GERBAM — Deuxième Colloque International de Bactériologie marine — CNRS, Brest, 1-5 octobre 1984
IFREMER, Actes de Colloques, 3, 1986, pp. 137-145
15
FACTORS AFFECTING BACTERIAL BIOMASS AND GROWTH IN THE DUPLIN RIVER ESTUARY AND COASTAL ATLANTIC OCEAN
R.D. FALLON, S.Y. NEWELL, B.F. SHERR. and E.B. SHERR
University of Georgia Marine Institute, SAPELO ISLAND, Georgia (USA)
ABSTRACT - Bacterial numbers and growth rates were measured in coastal, planktonic systems of the western
Atlantic ocean. Seasonal responses in growth rates of the bacterial assemblage were present at some sites, but
these may be related to seasonal changes in substrate supply rather than to changes in temperature. Bacterial
growth rates tended to decline with increasing distance from shore. There was evidence for predator-prey
population cycles in the bacteria and <17µm protozoa in the Duplin River estuary which may indicate that the
bacterial assemblage serves as prey for protozoan populations. In summer, a significant negative correlation
between µ (instantaneous growth rate) and cell numbers in the bacterial assemblage indicated that substrate
limitation of the bacteria may sometimes occur.
Key words : bacteria, growth rate, thymidine, grazing, protozoan
RÉSUMÉ - Les nombres de bactéries et les taux de croissance ont été mesurés dans des systèmes planctoniques
sur la côte ouest de l’Atlantique. Des réponses en fonction de la saison dans le taux de croissance des amas
bactériens sont observées sur certains sites mais elles sont plus reliées aux variations saisonnières des apports
nutritifs qu’aux variations de la température. Les taux de croissance bactériens ont tendance à décroitre avec
l’éloignement par rapport à la côte. Des cycles prédateurs-proies sont mis en évidence entre les bactéries et les
protozoaires <17 µm dans l’estuaire de la rivière Duplin, ceci peut indiquer que les amas bactériens servent de
proie pour les populations de protozoaires. En été une corrélation négative significative, entre µ (taux de
croissance instantané) et le nombre de cellules dans les amas bactériens indique que le substrat peut parfois être
un facteur limitant pour les bactéries.
Mots clés : bactéries, taux de croissance, thymidine, broutage, protozoaires.
INTRODUCTION
We have measured bacterial biomass and growth in a variety of marine environments
around Sapelo Island, Georgia, USA. In addition, by evaluating predator populations
and physico-chemical factors in relation to the bacterial data, we can try to better
understand what major controlling factors are influencing the bacterial populations.
Generally, of course, one might predict that physico-chemical factors will dominate in
temperate habitats. But, as microbial ecologists, we are interested in the specifics. What is
the relative importance of these controlling factors? How rapidly do the microbial
populations respond to their influences? Some of our progress to date in addressing these
questions is described below.
METHODS
Nearshore ocean sampling was done on four quaterly cruises in 1981 and 1982. Stations
were located at 0.25, 3, 6, 9, and 15 km offshore. The Duplin River sampling was
concentrated over two intensive three week sampling periods in late summer 1983 and
137
IFREMER, Actes de Colloques, 3, 1986, pp. 137-145
15
FACTORS AFFECTING BACTERIAL BIOMASS AND GROWTH IN THE DUPLIN RIVER ESTUARY AND COASTAL ATLANTIC OCEAN
R.D. FALLON, S.Y. NEWELL, B.F. SHERR. and E.B. SHERR
University of Georgia Marine Institute, SAPELO ISLAND, Georgia (USA)
ABSTRACT - Bacterial numbers and growth rates were measured in coastal, planktonic systems of the western
Atlantic ocean. Seasonal responses in growth rates of the bacterial assemblage were present at some sites, but
these may be related to seasonal changes in substrate supply rather than to changes in temperature. Bacterial
growth rates tended to decline with increasing distance from shore. There was evidence for predator-prey
population cycles in the bacteria and <17µm protozoa in the Duplin River estuary which may indicate that the
bacterial assemblage serves as prey for protozoan populations. In summer, a significant negative correlation
between µ (instantaneous growth rate) and cell numbers in the bacterial assemblage indicated that substrate
limitation of the bacteria may sometimes occur.
Key words : bacteria, growth rate, thymidine, grazing, protozoan
RÉSUMÉ - Les nombres de bactéries et les taux de croissance ont été mesurés dans des systèmes planctoniques
sur la côte ouest de l’Atlantique. Des réponses en fonction de la saison dans le taux de croissance des amas
bactériens sont observées sur certains sites mais elles sont plus reliées aux variations saisonnières des apports
nutritifs qu’aux variations de la température. Les taux de croissance bactériens ont tendance à décroitre avec
l’éloignement par rapport à la côte. Des cycles prédateurs-proies sont mis en évidence entre les bactéries et les
protozoaires <17 µm dans l’estuaire de la rivière Duplin, ceci peut indiquer que les amas bactériens servent de
proie pour les populations de protozoaires. En été une corrélation négative significative, entre µ (taux de
croissance instantané) et le nombre de cellules dans les amas bactériens indique que le substrat peut parfois être
un facteur limitant pour les bactéries.
Mots clés : bactéries, taux de croissance, thymidine, broutage, protozoaires.
INTRODUCTION
We have measured bacterial biomass and growth in a variety of marine environments
around Sapelo Island, Georgia, USA. In addition, by evaluating predator populations
and physico-chemical factors in relation to the bacterial data, we can try to better
understand what major controlling factors are influencing the bacterial populations.
Generally, of course, one might predict that physico-chemical factors will dominate in
temperate habitats. But, as microbial ecologists, we are interested in the specifics. What is
the relative importance of these controlling factors? How rapidly do the microbial
populations respond to their influences? Some of our progress to date in addressing these
questions is described below.
METHODS
Nearshore ocean sampling was done on four quaterly cruises in 1981 and 1982. Stations
were located at 0.25, 3, 6, 9, and 15 km offshore. The Duplin River sampling was
concentrated over two intensive three week sampling periods in late summer 1983 and
137