Photosynthesis in Antarctic sea-ice diatoms [Elektronische Ressource] / vorgelegt von Thomas Mock

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Sujets

• Biologie

Informations

• Publié par: universitat_bremen
• Publié le: 01 janvier 2003
• Nombre de lectures: 34
• Langue: Deutsch
• Poids de l'ouvrage: 6 Mo

Extrait

Aus dem Alfred-Wegener-Institut
für Polar- und Meeresforschung Bremerhaven
______________________________________
Photosynthesis in Antarctic sea-ice diatoms
Dissertation zur Erlangung des Grades eines Doktors der Naturwissenschafften
-Dr. rer. nat.-
Aus dem Fachbereich 2 (Biologie/Chemie) der Universität Bremen
Vorgelegt von
Thomas Mock
Bremerhaven 20031. Gutachter:
Prof. Dr. V. Smetacek
(Alfred-Wegener-Institut für Polar- und Meeresforschung, Bremerhaven)
2. Gutachter:
Prof. Dr. G.O. Kirst
(Universität Bremen)
Tag des öffentlichen Kolloquiums: _____09.05.2003_____Eidesstattliche Erklärung
Gem. § 6(5) Nr. 1 – 3 PromoO
Ich erkläre, daß ich
1. die Arbeit ohne unerlaubte fremde Hilfe angefertigt habe,
2. keine anderen als die von mir angegebenen Quelllen und Hilfsmittel benutzt
habe und
3. die den benutzten Werke wörtlich oder inhaltlich entnommenen Stellen als
solche kenntlich gemacht habe.
Bremerhaven, 21.02.2003
Thomas MockIn memoriam Gerhard MockTABLE OF CONTENTS
1 Introduction ................................................................................................................ 1
2 Results...........................................................................................................................5
3 Publications................................................................................................................10
3.1 List of publications............................................................................................10
3.2 Erklärung über den von mir geleisteten Anteil an den Publikationen...............11
3.3 Publication 1......................................................................................................12
Mock T (2002) In situ primary production in young Antarctic sea ice.
Hydrobiologia 470:127-132
3.4 Publication 2......................................................................................................18
Mock T, Dieckmann GS, Haas C, Krell A, Tison JL, Belem AL,
Papadimitiou S, Thomas DN (2002) Micro-optodes in sea ice: a new
approach to investigate oxygen dynamics during sea ice formation.
Aquatic Microbial Ecology 29:297-306
3.5 Publication 3......................................................................................................28
Mock T, Kruse M, Dieckmann GS (2002) A new microcosm to investigate
oxygen dynamics at the sea-ice water interface.
Aquatic Microbial Ecology 30:197-205
3.6 Publication 4......................................................................................................37
Mock T, Kroon BMA (2002) Photosynthetic energy conversion under
extreme conditions - I: important role of lipids as structural modulators
and energy sink under N-limited growth in Antarctic sea ice diatoms.
Phytochemistry 61:41-51
3.7 Publication 5......................................................................................................48
Mock T, Kroon BMA (2002) Photosynthetic energy conversion under
extreme conditions - II: the significance of lipids under light limited
growth in Antarctic sea ice diatoms.
Phytochemistry 61:53-60
3.8 Publication 6......................................................................................................56
Mock T, Valentin K (2003) EST analysis of freezing tolerance in the
Antarctic diatom Fragilariopsis cylindrus: Detection of numerous cold
acclimation-related genes and a gene transfer event.
submitted
3.9 Publication 7......................................................................................................78
Mock T, Valentin K (2003) Molecular cold adaptation in polar diatoms -
requirement for low light at low temperatures.
submitted
4 Discussion..................................................................................................................89
.....................................................................................................................955 Summary
6 Zusammenfassung....................................................................................................96
7 References..................................................................................................................97
8 Acknowledgements................................................................................................1001 INTRODUCTION
Photosynthesis is the process by which
generally adapted to their habitat still
