A study in this week's journal "Nature" contradicts a fundamental belief on how lakes change as they age. Scientists have long thought lakes become more overgrown with algae and other nutrients over time. But a six year study of lakes in Glazier Bay, Alaska, led by Science Museum researcher Dan Engstrom found just the opposite -- that lakes actually become clearer as they age. Engstrom says he hopes the information will help us better understand lake pollution: