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1

Measurement of phytoplankton photosynthesis rate using a pump-and-probe fluorometer

Antal T.K., Venediktov P. S., Matorin D.N., Ostrowska M., Woźniak B., Rubin A.B.

Oceanologia

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2001

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No. 43 (3)

291-313

EN

In this work we have studied the possibility of determining the rate of phytoplankton photosynthesis in situ using a submersible pump-and-probe fluorometer in water areas differing in their trophic level, as well as in climatic and hydrophysical characteristics. A biophysical model was used to describe the relationship between photosynthesis, underwater irradiance, and the intensity of phytoplankton fluorescence excited by an artificial light source. Fluorescence intensity was used as a measure of light absorption by phytoplankton and for assessing the efficiency of photochemical energy conversion at photosynthetic reaction centers. Parameters of the model that could not be measured experimentally were determined by calibrating fluorescence and irradiance data against the primary production measured in the Baltic Sea with the radioactive carbon method. It was shown that the standard deviation of these parameters in situ did not exceed 20%, and the use of their mean values to estimate the phytoplankton photosynthetic rate showed a good correlation between the calculated and measured data on primary production in the Baltic (r = 0.89), Norwegian (r = 0.77) and South China (r = 0.76) Seas.

2

Variability of the specific fluorescence of chlorophyll in the ocean. Part 2. Fluorometric method of chlorophyll a determination

Ostrowska M., Matorin D.N., Ficek D.

Oceanologia

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2000

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No. 42 (2)

221-229

EN

Two methods of determining the chlorophyll a concentration in the sea have been formulated on the basis of artificially induced fluorescence measured with the aid of submersible fluorometers. The method of statistical correlation is founded on the empirical relationship between fluorescence and chlorophyll concentration. The theoretical model of fluorescence described in Part 1 of this paper (see Ostrowska et al. 2000, this volume) provides the basis of the other method, the physical method. This describes the dependence of the specific fluorescence of phytoplankton on the chlorophyll concentration, a diversity of photophysiological properties of phytoplankton and the optical characteristics of the fluorometer. In order to assess their practicability, the methods were subjected to empirical verification. This showed that the physical method yielded chlorophyll concentrations of far greater accuracy. The respective error factors of the estimated chlorophyll concentration were x = 2.07 for the correlation method and x = 1.5 for the physical method. This means that the statistical logarithmic error varies from -52 to +107% in the case of the former method but only from -33 to +51% in the case of the latter. Thus, modifying the methodology has much improved the accuracy of chlorophyll determinations.

3

Variability of the specific fluorescence of chlorophyll in the ocean. Part 1. Theory of classical in situ chlorophyll fluorometry

Ostrowska M., Majchrowski R., Matorin D.N., Woźniak B.

Oceanologia

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2000

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No. 42 (2)

203-219

EN

The range of variability of the fluorescence properties of marine phytoplankton in different trophic types of seas and at different depths in the sea is analysed theoretically. An attempt is also made to interpret artificially induced in situ fluorescence measured with submersible fluorometers. To do this, earlier optical models of light absorption by phytoplankton (see Wozniak et al. 2000, this volume) and actual empirical data were applied. A straightforward theoretical model of artificially photoinduced phytoplankton fluorescence accounting for the complex influence of different photophysiological characteristics of phytoplankton and the optical characteristics of the instrument has been worked out. A physical method of determining chlorophyll a concentrations in seawater from fluorescence measured in situ with contact fluorometers can be based on this model.

4

Variability of the portion of functional PS2 reaction centres in the light of a fluorometric study

Ficek D., Ostrowska M., Kuzio M., Pogosyan S. I.

Oceanologia

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2000

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No. 42 (2)

243-250

EN

The paper contains a preliminary analysis of the links between the portion fc of functional PS2 reaction centres in the photosynthetic apparatus of marine phytoplankton and environmental factors. The analysis is based inter alia on fluorometric measurements of fc (see Kolber & Falkowski 1993) in water sampled from different depths and trophic types of sea. From the statistical generalisations was derived an analytical form of the relationship between fc, and the optical depth and trophic type of sea (the trophicity index was taken to be the surface concentration of chlorophyll a). According to this relationship, fc rises as the trophicity of the sea does so. Moreover, there is a certain optimal optical depth for each type of water at which the number of functional PS2 reaction centres reaches a maximum. Above or below this depth the value of fc falls. At the present stage of investigations it seems reasonable to assume that this drop in the number of functional PS2 reaction centres close to the surface is due to the destructive effect of excessive irradiance. On the other hand, their reduced number at greater depths, below the fc maximum, can be attributed to the deficit of light and the consequent destruction of reaction centres.