higher plants, algae and some bacteria
remained unresolved.
transform and store solar energy in the
form of energy-rich organic molecules.
The mechanisms of adaptation andThese compounds are in turn used as the
regulation of photosynthesis in Antarctic
energy source for growth and reproduction
sea-ice algae are under debate (e.g.
in these organisms. As such, virtually all
Palmisano et al. 1987, Bartsch 1989, Cota
life on the planet depends on
& Sullivan 1990, Kirst & Wiencke 1995,
photosynthetic energy conversion. Thus
Gleitz et al. 1995, Robinson et al. 1997,
each ecosystem on earth, which receives
Thomas & Dieckmann 2002). Only few in
solar irradiance in a sufficient dose, is
situ measurements have confirmed that sea
inhabited by photoautotrophic organisms.
ice algae still actively assimilate dissolved
The genetic diversity of aquatic
14inorganic carbon (H CO) at2 3photoautotrophs is extremely high (Medlin
temperatures as low as –15 °C, 1.5 µmol
et al. 1995), whereas the basic process of
-2 -1photons m s and a salinity of 150 PSU
photosynthetic energy conversion is highly
(e.g. Mock & Gradinger 1999)
conserved. Superimposed on the basic
Photosynthesis under such conditions
molecular mechanisms are variations in
requires special acclimation or even
light harvesting, electron transport and
adaptation including light harvesting,
carbon fixation (Falkowski & Raven
electron transport and carbon fixation, each
1995).
with different sensitivities to
environmental conditions and cellular
Antarctic sea ice represents one of the
controls.
largest and most unique ecosystems on
earth, inhabited predominantly by
The environmental conditions that have
psychrophilic diatoms (Bacillariophyceae).
been studied thus far include light intensity
Due to logistical and methodological
and spectral quality, temperature, salinity
constraints, this ecosystem also still is one
and nutrient depletion. Growth kinetics
of the most poorly investigated on earth.
(Bartsch 1989, Fiala & Oriol 1990, Aletsee
Consequently, how changes of
& Jahnke 1992), photosynthesis vs
environmental conditions influence
irradiance (PE) response curves have so far
photosynthesis and how these diatoms are
1been the most popular methods to study light limited growth (Falkowski 1980,
photoacclimation in sea ice algae Richardson et al. 1983, Dubinsky et al.
(Palmisano et al. 1987, Robinson et al. 1986).
1995, Glud et al. 2002). Derived
parameters included the light limited slope Carbon acquisition in ice algae has
received relatively little attention (Gleitz et( α, where photosynthesis is limited
al. 1995, Mitchell & Beardall 1996, Gleitzprimarily by light harvesting mechanisms),
et al. 1996), although dissolved CO [COthe maximum photosynthetic rate (P , 2 2m
(aq)] and O concentrations can differwhere enzymatic processes of carbon and 2
significantly from other aquaticnitrogen fixation limit photosynthesis) and
ecosystems. Dissolved CO and O presentthe photoadaption parameter (E, the 2 2k
in air-saturated sea water at the freezingquotient P / α). These parameters revealedm
point and 34 PSU (practical salinity units)that ice algae are good adapted to low light
are physically 1.5 times greater than in the(Cota 1985). The algae flourish under
same sea water at 15 °C. However,several meters of ice and snow at less than
dissolved CO and O concentrations are2 21 % of surface scalar irradiance (Eicken
influenced by photosynthetic active algae.1992). They already show severe
In semi-closed or closed systems such asphotoinhibition at moderate light levels
brine pockets dissolved CO can be rapidly2(Cota 1985). The low light adaptation is
exhausted due to carbon acquisition by iceaccomplished by an increase in α along
algae. The ability to utilise HCO and to3with an even larger reduction in P .(e.g.m
accumulate DIC (e.g. Kaplan & ReinholdRobinson et al. 1997). Accessory
1999, Thoms et al. 2001) and/or storephotosynthetic pigment concentrations
carbon in organic acids as observed in C4(e.g. fucoxanthin and chlorophyll c in
plants (e.g. Sage 2001, Hibberd & Quickdiatoms) are elevated relative to the main
2002) is likely more important in ice algaephotosynthetic pigment, chlorophyll a (chl
than in micro-algae from other marinea) (Boczar & Palmisano 1990). This
habitats (Gleitz et al. 1995, Gleitz et al.adaptation allows the algae to enhance
1996). In contrast dissolved oxygenlight harvesting at the wavelengths of light
concentrations my increase due topenetrating the ice and snow (Chl a is
accumulation of photosynthetic oxygenpoorly efficient in absorbing green light
under the ice cover (McMinn et al. 2000).(e.g. Falkowski & LaRoche 1991). The
Detoxification of molecular oxygennu