Effect of nitrogen forms on growth, cell composition and N2 fixation of Cylindrospermopsis raciborskii in phosphorus-limited chemostat cultures

Abstract

The aim of this research was to test whether NH 4 ? and NO 3 -affect the growth, P demand, cell composition and N 2 fixation of Cylindrospermopsis raciborskii under P limitation. Experiments were carried out in P-limited (200 lg l -1 PO 4 -P) chemostat cultures of C. raciborskii using an inflowing medium containing either 4,000 lg l -1 NH 4 -N, 4,000 lg l -1 NO 3 -N or no combined N. The results showed the cellular N:P and C:P ratios of C. raciborskii decreased towards the Redfield ratio with increasing dilution rate (D) due to the alleviation of P limitation. The cellular C:N and carotenoids:chlorophyll-a ratios also decreased with D, predominantly as a result of an increase in the chlorophyll-a and N content. The NH 4 ? and NO 3 -supply reduced the P maintenance cell quota of C. raciborskii. Consequently, the biomass yield of the N 2 -grown culture was significantly lower. The maximum specific growth rate of N 2 -grown culture was also the lowest observed. It is suggested that these differences in growth parameters were caused by the P and energy requirement for heterocyte formation, nitrogenase synthesis and N 2 fixation. N 2 fixation was partially inhibited by NO 3 -and completely inhibited by NH 4? . It was probably repressed through the high N content of cells at high dissolved N concentrations. These results indicate that C. raciborskii is able to grow faster and maintain a higher biomass under P limitation where a sufficient supply of NH 4 ? or NO 3 -is maintained. Information gained about the species-specific nutrient and pigment stoichiometry of C. raciborskii could help to access the degree of nutrient limitation in water bodies.

Seasonal variation in the net growth rate of the cyanobacterium Cylindrospermopsis raciborskii in a shallow artificial pond in northern Taiwan

“…Given the high phosphorus-storage capacity of phytoplankton (Cotner & Wetzel 1992) and the fact that cyanobacteria and/or green algae were abundant in the study pond all year round (Yamamoto & Shiah 2012), the extremely low SRP concentration in the pond appears to be largely owing to their uptake. Superior phosphorus uptake ability of C. raciborskii (Isvánovics et al 2000) may be responsible for its successful growth and bloom formation under low SRP concentrations (Burford et al 2006, Kenesi et al 2009). …”

The ecology of the invasive cyanobacteriumCylindrospermopsis raciborskii(Nostocales, Cyanophyta) in two hypereutrophic lakes dominated byPlanktothrix agardhii(Oscillatoriales, Cyanophyta)

“…faster and sustain a high biomass under phosphorus limitation during a sufficient supply of NH þ 4 or NO À 3 (Kenesi et al, 2009). In addition, NH þ 4 was shown to be effectively assimilated by C. raciborskii in previous experimental studies by Spro 00 ber et al (2003).…”

The success of the cyanobacterium Cylindrospermopsis raciborskii in freshwaters is enhanced by the combined effects of light intensity and temperature

“…To follow the mono-and mixed cultures absorbance at 750 nm was measured every day and was used as a proxy of bulk biomass. Light intensity within the bottles was derived from the light extinction coefficient calculated from the absorbance at 440 nm according to Kenesi et al (2009) and Kirk (1994). The growth rate (µ, d…”