Cyanobacteria are a self-sufficient system that is widely distributed across terrestrial and aquatic environments; and terrestrial cyanobacteria plays a fundamental role in the biological cycle of agriculture (Mareš et al. 2014; Shokravi and Bahavar 2021a). They produce various bio-available elements such as Nitrogen and phosphorus, which are the essential nutrients for plant cultivation (Chittora et al. 2020). Moreover, they generally exhibit a high level of adaptive abilities and tolerance to a large number of environmental factor (Singh 2018). In nature, cyanobacteria are exposed to a constantly changing environment including irradiance, temperature, pH, nutrient availability, salinity, dissolved inorganic carbon fluctuations, (Chris et al. 2006; Bouazzara et al. 2020). These changes continuously expose the cyanobacteria cells to multiple stressors of varying magnitude and duration (Borowitzka 2018). In practice, the survival and growth of cyanobacteria depend on their ability to acclimate to varying environmental conditions.
Among all cultural parameters, pH is one of the most important factors determining cyanobacteria growth and physiology (Pawlik-Skowrońska et al. 1997; Hinners et al 2015). Most cyanobacteria have the ability to grow over a wide range of alkaline pH. Elevated pH (Alkalinity) directly influences growth rate and cell yield (de Souza Santos et al. 2011; Shokravi & Bahavar 2021 a,b), enzyme activity (Li et al. 2013), biosorption (El.Din 2017), resistance to oxidative stress (Summerfield et al. 2013), and protection (Pathak et al. 2018). It also strongly affects the cyanobacterial abundance (Krausfeldt et al. 2019; Nguyen and Rittmann 2015). While in some cyanobacteria, the growth decreased with the increasing alkalinity (Shokravi & Bahava 2021a). Therefore, evaluation the effects of different pHs on cyanobacteria is important. In paddy fields, the pH of floodwater varies during the day. Likewise, DIC concentration in the floodwater varies daily and seasonally depending on photosynthetic and respiratory rate (Pederse et al. 2013). The chemical equilibrium between photosynthesis and respiration implies a balance between inorganic carbon and net ecosystem production (Khan et al. 2020). The carbon dioxide concentration mechanism (CCM) is the critical process that enables cyanobacteria to adapt to alkaline conditions (Klanchui et al. 2017). The operation of CCM requires a high operation of photosynthesis (Mangan and Brenner 2014).
Salinity is another environmental factor that could potentially determine the cyanobacteria community in natural ecosystems. Salinity as an essential factor induces diverse alterations in the growth and photosynthesis (Bemal and Anil 2018), biochemical like carbohydrate content (Singh et al. 2015), and physiological characteristics of cyanobacteria (Miriam et al. 2017; Lee et al 2021). Time (age of the culture) is another essential factor in the resistance and growth in different conditions (Alcorta et al. 2019) which less has been considered (Bouazzara et al. 2020; Jangir et al. 2021). Exposure to initial hours of new condition may create a significant effect on physiological activities during the next hours (Abbasi et al. 2019; Shokravi & Bahava 2021a). However, there is increasing evidence that the combined environmental factors can be modulated by other factors and led to regulation, acclimation, and adaptation (Müller et al. 1993; Shokravi & Bahava 2021a). Therefore, studying environmental fluctuations in the short-time regime on cyanobacteria is essential to serve the sustainable development economy in the future.
In the present study, we have selected the filamentous cyanobacterium Cylindrospermum sp. for the abundance, fixed Nitrogen, and environmental stability. So far, most studies on this genus have been focused on molecular biology (Srivastava et al. 2009; Katoch et al. 2016), physiological characteristics (Briand et al. 2004), proline accumulation (Chris et al. 2006), heavy metal stress (Singh et al. 1989; Abhishek 2012), Nitrogen forms effect (Kenesi et al. 2009) and chemical analysis (Mareš et al. 2014). Here, we investigated whether the combined effect of environmental factors could play a key role in adjusting and controlling the growth, biomass production, and photosynthesis of the cyanobacterium.