Chapter 17. Maybe it was all a coincidence.

It's four weeks on from Chapter XV and it is becoming clear that heating the AW to 70 C before using it for a water change did not result in an increase in cyanobacteria (possibly Jaagenima see Chapter XVI). Not only that, but the same process of gradual die-back has continued. I have made a slideshow covering the period week 114 through 124 focussing on an Amazon Sword plant. It's available on youtube.

The final two stills cover the period after heating the AW, the tank looks better than ever. For the last two changes (week 125-126) I have been using ordinary tap water (it's good not having the hassle of running a second air-stone and heater), and so far no sign of a return either. There's still cyano in there of course.

Week 125.  Cyanobacteria hunting

Waiting, patiently, the only remaining species 1 mat is on the plastic filter housing (top left). There's a little species 1 in amongst the Java Moss as well (it's obvious if your eye's in) and what looks to me like a mixed (species 1/2) fine mat on the bogwood.

Week 125.  Fix bayonets.

The fact that heating the AW didn't result in any increase in cyano might suggest (if you believe what you read in Chapter XIII) that it wasn't the microbial community in the AW that affected the cyano. But the fact that going back to tap water hasn't caused a recurrence means that it is a formal possibility that the whole thing was a coincidence. I don't think I can conclude anything because the fact is my aquarium has fundamentally changed.

1. The pH has lowered from 7.6+ to around 7.2. 
2. Nitrates now accumulate between water changes.
3. The plants are growing.
4. There is a lot less cyanobacteria.

1. As for the pH dropping, I think I made a big mistake in Chapter XII. I measured a drop in tank pH in week 115 it's true but, looking back at the calender I write all my tank notes on, I see that I first recorded a drop in tank pH in week 111, one week before the first AW change. It seems that this slipped my mind when I wrote Chapter XII. So the statement " It seems maturing my tap water for a week results in a lowering of its pH. And that by using it for water changes I have lowered the pH of my tank" was wrong. I don't know why the pH of my tank dropped and I don't know when because the closest pH reading I can find is 7.6+ in week 37. I gave up measuring the pH back then because it was always the same. Maybe the death of the Cardinal in week 115 suggests the pH drop had been recent. Or maybe the cardinal just died.

2. As I said in Chapter VII, at the height of my cyano problem levels of nitrate dropped between water changes even though I was adding KNO3. At the time (week 50) I gave up testing for nitrate because I had decided that nitrates and phosphates didn't have any effect on my cyano problem. I started testing again in week 115. Levels were close to zero and remained so until week 117, since then they have tended to increase. These last few weeks they have been around 1-2.5ppm. The simplest explanation of this would be that the cyano was using up a lot of nitrate, but that might not be the only reason. 

3. As you can see from the slideshow, the cyano die-off has had a dramatic effect on the plants. They're all growing, but the Amazon Swords are growing well. The mats that covered them were on both sides of the leaves so I'm amazed they survived. Amazon Swords are the ultimate low light plant.

4. I don't bother cleaning the remaining cyanobacteria any longer. Live and let live I say.

Whatever the cause, the change has been dramatic. It's like a totally new aquarium with a different balance of organisms, a new ecosystem if you will. One of the most dramatic changes is the amount of algae. I used to get some green spot algae on the tank walls (especially the back wall). As you can see from the slideshow, the green spot turned orange, then brown and was easily scraped off with a scouring pad on a stick. I haven't seen any green hair algae since I stopped adding nutrients. And yet I'm testing positive for nitrates, so by definition there must be an excess in my aquarium. It seems that the changes in my aquarium that disadvantage cyanobacteria also disadvantage green algae. Of course all this has made my life a lot easier. Cleaning the tank takes about 5 minutes and I can do a water change in 45 minutes. It used to take hours.

However, intellectually this is most dissatisfying. I have no idea what caused my cyanobacteria outbreak, and I am uncertain what solved it. The whole point of starting this blog was to say something sensible about the causes of cyanobacteria problems and to provide some advice that was based on reason. All that is left to me is to speculate.

It's possible it was all a coincidence, but it's also possible that using AW for ten weeks (weeks 112-122) set in motion a chain of events that could not be reversed by going back to tap water. I imagine it's possible that once the ecology of an aquarium changes, once new species become established, the previously dominant species can never naturally take over. Maybe if I'd gone back to tap water after five weeks I would have seen a recurrence. But I got spooked by the Cardinals demise, I didn't realise the pH of my tank had already dropped. There is a way to test my theory. If I have learn't anything about the causes of cyanobacteria in my fish tank, I should be able to trigger an outbreak by dosing with antibiotics. This should convert the tank to a state that previously has favoured the dominance of cyanobacteria after using tap water for changes. I would be very interested to know the effect that would have on tank pH. If the cyano returned I could then test if using heated AW could reduce the cyano, and if it didn't, I would be able to repeat the observation that AW did reduce cyano. It's Christmas eve tomorrow and I am in no mood to start a cyanobacteria outbreak, but in the new year, if I don't see any return after 10 weeks of tap changes, I'll think about it.

