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Modelling light and photosynthesis in the marine environment

Woźniak B., Dera J., Ficek D., Majchrowski R., Ostrowska M., Kaczmarek S.

Oceanologia

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2003

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No. 45 (2)

171-245

EN

The overriding and far-reaching aim of our work has been to achieve a good understanding of the processes of light interaction with phytoplankton in the sea and to develop an innovative physical model of photosynthesis in the marine environment, suitable for the remote sensing of marine primary production. Unlike previous models, the present one takes greater account of the complexity of the physiological processes in phytoplankton. We have focused in particular on photophysiological processes, which are governed directly or indirectly by light energy, or in which light, besides the nutrient content in and the temperature of seawater, is one of the principal limiting factors. To achieve this aim we have carried out comprehensive statistical analyses of the natural variability of the main photophysiological properties of phytoplankton and their links with the principal abiotic factors in the sea. These analyses have made use of extensive empirical data gathered in a wide diversity of seas and oceans by Polish and Russian teams as well as by joint Polish-Russian expeditions. Data sets available on the Internet have also been applied. As a result, a set of more or less complex, semi-empirical models of light-stimulated processes occurring in marine phytoplankton cells has been developed. The trophic type of sea, photo-acclimation and the production of photoprotecting carotenoids, chromatic acclimation and the production of various forms of chlorophyll-antennas and photosynthetic carotenoids, cell adaptation by the package effect, light absorption, photosynthesis, photoinhibition, the fluorescence effect, and the activation of PS2 centres are all considered in the models. These take into account not only the influence of light, but also, indirectly, that of the vertical mixing of water; in the case of photosynthesis, the quantum yield has been also formulated as being dependent on the nutrient concentrations and the temperature of seawater. The bio-optical spectral models of irradiance transmittance in case 1 oceanic waters and case 2 Baltic waters, developed earlier, also are described in this paper. The development of the models presented here is not yet complete and they all need continual improvement. Nevertheless, we have used them on a preliminary basis for calculating various photosynthetic characteristics at different depths in the sea, such as the concentration of chlorophyll and other pigments, and primary production. The practical algorithm we have constructed allows the vertical distribution of these characteristics to be determined from three input data: chlorophyll a concentration, irradiance, and temperature at the sea surface. Since all three data can be measured remotely, our algorithm can be applied as the "marine part" of the remote sensing algorithms used for detecting marine photosynthesis.

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Luminescence and photosynthesis of marine phytoplankton - a brief presentation of new results

Woźniak B., Dera J.

Oceanologia

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2000

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No. 42 (2)

137-156

EN

This volume contains a set of eight papers presenting the results of the latest research into the interaction of light with marine phytoplankton by teams from the Marine Physics Department at the IO PAS in Sopot, and the Department of Environmental Physics at the Pedagogical University of Slupsk. These results were presented at the 'Second Workshop on Luminescence and Photosynthesis of Marine Phytoplankton' (Sopot-Paraszyno, 11-15 October 1999) sponsored by the Polish State Committee for Scientific Research. This introductory article discusses the most important assumptions and objectives of the research, and outlines the latest results. These are subsequently discussed in detail in the following papers: (1) Majchrowski & Ostrowska, Influence of photo- and chromatic acclimation on pigment composition in the sea, (2) Wozniak et al., Model of the 'in vivo' spectral absorption of algal pigments. Part 1. Mathematical apparatus, (3) Majchrowski et al., Model of the 'in vivo'spectral absorption of algal pigments. Part 2. Practical applications of the model, (4) Ostrowska et al., Variability of the specific fluorescence of chlorophyll in the ocean. Part 1. Theory of classical 'in situ' chlorophyll fluorometry, (5) Ostrowska et al., Variability of the specific fluorescence of chlorophyll in the ocean. Part 2. Fluorometric method of chlorophyll a determination, (6) Ficek et al., Influence of non-photosynthetic pigments on the measured quantum yield of photosynthesis, (7) Ficek et al., Variability of the portion of functional PS2 reaction centres in the light of a fluorometric study. For the reader's convenience, we append a list of the symbols denoting the physical quantities used in the texts. The nomenclature and denotations are in line with the conventions employed in the subject literature.

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Influence of non-photosynthetic pigments on the measured quantum yield of photosynthesis

Ficek D., Majchrowski R., Ostrowska M., Woźniak B.

Oceanologia

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2000

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No. 42 (2)

231-242

EN

The aim of this work was to assess the effect of non-photosynthetic (photoprotecting) pigments on the measured quantum yield of photosynthesis in the sea. The energy absorbed by these pigments is not utilised during photosynthesis. As a result, the measured yield of this process, i.e. the photosynthetic yield referred to the total energy absorbed by all phytoplankton pigments, is less than the actual quantum yield of photosynthesis, i.e. the yield referred to the energy absorbed by photosynthetic pigments only. The model of the absorption properties of marine phytoplankton derived by the authors (see Wozniak et al. 2000, this volume) was employed to determine the relevant contributions of photosynthetic and non-photosynthetic pigments to the total energy absorbed by phytoplankton in different trophic types of seas and at different depths in the water column. On this basis the non-photosynthetic pigment absorption factor fa, which describes the relation between the true and measured quantum yields of photosynthesis, could be characterised. The analysis shows that fa varies in value from 0.33 to 1, and that it depends on the trophic type of sea and the depth in the water column. The values of this factor are usually highest in eutrophic waters and decrease as waters become progressively more oligotrophic. It is also characteristic of fa that it increases with increasing depth in the sea.