Impact of a temporal salinity decrease on growth and nitrogen metabolism of the marine diatom Skeletonema costatum in continuous cultures
Rijstenbil, J.W.; Mur, L.R.; Wijnholds, J.A.; Sinke, J.J. (1989). Impact of a temporal salinity decrease on growth and nitrogen metabolism of the marine diatom Skeletonema costatum in continuous cultures. Mar. Biol. (Berl.) 101: 121-129. https://dx.doi.org/10.1007/BF00393485
In: Marine Biology: International Journal on Life in Oceans and Coastal Waters. Springer: Heidelberg; Berlin. ISSN 0025-3162; e-ISSN 1432-1793, meer
In 1987 effects of salinity fluctuations on growth of the centric diatom Skeletonema costatum (Greville) Cleve, isolated from the brackish Krammer estuary (SW Netherlands) in 1981, were investigated. Continuous cultures (12 h light: dark cycle) of S. costatum were adapted to constant salinity in natural (16.1permil) and synthetic (13.5permil) media. For several days the ammonium-limited cultures were exposed to a salinity fluctuation (minimum 4.8permil). Decreasing salinity caused an inhibition of photosynthesis, dark respiration and cell growth. Cellular pools of glucose decreased. While the carbohydrate content remained constant, the protein content increased slightly. Net carbon fixation was more inhibited than nitrogen assimilation. Ammonium accumulated during a salinity decrease; a total decline of the overcapacity of ammonium uptake was noticed and nitrogen limitation was relieved. Amino acid pools decreased, probably as a result of excretion (osmoregulation). The enzymes invoilved in ammonium assimilation showed an increased activity. Cellular activities were resumed during a salinity increase. Chlorophyll a increased; photosynthesis, ammonium uptake and growth were stimulated. The ammonium uptake capacity recovered completely; glutamic acid accumulation and increased glutamate-dehydrogenase (GDH) activity indicated supplementary ammonium assimilation via GDH. The activities of glutamine synthetase/glutamate synthase (GS/GOGAT) and GDH stabilized, and the cells returned to steady state under ammonium limitation.
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