Diffusion or advection? Mass transfer and complex boundary layer landscapes of the brown algaFucus vesiculosus.
The role of hyaline hairs on the thallus of brown algae in the genusFucusis long debated and several functions have been proposed. We used a novel motorized set-up for two-dimensional and three-dimensional mapping with O2microsensors to investigate the spatial heterogeneity of the diffusive boundary layer (DBL) and O2flux around single and multiple tufts of hyaline hairs on the thallus ofFucus vesiculosus.Flow was a major determinant of DBL thickness, where higher flow decreased DBL thickness and increased O2flux between the algal thallus and the surrounding seawater. However, the topography of the DBL varied and did not directly follow the contour of the underlying thallus. Areas around single tufts of hyaline hairs exhibited a more complex mass-transfer boundary layer, showing both increased and decreased thickness when compared with areas over smooth thallus surfaces. Over thallus areas with several hyaline hair tufts, the overall effect was an apparent increase in the boundary layer thickness. We also found indications for advective O2transport driven by pressure gradients or vortex shedding downstream from dense tufts of hyaline hairs that could alleviate local mass-transfer resistances. Mass-transfer dynamics around hyaline hair tufts are thus more complex than hitherto assumed and may have important implications for algal physiology and plant-microbe interactions.
Marine Biological Section, Department of Biology, University of Copenhagen, Strandpromenaden 5, 3000 Helsingør, Denmark mads.lichtenberg@bio.ku.dk.
Mads
0000-0002-0675-4554
M
Lichtenberg
Arctic Research Center, Department of Bioscience, Faculty of Science and Technology, Aarhus University, Frederiksborgvej 399, 4000 Roskilde, Denmark.
Rasmus Dyrmose
RD
Nørregaard
Marine Biological Section, Department of Biology, University of Copenhagen, Strandpromenaden 5, 3000 Helsingør, Denmark.|Climate Change Cluster, University of Technology Sydney, PO Box 123, Ultimo Sydney, New South Wales 2007, Australia.
Michael
0000-0002-1792-4790
M
Kühl
D044645:Fucus / Q000166:cytology / Q000502:physiology*; D008954:Models, Biological; D010100:Oxygen / Q000378:metabolism
D010100:Oxygen
biological fluid mechanics; diffusive boundary layer; macroalgae; mass transfer; oxygen; topography