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An experimental-study of the regulation of nitrification in marine-sediments

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  • Chemistry


An experimental study of the regulation of nitrification in marine sediments OCEANO LOG 1 CA ACT A 1981 - VOL. 4 - No 4 . E'ai----- ·An experimental study Nitrification Marine sediment Organic matter Ammonia Oxygen of the regulation of nitrification Nitrification Sédiment marin Matière organique Ammoniac Oxygène in marine sediments ABSTRACT RÉSUMÉ G. Mevel, S. Chamroux Centre d'Étude d'Océanographie et de Biologie Marine du CNRS, Place Georges Teissier, 29211 Roscoff. Received 12/2/81, in revised form 4/5/81, accepted 5/6/81. The regulatory influence of organic matter, ammonia and oxygen saturation on nitrification in the marine environment was studied by means oflaboratory incubations of seawater and sediments, chemical changes in the incubation medium being used to monitor the kinetics of the nitriftcation process. The results indicate the existence of both auto- and heterotrophic nitriftcation, the predominance of either type being determined by the concentration of organic matter in the culture media. Wh en such matter is present in only very low concentrations or minute amounts, autotrophic nitrification predominates. Higher levels of organic matter lead to heterotrophic nitrification, this process increasing with the concentration of organic matter present. The influence of ammonia also varies according to the concentration in which it is present. At concentrations of ammonium sulphate equal to or less than 1 mg/l ammonia (7 .6 J.lM) inhibits nitriftcation; at between 8 and 100 mg/l (60.5 and 756.8 J.lM) ammonia is toxic and nitrification is virtually non-existent. Saturated oxygen concentration favours nitriftcation, white decreasing oxygen levels lead to the remplacement of nitriftcation by the converse process of nitrate respiration. The results of the study indicate that certain factors exercise a similar influence on the process of nitriftcation in the marine and terrestrial environments alike. Given the difference between experimen

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