Oxygen Production in
Some Northern Indiana Lakes
WILLIAM R. EBERLY, Associate Professor of Biology
Manchester College
North Manchester, Indiana
Dissolved oxygen is by no means uniformly distributed within the lakes of
northern Indiana. There is also a great deal of variation in the rate of oxygen production, vertical distribution of photosynthesis, and total oxygen production. While it is also true that there are often quite significant seasonal
and annual variations in lakes, enough has been learned in recent years to
permit certain generalizations regarding the classification of lakes according
to oxygen types and also the factors which control oxygen production.
An oxygen profile (a graph depicting the vertical distribution of dissolved
oxygen within a lake) is one of the most significant diagnostic characters of
a lake. The biota of a lake comprise a complexly interacting community.
The sum total of the biochemical reactions within the biotic community plus
the chemical interactions with the abiotic components of the environment
are often referred to as the metabolism of the lake. Many of the major
metabolic activities within the lake involve either the production or consumption of oxygen. Still other processes are necessitated by the absence of
oxygen. The distribution of most animals is controlled by the concentration
of oxygen, with high amounts of oxygen occasionally forming a barrier as
well as minimal amounts. Oxygen consumed by decomposition of organic
matter is often reflected in the disappearance of oxygen from the deeper
strata ofthe lake.
Oxygen profiles that are most indicative ofthe nature ofthe metabolic
activitiej of a lake characteristically develop during the period of summer
stratification. Between the periods of fall and spring circulation all dimictic
lakes show similar patterns of oxygen distribution, i.e., with more or less
equal amounts of oxygen (near saturation) at all depth. Though all lakes
emerge from the ice-cover of winter and pass through a similar homothermous
condition (theoretically at 4 C) with uniform oxygen conditions, certain well-
defined patterns of oxygen distribution usually develop during the summer
which indicate differences in the lakes.
TYPES OF OXYGEN DISTRIBUTION
The nomenclature of oxygen curve typology is essentially that proposed
originaUy by Ahberg and Rodhe (1942). The types of curves most common
in Indiana lakes are shown in Figure 1. The orthograde oxygen curve is
recognized by the presence of some dissolved oxygen in aU strata of the lake,
even in the deepest part. This type of curve is usually associated with
oligotrophic lakes, low in nutrients and productivity and with usually a very
large volume of deep water in relation to the volume of surface water.
Clinograde curves are produced in eutrophic lakes. In such lakes the
maximum oxygen concentrations are found in the upper straits while anaerobic
conditions develop in the bottom layers by mid-summer or earlier. The disappearance of the oxygen is correlated with the high productivity of these
lakes.    The increased amount of organic matter consumes a greater amount
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