Document Type

Thesis - Open Access

Award Date


Degree Name

Master of Science (MS)




The importance of nitrogen in an aquatic ecosystem is quite well known. Nitrogen, being originally derived from the atmosphere, enters into a complex cycle involving both the plant and animal components of the ecosystem. The nitrogenous compounds of natural waters may be broken down into the main categories according to their source, either allochthones or autochthonous. Allochthones nitrogen is that derived from the outside sources and includes those compounds carried into the lake by precipitation, by surface runoff containing terrestrial nitrogen, or by the inflow of ground water. Autochthonous nitrogenous compounds are those which result from the fixation of elemental nitrogen within the body of water itself. This investigation concerns the possible significance of bacterial nitrogen fixation in the over-all nitrogen balance of a lake. Very little work has been reported demonstrating the numbers of the various nitrogen-fixing bacteria which are capable of nitrogen fixation have been followed in five lakes within a 40-mile radius of Brookings, South Dakota. This study was initiated on a preliminary basis using samples taken from Lake Cochrane (Fig. 1). After a period of four months it was decided to expand the study to include an additional four lakes. It was not the purpose of this study to achieve a representative sampling of each lake, but only to take a composite sample of the same sites in each lake at designated time intervals.

Library of Congress Subject Headings

Bacteria, Nitrifying




South Dakota State University