Photo of John Mackey Mackey will remain CEO of Whole Foods, now a wholly owned subsidiary of Amazon.

SEATTLE—Amazon’s $13.7-billion acquisition of Whole Foods Market closed on Monday, and the new ownership wasted little time in making its presence felt at the high-end grocery chain. Shoppers at Whole Foods’ brick-and-mortar stores saw markdowns on selected grocery staples, and shares of the retailer’s common stock were converted into the right to receive $42 per share in cash.