The effects of temperature on the rates of
biological processes are well known, but the
importance of temperature in determining the
occurrence of particular phytoplankton species
is uncertain. Goldman and Ryther (9) studied
the effect of temperature on five species of marine
phytoplankton. The cell yield was independent
of temperature, but the outcome of
competition between species was highly dependent
on temperature. A literature survey of the
effect of temperature on algal growth rate indicated
that, as temperature increased, the algal
group with the highest growth rate changed
from diatoms to green algae to blue-green algae
(cyanobacteria) (6). However, Fogg (7) has commented
that because of the possibility of adaptation
and interaction with other factors, it is
unlikely that temperature alone is a major factor
in determining the occurrence of a particular
algal species.
A common observation is that blue-green algal
dominance of aquatic communities is greater
when water temperatures are warmer (3). In
Lake Mendota, Wis., blue-green algae are an
insignificant component of the phytoplankton in
t Present address: Department of Biological Sciences, Purdue
University, West Lafayette, IN 47907.
the spring, but become dominant as the water
temperature warms. In the present investigation,
the effect of temperature on photosynthesis of
natural blue-green algal populations from Lake
Mendota and on photosynthesis and growth of
cultures isolated from this lake was studied. The
objectives were to determine whether the absence
of blue-green algae in the spring was due
to the low temperatures present at that time and
whether autumn populations were better
adapted to lower temperatures than were the
summer populations.
MATERIALS AND