Effects of community composition and global change on the functioning of experimental marine phytoplankton communities
Humans are altering the composition of biological communities through a variety of activities at all scales, from local to global. These changes in components of the Earth's biodiversity cause concern for ethical and aesthetic reasons, but they also have a streng potential to alter ecosystem pr...
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| Format: | Thesis |
| Language: | English |
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2013
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| Online Access: | https://oceanrep.geomar.de/id/eprint/22631/ https://oceanrep.geomar.de/id/eprint/22631/1/Diss.%202013%20Eggers,SL.pdf |
| Summary: | Humans are altering the composition of biological communities through a variety of activities at all scales, from local to global. These changes in components of the Earth's biodiversity cause concern for ethical and aesthetic reasons, but they also have a streng potential to alter ecosystem properties and the goods and services they provide to humanity. Since the industrial revolution, atmospheric carbon dioxide (CO2) increased from 280 to 380 μatm and is expected to further increase to 700 μatm by the year 2100. Ocean acidification is the consequence of increasing atmospheric CO2, which dissolves in seawater and subsequently increases seawater acidity and decreases carbonate ion concentration. Changes in carbonate chemistry can act both as fertilizer in case CO2 is a limiting resource and as stressor, particularly for calcifying organisms. Ocean acidification represents a pervasive environmental change that is predicted to affect a wide range of species, yet our understanding of the emergent ecosystem impacts is very limited. Two most challenging questions largely remain uncertain. Firstly, how much of the expected change in community functioning due to elevated CO2 is owing to either changes in the physiology of individual species or in the relative abundance of species or is there a hint towards evolutionary adaptation? Secondly, how da effects of community composition on ecosystem functioning compare to direct effects of ocean acidification? In chapter 1, I tested whether varying initial dominance scenarios lead to different competitive outcomes and subsequently translate into altered community functioning. I used experimental communities consisting of four naturally co-occuring coccolithophore species and manipulated initial community structure by creating five different dominance scenarios: (1) all species contributing evenly to initial biomass, and (2-5) one of each species contributing 4x that of the remaining three species to total initial biomass. I was able to show that priority effects in the ... |
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