They actually do it, on a subset of electoral districts: www.bundeswahlleiterin.de/bundestagswa... So it's based on a representative sample and not the full electorate

So without further ado, HERE is the preprint: www.biorxiv.org/content/10.1.... The answer is YES—water masses do structure microbial communities for both prokaryotes and eukaryotes. In fact, they seem to be the single most important factor structuring microbial communities in the pelagic ocean.