I left linkedin for all the shady things they are doing, see my previous comment for more information: https://news.ycombinator.com/item?id=31762904#31767463.

I rely mostly on my my website for marketing and some twitter. I write articles in my field that focus on topics that are not well covered, but important. When I create relevant content, google picks it up.

It sounds like your field relies a lot on word of mouth, so maybe you can get your audience to talk about subjects that are important, by breaching topics that are a concern for your audience.