Inorganic carbon acquisition and isotope fractionation of marine phytoplankton with emphasis on the coccolithophore Emiliania huxleyi [Elektronische Ressource] / vorgelegt von Björn Rost

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• Biologie

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• Publié par: universitat_bremen
• Publié le: 01 janvier 2004
• Nombre de lectures: 25
• Langue: English
• Poids de l'ouvrage: 2 Mo

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Inorganic carbon acquisition and isotope fractionation
of marine phytoplankton with emphasis on the
coccolithophore Emiliania huxleyi




Dissertation
zur Erlangung des akademischen Grades eines
Doktors der Naturwissenschaften
- Dr. rer. nat. -
am Fachbereich 2 (Biologie/Chemie)
der Universität Bremen





vorgelegt von
Björn Rost

Bremen, April 2003













Björn Rost

Alfred-Wegener-Institut für Polar- und Meeresforschung
Projektgruppe Kohlenstoffflüsse
Am Handelshafen 12
D-27570 Bremerhaven
Germany

[e-mail]


Das vorliegende Dokument ist die inhaltlich unveränderte Fassung einer Dissertation, die im
April 2003 dem Fachbereich 2 (Biologie/Chemie) der Universität Bremen vorgelegt wurde.
TABLE OF CONTENTS
1 GENERAL INTRODUCTION................................................................................. 1
1.1 PHYTOPLANKTON AND THE GLOBAL CARBON CYCLE.................................................... 1
1.2 SEAWATER CARBONATE SYSTEM .................................................................................. 4
1.3 CARBON ISOTOPE FRACTIONATION ............................................................................... 6
1.4 PHOTOSYNTHESIS AND CARBON ACQUISITION............................................................. 11
1.5 OUTLINE OF THE THESIS.............................................................................................. 16
1.6 REFERENCES ............................................................................................................... 18
2 PUBLICATIONS..................................................................................................... 27
2.1 LIST OF PUBLICATIONS................................................................................................ 27
2.2 DECLARATION ON THE CONTRIBUTION OF EACH PUBLICATION ................................... 28
I REDUCED CALCIFICATION OF MARINE PLANKTON IN RESPONSE TO INCREASED
ATMOSPHERIC CO 29 2
II LIGHT-DEPENDENT CARBON ISOTOPE FRACTIONATION IN THE COCCOLITHOPHORID
EMILIANIA HUXLEYI...................................................................................................... 33
III CARBON ACQUISITION OF BLOOM-FORMING MARINE PHYTOPLANKTON...................... 43
IV CARBON ACQUISITION IN MARINE PHYTOPLANKTON: EFFECT OF THE PHOTOPERIODIC
LENGTH....................................................................................................................... 57
V COCCOLITHOPHORES AND THE BIOLOGICAL PUMP: RESPONSES TO ENVIRONMENTAL
CHANGES .................................................................................................................... 81
3 GENERAL DISCUSSION .................................................................................... 109
3.1 CARBON ACQUISITION AND PHYTOPLANKTON ECOLOGY .......................................... 109
3.2 CSITION AND BIOGEOCHEMISTRY........................................................ 113
3.3 CARBON ACQUISITION AND ISOTOPE FRACTIONATION............................................... 115
3.4 PERSPECTIVES FOR FUTURE RESEARCH ..................................................................... 118
3.5 REFERENCES ............................................................................................................. 121
4 SUMMARY ............................................................................................................ 127
5 ZUSAMMENFASSUNG....................................................................................... 131
6 DANKSAGUNG..................................................................................................... 135 GENERAL INTRODUCTION 1
1 GENERAL INTRODUCTION
1.1 Phytoplankton and the global carbon cycle
Carbon dioxide is the most important greenhouse gas after water vapor in the
atmosphere and contributes significantly to the warming of our planet. Variations in
global temperatures as they occur between glacial and interglacial times have thus been
partly ascribed to the variability in atmospheric CO levels (Barnola et al. 1987, Petit et al. 2
1999). The ocean represents the largest reservoir of exchangeable carbon, storing about 50
times as much carbon as the atmosphere. Understanding the dynamics in atmospheric CO 2
