I do not think your abstract reflects what you have going for you in this paper until the last three sentences. I would suggest that you revise your abstract if possible to sell your good work a bit better.
I greatly enjoyed this work and as I was scrolling through the feedback I ran across one of your responses which is exactly why I enjoyed the work -
"I want to test the discoverability of articles (regardless of OA or not). Yes, it does seem reasonable to pre-suppose that open access articles might be advantaged, but until we prove that with data I can't just make that assumption."
As a librarian I have struggled with blanketed complaints of the accessibility of materials without any sufficient data to really back up why we chose to use certain retrieval systems.
I see potential for subject liaison librarians to be able to apply your methods to better understand information retrieval from a different perspective. Typically we as librarians tend to approach retrieval from a materials perspective and rely on our data-savvy colleagues or technology librarians to assist us with understanding the technical aspects of information retrieval. I have learned over the past three years that this is a poor practice as all librarians in 2015 are technology librarians and have to obtain the skills to analyze these tools properly.
I found your idea to attempt to ascertain "causitive mechanism(s) preventing Zootaxa content from being more discoverable via services such as GS" to be another angle to approach the retrieval issues.
I appreciated that you "scored the sections of the article the keywords occurred in." I think this adds another layer to research and I hope that you continue to keep the "fine-grain" as a part of your future analysis.
I am specifically an Open Education Librarian and I find that some of my time is dedicated to finding work-arounds for access to materials. While it is true that open journal articles might appear more easily discovered we do need consistent data to support why this might be so. We can no longer get away with promoting open content without this data.
Good work, Ross. Thank you.