Form, function and physics: The ecology of biogenic stabilization

The effect of biological cohesion on the behaviour of sediments is gaining increasing notice. This is partly supported by ecological theory in terms of the role of organisms as “ecosystem engineers” and the associated discussion of “niche construction”, suggesting an evolutionary role for habitat modification by biological action. In addition there is a strong societal and policy drive toward the “ecosystem approach” supporting an integrated examination of the functional roles of biota in selected habitats. In this context the increasing recognition of the importance of biological activity in the mediation the erosion, transport, deposition and consolidation (ETDC) cycle of sediments is important and advances in technology will improve our ability to examine these effect under their natural settings. This will shortly be combined with vastly enhanced molecular tools that will allowthe discrimination of microbial biodiversity and examination of their metabolism contribution to ecosystem function. This may lead to a step-change in our ability to research the influence of microbiota on natural sediment dynamics and opens an exciting era for new interdisciplinary research

Surface adhesion measurements in aquatic biofilms using magnetic particle induction: MagPI

Natural sediment stability is a product of interacting physical and biological factors, and whereas stability can be measured, few techniques allow sensitive assessment of the sediment surface as conditions change. For example, stability gradually increases as a biofilm develops or as salinity rises, or it might be influenced by toxic compounds. This article introduces a new technique (magnetic particle induction: MagPI) based on the magnetic attraction of specially produced fluorescent ferrous particles. The test particles are added to a surface and subjected to an incrementally increasing magnetic field produced by permanent magnets or electromagnets. There is a strong correlation between magnetic flux density (mTesla) and distance from the surface (r(2) = 0.99) for permanent magnets and between magnetic flux density and the current supplied to an electromagnet (r(2) &gt; 0.95). The magnetic force at which the particles are recaptured is determined as a measure of surface adhesion. MagPI therefore determines the "stickiness" of the surface, whether a biofilm, sediment, or other material. The average magnetic flux density required to remove test particles from diatom biofilms (15.5 mTesla) was significantly greater than from cyanobacterial biofilms (10 mTesla). Controls of fine glass beads showed little adhesion (2.2 mTesla). Surface adhesion is an important bed property reflecting the sediment system's potential to capture and retain new particles and accumulate material. MagPI offers a straightforward and economic way to determine the surface adhesion of a variety of surfaces rapidly and with precision. The technique may have applications in physical, environmental, and biomedical research.</p

Surface adhesion measurements in aquatic biofilms using magnetic particle induction: MagPI

Natural sediment stability is a product of interacting physical and biological factors, and whereas stability can be measured, few techniques allow sensitive assessment of the sediment surface as conditions change. For example, stability gradually increases as a biofilm develops or as salinity rises, or it might be influenced by toxic compounds. This article introduces a new technique (magnetic particle induction: MagPI) based on the magnetic attraction of specially produced fluorescent ferrous particles. The test particles are added to a surface and subjected to an incrementally increasing magnetic field produced by permanent magnets or electromagnets. There is a strong correlation between magnetic flux density (mTesla) and distance from the surface (r(2) = 0.99) for permanent magnets and between magnetic flux density and the current supplied to an electromagnet (r(2) &gt; 0.95). The magnetic force at which the particles are recaptured is determined as a measure of surface adhesion. MagPI therefore determines the "stickiness" of the surface, whether a biofilm, sediment, or other material. The average magnetic flux density required to remove test particles from diatom biofilms (15.5 mTesla) was significantly greater than from cyanobacterial biofilms (10 mTesla). Controls of fine glass beads showed little adhesion (2.2 mTesla). Surface adhesion is an important bed property reflecting the sediment system's potential to capture and retain new particles and accumulate material. MagPI offers a straightforward and economic way to determine the surface adhesion of a variety of surfaces rapidly and with precision. The technique may have applications in physical, environmental, and biomedical research.</p

Spearman’s rank correlation coefficient (ρ), N = 30, (p<0.001 = ***, p<0.01 = ** and p<0.05 = *).

<p>Spearman’s rank correlation coefficient (ρ), N = 30, (p<0.001 = ***, p<0.01 = ** and p<0.05 = *).</p