Lab-cultured biofilm stabilization of non-cohesive sediments : Quantifying the elastic constant, k

A monoculture of cyanobacterium (Phormidium sp.) was grown for up to 10 weeks on spherical glass beads (d50 = 1.09 mm) under constant unidirectional flow conditions. Using a 0.3 m × 15m flume facility, the strength of biofilm-sediments adhesion was tested at the threshold of entrainment. High speed videographic analysis focussed on biofilm entrainment at two different scales (small = 4.5 cm × 3.4 cm; large =20cm × 20 cm) and image post processing employed the software ImageJ. Results indicated a 23-77% increase in the threshold of entrainment of biostabilized sediment, compared with that of abiotic sediment. The biofilm was sufficiently strong that tensile testing could be employed to elucidate its material properties and those of the composite of biofilm and sediment. Both exhibited elastic behaviour which could be characterized by Hooke's Law. Describing the strength of biofilm in this manner will allow modification of traditional abiotic models of sediment transport to incorporate the binding effects of an elastic biofilm