Influence of C/N ratios on the Heterotrophic activity of model brackish water systems

 

Author(s): Theivasigamani Anand, Gunalan Balakrishnan, Pandurangan Padmavathy, V.Rani, Anand Chandran

Abstract: The heterotrophic bacteria play a major role in pond mineralization. In the present investigation the effects of different C/N ratios and different carbon sources on the population and activities of heterotrophs in model brackish water systems were investigated under laboratory conditions. In brackish water and brackish water sediments irrespective of the carbon source, the C/N ratio would significantly influence the highest concentration of ammonia registered.  In brackish water the C/N ratio somewhat lower than 20:1 was observed to be optimal for the highest activity and population of heterotrophs irrespective of the carbon source. Among the different carbon sources tried glucose ranked first in ammonia uptake and also supporting the heterotrophic population followed by sucrose and starch. Due to different C/N ratios, and kinds of carbon amendments in brackish water sediments, ammonia assimilation by heterotrophs was observed to suppress the nitrification process. The population of heterotrophic nitrite oxidizers showed significant (P<0.01) positive correlation with the level of available nitrite both in sediment and water of all treatments. So the present investigation confirmed that the enhancement of C/N ratios with suitable carbon source may control the concentration of ammonia and nitrite in aquaculture systems.

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