THoughts on cyanobacteria

[asylumdown]

I've always thought there was something more going on with cyanobacteria than the common forum wisdom about algae has let on. Namely, it's because I've seen every single probable cause and remedy for it stated as though it's a fact - cyano thrives in low nutrient tanks, cyano is a sign of excess nutrients, cyano thrives when one nutrient is depleted relative to the other, cyano only occurs in low flow, cyano can occur anywhere, etc. etc. etc. Every single aquarium 'case' has at one point been blamed for cyano, even mutually exclusive cases. Also, other than chemical treatments like chemi-clean, there's not really an easy way to knock it out once it starts growing. I've seen cyano at some point in just about every tank I've seen in person, or seen pictures of online, regardless of the husbandry practice. True some tanks get it worse than others, and I lean towards thinking that high nutrients in general help it get out of control, but something about it has never really added up to me. I got really interested in it when I had a massive cyano explosion in my first tank upon adding biopellets, because so far, no one's been able to offer a good explanation as to why that happens. The best explanation I've seen is that since cyano is a bacteria and not a true algae, it's somehow able to capitalize on the sloughed off carbon polymers that make it in to the water column.

In any case, I have a small patch that started in the corner of my tank that's been slowly expanding for a couple of weeks. My tank is pretty darn close to ULN status, and no other algae really grows in my tank, and yet, day after day, the patch of cyano is advancing up the glass. It's the red wine coloured, slimy mat forming kind that I'm sure just about everyone has seen before.

Since I have a microscope now, I decided to look at it under magnification. I took two samples, one I pulverized in some tank water so that it was just reddish coloured water, and the other that I put on a slide relatively intact. The pulverized sample showed me exactly what the internet told me to expect, long strands of single cell chains of garden variety cyanobacteria. It was the intact sample that was really interesting. At low magnification, the cyano formed a tight weave that looked like a basket, but it was throbbing, almost like it had a pulse. At higher magnification, it was clear that was was causing the movement was thousands upon thousands of some other species of bacteria (diatoms maybe?) that were sliding in/amongst/through the threads of cyano. There were also much larger (but still invisible to the naked eye) worms actively sliding along, and a few spots of what appeared to be highly motile dinoflagellates.

I took a short video, hopefully it displays on the forum properly:


I edited it for the highlights. As you can see, the motile single cell organisms (bacteria? diatoms?) are almost as numerous as the strands of cyano, and they were pervasive and evenly spaced throughout the entire sample. All in all, the piece of 'cyano' that's presently in my tank is actually a living conglomeration of 4 distinct species of micro-organism, with cyano really only being the scaffold upon which the others seem to live.

I've looked at my sand, rock scrapings, tank water, dino outbreaks and all number of bio-films and slimes under my microscope, and I've never seen what appears to be such an intentional and consistent assemblage of organisms all living together. I tried doing a cursory search of 'cyano ecology' online and didn't find anything (there might be something and I just haven't found it), but from what I saw, to me it's starting to look as though the mats of 'cyano' that we can see at the macro scale in our tanks are actually a lot more complex than a simple blue-green algae. I have no idea how the things that make up the mat in my tank influence each other, who's eating who, or if there really is a relationship beyond the cyano providing an ideal substrate, but if there is some sort of synergistic relationship between the cyano and the things that live in it, I wonder if that might explain why cyano 'outbreaks' seem so baffling in some cases. Just like how a forest can set up enough feedback loops that it can begin to create the conditions necessary for it to spread, I'm wondering if the relationships between the cyanobacteria and it's commensal organisms are actually working together to support the development of the entire colony (which is that mat that we see) thus making their little 'forest' much more resilient in a broader range of environmental conditions.

Depending on what you guys think I might post this in the advanced topics section on Reef Central and see if anyone who's studied this more closely thinks there's anything to it.