GERBAM — Deuxième Colloque International de Bactériologie marine — CNRS, Brest, 1-5 octobre 1984
IFREMER, Actes de Colloques, 3, 1986, pp. 277-281
32
NITRATE RESPIRATION AND NITRIFICATION IN ESTUARINE SEDIMENTS
R.A. HERBERT
Department of Biological Sciences University of Dundee, DUNDEE (SCOTLAND)
ABSTRACT - Seasonal data and depth profiles using 15 N-labelled NO - 3 show that denitrification (77-90% of
NO -
3 respired) rather than NO -
3 dissimilation to NH +
4
was the principal route of nitrate reduction in Kingoodie
Bay sediments. Populations of both groups of NOS reducing bacteria were highest in the 0-20 mm horizon in
those sediments where highest rates of NO -
3 respiration were recorded (28.56 µg N.d -1 dry wt. sediment
Autotrophic nitrification rates shared a marked seasonality with highest rates (0.92 µg N.d"
1 .g dry wt.
sediment -1 ) occurring during the summer. Maximum populations of autotrophic nitrifying bacteria were also
found in the 0-20 mm sediment horizon and these data indicate that both processus occur simultaneously in the
oxidised surface sediments.
Key words : denitrification, nitrification, nitrate reduction to ammonia.
RÉSUMÉ - Les données saisonnières et les profils verticaux obtenus en utilisant
15 N.NO 3 , montrent que la
dénitrification est la voie principale de la réduction des nitrates dans les sédiments de la baie de Kingoodie. Ce
processus représente 77 à 90% des nitrates respirés et est plus important que la transformation des nitrates en
ammoniaque. Les deux groupes de bactéries pouvant réduire les nitrates sont les plus développés à la surface du
sédiment (0-20 mm) où les taux de respiration des nitrates sont aussi les plus élevés (28.56 µgN/jour/g de
sédiment sec). D’autre part, les taux de nitrification autotrophe présentent un rythme saisonnier marqué avec
des maxima en été (0.92 µg N/jour/g de poids sec). Les populations de bactéries nitrifiantes autotrophes sont
également maximales à la surface du sédiment (0-20 mm).
Mots clés : dénitrification, nitrification, réduction des nitrates en ammoniaque.
INTRODUCTION
Estuarine and inshore marine surface sediments (0-50 mm depth) are environments
where sharp discontinuities in dissolved oxygen tension occur over extremely small
vertical distances or within microniches (Jorgensen, 1977 ; Billen, 1982). In such habitats
micro-organisms of widely differing physiological types can co-exist and be metabolically active. In anoxic sediments the respiratory reduction of nitrate is an alternative to
aerobic metabolism and is energetically superior to fermentation. The end product(s) of
reduction depend upon the micro-organism and growth conditions and may be either
nitrite (NO2 ), ammonia (NH4 ), nitrous oxide (N -
2 O) or gaseous nitrogen (N2). When
the end-products are gaseous the process is more correctly termed denitrification, whereas if they are NO2 of NH4 the pathway is one of nitrate dissimilation (Herbert et al.,
1980; Macfarlane and Herbert, 1982).
The nitrogen intermediates involved in the anaerobic dissimilation of NO -
3 to NH +
4 are
the reverse of those involved in nitrification, the aerobic oxidation of NH
+
4 to NO
-
3 by
nitrifying bacteria (Herbert, 1982). The objective of this present investigation was to
determine the relationship between populations of nitrate respiring bacteria and nitri277
IFREMER, Actes de Colloques, 3, 1986, pp. 277-281
32
NITRATE RESPIRATION AND NITRIFICATION IN ESTUARINE SEDIMENTS
R.A. HERBERT
Department of Biological Sciences University of Dundee, DUNDEE (SCOTLAND)
ABSTRACT - Seasonal data and depth profiles using 15 N-labelled NO - 3 show that denitrification (77-90% of
NO -
3 respired) rather than NO -
3 dissimilation to NH +
4
was the principal route of nitrate reduction in Kingoodie
Bay sediments. Populations of both groups of NOS reducing bacteria were highest in the 0-20 mm horizon in
those sediments where highest rates of NO -
3 respiration were recorded (28.56 µg N.d -1 dry wt. sediment
Autotrophic nitrification rates shared a marked seasonality with highest rates (0.92 µg N.d"
1 .g dry wt.
sediment -1 ) occurring during the summer. Maximum populations of autotrophic nitrifying bacteria were also
found in the 0-20 mm sediment horizon and these data indicate that both processus occur simultaneously in the
oxidised surface sediments.
Key words : denitrification, nitrification, nitrate reduction to ammonia.
RÉSUMÉ - Les données saisonnières et les profils verticaux obtenus en utilisant
15 N.NO 3 , montrent que la
dénitrification est la voie principale de la réduction des nitrates dans les sédiments de la baie de Kingoodie. Ce
processus représente 77 à 90% des nitrates respirés et est plus important que la transformation des nitrates en
ammoniaque. Les deux groupes de bactéries pouvant réduire les nitrates sont les plus développés à la surface du
sédiment (0-20 mm) où les taux de respiration des nitrates sont aussi les plus élevés (28.56 µgN/jour/g de
sédiment sec). D’autre part, les taux de nitrification autotrophe présentent un rythme saisonnier marqué avec
des maxima en été (0.92 µg N/jour/g de poids sec). Les populations de bactéries nitrifiantes autotrophes sont
également maximales à la surface du sédiment (0-20 mm).
Mots clés : dénitrification, nitrification, réduction des nitrates en ammoniaque.
INTRODUCTION
Estuarine and inshore marine surface sediments (0-50 mm depth) are environments
where sharp discontinuities in dissolved oxygen tension occur over extremely small
vertical distances or within microniches (Jorgensen, 1977 ; Billen, 1982). In such habitats
micro-organisms of widely differing physiological types can co-exist and be metabolically active. In anoxic sediments the respiratory reduction of nitrate is an alternative to
aerobic metabolism and is energetically superior to fermentation. The end product(s) of
reduction depend upon the micro-organism and growth conditions and may be either
nitrite (NO2 ), ammonia (NH4 ), nitrous oxide (N -
2 O) or gaseous nitrogen (N2). When
the end-products are gaseous the process is more correctly termed denitrification, whereas if they are NO2 of NH4 the pathway is one of nitrate dissimilation (Herbert et al.,
1980; Macfarlane and Herbert, 1982).
The nitrogen intermediates involved in the anaerobic dissimilation of NO -
3 to NH +
4 are
the reverse of those involved in nitrification, the aerobic oxidation of NH
+
4 to NO
-
3 by
nitrifying bacteria (Herbert, 1982). The objective of this present investigation was to
determine the relationship between populations of nitrate respiring bacteria and nitri277