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Abstract

Influence exerted by various concentrations (0.01 to 50 ppm) of some chlorinated hydrocarbons (Aroclor 1254, Aroclor 1242, pp'DDE, pp'DDT and Lindane (ɣ НСН)) upon the photosynthetic assimilation of 14C02 in Antarctic marine diatom assemblage dominated by Corethron criophilum and some species of Nitzschia (Fragilariopsis group) has been investigated. The photosynthesis was fully inhibited by Lindane (ɣ HCH) in all applied concentrations To smaller extent the photosynthetic process was inhibited in turn by Aroclor 1242, pp'DDE and pp'DDT successively. Aroclor 1254 proved to be the least toxic. The possibility of the decrease of the primary production of the Antarctic diatoms caused by the chlorinated hydrocarbons was discussed.
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Abstract

Experiments have been carried out on the influence exerted by Aroclor 1254 upon the photosynthetic production of organic 14C by an assemblage of marine Antarctic diatoms (Thalassiosira sp. 48%, Nitzschia sp. 21%, Chaetoceros sp. 15% and Corethron iriophilum 10%). Samples of various numbers of cells per cm3 of water have been used. Incorporation of 14C02 by the diatoms proved to be proportional to the increased number of cells in the sample only at the lowest levels of concentration in per cm3. Further increase of the level of 14C in diatoms has not been found as number of cells in the sample kept growing. Calculation of brutto photosynthesis has indicated that low concentration of Aroclor 1254 (0,01 to 1 ppm) may stimulate the photosynthetic incorporation of carbon, yet the photosynthetic release of carbon from cells within the photorespiratory process is stimulated to a higher degree. High concentration of Aroclor (1 to 50 ppm) inhibit the brutto assimilation, yet the release of carbon during the photorespiratory process is inhibited to a higher degree. A hypothesis is being considered implying that the relation between the intensity of photosynthesis and intensity of photorespiration may vary according to the rate of concentration of Aroclor.
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Abstract

The influence of Lindane on net phytoplankton (mainly diatoms) in samples of waters from the Antarctic was investigated for 24 hours from the introduction of ɣ HCH 0,02 and 2 ppm into the environment. Changes in intensity of 14C incorporation in the light and in rate of release of 14C by the cells in the dark during consecutive light/dark periods were measured. The effect of two different Lindane concentrations in diatoms occurred 16 hours after introduction of the compound into the environment and was independent of concentration. The effect was manifested by delayed induction of photosynthesis following the dark period and also by changes in dynamic equilibrium between carbon assimilation and dissimilation. The presence of Lindane clearly stimulated 14C incorporation in the light and also enhanced the participation of 14C incorporation in overall CO2 exchange in the dark.
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