In 1498 the portuguese explorer vasco da gama discovered the first all-water route to asia from europe by sailing around the southern tip of africa to india. what effect did this voyage have on the ottoman empire? the ottomans benefited from the increase in intercontinental trade. the ottomans increased their navy in the indian ocean to stop portuguese merchant vessels. the ottomans lost income because overland trade through the middle east declined. the ottomans made money by taxing the portuguese trade.