The name is absent

Lakes and streams contain a diverse biota including bacteria, algae,
higher plants, and numerous animal forms. Pollution by foreign sub-
stances can be detrimental or beneficial depending on the species in ques-
tion. Excessive pollution by organic materials promotes bacterial growth
to the point that oxygen is depleted and fish and other animal life are
adversely affected. Heavily polluted streams may become anaerobic and
foul smelling because of bacterial action. The growth of algae tends to
counteract oxygen depletion by bacteria; oxygen is a biproduct of photo-
synthesis. Most of the oxygen liberated by aquatic photoautotrophs is dis-
solved in the surrounding medium and is available to other organisms, in-
cluding fish.

We wanted to gain a better understanding of the principles that gov-
ern the relationships between bacteria and algae and to determine the ef-
fects of bacteria on photosynthetic productivity. Investigations of this
nature can be conducted only with great difficulty, if at all, in the field.
Measurements on natural systems would be complicated by other vari-
ables to the extent that basic mechanisms probably would be obscured.

We chose to study pure cultures of algae and bacteria growing under
precisely controlled conditions of temperature, nutrient, light, pH, and
gaseous environment. Isolations of bacteria from algal cultures revealed
that a highly select bacterial flora is associated with algae in the absence
of pollution, indicating that pollution per se probably enhances bacterial
diversity. We found that bacterial growth is not dependent on exogenous
organic pollution, but is dependent on and strongly correlated with algal
growth (Figure 1). The pattern and magnitude of growth of bacteria

0     8     16    24    8    16    24    8    16    24

TIME IN HOURS

FIGURE I - GROWTH OF CHLORELLA PYRENOIDOSA TX7IIO5 AND
SELECTED BACTERIA IN MASS CULTURE (WARD et αl 1964)

when present as single species in algal cultures were species dependent

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