Nutrient Relationships and Eutrophication
DENNIS M. SIEVERS, EPA Pre-Doctoral Fellow
DARRELL L. KING, Associate Professor
Department of Civil Engineering
University of Missouri-Columbia
Columbia, Missouri
INTRODUCTION
An understanding of the relationships between algal activity and the
availability of the various nutrients they require for photosynthesis is a precursor to
the management and successful control of lake eutrophication. Argument and
controversy centering about which particular nutrient limits eutrophication (I, 2), is
counterproductive, for algal productivity in different lakes may well be limited by
different nutrients.
The purpose of this paper is to suggest a means of relating the type and amount
of algae a lake may support to the availability of nitrogen, phosphorus, and carbon in
that lake.
LABORATORY PROCEDURE
To evaluate certain basic relationships between nutrient availability and algal
growth, a laboratory microcosm study was initiated in which four different algal
types were grown under various nutrient conditions. Pure cultures of Anacystis
nidulans (625), Chlorella vulgaris (260) and Scenedesmus acutiformis (416) were
obtained from the R. C. Starr Collection, Indiana University, Bloomington, Indiana.
The fourth culture was an unidentified species of Oocystis isolated from a municipal
sewage lagoon.
The algae were grown in batch culture in one liter Erlenmeyer flasks at a
constant temperature of 25 degrees centigrade under constant illumination from
two—40 watt "Gro-Lux" fluorescent lamps. The flasks were sealed from the
atmosphere but were vented with 2.0 mm diameter glass tubing to maintain
atmospheric pressure.
The inorganic growth media was similar to that used by Kevern and Ball (3)
with slight modifications to meet our specific requirements. All nutrients were
supplied in luxuriant amounts except for the nutrient under study. For the carbon
studies, sodium bicarbonate was used as the sole source of carbon dioxide.
All carbon measurements were obtained from a Beckman Model IR315
Infrared Carbon Analyzer. Measurements of pH were obtained by a Fisher Accumet
Model 320 pH Meter from samples sealed in an enclosed container to minimize
reactions with carbon dioxide in the atmosphere.
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