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  • 1
    ISSN: 1365-2486
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Energy, Environment Protection, Nuclear Power Engineering , Geography
    Notes: Ecosystem processes are important determinants of the biogeochemistry of the ocean, and they can be profoundly affected by changes in climate. Ocean models currently express ecosystem processes through empirically derived parameterizations that tightly link key geochemical tracers to ocean physics. The explicit inclusion of ecosystem processes in models will permit ecological changes to be taken into account, and will allow us to address several important questions, including the causes of observed glacial–interglacial changes in atmospheric trace gases and aerosols, and how the oceanic uptake of CO2 is likely to change in the future. There is an urgent need to assess our mechanistic understanding of the environmental factors that exert control over marine ecosystems, and to represent their natural complexity based on theoretical understanding. We present a prototype design for a Dynamic Green Ocean Model (DGOM) based on the identification of (a) key plankton functional types that need to be simulated explicitly to capture important biogeochemical processes in the ocean; (b) key processes controlling the growth and mortality of these functional types and hence their interactions; and (c) sources of information necessary to parameterize each of these processes within a modeling framework. We also develop a strategy for model evaluation, based on simulation of both past and present mean state and variability, and identify potential sources of validation data for each. Finally, we present a DGOM-based strategy for addressing key questions in ocean biogeochemistry. This paper thus presents ongoing work in ocean biogeochemical modeling, which, it is hoped will motivate international collaborations to improve our understanding of the role of the ocean in the climate system.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    [s.l.] : Macmillan Magazines Ltd.
    Nature 400 (1999), S. 815-816 
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] Oceanographers often speak of physical or chemical pressure on primary ocean productivity (that is, the photosynthetic conversion of CO2to new organic matter), but there is increasing evidence that marine phytoplankton also influence the fertility of the sea through production and ...
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    [s.l.] : Nature Publishing Group
    Nature 382 (1996), S. 802-805 
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] Flavodoxin is a redox protein that contains a single molecule of riboflavin 5'-phosphate as a cofactor. Under iron-stress conditions, the iron-sulphur protein ferredoxin is replaced by flavodoxin in many microorganisms11 including diatoms12'13. Because iron is an essential component of several ...
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    [s.l.] : Macmillan Magazines Ltd.
    Nature 388 (1997), S. 132-132 
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] The nutrient-poor (oligotrophic) regions of the open ocean cover 30% of the Earth's surface. Microscopic plants (phytoplankton) living in this habitat account for about 10% of global CO2fixation. Most of this organic production is rapidly respired within a microbial food web ...
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  • 5
    ISSN: 1573-5079
    Keywords: activation ; deactivation ; induction ; irradiance ; kinetics ; photosynthesis ; phytoplankton ; Rubisco
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The activity of ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco) was examined in three marine microalgae: the chlorophyte t Dunaliella tertiolecta and the chromophytes t Pavlova lutheri and t Thalassiosira pseudonana. The three species differed in the sensitivity of Rubisco activity in crude extracts to magnesium ion concentration, the presence of protease inhibitors, the duration of the incubation on activity, and the potential for full activation of Rubisco with 20 mM magnesium chloride and 20 mM bicarbonate t in vitro. t D. tertiolecta had responses that were similar to those described in vascular plants: regulation of initial activity on a gradient of irradiances; maximum initial activities that were 80– 90% of light-saturated photosynthesis; total activities that exceeded light-saturated photosynthesis by 30–100%; and deactivation of Rubisco in darkness. Both initial and total activity declined in darkness and increased on a return to growth irradiance. First-order time constants were about 9 min for deactivation and 3 min for reactivation of initial activity. The decline in total activity after a transition into darkness could not be reversed t in vitro but could be reversed by exposing t D. tertiolecta to light, a characteristic of regulation by CA1P. The responses of t T. pseudonana were qualitatively similar, except that recovery of initial activity was low and could only account for 30–40% of light-saturated photosynthesis. Rubisco from t T. pseudonana exposed to low irradiance could be activated t in vitro but at growth irradiance and higher, total activity was lower than initial activity. The time constants for deactivation and reactivation of initial activity after reciprocal switches between growth irradiance and darkness were 12–18 min and 3 min in t T. pseudonana. t P. lutheri showed no regulation of Rubisco activity in response to changes in irradiance or light-dark transitions. This may have been an artifact of the conditions chosen to measure activity.
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