Fig 3.

Proportions of each genus in representative samples of an ultrabasic spring (WHC2B), a mixing site (WHC2C), and surface freshwater (WHB).White dots indicate sampling locations for WHC2B and WHC2C. The sampling location for WHB is located approximately 10 m upstream from the pool depicted in this photograph. Arrows indicate subsurface fluid exiting from WHC2B and surface freshwater entering the pool at WHC2C from upstream. The white lines indicate the width (∼1 m) and length (∼3 m) of the pool. Results in this figure are derived from JGI 16S rRNA tag sequencing. A full taxonomic summary is provided in Table S1 of the supplemental material.