The effect of salinity on growth rate and osmolyte concentration of Arthrospira (Cyanophyceae) isolated from wastewater treatment ponds in Maputo, Mozambique

Abstract

Arthrospira strains were isolated from wastewater treatment ponds in Maputo, Mozambique, where they grow as a dense, almost unialgal population. Growth experiments were conducted in batch cultures under constant light and temperature, to assess growth response and tolerance of Arthrospira strains to salinity. Growth rates of 0.072 and 0.074 g.day^-1 for strain 2 and strain 1 respectively, were estimated at the lowest salinity in standard Zarrouk medium. Growth rates of cells grown in Zarrouk medium supplemented with NaCl were unaffected when compared to cells grown in standard Zarrouk medium. The culture of Arthrospira in enriched seawater resulted in low growth rates of 0.051 and 0.056 g. day^-1 for strain 2 and strain 1 respectively, when compared to standard Zarrouk medium. Although at a slower rate, growth is maintained in seawater cultures supplemented with nutrients. Differences were found in carbohydrate content between cultures in different growth media. The highest carbohydrate content was observed in cultures growing in Zarrouk medium supplemented with 4 NaCl and in seawater medium supplemented with nutrients. The concentration of proline increased from 96.0 and 114.3 μmol proline g^-1 fresh weight to 154.6 and 141.5 µmol proline g^-1 fresh weight for strain 2 and strain 1 respectively in cultures growing in standard Zarrouk medium and in the seawater medium supplemented with nutrients. The results suggest that proline may have an osmoprotection function in Arthrospira growing in seawater.


Key words: Arthrospira, salinity stress, seawater, growth rate, osmoprotectants, carbohydrate, proline, Mozambique


Journal of Tropical Microbiology and Biotechnology Vol. 1 (1) 2005: 43-51