Chapter XVI. Retraction of chapter XIV and cyanobacteria identification 4

I know that the the world is an extremely volatile place, but nothing could have prepared me for the turmoil I discovered in the world of cyanobacteria classification. My mistake had been not to check how up to date the taxonomy keys I was using were. I now know that if you want to identify your cyanobacteria with more recent information the book to read is Freshwater Algae of North America: Ecology and Classification. By John D. Wehr and Robert Gordon Sheath. It contains a new key as of 2003. It seems that the previous system didn't consider enough consistent filament features and paid too much attention to features that tended to vary. As a result, during the 1990s/2000s, the thin (less than 3 microns) filamentous, non-heterocystous cyanobacteria were completely re-classified. Oscillatoria splendida and O. amphibia were removed from the genus Oscillatoria and into a new genus Geitlerinema. Not only that but the genus Geitlerinema is one of eight in the family Pseudoanabanaceae and the thin filaments had been distributed amongst them. At first I thought it would be no problem. I would find out the new names for O. splendida and O. amphibia. Then when I searched for information about them I would get the latest. Maybe then I could answer my questions:

1. Has my species 1 been found in cyanobacterial blooms in nature? 
2. Does it produce toxins?
3. Can it fix nitrogen?
4. Is it common in the environment/water supply?

It turns out O. splendida and O. amphibia are now called Geiterinema splendidum and G. amphibium but  one of the defining characteristics of the genus Geiternema is that the filaments exhibit "intense longitudinal gliding". I know what they mean by that because when I first examined the mixed sample from the moss ball (Chapter XIV) the species 2 filaments were moving out and into the field of view like freight trains. The species 1 filaments gently waved at the ends and it looked like there was some rotation to the movement but it was not longitudinal. As a result I can safely say I wrongly identified species 1 in Chaper XIV because filament movement  is one of the new genus defining features. So if it wasn't a Geiterinema sp. which of the other seven genera was it? I was back to square one but I had a new key to follow. I went back to the original photos and looked at them more closely. I'm going to ignore the filaments with one tapered end and one rounded (heteropolar filaments) for now. (Edit 7-9-14 see Chapter 22 for an update on the issue of longitudinal gliding.)

Picture A. Cyanobacteria species 1. Thin (2 microns) filament showing the 'granules'  at the cell junctions (arrows)

Things start off easy enough. Q1-Are there heterocysts? No. Q2-Are the filaments less than 3 microns wide? Yes. Q3-If the trichomes have sheaths, are the sheaths thin with one trichome per sheath? Yes. Q4-Do the trichomes have thin, fine or firm sheaths? I had to give this question a lot of thought. If I look at almost any photo of species 1 I can see a brownish layer round the outside and sometimes a thin diffuse light diffracting layer around that. Many species of cyano produce a sticky layer around their filaments called a mucilaginous layer. It helps then form matts. But is that what I see? or is it a thin sheath? The problem is, if I answer yes I end up at a genus that looks a lot like species 1. Here is a photo of a Leptolyngbya species from a website that is run by scientists so it should be trustworthy. The gaps between the cells in this photo remind me of my filaments and Leptolyngbya are defined in the key by their ability to form mats which mine certainly can. Looking at this photo I have to say that if these filaments have sheaths then maybe so do mine, they look 'as sheathed' if you know what I mean. However, in the description of the linked photo it says "Filaments sometimes lacking sheath material" and "Sheath highly variable in thickness" which contradicts the key as Leptolyngbya are supposed to have 'thin, fine or firm' sheaths.

Picture B. Cyanobacteria species 1 filaments showing  gaps between cells

Here is another Leptolygbya photo, again from academics. The description regarding sheaths is "Sheath thin, colorless, usually diffluent, indistinct, mucilaginous, rarely distinct". So maybe my filaments do have a thin mucilaginous sheath. For me, a sheath has to be a separate structure from the trichome. Here is a photo of species 2 from the moss ball in Chapter XIV

Picture C.  Cyanobacteria species 2 filaments showing the clear sheath

All my other cyano photos are from fresh samples examined within hours of sampling. This photo was taken after the sample had sat in a tube for a week. Because some of the trichome cells have died you can clearly see the sheath. Compare that with species 1

Picture D. Species 1 filaments apparently lacking sheaths but having a thin mucilagenous layer (small arrow). The process of filament fragmentation without necridia may be occurring (large arrow).

