This recipe can be prepared in 45 minutes or less.
In a small heavy saucepan combine maple syrup, water, and 1 1/2 cups blueberries and simmer mixture, covered, 5 minutes. Pour mixture through a sieve into a bowl, pressing on solids, and stir in lemon juice to taste. Syrup keeps, covered and chilled, 2 days. Reheat syrup or bring to room temperature before serving.
Serve remaining 6 1/2 cups blueberries topped with yogurt and maple-blueberry syrup.