Hidrológiai Közlöny 2006 (86. évfolyam)
6. szám - XLVII. Hidrobiológus Napok: Vizeink élővilágát érintő környezeti változások Tihany, 2005. október 5–7.
59 Köszönetnyilvánítás A munka az MTA MeH Balaton-kutatási Program anyagi támogatásával készült. Köszönjük Horváth Teréziának és Kozma Erikának a kutatás során nyújtott segítségét. Irodalom Bulgakov N. G. and Levich A. P. (1999) The nitrogen: phosphorus ratio as a factor regulating phytoplankton community structure - Arch. Hydrobiol. 146. 3-22. Droop M. R.. (1973) Some thougth on nutrient limitation in algae - J. Phycol. 17:257-265. Heath M. R„ Richardson K. and T. Kiarboe (1990) - Optical assessment of phytoplankton nutrient depletion - Arch. Hvdrobiol. 146. 3-22. Liu H„ Bidigara R R.. Laws E„ Landry M.R., Campbell L. (1999) Cell cycle and physiological characteristics of Synechococcus (WH7803) in chemostat culture. - Marine Ecology Prog. Ser. 189. 17-25. Meeks J. C., Elhai J. (2002), Regulation of Cellular Differentiation in Filamentous Cyanobacteria in Free-Living and Plant-Associated Symbiotic Growth States. - Microbiology and Molecular Biology Reviews 94-121. Présing M„ Herodek S„ Preston T., Vörös L„ (2000) Nitrogen uptake and the importance of internal nitrogen loading in Lake Balaton. Freshwater Biol. 46. 125-139. Présing M.. Kovács W. A., Kenesi Gy., Vörös L. (2005), A Balatoni fitoplankton nitrogénigényének és a különböző nitrogénforrások jelentőségének vizsgálata II. - A Balatonkutatásának 2004 évi eredményei 36-45. Shafik H. M„ Herodek S„ Présing M„ Vörös L. (2001) Factors effecting growth and cell composition of cyanoprokaryote Cylindrospermopsis raciborskii (Woloszynska) Seenayya et Subba Raju. Arch. Hydrobiol. Suppl. 140. (Algol. Stud. 103) 75-93. Sprőber P., Shafik H. M.. Présing M„ Kovács W. A., and Herodek S., (2003) Nitrogen uptake and fixation in the cyanobacterium Cylindrospermopsis raciborskii under different nitrogen conditions. - Hydrobiologia 506-509: 169-174. Wetzel R. G„ Likens G. E. ( 1991) Limnological Analyses, 2 n d edition. Springer-Verlag, New York Nitrogen uptake and fixation of Cylindrospermopsis raciborskii cyanobacteria in phosphorous-limited chemostats Gyöngyi Kenesi, Mátyás Présing, Hesham M. Shafik, Attila W. Kovács, Sándor Herodek Abstract The effects of NH 4* addition on the metabolism, growth and N2 fixation of Cylindrospermopsis raciborskii was investigated in phosphorous limited (N/P ratio = 20) chemostats. In the first series of chemostat experiment, the algal cultures were supplied with medium containing NH/, while in the second experiment the culture medium was free of dissolved nitrogen. At these slower growth rates, the C/N ratios did not differ significantly from the optimal Redfield ratio (5.6 by mass). With increasing dilution rates the C/N ratio decreased, especially in the presence of NTV. The reduction in the C/N ratio was caused by the increased PN to dry weight ratio as the PC to dry weight quotient did not change markedly. The carotenoid to chlorophyll-a ratio also was decreased in response to an increase in the dilution rate at both nitrogen forms. This tendency was due to the increase of chlorophyll-a to dry weight ratio. The algal biomasses of cultures growing exclusively on fixed nitrogen were markedly smaller, than with that of additional NIL' supply. NH/ addition reduced the minimum (maintenance) phosphorous cell quota (Q„) of the cells and increased the maximum growth rate of the culture. The fixation of atmospheric N2 was partly blocked by NH/ at the smaller dilution rates and was entirely stopped at higher ones. The blocking of the N 2-fixation was probably caused by the high PN content of the cells and the high NH/ concentration in the culture. Keywords: Cylindrospermopsis raciborskii, filamentous cyanobacteria, phosphorous limitation, N2 fixation, chemostat. Klossy Irén alkotása (Fametszet, Magyar tájak sorozat)
