@maxliboiron recently made a great post about using BabyLegs- a research trawl (net system) for monitoring plastic pollution, especially microplastics, in surface water. You can reference this page to learn how to build and deploy the BabyLegs trawl and how to process your samples. In the wiki page about microplastics analysis, she mentions the need for a dissecting microscope, which is different than a compound microscope.
Public Lab is curious if the community microscope, which is a compound microscope in its present state, can be converted into a dissecting microscope for this use. I've made a diagram below, illustrating what I believe to be the conversion process. I haven't tried it out myself but I encourage others to do so and let us know how it goes!
Read more about the difference between the compound and dissecting microscope here.