These are the packages that would be merged, in order:

Calculating dependencies ... done!
Dependency resolution took 0.98 s (backtrack: 0/20).

[ebuild  N     ] sci-biology/uchime-4.2.40-r1::gentoo  66 KiB
[ebuild  N     ] sci-biology/mothur-1.48.2::gentoo  USE="readline -boost -gsl -hdf5 -mpi" 24124 KiB

Total: 2 packages (2 new), Size of downloads: 24189 KiB