English: Supplementary Movie 1 Kopanang gold mine borehole at -1,4 km. The Kopanang gold mine borehole shows thick swats of white biofilm growing on the bottom of the borehole in the area covered by fissure water. Yellow, more solid appearing biofilm covered the left wall, an area probably submerged during attachment of the trapping filter as this slowed the flow of the borehole and led to water level rise in the borehole. Only a small area could be scanned as the borehole was obstructed as can be seen when the camera is lifted out of the water. The original recording was at a resolution of 1280 x 720 at 60 fps in MP4 format. Because of the briefness of the sequence, the fragment was slowed down by 50% using Camtasia Studio 8 (TechSmith Corp., MI, USA). The file was then converted to MOV format (H264) and deinterlaced as per journal instruction using WinX video Converter 5.0.4 (Digiarty Software Inc, Chengdu, China). No other changes were applied. For scale, the diameter of the borehole is 7.4 cm.