Fig. 2.

The effect of different biophysical processes and biological adaptations on the location of a given foraging strategy in the foraging mandala. a Each factor affects one or both axes of the mandala. The quadrants in panel a identify different growth regions, corresponding to inhospitable growth conditions (top left), oligotrophic growth (bottom left), copiotrophic growth (bottom right), and highly intermittent conditions (top right). The arrows corresponding to each element denote the direction in which that element moves the position of a forager in the mandala. The red and blue arrows indicate biological factors and environmental elements, respectively. The “sinking” arrow is represented in both colors because both resources and microorganisms can sink. The spatial location of each arrow is only indicative of (and not limited to) the growth region where that element may be mostly expected. Elements are further illustrated individually in panels b through h. b Size directly affects search time for non-motile microorganisms because smaller objects (red) diffuse further than larger objects (yellow) in a given time (see also Eq. 1). c Turbulence affects both search time and growth return by deforming resource patches into a plethora of filaments, for which the search time as well as the growth return are lower than for the original patch (reproduced from ref. 20). d Motile microorganisms (green) explore greater volumes of water per unit time compared to non-motile microorganisms (red), resulting in a considerable reduction in the search time. e Both sinking and rising reduce the search time because the associated flow enhances encounter rates (see also Eq. 2). f Smaller cells (green) attain greater growth returns for the same resource compared to larger cells (red). g Chemotactic microorganisms (blue) need only encounter the cloud of solutes around a resource (e.g., a particle) in order to rapidly move to the resource, thus reducing the search time compared to non-chemotactic microorganisms (green). h Retaining position relative to a resource patch, whether by chemotaxis (blue cells) or attachment (purple cells), enhances growth return, as purely randomly motile microorganisms (green) rapidly lose position relative to the patch