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 scums of Microcystis and Anabaena, the suspended clumps of Aphanizomenon, and large mats
of Oscillatoria or Lyngbya. There are three genera that historically have caused nuisance blooms
in lakes. These three have been referred to humorously as "Annie, Fannie, and Mike". Their
actual names are Anabaena spp. (Annie), Aphanizomenon spp. (Fannie), and Microcystis spp
(Mike). What they and other species are capable of is not humorous, however, and there exists
a perception that problems with blooms of these and other taxa are increasing.
Taken together, the cyanobacteria and the algae compose a highly diverse assemblage
of organisms that can do many things in aquatic environments. They can grow on surfaces,
among sand grains, float on the surface as a scum, accumulate in filamentous masses on the
bottom (floating up at any time), and some can control their position through active motility
(swimming) or changes in buoyancy. They can utilize nutrients in different forms and some of the
cyanobacteria can actually add nutrients to the aquatic system. Most photosynthesize, making
their own food (autotrophy) but some can also consume food particles (mixotrophy) and can
exist for times exclusively on external sources of food (heterotrophically).
And importantly, some have been identified as the source of very potent toxins in
aquatic ecosystems. This capability has been known for decades but the importance of this
characteristic has become widely known only during the last 10 or so years.
Other Important Differences Between Cyanobacteria and True Algae. The single
most important difference between cyanobacteria and algae has been described above.
However, there are other differences that are also important. Some of these are listed here:
1.
The cyanobacteria contain additional photosynthetic pigments, phycoerythrin and
phycocyanin, that allow use of light unavailable to other algae.
2.
The cyanobacteria are capable of utilizing free gaseous nitrogen as a nutrient source.
This is called `nitrogen fixation' and only occurs in these organisms and in the
bacteria (remember root nodules in members of the pea family?).
3.
The cyanobacteria are unable to swim as in some green algae. However, they can
alter their buoyancy allowing them to control their depth in the water.
4.
The cyanobacteria can efficiently store nutrients during luxuriant growth and uptake.
Then these can be utilized for nearly 10 additional doublings of cell growth under
subsequent low nutrient conditions. Algae have less ability for such storage.
5.
Cyanobacteria can produce different toxins and noxious substances from algae.
However, some of the toxins may be similar to those found in red tides.
1.2.15.3 Brief History of Toxic Algal Poisonings
Chorus and Bartram's (1999) book gives a brief history of cyanobacterial toxic
poisonings in the introduction. Because the book is limited to toxic cyanobacteria, it is important
to note that if accounts of poisonings due to other algae such as dinoflagellates had been
included, the history would be much richer but probably not older.
1.2.44
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