-2050 to an astonishing 1.1-1.2 billion tons of plastics per year in 2050. This means that next to replacing the current 325 million tons of plastics, there is a huge opportunity for bio-based and CO2-based, but low cost, high performance polymers that must be identified NOW to enable this transition. Applicants have identified a very interesting polyester compositional space based on the learning of PET and PEF, both high performing materials (Tg’s of 74°C and 86°C). They are high performing (superior thermal, mechanical and barrier properties) due to their composition: a rigid (cyclic) di-acid (terephthalic acid or TPA and 2,5-furan dicarboxylic acid or FDCA) respectively, coupled by the shortest possible aliphatic diol (mono ethylene glycol or MEG). In this project we will “invert” this approach by using a rigid diol, coupled to the shortest aliphatic di-acid, oxalic acid. Polyesters from oxalic acid and rigid diols can have Tgs above 150°C! As for all high volume applications this Tg is too high, fine-tuning by adding a linear diol or diacid as a third monomer allows targeting of many properties. This project will deal with synthesizing and evaluating a new series of polyesters. Applicants have found that Tg reduction is almost linear with % replacement of isosorbide by aliphatic diol such as MEG, PG, BDO, PDO, HDO and with % oxalic acid replacement by higher aliphatic di-acids such as succinic acid or adipic acid (= PhD-1 project). This PhD will explore this compositional parameter space and will develop scalable recipes, including catalysts for the production of these polymers. All of these terpolymers (polymers made from 3 monomers) have not been described before. The most likely reason for this is that oxalic acid decomposes above 160C, the polymerization conditions needed for producing polymers in the melt. Therefore it has not been investigated as a monomer for polyesters. However, applicants have identified certain di-esters that can overcome this monomer instability. PhD-1 will also evaluate which esters are the most promising precursors for oxalic acid polyester synthesis. In this project PhD-2 will use the products and recipes developed by PhD-1 to select compositions that are specifically of interest for LEGO. This PhD will make kilogram scale polymers using Avantium’s 2 liter polyester synthesis equipment and will focus his/her investigations on injection molding, crystallization behavior and ageing. PhD-3 will use the products and recipes developed by PhD-1 to select compositions that are specifically of interest for AVANTIUM. This PhD will make kilogram scale polymers using Avantium’s 2 liter polyester synthesis equipment and will focus his/her investigations on polymers that are particularly interesting for bottles and films and for fiber applications. Bio-degradability assessment will play an important role in identifying high potential targets. For most applications bio-degradability (as fast or faster than cellulose) is undesired but for new polymers bio-degradation should be much faster than for PET (500 years). A collaboration with Prof Peter Schoenmakers of Analytical Chemistry (UVA) is part of this project for polymer characterization. PhD-4 will develop new bio-degradation assessment equipment as today the experiments are too expensive to perform the 100’s of experiments that will be needed in this project to map the bio-degradability of the complete compositional parameter space for these co-polyesters. This PhD will study biodegradability, using the series of polymers produced by PhD’s 1-3 to systematically map the structure-property relationships and the external factors such as the environmental matrix and temperature and light, which are relevant for bio-degradation. PhD-5 will work in the department of Psychology and will provide insight into what causes consumers to experience a sense of urgency to combat climate change and 2) Investigate how consumer behavior can be modified to make the translation of this sense of urgency into behavior most likely. PhD-5 will work closely together with LEGO and Avantium and other brand-owners in the Avantium network.

Due to human activities the oceans are currently warming and acidifying. Consequences for the photosynthetic microbes that contribute 50% of global carbon fixation will affect entire ocean food webs. This project addresses a critical knowledge gap concerning these marine microbes: the present and future role of mixotrophs in the ocean. Mixotrophs cannot only photosynthesize, but also feed on other microbes. Thus they fix inorganic CO2 to synthesize their own biomass in a ‘plant-like’ manner, but also release CO2 back into the environment through feeding on other organisms in an ‘animal-like’ manner. Because the relative importance of these two processes depends on environmental conditions, their net impact on carbon cycling can take opposite directions. Quantifying carbon transformations by mixotrophs is technically challenging. Recent estimates suggest they contribute up to 30% to carbon fixation, and 60% to the total consumption of other microbes in the nutrient-poor, subtropical North Atlantic, representative of the largest biome on our planet. Shifts in future ecosystem functions of mixotrophs might thus have dramatic consequences for global carbon cycling. This project aims at providing a predictive understanding of how mixotrophs will respond to ocean acidification and warming. Novel stable-isotope probing techniques will be applied on two oceanographic cruises to provide the first direct measurements of resource acquisition rates via both plant-like and animal-like nutrition by mixotrophs. This will allow quantification of the impacts of ocean warming and acidification on evolutionarily diverse, uncultured mixotrophs within their natural communities. Furthermore, this project will apply in-depth physiological experiments using closely related mixotrophs with recently described contrasting physiologies to resolve how their responses depend on physiological strategies and underlying transcriptional regulation. Thus, by combining oceanographic measurements with physiological experiments, this project will provide the mechanistic basis to predict how these enigmatic mixotrophs will modify carbon cycling in our future oceans.