The influence of soil and water physicochemical properties on the distribution of Nostoc sphaeroides (Cyanophyceae) in paddy fields and biochemical comparison with indoor cultured biomass

A survey on the distribution of Nostoc sphaeroides, an edible cyanobacterium, growing in mountain paddy fields of Zouma Town in China was carried out in May 2012. The physical and chemical properties of paddy field soil and water were analyzed. We found that in a paddy field in which N. sphaeroides historically did not grow when the water was acidic (pH 6.30) and showed the lowest conductivity, and the soil contained the lowest content of total phosphorus (TP) and available phosphorus (AP) compared to other fields where N. sphaeroides did grow. The nitrogen (N) contents in both water and soil samples were sufficient compared with the high N. sphaeroides yield paddy fields. These results suggest that an acidic water environment, as well as low TP and especially low AP, was the main limiting factors for the distribution of N. sphaeroides. In addition, comparison of the biochemical composition of field-harvested, short-term-cultivated, and long-term-cultivated N. sphaeroides showed that the contents of photosynthetic pigments (chlorophyll a and carotenoids) and soluble protein including phycobiliproteins increased gradually from wild habitat to long-term indoor cultivation N. sphaeroides, while both total and soluble carbohydrates showed a decreasing trend during indoor cultivation.