Meeting Abstract
Algal biofilms are common fouling organisms on natural and man-made aquatic surfaces, and have a major impact on diverse systems ranging from corals, where they impede essential exchange of gases and particulates, to ship hulls, where they induce severe drag penalties while ships are in motion. Biofilms themselves have great diversity, but typically are algal or bacterial cells embedded in exocellular polymeric substance (EPS), and behave as a viscoelastic solid. When biofilms grow under hydrodynamic stress, they form thin, flexible streamers that protrude into the flow. Because biofilms typically form a compliant surface with protruding streamers, interactions between biofilms and hydrodynamics are complex and poorly understood. Here, we describe multiple studies of the effects of algal biofilms on hydrodynamic processes occurring over both natural and man-made surfaces to determine how morphologic variability in the algal community impacts turbulent flow, surface shear, and the exchange of gases and particulates. These studies include flows over corals, intertidal mudflats, and ship hulls. Findings suggest that hydrodynamic forces can result in spatially heterogeneous formation of biofilms, leading to patchy coverage. These biofilms, even with sparse, thin coverage, is shown to increase turbulence and Reynolds shear stresses above the canopy, but can substantially reduce exchange of gases and particulates at the attachment surface.
