Ontario is a deeper lake.
The Welland Canal gets shipping around a big drop (Niagara Falls) between Lake Ontario and Lake Erie, so I would agree that the vessel is downbound to Lake Ontario. Recently I watched a new show on the Discovery Channel called Mighty Ship, it documented the new vessel Algoma Equinox transiting Lake Superior in mid November with a load of grain heading for Port Cartier then to Hamilton with a load of iron ore. When inbound to Lake Erie, high winds had made the western end of Lake Erie almost too shallow for Lakers to pass, then it was onto the Welland Canal with some of the same shots as Sharla's video.
Trailer;
https://vimeo.com/135252731
Algoma Equinox
Algoma Equinox is built to haul more cargo faster, using less fuel than any other Laker. On this voyage, her crew scrambles to load and transport grain from one end of the world's largest inland waterway to the other - passing through four Great Lakes, as well as the mammoth locks and tight canals that comprise the St. Lawrence Seaway. Equinox and her crew battle the fierce ice and winds, encountering sudden and enormous shifts in water depth. And after offloading the grain, she takes on a load of iron ore heavy enough to bend the hull of the ship!