Sea Technology

DEC 2018

The industry's recognized authority for design, engineering and application of equipment and services in the global ocean community

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www.sea-technology.com December 2018 | ST 25 The community diversity can range from biofilms dominated by only a few species of bacteria to highly diverse environmental biofilms that contain thousands of species of bacteria, microalgae, fungi, protozoa and other species, all living in close association. The archi- tecture, chemical compositions and physical properties of biofilm matrices are likewise variable, reflecting the species that form the biofilm and the local environmental conditions, such as local flow conditions. Finally, these diverse microbial systems are highly adaptable and can respond to environmental change on a time scale of min- utes, hours or days by modifying their biological, chemi- cal and physical properties. The Matrix: A Slime Shield Living within the slimy biofilm matrix provides mi- cro-organisms with notable advantages. The matrix is not a rigid material but rather is viscoelastic, which means that biofilms will both stretch (like a rubber band) and deform (like clay) in response to shear forces, such as wa- ter flow, jet washing or toothbrushing. That means bio- films are resistant to removal by physical disruption. The viscoelastic matrix will stretch and ripple before breaking or dislodging from a surface, anchoring the microbes into a favorable growth environment. The matrix also shields the microbes from chemical attacks by antibiotics or biocides, and that has been put forward as a contributing factor as to why slime grows on biocidal marine coatings. In some instances, substances in the matrix would directly sequester chemical agents, while in other cases, the matrix provides a simple physi- cal diffusion barrier, where less and less of the chemical actually moves into the deepest areas of the matrix. Cells inside this most protected zone of the matrix may be effectively starving and fall dormant, because nutrients would also have to cross the diffusion barrier. However, these dormant cells are a kind of microbial reservoir, and should all the other cells die and the outer layers of the biofilm disintegrate, the inner cells may jump-start the community all over again and refresh the biofilm. Slime and Ships Bottom line: The amazing resilience of biofilms to physical and chemical stresses, combined with the diver- sity of marine microbes, is why biofilms will eventually grow on any immersed marine coating in real-world ves- Microalgae in marine photosynthetic biofilms auto-fluoresce in bright colors, reflecting their individual photosynthetic and accessory pigments. State-of-the-art Motion & Navigation Solution Navsight Marine Solution Qinertia The Next Generation INS/GNSS Post-processing Software Courtesy of Cadden Making Hydrographers' Tasks Easier www.sbg-systems.com HYPACK 19 Booth #25

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