GERBAM — Deuxième Colloque International de Bactériologie marine — CNRS, Brest, 1-5 octobre 1984
IFREMER, Actes de Colloques, 3, 1986, pp. 191-197
21
THE USE OF SIZE FRACTIONATION FOR DETERMINING THE BACTERIAL
CONTRIBUTION TO OVERALL PELAGIC OXYGEN CONSUMPTION RATES
H.J. LAANBROEK* and J.C. VERPLANKE
Delta Institute for Hydrobiological Research, Royal Netherlands Academy of Arts and
Sciences, YERSEKE, (THE NETHERLANDS),
* Present adress: Institute for Ecological Research, Boterhoeksestraat 22, 6666 GA
HETEREN, (THE NETHERLANDS)
ABSTRACT - Size fractionations in combination with precise oxygen measurements, determinations of bacterial
cell numbers and chlorophyll a analyses were used in the Oosterschelde basin and Lake Grevelingen to establish
the bacterial contribution to overall pelagic oxygen consumption rates. On computation, 101 and 59 % of total
respiration could be attributed to bacterial activity in winter in the basin and in the lake, respectively. In
summer, the bacterial component of total activity was calculated to amount to 54 and 57% in the basin and in the
lake, respectively. Microbial contribution to in situ overall activity may slightly be overestimated by growth of
the bacteria observed during incubation of the samples in oxygen bottles in the dark at in situ temperatures.
Key words : size fractionation, bacterial activity, oxygen consumption.
RÉSUMÉ - Afin de déterminer la contribution des peuplements bactériens dans la consommation d’oxygène
totale en milieu pélagique, des études ont été effectuées dans le bassin de l’Oesterschelde et dans le lac de
Grevelingen. Après fractionnement en différentes classes de taille, des dosages d’oxygène et de chlorophylle a et
des dénombrements bactériens ont été réalisés. En hiver, la respiration liée à l’activité bactérienne représente,
comparée à la respiration totale, 101 % dans le bassin et 59 % dans le lac. En été, la contribution bactérienne dans
l’activité totale correspond à 54 % dans le bassin et 57 % dans le lac. La part des bactéries dans l’activité totale in
situ peut être légèrement surestimée en raison de la croissance des cellules pendant l’incubation des échantillons.
Celle-ci se fait en bouteille à oxygène, à température ambiante et à l’obscurité.
Mots clés : fractionnement en classe de taille, activité bactérienne, consommation d’oxygène.
Bacteria are more and more recognized as major components of the marine pelagic food
web (Larsson and Hagstrom, 1982; Lancelot and Billen, 1984; Williams, 1981a). Determinations of oxygen consumption rates provide a simple and hence widely used method
for measuring heterotrophic activity in aquatic ecosystems (Straskrabova, 1979). However, this method is little selective with regard to heterotrophic activity. In order to
determine the specific bacterial component of total pelagic activity, Williams (1981b)
introduced size fractionation. In a study concerning mineralization in the water bodies of
the marine Oosterschelde basin and the saline Lake Grevelingen in the South-Eastern
part of the Netherlands, precise oxygen measurements in combination with reverse
filtration, has been used. Determinations of bacterial cell numbers and chlorophyll a
concentrations were also done.
Description of the area and the sampling stations
Samples were taken in the Oosterschelde basin as well in Lake Grevelingen both located
191
IFREMER, Actes de Colloques, 3, 1986, pp. 191-197
21
THE USE OF SIZE FRACTIONATION FOR DETERMINING THE BACTERIAL
CONTRIBUTION TO OVERALL PELAGIC OXYGEN CONSUMPTION RATES
H.J. LAANBROEK* and J.C. VERPLANKE
Delta Institute for Hydrobiological Research, Royal Netherlands Academy of Arts and
Sciences, YERSEKE, (THE NETHERLANDS),
* Present adress: Institute for Ecological Research, Boterhoeksestraat 22, 6666 GA
HETEREN, (THE NETHERLANDS)
ABSTRACT - Size fractionations in combination with precise oxygen measurements, determinations of bacterial
cell numbers and chlorophyll a analyses were used in the Oosterschelde basin and Lake Grevelingen to establish
the bacterial contribution to overall pelagic oxygen consumption rates. On computation, 101 and 59 % of total
respiration could be attributed to bacterial activity in winter in the basin and in the lake, respectively. In
summer, the bacterial component of total activity was calculated to amount to 54 and 57% in the basin and in the
lake, respectively. Microbial contribution to in situ overall activity may slightly be overestimated by growth of
the bacteria observed during incubation of the samples in oxygen bottles in the dark at in situ temperatures.
Key words : size fractionation, bacterial activity, oxygen consumption.
RÉSUMÉ - Afin de déterminer la contribution des peuplements bactériens dans la consommation d’oxygène
totale en milieu pélagique, des études ont été effectuées dans le bassin de l’Oesterschelde et dans le lac de
Grevelingen. Après fractionnement en différentes classes de taille, des dosages d’oxygène et de chlorophylle a et
des dénombrements bactériens ont été réalisés. En hiver, la respiration liée à l’activité bactérienne représente,
comparée à la respiration totale, 101 % dans le bassin et 59 % dans le lac. En été, la contribution bactérienne dans
l’activité totale correspond à 54 % dans le bassin et 57 % dans le lac. La part des bactéries dans l’activité totale in
situ peut être légèrement surestimée en raison de la croissance des cellules pendant l’incubation des échantillons.
Celle-ci se fait en bouteille à oxygène, à température ambiante et à l’obscurité.
Mots clés : fractionnement en classe de taille, activité bactérienne, consommation d’oxygène.
Bacteria are more and more recognized as major components of the marine pelagic food
web (Larsson and Hagstrom, 1982; Lancelot and Billen, 1984; Williams, 1981a). Determinations of oxygen consumption rates provide a simple and hence widely used method
for measuring heterotrophic activity in aquatic ecosystems (Straskrabova, 1979). However, this method is little selective with regard to heterotrophic activity. In order to
determine the specific bacterial component of total pelagic activity, Williams (1981b)
introduced size fractionation. In a study concerning mineralization in the water bodies of
the marine Oosterschelde basin and the saline Lake Grevelingen in the South-Eastern
part of the Netherlands, precise oxygen measurements in combination with reverse
filtration, has been used. Determinations of bacterial cell numbers and chlorophyll a
concentrations were also done.
Description of the area and the sampling stations
Samples were taken in the Oosterschelde basin as well in Lake Grevelingen both located
191