As well, during the control experiments, the biofilm release occurred continuously, displaying a continuous periodic sloughing mode, which we refer to as 'pseudo-continuous sloughing', whereas the Mg 2+ -exposed biofilms followed a stepwise release pattern resulting from singular catastrophic sloughing events. Interestingly, by the end of the experiment, the cumulative release of control and Mg 2+ -exposed biofilms were statistically the same. Nevertheless, it is expected that the liberated biofilm segments from the Mg 2+ -crosslinked biofilm would not be as efficient in downstream colonization as the control samples because most bacteria would be contained within dense and highly crosslinked ejecta with relatively low surface-area-to-volume ratios. In addition, large solid biofilm segments present the opportunity for filtration, whereas smaller deformable biofilm segments from control experiments may pass through filters to access and colonize downstream conduits. These results suggest that the application of divalent solutions coupled with high flow conditions could result in shear removal and filtration of large biofilm as a potential route to better decontamination. This goal could be achieved without aggressive antibacterial agents by provoking catastrophic sloughing after Mg 2+ exposure or by applying antibacterial treatments after Mg 2+ -aided catastrophic sloughing to limit or prevent regrowth from exposed residual layers. We conclude this study with a comparison of critical shear stress values for the three experimental conditions used in this paper. This was accomplished by simulations using the threedimensional reconstructed biofilm shape to calculate the shear stress (τc) immediately before the sloughing events, and shear stress after sloughing was determined in the same manner. Average τc values were obtained from multiple sloughing events recorded during time-lapse videos from each experiment to obtain statistical significance. We also compared the average τc values with the shear stress values after sloughing to determine how significantly sloughing affected the hydrodynamic conditions in the vicinity of the biofilm. Data for PPF-1 in the control condition (no Mg 2+ addition) were averaged over 4 separate experiments, yielding a critical shear stress value of τc = 1.42 +/-0.32 Pa. Due to the relatively insignificant effect of the pseudo-continuous sloughing events on the remaining biofilm volume, the post-sloughing shear stresses (0.95 +/-0.27 Pa) were not statistically different from τc. It can be concluded that the slough/regrowth states became intertwined after the sloughing started, leading to a pseudo-continuous biofilm ejection. Interestingly, in a previous study, a similar observation was made for the release of planktonic cells from Pseudomonas sp. biofilms in a microchannel at subcritical shear stresses by counting CFU from effluent. In comparison, the addition of 20 mM MgCl2 to the nutrient solution (LB 1/10 medium) dramatically increased the PPF-1 resilience to sloughing, enabling the biofilm to continue to grow until critical shear stress values of τc = 5.43 +/-1.52 Pa were applied. As a reminder, the LB 1/10 medium used in this study contains less than 0.03 mM of Mg 2+ . The stronger cohesion that enhanced resistance to shear stress also resulted in the tendency for the selfcohesive and brittle biofilm to rip from the channel in a large single ejecta via a similar viscoplastic deformation observed for PAO1 biofilms. The large loss of biofilm led to a significant reduction in applied shear stress after sloughing of τc = 0.50 +/-0.38 Pa, after which the biofilm began to grow again. Thus, the addition of MgCl2 causes the sloughing and regrowth phases to become separate and distinct. This behaviour was similar to that of the PAO1 reference strain, which experienced distinct τc and post-sloughing shear stresses of 4.23 +/-1.22 Pa and 1.67 +/-0.22 Pa, respectively. We also note that elevated critical shear stress values correlated to larger slough volumes during any singular event. However, it should be reiterated that the total cumulative detached biofilm volume involving PPF-1 strains under different ionic concentrations was similar despite the significant differences in the biofilm volume released per sloughing event. Please do not adjust margins Please do not adjust margins