Journal article
Hydrodynamics of microbial filter feeding
National Institute of Aquatic Resources, Technical University of Denmark1
Centre for Ocean Life, National Institute of Aquatic Resources, Technical University of Denmark2
Department of Mechanical Engineering, Technical University of Denmark3
Fluid Mechanics, Coastal and Maritime Engineering, Department of Mechanical Engineering, Technical University of Denmark4
Department of Physics, Technical University of Denmark5
Biophysics and Fluids, Department of Physics, Technical University of Denmark6
Microbial filter feeders are an important group of grazers, significant to the microbial loop, aquatic food webs, and biogeochemical cycling. Our understanding of microbial filter feeding is poor, and, importantly, it is unknown what force microbial filter feeders must generate to process adequate amounts of water.
Also, the trade-off in the filter spacing remains unexplored, despite its simple formulation: A filter too coarse will allow suitably sized prey to pass unintercepted, whereas a filter too fine will cause strong flow resistance. We quantify the feeding flow of the filter-feeding choanoflagellate Diaphanoeca grandis using particle tracking, and demonstrate that the current understanding of microbial filter feeding is inconsistent with computational fluid dynamics (CFD) and analytical estimates.
Both approaches underestimate observed filtration rates by more than an order of magnitude; the beating flagellum is simply unable to draw enough water through the fine filter. We find similar discrepancies for other choanoflagellate species, highlighting an apparent paradox. Our observations motivate us to suggest a radically different filtration mechanism that requires a flagellar vane (sheet), something notoriously difficult to visualize but sporadically observed in the related choanocytes (sponges).
A CFD model with a flagellar vane correctly predicts the filtration rate of D. grandis, and using a simple model we can account for the filtration rates of other microbial filter feeders. We finally predict how optimum filter mesh size increases with cell size in microbial filter feeders, a prediction that accords very well with observations.
We expect our results to be of significance for small-scale biophysics and trait-based ecological modeling.
Language: | English |
---|---|
Publisher: | National Academy of Sciences |
Year: | 2017 |
Pages: | 9373-9378 |
ISSN: | 10916490 and 00278424 |
Types: | Journal article |
DOI: | 10.1073/pnas.1708873114 |
ORCIDs: | Nielsen, Lasse Tor , Kiørboe, Thomas , Asadzadeh, Seyed Saeed , Walther, Jens Honore and Andersen, Anders Peter |
Dinoflagellida Feeding Behavior Hydrodynamics Particle Size Video Recording