BUCHAREST, Feb 20 (Reuters) - Romania said on Monday it was concerned by signs that neighbouring Ukraine was dredging a canal that sliced through a shared, ecologically sensitive coastal region, and asked if it could check the site. Danube river access to the Black Sea became key for Ukraine, one of the world’s leading grain and oilseed exporters, following Russia’s blockade of the ports during what Moscow calls its “special military operation”. Ukraine first started expanding its shipping canal through the Delta in 2004 without formally notifying Romania