Ecological Factors
Governing Blue-Green Algae Blooms
DANIEL F. JACKSON, Professor
Department of Civil Engineering
Syracuse University
Syracuse, New York
INTRODUCTION
Although algal blooms are not recent twentieth century phenomena, they
are, however, more prevalent today than they were 50 years ago. Evidences for
this may be found in the increased research and literature associated with the
mechanism and control of algal blooms. There is to date no universally accepted formal definition of wnat an algal bloom is. Lackey (1) defined a bloom
as "an unusually large number of plankters, usually one or a few species, per
unit of the first few centimeters of surface water." An attempt to express a
bloom quantitatively was made by Sawyer et al. (2) by assigning it the arbitrary
unit of 500 individuals per ml. It is obvious that there is a distinct difference
between a plankton population of 500 cells of Microcystis and one with 500 cells
of Oscillatoria. Jackson (3), for simplicity's sake, had defined an algal bloom
as "a visible change in the water mass produced by an increased growth of algal
cells."
The divisions of algae which contain species associated with phytoplankton
blooms include the Chlorophyta, Chrysophyta, Pyrrhophyta, and Cyanophyta. In
the past, investigators have not distinguished among the causes and effects associated with each kind of algal bloom. Individual phytoplankton blooms have
been evaluated collectively and, as a result, contradictory and nebulous statements have emerged. The objective of this paper is to incorporate from the
literature and from experimental observation, data related to blue-green algae
blooms and to evaluate the possible mechanisms concerned with their formation.
Of the many problems associated with the continuous eutrophication of rivers
and lakes, it is with the blue-green algae that most of the vicissitudes of man are
related. The literature is replete with references to the changes of a beautiful
clear lake into a highly colored green cesspool, produced by algae. Hundreds of
miles of beaches and shorelines are laden with tons of decomposing algae which
pollute the atmosphere. The destruction of myriads of fish from the depletion of
dissolved oxygen, the deaths of cows, horses, sheep, waterfowl and even serious
human illness, all these resulting from algae, are on the increase. The blue-
green algae are the only freshwater algal forms which have been demonstrated to
be toxic (4).
Many non-biologists are of the opinion that all algae are the same. This is
somewhat analogous to the concept that all small fish are minnows. Among the
different divisions of algae, the blue-green group is the most distinctive. The
blue-green algal cell is a procaryotic type. The characteristics of this type of
cell are common to the bacteria, but not to any other kinds of algae. The
procaryotic cell nucleus is never separated from the cytoplasm by a nuclear membrane and it contains no chromosomes. Mitosis does not occur; instead the entire
nuclear body splits into two smaller parts without any significant change of shape.
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