Week Three Lecture

[James S. Baker]

Jason,

I’ve seen references in the hobby literature to biofilms getting “old” and not processing nutrients as efficiently as they did previously. I’ve seen this used as an argument in favor of fluidized bed filtration, the idea being that the constant mechanical abrasion keeps the microbial communities “young” and growing. Is there any reality to this?

PS – Regarding the illustration on page 6, it really is amazing just how specialized some microorganisms’ microenvironmental requirements are!

 

[java1]

Considering that biofilms thicken with age, then when this happens it is likely that ability for bacteria to obtain nutrients from the water column would possibly decrease. The reason is that as in the illustration of a biofilm in the lecture shows, a matrix of organic goo forms, holding the bacteria together but also slowing diffusion of water and thereby nutrients to the deeper parts of the biofilm. So, what you suggest DOES make sense.

However, (in my opinion) I would imagine that the abrasion of sand particles might be a little too active in keeping the biofilm "young", in that I think biofilms would have a tough time establishing to any significant total area. Perhaps there might be nooks within the sand grains where they could form, but I think that the structure of sand grains is a little too solid and crystalline for this to happen. With a fluidized sand bed, I would worry about too little biofilm.

Interesting idea though... I think if a middle ground could be found for constant, but very slow-rate sloughing to occur, then that would be optimal.

 

[James S. Baker]

I think if a middle ground could be found for constant, but very slow-rate sloughing to occur, then that would be optimal.

So I guess a basic sand bed, with the right mix of meio/macrofauna stirring it, could come fairly close to that ideal.