The only thing holding these two four celled filaments together is the two dead cells between (large arrow). The thin diffuse layer around the trichome does not extend to the dead cells so that's no sheath in my view. It's a coating that the living cells seem to exude but that doesn't behave as a cohesive structure. So I'm going to answer no to Q4. Q5-Are the trichomes straight/wavy/irregularly coiled? Yes. Q6-Are the trichomes cylindrical and multi-celled without wide mucilaginous envelopes? Yes. Q7-Are the filaments solitary or in fine colonies and are the trichomes constricted at the cross walls, sometimes with polar aerotopes? I don't think I could describe the mats that used to cover my tank as 'fine colonies' and I don't think the trichomes are constricted at the cross walls either. But what about polar aerotopes? An aerotope is a collection of gas vesicles which give some species of cyanobacteria buoyancy. They can regulate how much gas is stored and so move up and down in the water during the day. As you can see from all three of the species 1 photos in this post, the cells in my filaments contain objects.

Enlargement of Picture A. Cyanobacteria species 1

These two enlargements are from Picture A. I think the fact the objects look pale at the top of the filament and dark at the bottom is a trick of the light. Could these be polar aerotopes? They do seem to be mainly at the ends (poles) of the cells. Here is a photo of  Limnothrix redekei a species which has polar aerotopes. Unfortunately you can't zoom in but if you download the picture and have a good look you will see that aerotopes seem to vary in size. I've read that some can take up 50% of the cell. The objects in my filaments all look roughly the same size. So if it's no to Q7 then it's yes to "Trichomes in larger clusters/mats, not constricted at the cross walls. No aerotopes but scattered or polar granules". Q8-Are the filaments motile? No, not if they mean 'intense longitudinal gliding' and I think they do because if I answer yes I get Geitlerinema. So in conclusion, my new best guess is that my tank was overran by a species from the genus Jaaginema. There are very few photos of Jaaginema I can find and some of them I think have been wrongly identified because their cells are thinner than the trichomes are wide and the trichomes look to be >3 microns wide. I find quite a lot of wrongly captioned photos of cyanobacteria, this is why I don't include genus or species names in my photos. Here is a link to a photo of a Jaaginema species that looks similar to my filaments, allowing for the fact that they seem to have used a fluorescent light source for the photo. And here is the description of Jaaginema from cyanodb, a website run by the guys who reclassified these thin filamentous cyanobacteria.

Descriptions:Komárek (1992): Filamentous; filaments usually solitary or freely clustered (tangled and coiled) into small colonies, rarely forming macroscopically visible mats; trichomes always without sheaths, cylindrical, isopolar, usually wawed or coiled, narrow, thin, 0.5-3 μm wide, uniseriate, usually not narrowed to the ends, slightly constricted or unconstricted at the cross walls, always immotile. Cells cylindrical, elongated, longer than wide (up to several times), without aerotopes, sometimes with solitary granules (rarely at the cross walls); end cells rounded_or narrowed, pointed or conical – rounded, always - without calyptra. Cell content pale blue-green, grey, yellowish or olive-green; in some species ability of chromatic adaptation (changeable phycobiline ratio).
Reproduction strategies, life cycles, cell division:Komárek (1992): Cell division by the crosswise binary fission, perpendicularly to the long axis of a trichome, daughter cells grow +/- up to the original size before the next division. All cells capable to divide. Reproduction by the fragmentation of trichomes without necridic cells into immotile hormocytes (indistinct motility was not proved yet).
Ecology, ecophysiology, ecological significance:Komárek (1992): Mainly benthic organisms, growing on the bottom of diverse water biotopes, pools, lakes, reservoirs with rich vegetation of water plants, commonly in metaphyton. Several species known from mineral, thermal or salinic waters.

Most of this info fits with what I see although "always immotile" is a worry as the filaments from the tropical tank and goldfish tanks did wave about as I mentioned in Chapter XIV. Perhaps "rarely forming macroscopically visible mats" suggests that this cyano behaved unusually in my tank if it is a Jaaginema.  I notice "end cells rounded or narrowed, pointed or conical - always without calyptra" means I don't have to worry about filament ends any more (this must be one of the features they stopped using to classify these species). Calyptra are thickened or enlarged tips to a filament, they can be hood-like, lid-like, or cap-like and I can't see anything like that. Mainly benthic means that this genus usually lives on the bottom of water bodies, usually freshwater. Uniseriate just means the cells are in a single chain. Jaaginema is a little known genus with  27 species according to cyanodb. The question is, if I now search for information on these 27 Jaaginema species (and their previous names from the Oscillatoria days) will I be able to answer any of the questions I listed at the start of this post?