Chapter 22. An unloved season. Cyanobacteria identification 7

Regular visitors to this blog (if any) will know, that at some point after Chapter 21 (W160) I observed an increase in the abundance of cyanobacteria in my tank. Early signs were that a rapid return was likely.

W165. The cyanobacteria growing on the tank walls is a bad sign in my experience.

But the infection didn't take hold, when I syphoned off the mats on the gravel in the above photo, they did not re grow by the following week (W166). In fact the tank looked relatively cyanobacteria free for a long time. All photos taken immediately before water changes as always.

W190. Unicellular cyanobacteria in a freshwater aquarium.

Thirty weeks later by W190 (using fresh tap water for water changes for the previous 28 weeks) I could not honestly claim to have a cyanobacteria problem. This was the longest period that the tank had ever gone without one. There is obviously abundant brown unicellular cyanobacteria on the Amazon Sword and some on the gravel (there's even some growing on the tank walls near the gravel) but I did not feel there was enough to test if using aged water reduced it.  I began to question my belief that my fish-tank was fundamentally predisposed to the excessive growth of cyanobacteria.

W196. An inventory of cyanobacteria from a freshwater aquarium, see below for microscopic examinations of material from the labelled areas. 

I feel I should stress that I had not consciously changed my tank management practices in any way during the six weeks separating the taking of these photos. I continued the same weekly 37% water changes and gravel syphoning as for the previous 30 weeks. And yet by W196 there had been an obvious shift from brown unicellular cyanobacteria to blue green filamentous species. This is significant as it seems that these filamentous forms are much more capable of growing on the tank walls and gravel and consequently make the tank look far less healthy. In a way I was pleased as it gave me another opportunity to test if using aged water reduced the abundance of cyanobacteria. It also gave me the opportunity to test my belief that I can identify which species of cyanobacteria is growing in my aquarium from its colour and growth habits. Sample 1 has the lime blue green (almost turquoise) of species 2 (possibly Lyngbya, see Chapter 20), as does the species on the tank wall (Sample 3). The fact it can't grow far up the tank wall is also characteristic of species 2. Sample 2 intrigued me, it looks strangely green. I guessed it was some sort of mixture. Sample 4 has the dark blue green colour and tendency to form sheets around plants characteristic of species 1 (see Chapter XVI).

Sample 4. W196. The sheet forming cyanobacteria growing on the Java in mid-water is probably either Jaaginema or Geitlerinema.  

Sample 1

Sample 1. Scraped from an Ellodea plant. Unicellular (multiple species) and filamentous cyanobacteria (possibly Lyngbya) from a freshwater aquarium. The filaments are 8-10 microns wide. 

These filaments look like Lyngbya as identified in Chaper 20. I'm not surprised there is so much unicellular in this sample as, when I took it, it was clear the blue green mat was growing on top of brown material (see Chapter 18 for higher magnification images of the unicellular cyanobacteria).

Sample 3

Sample 3. Scraped from the front tank wall. Filamentous (8-10 microns) cyanobacteria (possibly Lyngbya).  

Again, very similar to the thick filaments in Chapter XIV and Chapter 20. I observed abundant evidence that these filaments have sheaths, which is a defining characteristic of this genus. Lyngbya is dominating the tank walls at this stage it seems as the sample contained little else . I notice now I upload this picture that there's a mystery filament running diagonally across the top right corner.

Sample 4

Sample 4. Sheet forming cyanobacteria sampled from a Java Moss tendril. Possibly Jaaginema or Geitlerinema. Filaments are approx. 2 microns wide.

I didn't take any good low magnification photographs of this sample but it consisted almost exclusively of the above filaments. They look very similar to the filaments identified as Jaaginema in Chaper XVI, but that I now think may be Geitlerinema (see below).

Sample 2

Sample 2. Scraped from the bog-wood. A complex mixture of cyanobacteria and algae? 

The sample was very diverse under the microscope but was mainly composed of all cyanobacteria species described here so far except the mysterious species 3 (Chapter XVI). There is also a new type of filament. The jagged filaments (there are three in this picture) are unlike the others. I could find no mention of cyanobacteria filaments articulating at the cell junctions in this way in either phytokey or the identification key I use. Notice how the species 2 filaments are laying on the glass slide like wet string. The new filaments move in and out of the focal plane of the microscope continually. This suggests to me that their cell walls have more rigidity and presumably are made of different stuff.

Sample 2. Possible algal filament, a eukaryote at last!?

One possibility is that they are algal filaments. If so the cells should contain discreet structures that contain the photosynthetic pigments called chloroplasts. There do appear to be flecks of coloured pigment in the above image so it's a possibility. It would explain why the bog-wood looks so green.

Jaagenima or Geitlerinema?

As you can see in this video, both the thick and thin cyanobacterial filaments are moving longitudinally. In Chapter XVI I identified the thin filaments as Jaaginema because they didn't move. Here I have to say they're more likely to be Geitlerinema filaments. It's possible that I used to have a Jaaginema infestation but now have Geitlerinema, which might explain why species 1 hasn't taken over the tank on this occasion  It's also possible that I have always had Geitlerinema in the tank. The description of Geitlerinema on algaebase sounds much more like what I have observed of species 1 than the Jaaginema description I posted in Chapter XVI.