Deserted like the wharves at dawn. (3)
Why are the wharves the image that the poem uses to exemplify being deserted? Perhaps it has something to do with the way that wharves typically welcome ships into harbor, and connect with them—at least until they head back out to sea…
It is the hour of departure, oh deserted one! (4)
The wharves are deserted at the hour of departure, when all the ships leave. The speaker, too, feels like he's been left behind.
There was the black solitude of the islands, (25)
The speaker's state of mind before he met his lover was dark, lonely, and like an island that is completely isolated. Of course, after they split, he's not much happier. Maybe it's him?