Strategies adopted by Aphanizomenon flos-aquae in response to phosphorus deficiency and their role on growth

Abstract

Background: The N 2 -fixing cyanobacterium, Aphanizomenon flos-aquae is a globally distributed bloom causing species that degrades water quality of fresh and marine water bodies. Overcoming phosphorus (P) deficiency is one of the ecological advantages for bloom-forming cyanobacteria. It remains unclear to what extent can A. flos-aquae alleviate P deficiency by regulating P using strategies.Results: Based on in situ observations of extracellular alkaline phosphatase (APase) in A. flos-aquae via enzymelabeled fluorescence in freshwater bodies in China, Poland and Czechia, we further investigated responses of isolated A. flos-aquae to different P supplies (dissolved inorganic P (Pi) as +DIP, dissolved organic α-glycerophosphate and β-glycerophosphate as +DOP α and +DOP β , P-free condition as P-depleted). The significantly negative relationships between percentage of APase producing cells and soluble reactive P concentration in both fields and cultures suggested that the excretion of APase in cyanobacterium was regulated by ambient Pi supply. Suffering from P deficiency in the P-depleted treatments, A. flos-aquae showed the highest APase activity but a vigorous growth at the early culture stage, which might also benefit from the formation of polyphosphate body (PPB) and the decrease of cell P quota. In the +DOP treatments, the coordination of dissolved DOP mineralization and continuous prompt utilization of PPB might contribute to a maintenance but not reproduction of A. flos-aquae when relying on DOP, since the specific growth rate kept around 0 cells L −1 day −1 at the second half culture period and the highest cell density reached only 13.38% of that in +DIP treatments while photochemical efficiency was comparable during the whole experiment. Luxury uptake of phosphate as PPB in the +DIP treatments was consistent to the canonical view of polyphosphate as P storage. Conclusion:Aphanizomenon flos-aquae could achieve an instantaneous growth in response to P deficiency with the coordination of P utilization strategies, while it maintained a long-term sustainable growth but not reproduction under sole DOP supply. Persistent and active reproduction could only be achieved in high Pi supply, which implying that an effective consequence can be expected for combating the bloom of A. flos-aquae when controlling P supply.

The Effects of Ferric Sulfate (Fe2(SO4)3) on the Removal of Cyanobacteria and Cyanotoxins: A Mesocosm Experiment

“…[26][27][28]. The Aphanizomenon genus might be adapted to environments with higher P concentrations having been sensitive to changes in ambient DP [29,30]. Aphanothece clathrata was also observed in some events at both sites (MB, 10 and 24 September 2018; PLSF 24 July and 5 August 2019) (Figure S2).…”

“…[26][27][28]. The Aphanizomenon genus might be adapted to environments with higher P concentrations having been sensitive to changes in ambient DP [29,30]. The bottom and top of the box shows the lower and upper quartiles, the band in between them shows the median, whiskers show the minimum and maximum (excluding outliers) and circles show the outliers.…”

“…For the event on 15 August 2019, total taxonomic cell counts suddenly decreased by more than 90% in the control mesocosm in MB (Figure 1), and D. spiroides became a dominant species in the control mesocosm accounting for 43.1% of total taxonomic cell counts, followed by Aphanizomenon flos-aquae (36.2%) (Figure S2). Since the total cell abundance in MB (13 August 2019) exceeded 10 7 cells/mL at T0, the decomposition process would release CO 2 and organic acids into the water body leading to a decrease in pH [30,33]. A decrease in pH (<7.1) (Table S7) may cause growth suppression of Aphanizomenon flos-aquae in the control mesocosms [34].…”

Monitoring planktonic cyanobacteria in Lake Maninjau, West Sumatra, Indonesia

“…As reported, lakes rich in nitrogen can support the growth of diazotrophic species such as Aphanizomenon [29]. The growth of Aphanizomenon under phosphorus deficiency is probably related to their ability to use organic P from enzymatic process which takes from either intracellular or extracellular sources [30,31]. A study also reported that Merismopedia, which is non-nitrogen-fixing Cyanobacteria, dominates in water with high nitrogen concentration [32].…”

Phosphorus storage and utilization strategies of two bloom-forming freshwater cyanobacteria

“…Overall, it appears that C. ovalisporum competes strongly for DOP compared with other cyanobacterial species, hence may give it the capacity to dominate phytoplankton populations when DIP becomes limited. Chen et al [42] found that another cyanobacterium, Aphanizomenon flos-aquae could maintain growth from a one-off DOP supply for approximately 60 days via APA. The authors concluded that the coordination of dissolved DOP mineralization and continuous utilization of polyphosphate (a typical form of cellular P) might contribute to the maintenance of A. flos-aquae when relying on DOP.…”