The role of nitrilotriacetic acid as a modyfying factor of phytoplankton growth
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The paper presents results of studies on the influence of fresh and aged for 6-12 months aqueous solutions of nitrilotriacetic acid (NTA) on the growth of phytoplankton cells. Axenic strain of unicellular algae Scenedesmus microspina (B2-76) and cyanobacteria Chroococcus minor (A-101) (Gleocapsa minor) were used in the experiments as test organisms. These or-ganisms are common in waters of the Gulf of Gdansk and are important components in the food chain. Concentration of chlorophyll a in test cultures served as a measure of the growth of phytoplankton cell studied. NTA, when added to the culture of Scenedesmus or Chroococcus in the concentration range from 1 to 50 mmol/dm3 exerted a strong growth promoting effect on the cells. NTA solutions aged for 9-12 months stimulated the growth of cyano-bacteria Chroococcus minor to a much larger extent than green algae Scenedesmus microspina. These results indicate that the biological activity of NTA, after long-term incubation as an aqueous solution, undergoes a considerable modification. The effects biological of the end products of such a modification depend on the time of adding of NTA, its initial, concentration as well as on the sensitivity of phytoplankton strains. It is concluded therefore that, the presence of NTA in estuarine and coastal waters may significantly affect the metabolism and growth of phytoplanktonic cells, especially cyanobacteria.
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A.Kosakowska, Institute of Oceanology, Polish Academy of Sciences, 81-712 Sopot, P.O. Box 68, Poland, e-mail: email@example.com