FIG. 3.

(A) Longitudinal cross section of an ETM region of the Columbia River estuary, showing inputs of river and coastal ocean water and particles and the location of the ETM at the head of the salt wedge. Curved arrows indicate mixing of freshwater (white) and seawater (dark gray). (B) Compositions of clone libraries at the phylum and subphylum levels. Arrows show movement of bacterial types from source populations into the estuary. Estuarine clone libraries are separated into clones unique to the estuary (bottom section of free-living and particle-attached charts), clones similar to those found in the river (upper left sections), and clones similar to those found in the coastal ocean (upper right sections). Estuarine clones were designated river or coastal ocean when they clustered with clones from these source communities. Most had at least 96% sequence similarity to river and coastal ocean clones.