Petra Larissa Schoon Promotoren Prof

Impact of CO2 and pH on the distribution and stable carbon isotopic composition of microbial biomarker lipids Petra Larissa Schoon Promotoren Prof. dr. ir. S. Schouten, Utrecht University and Royal Netherlands Institute for Sea Research, The Netherlands Prof. dr. ir. J.S. Sinninghe Damsté, Utrecht University and Royal Netherlands Institute for Sea Research, The Netherlands Thesis committee Prof. dr. H. de Baar, Royal Netherlands Institute for Sea Research, The Netherlands Dr. H. Brinkhuis, Royal Netherlands Institute for Sea Research, The Netherlands Dr. J.W. de Leeuw, Royal Netherlands Institute for Sea Research, The Netherlands Prof. dr. T. Wagner, School of Civil Engineering and Geosciences, United Kingdom The research presented in this thesis was funded by the Darwin Center for Biogeosciences and the Royal Netherlands Institute for Sea Research (NIOZ). ISBN 978-94-6203-299-6 Cover design by Petra Schoon Printed by Wöhrmann Print Service, Zutphen Impact of CO2 and pH on the distribution and stable carbon isotopic composition of microbial biomarker lipids Invloed van CO2 en pH op de distributiepatronen en stabiele koolstofisotoopsamenstelling van microbiële biomarkerlipiden (met een samenvatting in het Nederlands) Proefschrift ter verkrijging van de graad van doctor aan de Universiteit Utrecht op gezag van de rector magnificus, prof. dr. G.J. van der Zwaan, ingevolge het besluit van het college voor promoties in het openbaar te verdedigen op woensdag 3 april 2013 des middags te 2.30 uur door Petra Larissa Schoon geboren op 5 september 1980 te Rotterdam Promotoren: Prof. dr. ir. S. Schouten Prof. dr. ir. J.S. Sinninghe Damsté “The presence of those seeking the truth is infinitely to be preferred to those who think they’ve found it.” From: The Monstrous Regiment – A Discworld Novel by Terry Pratchett Voor mijn ouders TABLE OF CONTENTS Chapter 1 9 General Introduction Part 1 Contemporary Systems Chapter 2 23 Stable carbon isotopic fractionation associated with photosynthesis in Phaeocystis antarctica and Proboscia alata is mainly controlled by variations in aqueous CO2 concentrations Petra L. Schoon, Astrid Hoogstraten, Jaap S. Sinninghe Damsté, and Stefan Schouten Chapter 3 35 The influence of lake water pH and alkalinity on the distribution of core and intact polar lipid branched glycerol dialkyl glycerol tetraethers in lakes Petra L. Schoon, Anna de Kluijver, Jack J. Middelburg, John A. Downing, Jaap S. Sinninghe Damsté, and Stefan Schouten Submitted to Organic Geochemistry Chapter 4 57 Environmental controls on the distribution of intact polar lipids in oligotrophic and eutrophic lakes Ellen Hopmans, Petra L. Schoon, Anna de Kluijver, Jack J. Middelburg, John A. Downing, Jaap S. Sinninghe Damsté, and Stefan Schouten Submitted to Limnology and Oceanography Part II Ancient high CO2 and low pH worlds: Eocene Hyperthermals Chapter 5 81 Extreme warming and environmental change of the North Sea Basin across the Palaeocene-Eocene boudary as revealed by biomarker lipids Petra L. Schoon, Claus Heilmann-Clausen, Bo Pagh Schultz, Jaap S. Sinninghe Damsté, and Stefan Schouten Submitted to Organic Geochemistry Chapter 6 99 Constraining the magnitude of Early Eocene global carbon isotope excursion using lipids of marine Thaumarchaeota Petra L. Schoon, Claus Heilmann-Clausen, Bo Pagh Schultz, Appy Sluijs, Jaap S. Sinninghe Damsté, and Stefan Schouten Submitted to Earth and Planetary Science Letters Chapter 7 119 Stable carbon isotope patterns of marine biomarker lipids in the Arctic Ocean during Eocene Thermal Maximum 2 Petra L. Schoon, Appy Sluijs, Jaap S. Sinninghe Damsté, and Stefan Schouten Published in: Paleoceanography 26: PA3215, 2011 References 143 Summary 172 Samenvatting 176 Acknowledgements / Dankwoord 182 Curriculum Vitæ 185 CHAPTER 1 General Introduction “Carbon dioxide, that is, the aerial form of carbon ...: this gas which constitutes the raw material of life, the permanent store upon which all that grows draws, and the ultimate destiny of all flesh, is not one of the principal components of air but rather a ridiculous remnant, an ‘impurity’, thirty times less abundant than argon, which nobody even notices. ... This, on the human scale, is ironic acrobatics, a juggler’s trick, an incomprehensible display of omnipotence- arrogance, since from this ever renewed impurity of the air we come, we animals and we plants, and we the human species, with ... our millenniums of history, our wars and shames, nobility and pride.” Fragment from: The Periodic Table by Primo Levi Chapter 1 1.1 OCEAN ACIDIFICATION: “THE OTHER CO2 PROBLEM” he ongoing emission of fossil fuels, in combination with deforestation, ce- T ment production and agricultural development, has led to an increase in the atmospheric carbon dioxide pressure (pCO2) since the industrial revolution, which encompasses the last ~250 years (IPCC 2007). From the background pre-industrial level of about 280 ppmv, pCO2 levels have increased rapidly and will most likely reach 400 ppmv in 2015 and will increase even further to 500-1000 ppmv at the end of this century (IPCC 2007). The main concern of this predicted rise in atmospheric CO2 is a global warming of ca. 0.1 °C per decade (IPCC 2007). Other re- lated climate responses likely to occur, are a reduction in Greenland and Antarctic ice sheet volumes, a global sea level rise, melting of the upper Arctic permafrost layer, high local variability in precipitation, enhanced strength of mid-latitude west- erly winds, and an intensification of tropical cyclone activityIPCC ( 2007). Nevertheless, the actual CO2 concentration could have been much higher, was it not that the world oceans act as a major sink of carbon dioxide. In fact, since the industrial revolution, about half of the emitted anthropogenic CO2 has been taken up by the oceans (Sabine et al., 2004), due to its high solubility in water. The addition of CO2 in water leads to an array of chemical reactions (Fig. 1.1), and a shift in ocean chemistry. That is, the balance between the concentrations of carbon diox- - 2- ide (CO2), bicarbonate (HCO3 ) and carbonate (CO3 ), which are the major carbon species that make up dissolved inorganic carbon (DIC). As illustrated in figure 1.1, dissolved CO2 dissociates in carbonic acid (H2CO3). In turn, this weak acid dissoci- - + ates almost immediately in HCO3 and a hydrogen ion (H ). Thus, it is this increase in the concentration of hydrogen ions, initiated by the absorption of atmospheric gaseous CO2 by surface ocean waters, that in the end results in a decrease of the ocean water pH (Zeebe et al., 2008; Feely et al., 2004; Cao et al., 2007), a process termed + 2- ocean acidification. Some of these excess H react with CO3 to form an additional - HCO3 ion (Fig. 1.1). This natural buffering mechanism of the ocean waters keeps the pH always slightly alkaline between 7.8 and 8.3. It also has moderated the actual magnitude of anthropogenic-induced ocean acidification. The average change in seawater pH in the world oceans for the period between 1900 to 1990 is approxi- mately 0.1 unit (Raven et al., 2005). This seems low, but, keeping in mind that pH is based on a log-scale, it still corresponds to a massive 30% increase in hydrogen ion concentration. When CO2 emissions unabatedly continue, a further decrease of ~0.6 pH units is expected for the coming centuries (Caldeira & Wickett, 2003; Orr et al., 2005; Zeebe et al., 2008). Due to the reduction in the carbonate saturation state of the oceans, the addition of anthropogenic carbon will also promote the dissolution of calcium carbonate (CaCO3) (Fig. 1.1), thereby enhancing the carbonate buffering capacity of the ocean. It has been suggested from modelling and experimental studies that this will negatively affect the calcification rate of certain calcifying marine microorganisms 10 General Introduction (Kleypas et al., 1999; Riebesell et al., 2000; Orr et al., 2005; Raven et al., 2005), and may cause major changes in ecosystem dynamics and biodiversity. Corals are believed to be especially vulnerable to changes in ocean chemistry, because of their arago- nite skeletons. This in contrast to organisms which make their tests out of calcite (e.g. foraminifera and coccolithophores), the more stable and therefore less soluble form of calcium carbonate. However, the response of most marine microorganisms on elevated aqueous CO2 conditions may not be that straightforward and have been shown to be highly dependent on morphological variations between species and environmental factors (Langer et al., 2006; Fabry et al., 2008; Iglesias-Rodriguez et al., 2008). A decrease in seawater pH level is also shown to effect non-calcifying organisms, although the exact impact is less clear. For instance, Beman et al. (2010) showed that ocean acidification may lead to a considerable decrease in nitrification rates, and thus changes the availability of nitrogen in the ocean. Important groups of photosynthetic phytoplankton, such as diatoms and dinoflagellates, but also bacteria, archaea and viruses that stand at the basis of the marine food chain, are key contributors to biogeochemical processes. A clear understanding of the impact of ocean acidification on these organisms is, therefore, of paramount importance. Figure 1.1| Seawater carbonate reactions. The uptake of atmospheric CO2 leads to an increase in hydrogen ion concentrations, and in turn, promotes the dissolution of calcium carbonates. 11 Chapter 1 1.2 PAST CARBON CYLCE PERTURBATIONS he current carbon cycle perturbation by human activity is not unique: the Tgeologic record documents several prolonged periods of elevated levels of atmospheric carbon dioxide and concomitant global warming, and are in these cases mainly induced by enhanced tectonic activity. However, the main difference between present-day and past carbon cycle perturbations is the time scale at which the forcing mechanisms operate (Zeebe et al., 2008; Zachos et al., 2010). Current rates of atmospheric carbon release is on average 9 Pg per year (Le Quéré et al., 2009), which is most likely higher than for any greenhouse period in the geological past (Hönisch et al., 2012).

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