Bacterial Regulation in Aquatic Ecosystems
PAT C. KERR, Biologist
D. L. BROCKWAY, Biologist
DORIS F. PARIS, Chemist
JOHN T. BARNETT, Jr., Biological Aide
Environmental Protection Agency
Southeast Water Laboratory
National Pollutants Fate Research Program
Athens, Georgia
INTRODUCTION
The role of the decomposer organisms—bacteria, fungi, and protozoa—has
received little attention in eutrophication studies during the last 30 years. Prior to
that time, a great deal of emphasis had been placed on the role of these organisms in
stream self-purification (1), in nutrient regeneration in lakes (2, 3, 4), and in oceans
(5, 6). Within the last two years, increased interest in nutrient cycling in aquatic
ecosystems—particularly studies on the role of carbon in eutrophication (7, 8, 9, 10,
11)—has created renewed interest in studies of aquatic bacteria.
Bacteria, like other small organisms, have high metabolic rates and short
generation times. Thus, instantaneous estimation of the bacterial population cannot
assess the impact of these organisms on ecosystems. The growth and death of
organisms and the concomitant nutrient cycling is a dynamic process which can only
be understood from kinetic studies.
Genetic, nutritional, physical, and chemical factors can all regulate the extent
and rate of biological activities. An attempt will be made in this paper to
demonstrate some specific effects of selected parameters on the growth of aquatic
bacteria, the importance of bacteria in eutrophication, and some of the difficulties
inherent in the interpretation of data from field studies.
MATERIALS AND METHODS
All chemical and biological analyses were performed on aliquants from the
same water sample. No chemical analyses were done on the sediment samples.
Total inorganic carbon (TIC), total organic carbon (TOC), inorganic phosphorus (P), total phosphorus (TP), nitrate-nitrogen (NO3-N), ammonium-nitrogen
(NH4-N), oxygen (O2), pH, and numbers of bacteria were determined from water
samples as described in Brockway, Kerr, Paris, Barnett, this volume.
Bacterial data will be reported from:
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