Zur Rolle der Stickstoffixation im Stoffhaushalt eines geschichteten Sees |
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| Authors: | H Rnicke K Bahr |
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| Institution: | H. Rönicke,K. Bahr |
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| Abstract: | In the dimict lake Arend (5.1 km2, 146 hm3, 49.5 m zmax), nitrogen is production-limiting with concentrations below the detection limit during the production period. Phytoplankton achieves biomasses of up to 18 mg/l fresh matter, essential contributions being made by Aphanizomenon with 2 mg/l and Anabaena with up to 10 mg/l. Nitrogen fixation was measured by the ethine reduction technique (acetylene reduction) during periods of the occurrence of heterocystforming Cyanophyceae and achieved peak values up to 6.59 μg N2 · h?1 · l?1 or 14.87 m?2 · h?1 g N2 · m?2 · h?1. The rates of fixation show a safe correlation with the biomass of heterocyst-containing Cyanophyceae (r = 0.88), their development beginning at values below the N : P-ratio of 2.66. |
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