In 1850 start Russian controlled crimea region specificly Sevastopol has 100 loyalty to Russia and consist of %80 russian %20 ukranian. And in the Dobruja region(Costanza) has 85% Romanian population. I think those values can be a bit wrong.
AFAIK historically Ottoman controlled; Russian objective city Costanza(Dobrudja region) had few Romanian population in 1850's as the Ottomans moved some population there and also Tatars migrated(200k-300k estimated,from Crimea) there or to Ottomans from Sevastopol after the crimean war.(I think there is an event about it) .