It looks like the problem is your parameters file is using the workflow name (pick_open_reference_otus) instead of the steps that that workflow runs (pick_otus).
For example, the first line is currently:pick_open_reference_otus:otu_picking_method sortmerna_sumaclust
However, it should be:pick_otus:otu_picking_method sortmerna_sumaclust
As a heads up, it also looks like the rest of your parameters are referencing the parameter names of the workflow instead of the underlying script.
So they will all need to be removed and passed directly into your pick_open_reference.py
command. (Basically you should just need one line in your parameters file.)
Here is some further documentation
about formatting the parameter files.
Hope that helps!