Fig. 1 All four columns side by side. From left, Columns A (Potting Soil + Tap Water), B (Potting Soil + Thames Water), C (Thames Mud + Tap Water) and D (Thames Mud + Thames Water).By far, Column C (Thames Mud + Tap Water) has been the most productive, having developed a very thick biofilm on the surface of the water. There are two large "bubbles" of growth (fig. 2), and the entire film is a dark brown color with bits of light splotches, and dark patches where the growth is closer to the water. The biofilm is about 2-3 mm thick on the surface of the water, however the "bubbles" are almost a centimeter thick!
Fig. 2 - Column C's beautiful, thick biofilm layer on the surface. The large rise (seen at the bottom of the photo) is about a centimeter high from the surface of the water!The rest of Column C has been pretty productive. As seen in Fig. 1 and in Fig. 3, the entire water column has gone very dark. There seems to be a darker ring right where the water meets the mud, but the entire water column is pretty opaque. It looks as though Column D is following suit, just more slowly. There is a strong, dark ring where the mud meets the water, and right above that the water is a gray color, but above that the water is still transparent. Whereas in Column C, the biofilm dominates the entire surface area of the water, in Column D growth is more subdued. There is biofilm formation occuring, (fig. 4), but it is not growing nearly as fast as Column C. There does seem to be some filamentous growth at the water's surface, where the water meets the bottle, which cannot be seen in Column C. However, Column C's coloration makes seeing filaments like that in Column D incredibly difficult.
Fig. 3 Column C (on left) and D (on right). In this photo you can clearly see the color difference in the water layer. Column D has a bit of shading right above the mud layer, whereas Column C is dark throughout the entire water column. You can also see the difference in the size of the biofilm layer - well, you can see Column C's considerable biofilm layer. For Column D's you have to get up closer (fig. 4). But do note the filamentous growth where the water meets the bottle in Column D (you may have to zoom in to see it better).
Fig. 4 Column D's gas production. You can clearly see bubbles that have risen from the bottom. As well, you can see biofilm starting to form, but it is nowhere close to the amount of growth seen in Column C.As for Columns A and B, there does not seem to have been much change since the initial set up (fig. 5). The water level has gone down slightly, which I'm guessing is due to evaporation. In both columns there is a layer of sediment (bark pieces, etc.) on the surface, which limits my ability to see if there's microbial growth. I plan on leaving the sediment at the surface for now, to see if any growth appears at the top. As well, I have not been able to tell if there's growth at the layer between the water and the soil. Occasionally bubbles rise to the surface, however these are minimal compared with Columns C and D.
Fig. 5 Columns A (left) and B (right). Little observable change since the initial set up.
