Fig 1.

Two views of the ocean at the microscale, emphasizing the heterogeneity of resources and related microbial interactions and distributions. (A) “Hot spots” of microbial activity occur in association with detritus, marine snow particles, and phytoplankton cells. Panel A further emphasizes the rich texture of particles, filaments, and polymers of various sizes and origins, which contribute to microscale heterogeneity. (Reprinted from reference 13 with permission from AAAS.) (B) Organic substrates diffuse from a range of sources, including zooplankton excretions (left), phytoplankton exudation (the “phycosphere”) (top; bottom right), phytoplankton lysis (top right), and settling marine snow particles (center bottom). The last, in particular, can produce intense, comet-like plumes of dissolved matter. (Adapted from reference 186a with permission.) Both panels emphasize the distinction between nonmotile cells and flagellated, motile cells; the latter often are able to cluster at hot spots by chemotaxis. We estimate an approximate scale for each image to be 1 cm.