levels requires the knowledge of processes that alter the CO storage capacity of the 2
ocean.
The uptake of atmospheric CO by the ocean is mediated by so-called carbon pumps. 2
These pumps generally describe processes that lead to the depletion of dissolved inorganic
carbon (DIC) in the surface ocean relative to the deep ocean. Based on whether
physicochemical or biological processes are responsible for the vertical carbon flux, Volk
and Hoffert (1985) defined a physical and a biological carbon pump. The physical pump
describes the vertical carbon flux resulting from differences in CO solubility of warm and 2
cold water. As warm surface water moves from low to high latitudes, subsequent cooling
results in an increasing solubility for CO . Owing to deep-water formation in high 2
latitudes, this cold DIC-rich water is then transported to the deep ocean. The biological
pump is driven by the fixation of DIC into biogenic compounds in the surface ocean and
subsequent sinking to the deep ocean where the material is remineralized or dissolved.
Approximately 75% of the vertical DIC gradient is thought to be caused by biological
activity (Sarmiento et al. 1995). If all marine biogenic production was ceased instantly,
atmospheric pCO would nearly double (Maier-Reimer et al. 1996). This model’s result 2
underlines the central role of the biological pump in the CO uptake capacity of the ocean. 2
Depending on whether organic or inorganic particles are formed, two types of
biological pumps can be distinguished, each having different effects on the ocean-
atmosphere CO exchange (Fig. 1). The organic carbon pump, also called soft-tissue 2
pump, is driven by the photosynthetic carbon fixation of phytoplankton, causing a draw
down of CO in the surface ocean. Particulate organic carbon (POC) sinks out of the 2
photic zone and is subsequently remineralized on its way to the deep ocean, thereby 2 GENERAL INTRODUCTION
causing high DIC concentrations in intermediate waters. Less than 1% of POC reaches the
deep-sea floor and is buried in the sediments for geological timescales. The carbonate
pump, also termed carbonate counter pump, is driven by the biogenic formation of CaCO 3
skeletons. Due to the consumption of calcium and carbonate ions during calcification,
alkalinity in ambient seawater is reduced, causing a shift in the carbonate system towards
higher pCO . In deeper waters, where the ocean gets under-saturated with respect to 2
CaCO due to the pressure-dependent increase in solubility, calcareous shells dissolve and 3
release alkalinity. In summary, the formation of particulate inorganic carbon (PIC) in
surface waters represents a potential source of CO , which counteracts the effect of POC 2
production. The relative importance of the two biological carbon pumps, represented by
the so-called rain ratio (the ratio of particulate inorganic to organic carbon in exported
biogenic matter), to a large extent determines the flux of CO between the surface ocean 2
and the overlying atmosphere. In the present ocean, about four times as much carbon is
transported by the organic carbon pump than by the carbonate pump (Broecker and Peng
1982, Tsunogai and Noriki 1991).
ORGANIC CARBON PUMP CARBONATE PUMP
ATMOSPHERE CO CO CO CO2 2 2 2
CaCO ProductionPhotosynthesis, 3
SURFACE
Alk. + DIC consumptionDIC consumptionOCEAN
POC Flux CaCO Flux3
Remineralization CaCO dissolution, 3
DEEP SEA
DIC release Alkalinity release
SEDIMENT

Fig. 1: Schematic diagram of the biological carbon pumps (modified after Heinze et al.
1991): Photosynthetic production of POC in the surface layer and its subsequent transport
to depth generates a CO sink in the ocean. In contrast, CaCO production and its transport 2 3
to depth release CO in the surface layer. As the counterpart of POC and CaCO downward 2 3
flux, DIC and Alkalinity are transported from deeper layers to the surface by upwelling
and mixing.
Upwelling
UpwellingGENERAL INTRODUCTION 3
Over geological timescales earth’s climate has undergone major changes, influencing
the structure and productivity of ecosystems and the proliferation or disappearance of
organisms. As outlined above, biological activity also influences the climate by driving
many of the global elemental cycles. These feedback-effects may mitigate, amplify or
contribute, as suggested by the Gaia hypothesis (Lovelock 1979), to stabilize the climate.
We are currently observing an exceptional increase in atmospheric CO caused by human-2
induced activities such as fossil fuel burning and changes in land use. The invasion of
‘anthropogenic’ CO into the ocean has already caused changes in the carbonate chemistry 2
since the year 1800. By the end of this century, the expected increase in the atmospheric
CO will cause surface water CO concentratio