Seasonal and spatial distribution pattern of nitrogen fixing bacteria in fish ponds under different management systems

Abstract

Enumeration of nitrogen fixing bacterial population in water and sediment samples of six fish farming ponds (polyculture, monoculture and traditional systems) over a period of two and a half years revealed significant differences between the culture systems with maximal and lowest counts in the monoculture and traditional systems, respectively. Polynomial equations of the 2nd to 4th degree were used to represent the observed seasonal data in these ponds. The bacterial populations peaked in summer, while the lowest count was observed in winter. The environmental factors such as pH, different species of nitrogen, dissolved organic carbon were responsible for the seasonal changes in nitrogen fixing bacteria.

Evaluation of Azotobacter and Azospirillum as Biofertilizers in Aquaculture

“…after immobilizing them on suitable substrates is an already established practice in agriculture (Murkute et al 1991;Fallik et al 1993;Okon & Itzigsohn 1995;EI Ghany 1996;Okon & Fallik 1996;Nagaraju et al 2000;Yadav et al 2000). The potential of these to fix nitrogen has been demonstrated by several workers (Jana & Roy 1986;Ninawe & Paul Raj 1995;Garg & Bhatnagar 1999) and they reportedly occur (Jana & Roy 1986;Dash & Ayyappan 1998) and fix nitrogen (Niewolak 1972;Tripathy & Ayyappan 1998;Tripathy et al 2001) in aquatic systems. However, Azotobacter seems to be a relatively abundant species in aquatic ecosystems due to its aerobic nature compared to the micro-aerophilic nature of Azospirillum, for which reason the latter may be a preferred species in the sediment medium which is relatively slow in recycling minerals in comparison to its aqueous counterpart.…”