Who looks sad, dejected, and worried? What does Salerio say about Antonio's sadness?

In the opening scene of The Merchant of Venice, it's Antonio who's feeling depressed. What makes it worse is that he doesn't seem to know why. Salerio and Solanio try to help out by offering their own suggestions as to what may be bugging their friend. Salerio thinks that Antonio might be worried over his merchant ships. It's a hazardous business and ships and their valuable cargo are often lost at sea due to pirates, stormy weather, and all manner of unavoidable hazards. Salerio tries to reassure Antonio that, as his ships are so big, they will fly across the ocean, dwarfing the smaller ships and boats as they sail majestically past:

Your mind is tossing on the ocean, There, where your argosies with portly sail, Like signors and rich burghers on the flood—Or, as it were, the pageants of the sea—Do overpeer the petty traffickers That curtsy to them, do them reverence As they fly by them with their woven wings. (act 1, scene 1)

Salerio then tries a different approach. Instead of reassuring Antonio over the fate of his ships, he tries to empathize with what he thinks is his predicament. He tells Antonio that, if he were in his position, he'd never stop fretting. Whatever he did during the day would act as a reminder of what could happen to his ships at sea: blowing on his hot soup would make him think of his ships being buffeted by a storm; every time he looked at the sand in an hourglass he'd have terrible visions of ships being wrecked on sandbars; and he'd think of dangerous rocks when he went to church and saw the stone it was made out of.

In the opening scene of the play, Antonio tells Salerio that he is very depressed, worried, and tired. Salerio comments that Antonio is feeling upset because his merchant ships are out on the treacherous sea where he risks losing much of his wealth. However, Salerio doesn't blame Antonio for feeling depressed and dejected because he understands that if his precious ship Andrew were in similar danger, he would be reminded of his potential loss everywhere he went. Salerio mentions that he couldn't imagine the stress that Antonio is under and is sure that Antonio is lamenting about his merchant ships. Despite Salerio's sensible assumption as to why Antonio is depressed, Antonio reassures Salerio that he is not worried about his merchandise because his investments are not all on one ship.