Stable carbon isotope signals in particulate organic and inorganic carbon of coccolithophores - A numerical model study for Emiliania huxleyi.

A recent numerical cell model, which explains observed light and carbonate system effects on particulate organic and inorganic carbon (POC and PIC) production rates under the assumption of internal pH homeostasis, is extended for stable carbon isotopes (C, C). Aim of the present study is to mechanistically understand the stable carbon isotopic fractionation signal (ε) in POC and PIC and furthermore the vital effect(s) included in measured ε values. The virtual cell is divided into four compartments, for each of which the C as well as the C carbonate system kinetics are implemented.

Simulating the effects of light intensity and carbonate system composition on particulate organic and inorganic carbon production in Emiliania huxleyi.

Coccolithophores play an important role in the marine carbon cycle. Variations in light intensity and external carbonate system composition alter intracellular carbon fluxes and therewith the production rates of particulate organic and inorganic carbon. Aiming to find a mechanistic explanation for the interrelation between dissolved inorganic carbon fluxes and particulate carbon production rates, we develop a numerical cell model for Emiliania huxleyi, one of the most abundant coccolithophore species.

Ocean acidification decreases the light-use efficiency in an Antarctic diatom under dynamic but not constant light.

There is increasing evidence that different light intensities strongly modulate the effects of ocean acidification (OA) on marine phytoplankton. The aim of the present study was to investigate interactive effects of OA and dynamic light, mimicking natural mixing regimes. The Antarctic diatom Chaetoceros debilis was grown under two pCO2 (390 and 1000 μatm) and light conditions (constant and dynamic), the latter yielding the same integrated irradiance over the day.

Numerical cell model investigating cellular carbon fluxes in Emiliania huxleyi.

Coccolithophores play a crucial role in the marine carbon cycle and thus it is interesting to know how they will respond to climate change. After several decades of research the interplay between intracellular processes and the marine carbonate system is still not well understood. On the basis of experimental findings given in literature, a numerical cell model is developed that describes inorganic carbon fluxes between seawater and the intracellular sites of calcite precipitation and photosynthetic carbon fixation.

Substrate supply for calcite precipitation in Emiliania huxleyi: assessment of different model approaches.

Over the last four decades, different hypotheses of Ca(2+) and dissolved inorganic carbon transport to the intracellular site of calcite precipitation have been put forth for Emiliania huxleyi (Lohmann) Hay & Mohler. The objective of this study was to assess these hypotheses by means of mathematical models. It is shown that a vesicle-based Ca(2+) transport would require very high intravesicular Ca(2+) concentrations, high vesicle fusion frequencies as well as a fast membrane recycling inside the cell.