Microscopic filter feeders at an angle to nearby boundaries: Feeding restrictions and strategies

Microscopic sessile filter feeders are an important part of aquatic ecosystems and form a vital link in the transfer of carbon in marine food webs. ~These filter feeders live attached to boundaries, consume bacteria and small detritus, and are in turn eaten by larger organisms. Such filter feeders survive by creating a feeding current that draws fluid towards them, and from which they filter their food of interest. Eddies form near these organisms as a result of fluid forcing near a boundary. ~The extent of these eddies, and their effect on the nutrient uptake of the organism, depend on the angle of fluid forcing relative to the boundary. For a model with perfect nutrient capture efficiency, and in the absence of diffusion, we show that feeding at an angle greatly increases the feeding efficiency of~filter feeders. We also show experimental data that living filter feeders in culture feed at an angle to the substrate. ~We discuss the effects of nutrient diffusion and inefficient nutrient capture on our model, as well as a possible mechanism for filter feeders to change their orientation.