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[APD] RE: Algae spores
1) Aquatic filament algae do not produce air-borne spores. (see below)
Regarding green sidewalks etc.:
2) Algae that grow outdoors on surfaces like roofs, sidewalks etc are
probably getting N from acid rain as a result of pollution from cars.
There is a certain amount of nitrogen naturally available in the
environment due to lightning breaking down N2 into Nitrogen-oxide forms.
Virtually all other fixed, biologically available nitrogen in the
environment came originally from cyanobacteria.
In Vancouver we have chronic problems with green coating on sidewalks
and other places because it rains so darn much. That rain carries enough
nutrients from airborne dust to provide the extremely low amounts to the
I wouldn't be surprised if some of those green algae sidewalks actually
have a few dozen different kinds of cyanobacteria. They certainly are
not filament algae at all.
The cyanobacteria category is so different from other kinds of life on
earth that scientists classify them in their own phylum in the Monera
kingdom (bacteria). They are not even in the same kingdom as filament or
unicellular algae. They are prokaryotes, which means that their
metabolic cell structure is fundamentally different from animals and
plants. In biological terms, filament algae are more closely related to
people than they are to cyanobacteria!
In biology every organism is classified according to a hierarchical
taxonomy like a tree. At the top of the tree in decreasing generality
are: Kingdom, Phylum, Class, Order, Family, Genus, and Species.
Cyanobacteria are in the Bacteria kingdom in the phylum Cyanobacteria
and are broken into 5 groups. To learn more about them go to
Filament algae and unicellular algae are in the Protista kingdom in the
subkingdom Algae. They are eukaryotes: cells are membrane-bound, have
structurally discrete nucleus and other well-developed subcellular
compartments. Cyanobacteria do not have membrane bound cells, discrete
nucleus or subcellular compartments and are probably one of the earliest
life-forms to evolve on the planet. Cyanobacteria generate most of the
free oxygen on the planet and the bio-available, fixed nitrogen.
Lots of kinds of cyanobacteria can produce air-borne spores in order to
spread. This is the reason why you probably can't ever 100% prevent the
introduction of cyanobacteria into your aquarium; they are ubiquitous in
our environment. You can certainly avoid conditions that lead to
cyanobacteria reproducing in large amounts by methods described by Tom
Barr and others.
Fungi are the other champions of spreading via air-borne spores. Fungi
are in the Kingdom Myceteae and have eukaryotic cells.
Filament algae and unicellular algae are in the Kingdom Protista
The class Chlorophyceae have Chlorophyll a, b
and store energy as starch. Flagellated cells are common and the cell
wall is comprised of cellulose. Interesting orders include:
Order Volvocales (e.g. Volvox)
Order Chlorococcales (e.g. Pediastrum, Scenedesmus , Ankistrodesmus)
Order Ulotricales (e.g. Ulothrix)
Order Oedogoniales (e.g. Oedogonium, Bulbochaete)
Order Cladophorales (e.g. Cladophora, Rhizoclonium)
The class Charophyceae is similar to the chlorophytes, but in cellular
ultrastructure are distinctly different. Interesting orders include:
Order Charales (stoneworts) (e.g. Chara, Nitella)
Order Zygnematales (e.g. Spirogyra, Zygnema, Mougeotia, Cosmarium,
Diatoms fall into the class Bacillariophyceae and have a cell wall
comprised of silica.
Note that the names Spirogyra, Cladophora and Oedogonium refer to genera
not species. Each genus is further divided into many numerous species.
Spirogyra for example has several hundred different species!
It is a gross over-simplification to talk about algae spreading by
spores in the air as if algae were all one biologically similar
life-form. They are not! Filament algae, the algae we need to concern
ourselves with, live EXCLUSIVELY in the aquatic environment. Many kinds
of aquatic algae can survive extended periods of desiccation (drying) by
slowing down biological processes and encysting (so-called resting
spores). As a rule, they do not grow up into the atmosphere and disperse
spores in the manner of fungi. They do NOT, I REPEAT, DO NOT spread by
air-borne spores. Several types can produce a SWIMMING life-stage that
helps them to reach new locations for colonization; Oedogonium for
Any errors in the above information are probably my own; I welcome any
End of lecture. I now return you to regularly scheduled programming. ;-)
Steve Pushak in city Vancouver, country Canada,
kingdom animal, phylum chordate, class mammal,
order primate, family Hominidae, genus Homo,
species Homo sapiens
Proud to be a eukaryote!
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